This PDF file contains the front matter associated with SPIE Proceedings Volume 7917, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

We demonstrate a frequency doubled dual-gain quantum dot semiconductor disk laser operating at 590 nm. The reflective gain element, grown by molecular beam epitaxy, has active region composed of 39 layers of InGaAs Stranski- Krastanov quantum dots. The gain mirrors produce individually 3 W and 4 W of output power while the laser with both elements in a single cavity reveals 6 W at 1180 nm with beam quality factor of M²<1.2. The loss induced by the nonlinear crystal is compensated by gain boosting in the dual-gain laser and 2.5 W of output power at 590 nm was achieved after frequency conversion.

In this work, we investigate experimentally second-harmonic generation (SHG) in a periodically poled 5 %mol MgO doped LiNbO3 (ppMgO:LN) planar waveguide. As a pump source a 6 mm long distributed Bragg reflector (DBR) tapered diode laser is applied. The laser emits nearly diffraction limited, spectrally single-mode continuous-wave radiation at 1063 nm and is therefore well suited for the SHG process. With the applied lens system in a bench-top experiment a coupling efficiency into the planar waveguide of 73 % is reached. A maximal SH power of 1.07 W is generated at an opto-optical and electro-optical conversion efficiency of 26 % and 8.4 %, respectively. This is, to the best of our knowledge, the highest power level generated in a waveguide structure by means of frequency doubling of diode laser radiation in a single-pass configuration.

We demonstrate a compact high-power green (532nm) laser module based on single-pass second harmonic generation. The pump source is a distributed Bragg reflector tapered diode laser. The frequency conversion is achieved with a 2.5 cm long periodically poled MgO:LiNbO₃ bulk crystal. The entire module is integrated on a compact micro-optical bench with a footprint of 2.5 cm³. Up to 1.1 W output green light power is achieved at a pump power of 7.6 W with an optical conversion efficiency of about 15% and a corresponding module wall-plug efficiency of more than 4%. The green laser beam has a relatively good beam quality (measured at output power level of ~0.9 W) with M²_σ=1.8 in the vertical direction and M²=4.9 in the lateral direction, respectively. The long-term output power stability is ±10% (tested at output power level of ~0.6 W).

We report on highly efficient diode-pumped solid-state (DPSS) green laser source based on a monolithic cavity microchip laser platform. The use of periodically poled MgO-doped Lithium Niobate (PPMgOLN) as the nonlinear frequency doubler together with gain material Nd³⁺:YVO₄ allows obtaining a significant increase in the overall efficiency of green microchip laser in comparison with other compact green laser source architectures with comparable output power. We discuss our progress in miniaturization and efficient operation across a wide range of temperatures and application-specific modulation conditions. In particular, we demonstrate 50mW-120mW average green output power (30% duty cycle) with wall-plug efficiency over 13%. Efficient laser operation with duty cycle ranging from 10% to 60% in a wide range of repetition rates is also demonstrated. The laser is designed to be a part of the miniature and efficient RGB light source for microdisplay-based (LCOS, DLP or similar) mobile projector devices. While these projection architectures typically require modulation rates from 60Hz to about 2000Hz depending on design, we extended modulation speed up to 2MHz that can be of interest for other applications. A very efficient and small microchip as well as alignment-free design allow us to package this laser source into the very small volume of only 0.23cm3 (bounding box). We present results of performance tests for this packaged laser and demonstrate that such a miniature package can support laser operation with average power output of over 250mW.

We report a continuous-wave, watt-level, red, green, and blue (RGB) laser pumped by a multi-longitudinal-mode Ybfiber laser at 1064 nm. A singly resonant optical parametric oscillator at 1.56 μm has two intracavity sum-frequency generators for red and blue laser generation. An extracavity second harmonic generator converts the residual pump power into green laser radiation. At 25-W pump power, the laser generated 3.9, 0.46, and 0.49 W at 633, 532, and 450 nm, respectively. By replacing the multi-mode pump laser with a single-frequency one, we further increased the output power of the green laser to 2 W.

We present a compact frequency-doubled laser source with fundamental wavelength operation at 1062 nm. A freely triggerable seed diode laser delivers sub-100 ps pulses in the picojoule range at variable repetition rates up to 80 MHz. After amplification in a Ytterbium-doped fiber amplifier, the average power exceeds 380mW at 40 MHz, which corresponds to 9.5 nJ pulses and about 75W of peak power. The output beam is then focussed into periodically poled lithium niobate for second harmonic generation (SHG). In this way, green picosecond pulses with an energy of up to 2 nJ at 40MHz are generated. The pulse energy and pulse shape of the second harmonic pulses are systematically studied for various repetition rates, allowing conclusions on the amplifier performance under different operating conditions.

Recently, hybrid integrated compact laser sources with high optical output powers in the visible range around 488 nm were demonstrated using tapered diode lasers. This was done by single-pass second harmonic generation (SHG) using a periodically poled LiNbO3 crystal of 30 mm length. The conversion efficiency depends on the light source but is also a function of the temperature distribution along the length of the crystal. The maximum conversion efficiency of a given beam is theoretically achieved by a homogenous temperature distribution. Experiments have shown that for high power SHG different absorption mechanisms are causing a temperature gradient in the crystal. This gradient leads to an inhomogeneous poling period, which diminishes the effective crystal length and leads to a smaller conversion efficiency. In this paper we present a method for the optimization of the temperature management during the SHG. This is done by a multizone heater package that can be integrated into compact laser sources. This package can be used to create arbitrary temperature distributions and is especially able to compensate an arising temperature gradient.

Coherent all-solid-state light source of a wavelength below 200nm is attracting a lot of attention for industrial applications such as semiconductor processing, eye surgery, and micro machining. Multi-stage wavelength conversion from a high power infrared solid-state laser is a promising solution. We have developed a technology for quasi-phasematching (QPM) in crystalline quartz that utilizes stress-induced twinning. In the present paper, we report a novel stressmaintaining module that suppresses back-switching of twinning and enables QPM-SHG in the vacuum ultraviolet (VUV) region. We demonstrated the fabrication of finest periodic twins with a period of 9.6 μm and performed QPM-SHG experiment. Vacuum ultraviolet 193.4 nm light of 17 mW was generated from 177 mW fundamental light. To the best of our knowledge, this is the shortest emission wavelength ever obtained with QPM technology.

The importance of the light source in the UV and VUV region has increased in industrial and scientifical fields. In general, the second harmonic generation of near-infrared coherent light in an external enhancement cavity has been used to obtain high-efficiency and high-power coherent UV lights. However, the pump light of the high average power has been necessary for such high-effective wavelength conversions. We studied high-efficient and simple generation of UV continuous and quasi-continuous waves by optimizing an external cavity and using a BiB₃O₆ (BiBO) as a nonlinear crystal of relatively high nonlinear optical coefficient. We report the generation of high-efficient 389nm coherent light based on the second harmonic generation of a mode-locked Ti:sapphire picosecond pulses laser with BiBO. As a result, more than 500mW of output at 389nm was obtained with the maximum input of 800mW and a maximum efficiency of 63%. Furthermore, considering the reflective loss of output mirror of 389nm light, we could obtain 70% conversion efficiency. This value was one of the best results of the second harmonic generation of less than 1W of average pump power.

We demonstrate a frequency-converted green laser source simultaneously emitting three spectral lines with nearly equal intensity and ~ 0.5 nm separation, enabling a factor of √3 reduction of speckle contrast in pico-projector applications. The source consists of an external cavity 1060 nm diode laser pump with dual-wavelength reflection provided by a volume Bragg grating and a quasi-periodically poled MgO-doped lithium niobate waveguide engineered to phase-match multiple-wavelength frequency conversion. 62 mW output power and 33% conversion efficiency are demonstrated.

We present a table-top source of extremely intense multi-THz transients covering the spectral region between 0.1 and 140 THz. Electric field amplitudes of up to 108 MV/cm and pulse durations as short as a single cycle are demonstrated with our hybrid Er:fiber-Ti:sapphire laser system. All THz waveforms are electro-optically detected. This source opens the door to a regime of non-perturbative THz nonlinearities in condensed matter. First examples range from coherent control of excitons, via a breakdown of the power expansion of the nonlinear polarization in bulk semiconductors to twodimensional multi-wave mixing and direct femtosecond spin control by magnetic field excitation.

We present a theoretical investigation of a non-collinear sum frequency generation in an electro-optic crystal between visible and THz radiation. This coherent mixing results in the encoding of the spatial phase of the THz object field onto the visible wave. The "crystal + optical pump" system behaves as a lens for the THz field. The THz field is converted into the visible range, but with a phase-preserving transformation analogous to holography. This scheme provides an imaging capability, and we can thus record THz scenes with conventional optical detectors that are much more sensitive than THz sensors. We show that a Nonlinear Snell-Descartes' Lens Formula can be derived from our analysis; in comparison to the classical one, this generalized lens formula exhibits an additional magnification factor proportional to the ratio between the optical and THz wavelength.

Metamaterials are artificial materials with unusual properties that do not exist in nature and basically could consist of subwavelength metallic patterns printed on dielectric substrate. In this paper, we present a theoretical and experimental investigations of metamaterials designed for THz applications. First, fishnet metamaterials which are composed with a thin dielectric material sandwiched between two metallic layers. Two techniques were used in order to fabricate our prototypes: double layer optical lithography and laser micromachining. We performed simulations and experiments using commercial software simulator based on finite element method (HFSS) and terahertz time domain spectroscopy THz- TDS respectively. A good agreement was reported between simulations and experiments while pointed out the dramatic influences of dielectric losses in the effective response.

We developed parametric generation of terahertz (THz) wave based on noncollinear phase-matching condition in 5 mol% MgO-doped LiNbO₃ (MgO:LN) crystal synchronously pumped by a low-power mode-locked picosecond Ti:sapphire laser whose average output power was less than 1 W in simple external enhancement cavity. Considering the idler (Stokes) light made an angle of approximately 1 degree with the pump light corresponding to the noncollinear phase-matching condition, we built the extremely-simple doubly-resonant cavity, which composed of only four mirrors, in which the idler light was resonated as well as the pump light simultaneously without any feedback systems for the idler light to reduce the pumping threshold of the THz wave parametric process. As a result, we obtained a broad output THz wave at around 0.9 THz confirmed by Michelson interferometer and achieved the pumping threshold of peak intensity of 50 MW/cm². This threshold is, to the best of our knowledge, the lowest value of externally pumped THz wave parametric oscillation.

THz time domain spectroscopy has been largely applied on the measurement of semiconductor, electro-optic crystals, and selected chemical, biological and explosive materials. The objective of this paper is to report THz gas photonics and its applications, with an emphasis on remote sensing capabilities. The most recent results of using air (and selected gases) as the emitter and sensor material for both generation and detection of broadband THz waves will be reported. Air, especially ionized air (plasma), has been used to generate intense peak THz waves (THz field > 1.5 MV/cm) with a broadband spectrum (10% bandwidth from 0.1 THz to 46 THz). THz-enhanced-fluorescence (TEF) and THz-enhanced acoustic (TEA) techniques have been developed for remote sensing purpose. By "seeing" the fluorescence, or "hearing" the sound, coherent detection of THz waves at standoff distance is feasible.

We report coherent monolithic THz generation in GaP QPM bonded structures based on difference-frequency generation (DFG) using two pulsed fiber lasers in the C-band. We observed that the QPM-GaP crystals effectively increase the THz generation power and efficiency with increasing periods of QPM structures. The azimuthal dependence of the THz generation for the GaP QPM bonded structure has been measured when the polarization directions of the two pump beams are orthogonal and parallel, respectively. Moreover, we observed the external cavity enhanced THz DFG when we put the QPM-GaP crystal in an external ring cavity, for the first time. The THz cavity enhancement factor of ~250 has been achieved compared with the single-pass THz DFG. The maximum THz average power can reach 339 μW, corresponding to a power conversion efficiency of 2.43×10-4 and quantum efficiency of 3.16%.

Some believes that the useful length of THz different frequency generation (DFG) in a highly absorptive material is comparable to the absorption length of the THz wave. We show in theory and experiment that it is only true for backward THz DFG. For forward DFG with strong idler absorption, the THz wave can continue to grow with the length of a DFG crystal.

We develop a theory of terahertz emission from a femtosecond laser pulse with tilted intensity front propagating through a prism-shaped electro-optic crystal. The theory accounts for transient effects at the entrance boundary of the crystal and allows us to explore the dynamics of terahertz generation in the crystal. In particular, transverse walk-off length is introduced as an important parameter of the terahertz field formation process. Two typical experimental situations - LiNbO3 excited with Ti:sapphire laser (0.8 μm wavelength) at room and cryogenic temperatures - are considered, and new schemes, in which GaAs is excited at 1.8 and 3.5 μm, are proposed and analyzed. The parameters of the laser pulse (transverse size, tilt angle, and pulse duration) and crystal size maximizing the terahertz yield are calculated.

We report efficient generation of picosecond pulses in the near- and mid-infrared in the new nonlinear material CdSiP₂pumped at 1.064 μm by an amplified mode-locked Nd:YVO₄ laser at 100 kHz repetition rate. Using single-pass optical parametric generation in 8-mm-long crystal cut for type I (e→00) noncritical phase-matching, an average idler power of 154 mW at 6.204 μm together with 1.16 W of signal at 1.282 μm has been obtained for 6.1 W of pump at photon conversion efficiencies of 15% and 23%, respectively. Signal pulse durations of 6.36 ps are measured for 9 ps pump pulses, with both signal and idler beams in near-Gaussian spatial profile.

We have demonstrated a novel folded linear resonator for walk-off compensated (WOC) optical parametric oscillation (OPO) in a single ZGP crystal. The OPO uses the doubled ZGP crystal length in a WOC configuration while simplifying requirements on crystal alignment. With a Q-switched Ho:YAG laser as a pump source, a maximum output power of 2 W at a wavelength of 4.72 μm has been measured for a pump power of 11.9 W in a 15-mm long type-I phase-matched ZGP crystal. The measured OPO quantum slope efficiency is above 50%.

A compact and high-energy pulsed mid-infrared laser using an optical parametric oscillator (OPO) has been developed using a diode-pumped and Q-switched Tm,Ho:YAG ceramic laser with a wavelength of 2.09 μm as a pump source. A singly-resonant OPO with a 20 mm long AgGaSe2 crystal was used, and the crystal was set at an angle normal to the pump beam. The output idler pulse energy was up to about 200 μJ with the pump energy of about 6 mJ for both the type I and type II phase matching conditions. The wavelength of the idler pulses was 5.97 and 6.37 μm for type I and type II, respectively. The output characteristics predicted using a model calculation were in good agreement with the experimental results. It is suggested that the output idler pulse energy in the experiment is limited by the surface damage threshold of the AgGaSe2 crystal. By increasing the pump beam diameter from 1 to 3 mm (3-fold) and the pump energy from 6 to 54 mJ (9-fold), the idler pulse energy of 1.8 mJ (= 200 μJ × 9) will be obtained without increasing the pump intensity and without saturation of the output idler pulse energy.

We report on watt level mid-infrared (MIR) wavelength generation using intra-cavity ZnGeP₂ (ZGP) optical parametrical oscillator (OPO) within a 2.1μm Ho:YAG laser. A compact cavity of less than 50cm was designed for the intra-cavity OPO setup. With the same laser setup, watt level of both 2.1μm and MIR wavelengths were generated. An average output power of >20W of 2.1μm and >1W of MIR wavelength at 10 KHz repetition rate were achieved from a 46W Tm fiber pump laser. The Ho:YAG laser was resonantly pumped by a 1.9μm Tm:fiber laser and nanosecond pulses were generated using an electro-optics q-switch modulator. With the use of a λ/4 waveplate and a thin film polarizer, a variable output coupler for the Ho:YAG laser was formed where we could optimize the output coupling to achieve 21W of 2.1μm wavelength. MIR wavelengths were generated using commercial ZGP crystals from Inrad. A HR mirror for the MIR wavelengths was inserted into the Ho:YAG cavity to form the intra-cavity ZGP OPO. The rear mirror of the Ho:YAG cavity act as the output coupler with R=70% for the MIR wavelengths. Optimizing of the MIR generation was done by tuning the phase-matching angle of the ZGP and adjusting the cavity length of the OPO. A preliminary result of the intra-cavity ZGP OPO generates >1W of MIR wavelength.

We demonstrate three-dimensional Airy-Bessel optical wave packets that propagate without broadening in time or space. We also demonstrate the non-dispersive and the self-healing nature of the Airy pulse. Since the propagation of an Airy- Bessel wave packet does not critically depend on the material properties, we believe the Airy-Bessel wave packet will find its usage in applications as practical devices.

vHere, we consider the possibility of involving the photo-EMF detectors in registration of the parameters peculiar to ultrashort optical pulses, and it is compared whit the recently triple correlator via Direct and Cascade Third Harmonic Generation. Knowledge of triple auto-correlation function, whose Fourier transformation shapes the corresponding bispectrum, makes possible recovering such train-average parameters as, for instance, the pulse width and frequency chirp as well as revealing asymmetry of ultra-short pulse envelope. The main advantage of applying the photo-EMF detectors lies in an opportunity to detect triple correlations directly, without any intermediate frequency conversion with optical nonlinear processes in additional crystals. Then, the theory of three-beam-correlations at photosensitive layer of the photo-EMF detector is developed, so that principal possibility of registering the high-order-correlations is demonstrated. It can be done within schematic arrangement including the three-beam Michelson interferometer, so that the obtained high-order-correlations have non-traditional form and need rather specific algorithm for their further processing. Also, the experimental characterizations are presented for gallium arsenide (GaAs) semiconductor and the poly-fluoren 6-co-triphenyldiamine (PF6-TPD) photo-conductor-polymer, which both exhibit the photo-EMF-effect. They both exhibit high-pass transfer functions that give us high vibration stability. This novel approach provides more reliable analyzing train-average parameters of picosecond pulses due to significantly higher level of the output optical signals under processing.

We report on third-harmonic generation (THG) in optical materials using femtosecond pulses and Z-scan method. Here we have played with beam focusing parameters and, in this way, we could track the THG signal at function of Rayleigh ranges. We observed that the femtosecond pulse has broadband spectrum and such property also affects the thirdharmonic (TH) spectrum. In this experiment we were able to distinguish the contribution of bulk and interface on the THG by measuring the intensity and spectral profile of the TH signal.

Using YVO₄ as a Raman medium, stimulated Raman amplification of white-light continuum was successfully demonstrated. Only microjoule-level of pulse energies was needed to achieve efficient energy conversion to the first and the second Stokes radiation. Nonlinear optical mixing in a series of BBO crystals was used to attain discretely tunable picoseconds laser pulses in the visible and the ultraviolet spectral regions. A potential application of this radiation for resonance Raman spectroscopy is discussed.

We demonstrate an extremely simple frequency-resolved-optical-gating (GRENOUILLE) device for measuring the intensity and phase of relatively long-ps-pulses. In order to achieve the required high spectral resolution and large temporal range, it uses a few-cm-thick second-harmonic-generation crystal in the shape of a pentagon. This has the additional advantage of reducing the device's total number of components to as few as three simple easily aligned optics, making it the simplest device ever developed for complete pulse measurement. We report complete intensity-and-phase measurements of pulses up to 15ps long with a time-bandwidth product of 21.

Recent investigations in nonlinear fiber optics have shown a renewed interest in certain classes of analytical solutions of the Nonlinear Schrödinger equation which, although present in the mathematical literature for 25 years, have been largely overlooked in studies of nonlinear fiber propagation. In this paper we review recent experiments that have shown the power of this analytic approach.

It is well-known that the properties of the supercontinuum (SC) radiation depend critically on the initial pumping conditions. For instance, if the SC is initiated by noise, namely modulation instability (MI), statistically rare "rogue waves" can be observed with sizable spectral broadening and intensity enhancement in SC. Interestingly, such rouge events can be actively controlled by adding an external weak pulse or by modulating the pump-pulse envelopes. In contrast, we here present that a simple triggering mechanism using an extremely weak continuous wave (CW) can also achieve such "rogue" enhancement. We experimentally demonstrated that a weak CW trigger (~200,000× weaker than pump) can considerably broaden the SC bandwidth compared to the untriggered SC case (~100 nm wider). Such enhancement was found to occur when the CW trigger's wavelength falls roughly within the modulation instability gain bandwidth. CW triggering also significantly alters the SC amplitude statistics, i.e. from extreme-value statistics in the untriggered SC to almost normal distribution in the triggered SC. Interferometric measurements also revealed the improvement in the SC coherence when the SC is CW-triggered. The enhanced SC by minute CW triggering only requires the CW-wavelength tuning for optimization and eliminates the necessity of high-precision (down to picoseconds) timing between the pump and the seed as in the pulse-seeding case. It thus offers a more convenient and practical approach to realize an enhanced and stable SC for many applications, especially in which real-time, ultrafast and singleshot spectroscopic measurements are essential.

Pulse breakup and the formation of a bunch of solitons are the principal processes at the initial stage of the supercontinuum generation using long pulses for pumping. Most investigations use the measurement of the output spectrum to characterize the development of the supercontinuum. The extraction of an individual soliton or a group of solitons with similar parameters from the bunch can reveal details that are usually hidden when only the output spectrum is measured. Earlier we have studied the NOLM including a twisted fiber and a quarter wave retarder (QWR) in the loop. Its operation is based on the nonlinear polarization rotation effect. We showed that this NOLM is stable to changes of environmental conditions, and allows simple and predictable changes of its characteristics. In previous works we demonstrated its application for mode-locked lasers, pedestal suppression, or retrieval of a pulse shape. In this work we demonstrate that the NOLM is a viable device for the investigation of pulse breakup process and soliton formation. The operation principle is based on the fact that the NOLM has a maximum transmission for the solitons with specific durations while solitons with shorter and longer durations are strongly rejected. The duration associated with high transmission depends on the NOLM length and can also be changed by amplification of the solitons before entering the NOLM. By an appropriate choice of the NOLM parameters and the amplification of the bunch of solitons, the extraction of the solitons with selected parameters is possible.

We observe efficient forward stimulated Brillouin scattering (FSBS) in a standard 2-km highly-nonlinear optical fiber (NHLF), where we see multiple resonance peaks between 425 MHz to 1.1 GHz. The most efficient acousto-optical coupling appears for the 20th radially-guided acoustic mode at 933.8 MHz, which has maximum spatial overlapping with the tightly confined optical mode in the NHLF fiber. A large gain coefficient of 34.7 W^-1 is obtained at this resonance when pumped with a 8 mW continuous-wave (cw) beam at 1550 nm, and an enhanced gain of 57.6 is obtained by using a pulsed pump beam at 80 mW. Interference between the FSBS process and the Kerr effect is observed to enhance the resonance and cause asymmetric profile for the observed resonances.

The propagation of short pulses in optical fibers is commonly modeled by the generalized Nonlinear Schrodinger equation which includes the frequency-dependence of the dispersion and nonlinear response and the non-instantaneous part of the nonlinear response of silica. It is also common to model the delayed -or Raman- response of silica based on the assumption of a material response that varies linearly with frequency. Here, we examine in detail the accuracy and limitations of this widely used approach. Our major conclusion is that the linear Raman gain approximation performs very poorly in parameter regimes typical of many experimental studies, introducing significant errors and artifacts into the spectral and statistical properties of the supercontinuum spectrum.

We demonstrate ultra-sensitive optical detection of terahertz by using nonlinear parametric upconversion. Terahertz radiation is mixed with pump light at 1550 nm in a nonlinear crystal to generate an optical sideband or idler wave. The idler signal is separated from the optical pump, coupled into an optical fiber and detected using a Geiger-mode avalanche photo-diode. Our scheme to detect THz waves leverages mature technology at 1550 nm developed for telecommunications to enable ultra-sensitive detection at room-temperature. We have fabricated a diffusion-bonded, quasi phasematched GaAs crystal, a χ⁽²⁾ nonlinear material, that is pumped with a readily obtainable erbium doped fiber amplifier to perform the parametric conversion. We demonstrate efficient upconversion of terahertz radiation using both a continuous-wave THz source operating at 0.82 THz and a pulsed sub-picosecond THz source with spectral coverage from 0.5 THz to 1.5 THz. The resulting THz detector has a noise equivalent power of 78 fW/Hz1/2 with a timing resolution of 1 ns. χ⁽²⁾ nonlinear interactions are intrinsically very fast; our temporal bandwidth is limited by the optical detector. Additionally, the THz detector demonstrates a broadband response with a phase-matching bandwidth exceeding 1 THz. This noise equivalent power of 78 fW/Hz^1/2 and the corresponding power conversion efficiency of 1.2× 10^-3 are the best reported, to our knowledge. This paper presents both theoretical and experimental results.

We used ultrafast Fourier-plane optical-parametric-amplification (OPA) imaging to simultaneously image, wavelength-shift, and amplify complex two-dimensional objects with spatial features from 1.1 to 11.3 line-pairs/millimeter, corresponding to a two-dimensional space-bandwidth product (SBP) of 13,790. This represents an increase in image complexity over previous analogous OPA imaging systems by almost three orders of magnitude. In wavelength-shifting the image from 930nm to an idler wavelength of 700nm, we observed image amplification by up to two orders of magnitude.

An optimized method for continuous wave 2-dimensional (2-D) upconversion of incoherent or thermal light is demonstrated and quantified. Using standard resolution targets a resolution of 200x1000 pixels is obtained. The suggested method is viewed in scope of modern CCD cameras operating in the near infrared (NIR) portion of the electromagnetic spectrum. The key is optimization of the upconversion process. This include Quasi-Phase-Matching leading to higher effective nonlinearities and elimination of walk-off, an intra-cavity design enhancing the upconversion process, and finally the use of modern NIR CCD detectors. Furthermore, we discuss the exceptionally good depth of field possible for imaging systems based on the proposed method.

We present a simple theoretical model for 2 dimensional (2-D) image up-conversion of incoherent light. While image upconversion has been known for more than 40 years, the technology has been hindered by very low conversion quantum efficiency (~10^-7). We show that our implementation compared to previous work can result in a feasible system: Using intracavity upconversion and Quasi Phase Matching (QPM) nonlinear materials provide increased conversion efficiency. Using a QPM crystal and choosing the wavelengths so the first order term in the phasematch wavelength acceptance vanishes, results in very large wavelength acceptance. This work describes how the bandwidth acceptance can be predicted and designed. This gives promise of a new way to make infrared imaging devices with tunable spectral sensitivity.

In 1970 - 80s, novel optical spectral devices, electronically tunable acousto-optical filters (AOFs) had been proposed and developed. During the years gone AOFs have been remarkably progressed, and now they are widely exploited, for instance, in astrophysical observations. Schematically, AOFs can be separated on collinear and non-collinear filters, depending on the relative directions of passing the waves through crystalline cell, as well as on sequential and parallel ones, depending on the algorithm of spectrum analysis. Their features are characterized by the amplitude and spectral parameters. Here, we consider a few estimations of an advanced collinear AOF based on calcium molybdate single-crystal. In principle, this new AOF with a 15-microsecond time-aperture operates over all the visible range exhibiting 60%-efficiency at the electric power 1.0 W. Direct square-law dependence for crystal's length and inverse square-law dependence for its bandwidth on this minimal size make possible optimizing this advanced collinear AOF.

We implement a new approach for generating broadband mid-infrared frequency combs via degenerate optical parametric oscillation. This technique efficiently transfers the desirable properties of shorter wavelength mode-locked sources to the mid-IR. Our OPO resonator is a 3m ring cavity composed of one pair of concave mirrors with R=50mm and four flat mirrors, all but one of which are gold coated with > 99% reflection. A single dielectric mirror is used to introduce the 1560nm pump (Menlo Systems C-fiber, 100 MHz, 70 fs, 350 mW or Toptica Photonics FemtoFiber Pro, 80 MHz, 85 fs, 380 mW). The dielectric mirror is transmissive for the pump and reflective in the 2.5- 4 micron range. Broadband parametric gain around 3.1-micron subharmonic is provided by short (0.2-0.5mm) periodically poled lithium niobate (MgO:PPLN) at Brewster angle. Crystals were cut from Crystal Technology Inc. material having QPM period of 34.8 microns for type 0 (e=e+e) phase matching at t=32 deg. C. The enormous acceptance bandwidth at degeneracy, typical for OPOs with type 0 (or type I) phase-matching, gives broad bandwidth and makes temperature tuning insignificant. Broadband oscillation is achieved when signal/idler are brought into degenerate resonance by fine-tuning the cavity length with a mirror on a piezo stage. Using an 8% reflective pellicle, we outcouple a frequency comb of more than 1000nm bandwidth, centered around 3.1 microns. A 1mm or 2.5mm thick ZnSe plate at Brewster angle provides 2nd-order group velocity dispersion compensation, improving the OPO bandwidth. The OPO threshold was measured to be < 30mW. When locked, the OPO outputs 60 mW of average power centered at 3.1 microns. With proper intracavity dispersion management including chirped mirrors, we expect to extend the spectral width to an octave or more.

Silicon waveguides have, to date, largely been designed to operate near the telecommunication bands in the near infrared. The mid-infrared (MIR) wavelengths, which range from two to twenty microns, are critical for a number of application areas, including chemical bond spectroscopy and thermal imaging. We show results, using commercially available silicon-on-sapphire wafers, for low-loss (4.0 dB/cm) waveguides and what we believe to be the first working microresonators operating at wavelengths around 5.5 um in silicon guides with Q-values as high as 3.0 k. This talk will discuss the applications for mid-infrared integrated photonics in the silicon system, particularly for sensing and nonlinear optics.

We present experimental results demonstrating the direct third harmonic generation (THG) in a periodically poled lithium niobate (ppLN) crystal. The method we propose relies on standard ppLN architecture (constant poling period) that is properly chosen to satisfy the quasi-phase matching (QPM) between the fundamental and the third harmonic wave. Neither the second harmonic generation (SHG) nor the sum frequency generation (SFG) optimization or their coupling is mandatory for cascaded THG. Indeed, in our approach, the SHG signal remains weak and only serves as "virtual state" to seed the THG that satisfies the overall QPM-THG condition. Numerical simulations reveal that under QPM-THG condition, SHG intensity has rapid spatial variations and its intensity remains weak along the propagation. The theoretical analysis shows that the adiabatic elimination of the second harmonic virtual state allows for an efficient THG, which is experimentally observed. Using this approximation, we show that the set of non-linear coupled wave equations reduce to an effective THG process.

We investigate the role of step-chirped gratings (SCG) for flattening of conversion efficiency response and enhancing the pump bandwidth in cascaded sum and difference frequency generation (SFG + DFG) with a large pump wavelength difference. To obtain a flat response with maximum efficiency, using SCG instead of uniform grating with the same length, the appropriate critical period shifts are presented for the reasonable number of sections and chirp steps feasible for fabrication. Furthermore, it is shown that adding the section numbers for SCG structure increases the pump bandwidth.

Potassium lithium niobate (KLN), a nonlinear optical material with high nonlinearity and other desirable properties, has the potential to improve the performance and reduce the cost of blue and UV lasers. KLN crystals have not entered the commercial mainstream because it is impossible to grow them reproducibly by conventional techniques. We have developed a proprietary process based on the laser heated pedestal growth (LHPG) technique that eliminates technical barriers to manufacturing KLN crystals. This paper describes the LHPG method of KLN crystal growth including improvements in crystal uniformity and transparency, and our latest harmonic generation results in the UV.

Quasi-phase-matched (QPM) materials such as periodically poled lithium niobate (PPLN) and tantalate (PPLT) have led to extremely efficient frequency-shifted laser sources in the visible and near-infrared, and QPM semiconductors promise to extend this performance beyond 4um. Orientation patterned semiconductors are not only transparent far deeper into the mid-IR but also offer higher nonlinear coefficients, higher thermal conductivity, higher purity levels, and very low losses when grown from the vapor phase. We compare the properties, processing, and performance of orientationpatterned GaAs (OPGaAs) with candidate compound semiconductors being for development as the next generation QPM nonlinear optical materials in the mid-infrared, and identify gallium phosphide as the most promising material for near-term development.

Two essential advantages can be expected from adding S to the well known nonlinear crystal GaSe: increase of the bandgap value or the short wave cut-off limit and improved hardness. Recently, we confirmed that the non-centrosymmetric structure of GaSe is preserved up to a GaS content of 40 mol. % while the nonlinear coefficient d22 is reduced by only 24%. The increased band-gap results also in higher surface damage threshold. Our preliminary Sellmeier equations for GaS_0.4e_0.6 were based on refractive index measurements. These equations are refined in the present work by fitting second-harmonic generation and optical parametric amplification phase-matching angle data in the mid-infrared as well as birefringence data in the visible and near-infrared obtained with thin phase retardation plates. The two-photon absorption effect was studied for GaS_0.4e_0.6 and GaSe using amplified picosecond pulses at 1064 nm, at a repetition rate of 10 Hz. For intensities in the GW/cm² range, the two-photon absorption coefficient of GaS_0.4e_0.6 for the o-polarization is 3.5 times smaller than the corresponding coefficient of GaSe. This means that GaS_0.4e_0.6 could be safely used in Nd:YAG laser pumped nanosecond optical parametric oscillators or picosecond optical parametric amplifiers, without nonlinear absorption losses. The dynamic indentation measurements with Berkovich type indenter of c-cut GaS_0.4e_0.6and GaSe plates indicate about 30% higher indentation modulus and microhardness of GaS_0.4e_0.6 in comparison to GaSe.

High efficiency second harmonic generation of a pulsed TEA CO₂ laser operating at 9.569 μm was demonstrated in a quasi-phase-matched GaAs structure, 1.48 mm thick, 39.7 mm long and 8.3 mm wide, and having a grating period of 219.6 μm. The structure was grown by hydride vapor phase epitaxy and was dual-band anti-reflection coated on both entrance and exit surfaces. Energy of 1.2 mJ was obtained at 4.78 μm from single pass conversion with incident energy of 2.56 mJ.

The third order optical nonlinearities cover a vast and diverse area in nonlinear optics. The third order nonlinear susceptibility χ⁽³⁾ is a complex quantity and its real and imaginary components represent nonlinear refraction and nonlinear absorption, respectively. Measurement of these parameters is important for many practical applications. Z-scan is a simple optical technique for determining these characteristics with high accuracy. Here we present a novel photoacoustic Z-scan (PAZ-scan) technique that combines the advantages offered by the conventional Z-scan method and the sensitivity of the photoacoustic detection. In PAZ-scan, instead of measuring the transmitted optical signal as in the case of traditional Z-scan, we record the generated photoacoustic (PA) signal using a 10 MHz focused ultrasound transducer while the sample is translated along the focused laser beam. Since the photoacoustic signal strength is directly proportional to the optical absorption, PAZ-scan displays nonlinear behavior depicting the nonlinear optical absorption of the material. For reverse saturable absorber (RSA) materials, absorption and hence the PA signal increases with the increase of input intensity. Similarly for saturable absorber (SA) materials, absorption and the associated PA signal decreases with increase in input intensity. We studied the nonlinear absorption properties of SA and RSA materials. Our calculations of nonlinear absorption coefficient are in good agreement with conventional the Z-scan data.We believe that PAZ-scan will be a valuable tool for material characterization and has potential for applications in the fields of chemistry, physics, material science, biomedical, and manufacturing.

When parametric nonlinear processes are employed in the cause of efficient optical frequency conversion, the media involved are generally subjected to substantially off-resonant input radiation. As such, it is usually only electronic ground states of the conversion material that are significantly populated; higher levels are engaged only in the capacity of virtual states, and it is frequently assumed that just one such state dominates in determining the response. Calculating the nonlinear optical susceptibilities of molecules on this basis, excluding all but the ground and one excited state in a sum-over-states formulation, signifies the adoption of a two-level model, a technique that is widely deployed in the calculation and analysis of nonlinear optical properties. The two-level model offers tractable and physically simple representations of molecular response, including wavelength dependence; it is also the origin of the widely applied 'push-pull' approach to designing optically nonlinear chromophores. By contrast, direct ab initio calculations of optical susceptibility are commonly frustrated by a complete failure to determine such dispersion features. However, caution is required; the two-level model can deliver potentially misleading results if it is applied without regard to the criteria for its validity, especially when molecular excited states are significantly populated. On the basis of a precise, quantum electrodynamical basis for the theory, we explore in detail why there are grounds for questioning the general validity of two-level calculations in nonlinear optics; we assess the criteria for high frequency conversion efficiency and provide a new graphical method to assist in determining the applicability of a two-level model for hyperpolarizability calculations. Lastly, this paper also explores the applicability and detailed conditions for the two-level model for electronically excited molecules, identifying problematic results and providing tractable methods for improving the accuracy of calculations on real molecule-photon interactions.

LiGaSe₂ and LiInSe₂ are promising nonlinear crystals for conversion of laser radiation to the mid-IR spectral range which are transparent down to the visible and UV. We successfully grew a new mixed crystal as a solid solution in the system LiGaSe₂ - LiInSe₂, with a composition of LiGa_0.5In_0.5Se₂ which has the same orthorhombic structure (mm2) as the parent compounds (LiGaSe₂ and LiInSe₂). The new crystal is more technological with regard to the growth process in comparison with LiGaSe₂ and LiInSe₂ since its homogeneity range is broader in the phase diagram. We established that about 10% of the Li ions are found in octahedral position with coordination number of 3. The band-gap of LiGa_0.5In_0.5Se₂ is estimated to be 2.94 eV at room temperature. The transparency at the 0-level extends from 0.47 to 13 μm. The dispersion of the principal refractive indices was measured and Sellmeier equations were constructed. The fundamental wavelength range for the SHG process extends from 1.75 to 11.8 μm. The nonlinear coefficients of LiGa_0.5In_0.5Se₂ have values between those of LiGaSe₂ and LiInSe₂.

Using the amplification transfer function of type1BaAlBO3F2 (BABF) crystal, the parametric fluorescence properties of new BABF crystal have been investigated in the different quasi-phase matched modes. The parametric fluorescence signal lifetime study is presented based on amplification gain obtained in the quasi-phase matched modes. This analysis of parametric fluorescence signal lifetime is shown to be equal to the results obtained from the amplification transfer function.

All-solid-state intracavity Raman laser using a ceramic Nd:YAG laser and a KGd(WO₄)₂ nonlinear crystal has been fabricated and its output characteristics has been investigated for the purpose of medical application. Yellow laser light at the wavelength of 579 nm could be obtained by second harmonic generation of LBO crystal from the first Stokes wavelength of 1159 nm which was converted by stimulated Raman scattering with the fundamental wavelength of Nd:YAG laser. In the case of using output coupler of reflectivity of 95%, the maximum peak power was 230 W/pulse with the pulse width of 9.3 ns under the condition of Q-switched mode operation. The maximum average power of about 30 mW was achieved at the pump power of 20 W.

The terahertz wave has been attracted recently because of its wide ranging applications in various fields. Since the appearance of a high power near-infrared light source, coherent terahertz waves have been generated successfully using PC antennas, Q-switch Nd:YAG laser or femto second ultrashort pulses laser. Actually, however, there is no tunable and high-reputation terahertz wave source. Then, we have been focusing on picosecond pulsed laser, because picosecond pulsed laser has smaller linewidth than femtosecond pulse and higher-reputation than Q-switch Nd: YAG laser. In addition, picosecond pulses' peak power can be enhanced in a high finesse compact external cavity to overcome the threshold of terahertz parametric generation and oscillation, because the pulse is relatively small spatially, and the spectrum is relatively narrow. Therefore, we developed a terahertz parametric generator with an MgO-doped LiNbO₃(MgO: LN) nonlinear crystal in an external ring cavity for the enhancement. Moreover, the generated idler light was recycled in the ring cavity to provide a contribution to parametric oscillation. As a result, we obtained terahertz wave radiation at high-reputation of 80MHz.

BaMgF₄ is a novel ferroelectric fluoride which is transparent in the wavelength regions from 125 nm to 1300 nm. Recently, the trial production of the frequency conversion device with BaMgF₄ single crystal was reported for the ultraviolet (UV) and vacuum ultraviolet (VUV) wavelength regions, but there has been a few report on it. The BaMgF₄ is very attractive ferroelectric crystal because it can be used as a quasi phase matching (QPM) device such as LiNbO₃ or LiTaO₃. Nonlinear crystals have very large nonlinear coefficients generally, but these coefficients limited wavelength regions to use due to the birefringent phase matching, which limited to the wavelength from 573 nm to 5634 nm. Thus the QPM technique is attractive to fabricate frequency-conversion device in the UV/VUV region. In this study, we have purpose to fabricate BaMgF₄ hetero-epitaxial thin films toward frequency conversion devices. The optical-grade BaMgF₄ single crystal has been fabricated by Bridgman method. Rather we focus on fabrication of BaMgF₄ thin films by the precise and careful method of ion beam sputtering. It will be possible to fabricate also its waveguide structure under the vacuum-consistent process.

Quartz has been attracted attention as a nonlinear optical material without spontaneous polarization. Supposing that twinning of quartz crystal could be achieved effectively rather by impressing bending stress, we studied on making a periodically inverted structure to generate VUV lights by quasi-phase matching. We fabricated experimentally the inverted structure locally by impressing the stress for the AT-cut quartz substrate that was heated. Moreover, the stress distribution was calculated when the bending stress was impressed to the substrate with the rectangle structure, and then the condition for the polarization inversion was also calculated.

High chalcogen volatility and Li interaction with the container walls result in variation of crystal composition and presence of both extended and point defects in as-grown LiGaS2 nonlinear crystals. Annealing in appropriate conditions is used to correct the composition and improve the optical quality. We annealed LiGaS2 in vacuum, in the presence of Li₂S, Ga₂S₃, and S, and studied changes in transmission, photoluminescence and photo-induced absorption. OH groups, S-H and S-S complexes, sulfur vacancies and cation antisite defects (GaLi) are most important. Photo-induced absorption is reversible: It appears after illumination with UV/blue light and disappears after illumination with IR light or by heating the sample.

A method to carry out the compression of parabolic pulse in the nonuniform fibre cascade was proposed. The periodic modulation of the dispersion along the fibre length can be used to control subpicosecond pulses in time and frequency domains. Good agreement between simulations and experimental data takes place.

This paper reports the modified Sellmeier equations for ZnGeP2 (ZGP) that provide excellent reproduction of the phase-matching conditions for DFG between the two CO2 laser wavelengths, and the Nd:YAG laser and the Nd:YAG laser-pumped OPO in the THz region. Model calculations based on these Sellmeier equations strongly indicate that there is no significant difference in the refractive indices of the non-annealed and annealed crystals from 1.0642μm to 1640μm (0.18THz).

We present theoretical and experimental results on the scalability of amplifying a single-frequency diode laser operating at 1178 nm through the utilization of a core pumped Raman fiber amplifier. A model that accounts for stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in both co-pumped and counter-pumped configurations is developed. In order to mitigate the SBS process, a multi-step temperature distribution that is spatially optimized along the length of fiber is investigated numerically. We also present preliminary experimental results on a co-pumped Raman amplifier with an output power of 12 W and a measured Brillouin gain coefficient of approximately 1.2×10^-11 m/W.

A detailed quantitative numerical analysis of partially coherent quasi-CW fiber laser is performed on the example of high-Q cavity Raman fiber laser. The key role of precise spectral performances of fiber Bragg gratings forming the laser cavity is clarified. It is shown that cross phase modulation between the pump and Stokes waves does not affect the generation. Amplitudes of different longitudinal modes strongly fluctuate obeying the Gaussian distribution. As intensity statistics is noticeably non-exponential, longitudinal modes should be correlated.

A high output power, eye-safe, lidar transmitter based on a KTA optical parametric oscillator (OPO) was demonstrated. The OPO was based on a two crystal, doubly resonant, non-critically phase-matched, KTA ring cavity. An injection seeded, 7ns, 30Hz, flashlamp-pumped, Q-switched Nd:YAG laser was used to pump the OPO. The OPO converted the 1064nm pump beam into a 1533nm signal wave and 3475nm idler wave. In addition to demonstrating a high power OPO system, we investigated the effects of seeding the pump laser on the OPO's conversion efficiency, oscillation threshold, maximum signal power, and beam quality. The power conversion efficiency between the signal and the injection seeded pump was 22% with an oscillation threshold of 104MW/cm² (500mJ) and a maximum signal power of 6.44W (215mJ). The power conversion efficiency between the signal and the unseeded pump was 24% with an oscillation threshold of 77MW/cm² (367mJ) and a maximum signal power of >7W (243mJ). When the pump laser was seeded, the full angle divergence improved by nearly a factor of five.

We describe reverse-proton exchanged (RPE) waveguides in MgO-doped lithium niobate capable of stable secondharmonic generation (SHG) of over 100 mW of CW green light with conversion efficiency exceeding 200%/Wcm². Substantially higher green power would require careful thermal management to limit the phase mismatch due to heating produced by optical absorption. RPE waveguides show ability to support high-power generation of green light superior to anneal-proton exchanged (APE) waveguides containing a higher-index layer. We also demonstrate devices with multipeak spectral response for speckle-reduced green laser by using phase-modulated, quasi-periodic ferroelectric domain structure.