Fiber lasers have made significant progress in terms of power output, beam quality and operational robustness over the
past few years. Key to this progress has been advances in two technologies - fiber technology and 9xx nm diode laser
pump technology based on single emitters. We present the operational characteristics of our new high brightness 9xx nm
fiber laser pump sources based on diode laser bars and diode laser bar arrays and discuss the design trade offs involved
for realization of devices focused on this application. These trade offs include achieving the lowest slow axis divergence
while maintaining high wall plug efficiency and minimizing facet power density to maximize reliability.
We present results from a survey of materials used for packaging semiconductor lasers, including Cu, CuW, BeO,
diamond composite and other advanced materials. We present the results of residual bonding stress from various solders
and consider the direct effects on wavelength and spectral width. We also provide data on the second order effects of
threshold current and slow axis divergence. Additionally, we consider the heat spreading through different materials for
a laser bar and present modeled and experimental data on the thermal performance. Finally, we consider the reliability
under on-off life-testing and thermal cycling tests.
Developments in Nd-based lasers pumped on the 4I9/2→4F3/2 transition have led to
demands for increased power, brightness, and spectral stability from diode pump sources.
We describe the development of fiber coupled diode pump sources that generate >120W
of power from a 400μm, 0.22NA fiber at 88Xnm wavelengths. In order to maintain
spectral purity at these high powers, we investigated the use of Volume Bragg Gratings to
stabilize the wavelength of these multi-bar systems. A detailed study of the trade-offs
between facet reflectivity and VBG reflectivity was conducted in order to determine an
optimal combination that balances output power and locking range.
In complement to the developments in 88Xnm pumping, recent interest in eye-safe fiber
lasers have resulted in the development of Tm-doped fiber lasers pumped at 79X
wavelengths. We describe the development of fiber coupled products with >80W from a
200μm, 0.22NA fiber, including the use of optimized bar geometries to improve fiber
coupling efficiency.
We describe the performance of diode laser bars mounted on conductive and water cooled platforms using low smile processes. Total smile of <1μm is readily achieved on both In and AuSn based platforms. Combined with environmentally robust lensing, these mounts form the basis of multiple, high-brightness products.
Free-space-coupled devices utilizing conductively-cooled bars delivering 100W from a 200μm, 0.22NA fiber at 976nm have been developed for pumping fiber lasers, as well as for materials processing. Additionally, line generators for graphics and materials processing applications have been produced. Starting from single bars mounted on water-cooled packages that do not require de-ionized or pH-controlled water, these line generators deliver over 80W of power into a line with an aspect ratio of 600:1, and have a BPP of <2mm-mrad in the direction orthogonal to the line.
Laser-based projection displays have long attracted interest because of the multiple advantages (expanded color gamut, high resolution, longer lifetime, etc.) expected from lasers as compared to lamps. However, most of these advantages have been largely negated by the significant cost, size, and cooling requirements associated with lasers, and their inability to produce red, green, and blue colors in the same platform. In this paper, we review a new, laser array
technology based of frequency-doubled, semiconductor, surface-emitting lasers. The key features of this technology, such as demonstrated multi-Watt output for rear-projection TVs, power levels scalable with the number of emitters, speckle suppression due to multi-emitter array, and a low-cost and compact design are discussed in detail.
Compact and efficient blue-green lasers have been receiving increasing interest in the last few years due to their applications in various industries: bio-instrumentation, reprographics, microscopy, etc. We report on the latest developments in frequency-doubled, compact blue-green lasers, based on Novalux extended-cavity surface emitting laser (NECSEL) technology. This discussion will touch upon using NECSEL technology to go beyond a 5-20 milliwatt cw laser design for instrumentation applications and obtain a compact design that is scalable to higher power levels in an array-based architecture. Such a blue-green laser array platform can address the needs of laser light sources in the projection display consumer electronics markets, particularly in rear-projection televisions.
We introduce a novel type of cw green laser source, the Protera 532, based on the intracavity frequency doubling of an extended-cavity, surface-emitting diode laser. The distinguishing characteristics of this platform are high compactness and efficiency in a stable, single-longitudinal mode with beam quality M2 < 1.2. The laser design is based on the previously reported NECSEL architecture used for 488nm lasers, and includes several novel features to accommodate different types of nonlinear optical materials. The infrared laser die wavelength is increased from 976nm to 1064nm without compromising performance or reliability. The intracavity frequency doubling to 532nm has been demonstrated with both bulk and periodically poled nonlinear materials, with single-ended cw power outputs of greater than 30 mW.
Laser sources emitting at 460nm have been developed through intracavity doubling of an extended cavity, surface emitting semiconductor laser. These lasers are compact, spectrally pure, efficient, and have a high quality beam. The basic design is similar to previously reported work[1] at 488nm using Novalux Extended Cavity Surface Emitting Laser (NECSEL) structures. The choice of nonlinear material was found to be critical, with periodically poled materials providing distinct benefits over bulk materials. Output powers exceeded 20mW. The reliability of the completed lasers was found to be excellent.
We describe the design, fabrication and performance of novel, electrically pumped, vertical compound cavity 976nm InGaAs lasers that emit at 488nm via intracavity second harmonic generation. The resulting light source is an ideal replacement for Ar-ion lasers used in a wide variety of bio-analytical instruments. We present characterization data for the laser to demonstrate its capabilities. Lastly, future directions for the technology are discussed, including a monolithic form and devices operating at 460 and 532nm.
We describe the properties of novel blue-green sources based on intracavity frequency doubling of the Novalux family of high-brightness infrared surface-emitting lasers. They are highly compact, efficient, reliable, stable and manufacturable, capable of emitting over 40-mW cw power at 488 nm and other custom wavelengths in the range 460-532 nm with single frequency and single-spatial mode.
We describe design and performance of novel, electrically pumped, vertical compound cavity semiconductor lasers emitting at 980 nm. The laser combines a vertical cavity semiconductor laser with a partially reflecting output coupler and an external cavity for mode control. The concept is scalable and has been demonstrated in monolithic low power (few miliwatts) devices all the way to high power extended cavity devices which generate over 950 mW CW multimode power and 0.5 W CW power in a TEM00 mode, the latter with 90% coupling efficiency into a single mode telecommunication fiber. The concept has been applied to the development of uncooled lasers, mounted in TO-56 cans, capable of producing 50 to 100 mW of fiber-coupled power. We have also demonstrated the extended cavity lasers at wavelengths of 920 nm and 1064 nm. We present reliability data for the chips used in the extended cavity lasers.
We have developed novel electrically pumped, surface-emitting lasers emitting at 980 nm with an extended coupled cavity. The concept is scalable from monolithic low power (~10 mW) devices all the way to high power extended cavity lasers. The latter have demonstrated ~1 W cw multi-mode and 0.5 W cw in a TEM00 mode and a single frequency, with 90% coupling efficiency into a single-mode fiber. By inserting a nonlinear optical medium in the external cavity, efficient and compact frequency doubling has been achieved with CW output powers 5-40 mW demonstrated at 490 nm. The latter devices are especially noteworthy due to their very low noise (0.05% rms from dc-2 MHz), sub 10 mrad beam pointing stability combined with small size, low power consumption (<10 W) and high efficiency.
We describe a novel blue-green laser platform, based on the intracavity frequency doubling of Novalux Extended Cavity Surface Emitting Lasers. We have demonstrated 5 to 40mW of single-ended, 488nm, single-longitudinal mode emission with beam quality M2<1.2. The optical quality of these lasers matches that of gas lasers; their compactness and efficiency exceed ion, DPSS, and OPSL platforms. These unique properties are designed to serve diverse instrumentation markets such as bio-medical, semiconductor inspection, reprographics, imaging, etc., and to enable new applications. We also present data on the reliability of this novel laser platform and its extensions to different wavelengths (in particular, 460nm and 532nm) and to next-generation, highly compact, monolithic intracavity-doubled lasers.
We have developed novel electrically pumped, surface-emitting lasers emitting at 980 nm with an extended coupled cavity. The concept is scalable from monolithic low power devices all the way to high power extended cavity lasers. The latter have demonstrated 1W cw multi-mode and 0.5 W cw in a TEM00 mode and a single frequency, with 90% coupling efficiency into a single-mode fiber. By inserting a nonlinear optical medium in the external cavity, efficient and compact frequency doubling has been achieved with CW output powers 5-40 mW demonstrated at 490 nm. The latter devices are especially noteworthy due to their very low noise, sub 10 μrad beam pointing stability combined with small size, low power consumption and high efficiency.
We describe design, fabrication and performance of novel, electrically pumped, vertical compound cavity InGaAs lasers emitting at 980 and 920 nm. The concept is scalable and has been demonstrated using monolithic low power (~10 mW) devices all the way to high power extended cavity devices which have demonstrated 1 W cw multi-mode and 0.5 W cw in a TEM00 mode and a single frequency, with 90% coupling efficiency into a single-mode fiber. We also describe uncooled vertical compound cavity lasers in TO-56 can packages which produce 50-100 mW of fiber coupled power. Finally, recent developments in intracavity frequency doubling are summarized.
Cooperative upconversion and Yb3+-Er3+ energy transfer in newly developed phosphate glasses were studied in this paper. The cooperative upconversion coefficients of 4I13/2 level for different Er3+ concentrations were deduced from the pump intensity- dependent luminescence decay curves. Yb3+-Er3+ energy transfer efficiencies for different Yb3+ concentrations codoped with Er3+ (approximately 2 X 1020 ions/cm3) were estimated from the lifetime measurements of 2F5/2 level of Yb3+ ions. The small cooperative upconversion coefficients and high Yb3+-Er3+ energy transfer efficiencies indicate these newly developed Er3+ and Yb3+/Er3+ doped phosphate glasses are excellent for amplifier and laser applications.
Er$3+) doped tellurite glasses with various Na2O/Li2O, Na2O/K2O and K2O/Li2O ratios were prepared. Absorption and emission spectra, glass transition temperatures, crystallization temperatures, densities, and refractive index of these glass samples were characterized. For all studied glass samples, the highest effective linewidth was obtained with mixed alkali molar ratio of Na2O/Li2O equals 1, Na2O/K2O equals 1 and K2O/Li2O equals 1. The studied glasses have a (Tx- Tg) exceeding 100 degree(s)C, indicating these glass samples are stable against devitrification. In addition, Judd-Ofelt analysis of several glasses was also performed.
A Q-switched Nd:YAG laser generating 160 mJ in 60 ns at 1.3 micrometers has been shifted to 2.9 micrometers by Raman conversion in hydrogen. The energy of the 2.9 micrometers photons is insufficient to undergo further Stokes shifts. Thus the first Stokes line is the terminal wavelength for this process. While terminal Stokes components have been reached in previous Raman shifting studies, these components have always been the result of multiple Stokes shifts. In a single pass configuration photon conversion of up to 0.37 was realized. Conversion into anti-Stokes lines of up to third order was observed, albeit at insignificant energies. With the addition of an unoptimized resonator the photon conversion rose to 0.49. The pressure dependence of Stokes conversion was also investigated. The data show a smooth increase in output followed by saturation. This is in accordance with conversion into a single terminal Stokes lines. However, in contradiction with theory, the pump linewidth was observed to matter a great deal. Amplified elastic or near elastic scattering is suggested as an explanation for this result. Overall, the success of this work bodes well for forthcoming attempts to obtain tunable mid-IR radiation by means of a terminal first Stokes shift.
A silylated Coumarin 4 (derCoum) laser dye has been incorporated over a large range of concentrations in sol-gel silica composites. Optically transparent films of derCoum and Coumarin 4 (Coum) doped silica were obtained; and their absorption and fluorescence spectra and fluorescence efficiency were measured. Dye extraction was investigated as a function of sol-gel processing conditions. Dye extraction results indicated that prehydrolysis of the derCoum and full hydrolysis of TMOS resulted in films from which the dye could not be extracted, suggesting that all the dye is bonded within the sol-gel matrix. The silylated dye films showed higher fluorescence efficiency at all concentrations with respect to the normal dye film.
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