This PDF file contains the front matter associated with SPIE Proceedings Volume 11545, including the Title Page, Copyright information, and Table of Contents.

For current 905nm pulsed laser diode(PLD) for LiDAR applications, most of them are single channel chips each with a power range of 75W-120W designed for scanning multiple single points. In this work, kilowatt 905nm light source based on eight channel 905nm PLD mini-bars had been designed and packaged using flip chip bonding technology. A series of kilowatt 905nm PLD modules were fabricated and characterized. The maximum output power of 982W limited by the pulse driver was obtained for the first time under the condition of 100V@5ns,100kHz at room temperature. The spectral width of FWHM and FW90%E was 5.1nm and 7.2nm, respectively. The far field divergence test data indicated that the fast axis divergence@1/e2 and slow axis divergence@1/e2 was 0.38°and 27.59°, respectively. In the future, the fast axis divergence@1/e2 and the slow axis FoV can be designed and optimized for any particular LiDAR system.

A GaN surface emitting laser (SEL) based on angular-symmetry-breaking concentric-ring surface grating (ASB-CRSG) is proposed in this paper. The second-order CRSG located in the p-contact and p-cladding of an EPI wafer of GaN FP laser is adopted to select the radial mode and couple the optical power vertically out of the laser cavity. As the zero-order azimuthal CRSG with a two-lobe far field has the lowest mode loss in the angular-symmetric CRSG, the first-order ASB is adopted by the removal of two circular sections of GaN epitaxial layers to break the angular symmetry of the lasing modes. The simulation results show that degenerate modes in angular-symmetric CRSG have different mode losses with the help of the first-order ASB and the bigger breaking angles of CRSG results to higher loss difference between the first-order and other azimuthal modes. The loss and divergence angle decrease with the increasing area of CRSG, and the deeper CRSG results to the higher out-plane coupling. The first-order azimuthal mode has the lowest mode loss whose value is ~ 84% of that of the second-lowest-loss mode. A single-lobe far-field with a divergence angle of 1.33° in the wavelength of 450nm will be realized by an ASB-CRSG with the diameter of 10.6μm, the breaking angles of 12° and the depth of 325nm. Therefore, the single-mode operation of the first-order azimuthal mode which has a single-lobe far field is expected with the combination of the second-order CRSG and the first-order ASB.

We present threshold ion number measurement in the formation of an ultracold plasma in a rubidium magneto-optical trap using the photoionization of laser-cooled atoms technique. The density and temperature of the trapped atoms in the magneto-optical trap were about 10¹⁰ cm^-3 and 500 μK, respectively. The measured value of the lifetime of the ultracold plasma was exactly matched with the calculated value. The threshold ion number in the formation of ultracold plasma was obtained from the linear relationship between ion and electron numbers for different laser energies. The dependence of the threshold ion number on the depth of the potential well was investigated experimentally. The experimental results were explained by the Coulomb potential well model.

In recent years, the generation of wideband l random optical chaos has attracted extensive interest for its extensive applications in the fields of secure communications, radar, and random number generations. In this talk, the presenter demonstrate a novel method for the semiconductor laser-based wideband optical chaos generation with excellent randomness, in virtue of the optical spectrum expansion of self-chaotic-phase-modulation-modulated optical feedback and the phase-to-intensity conversion of nonlinear filtering. It is experimentally demonstrated that, with the proposed method, wideband chaos with flat spectrum can be easily obtained, and simultaneously, the time-delay signature that directly indicates the privacy of chaos source can also be totally suppressed, which means that the physical randomness of chaos is also significantly improved. This paper presents a novel way to generate wideband physical random chaos for the implement of high-speed secure chaotic communication, high-resolution and high-precision radar, and high-rate random bit generation.

We propose and fabricate a linear frequency-swept DFB laser array based on the reconstructed-equivalent-chirp (REC) technique used in sensing system. During the fabrication process of the laser arrays, the reconstructed-equivalent-chirp technique is utilized to simplify the fabrication of the grating and precisely control the grating phase. A semiconductor optical amplifier (SOA) is monolithically integrated to enhance and balance the output optical power. The module achieves a wavelength range of more than 3 nm by covering 4 channels with an interval of 0.8 nm. The side mode suppression ratios (SMSRs) of all channels are above 50 dB and the output power are guaranteed above 10 dBm with the SOA providing 14 dBm saturation output power. To tune the wavelength on the microsecond scale, we adopt a combination of a MCU and a FPGA as the controlling core to turn on and off the driving current of all the 4 lasers on the DFB laser array, and the switching time between 2 channels is well controlled within 50 ns. At the same time, the module makes the wavelength output linearly with the current through the filter circuit, and achieves the sweep speed of 100 nm/s. This sweep speed, sweep range, output power, and good single-model performance meet the needs of sensing system for light sources.

Fast tunable lasers with switching time less than one microsecond are key components in high-speed optical switching networks. In this paper, we propose an effective method to achieve high wavelength switching speed by turning on/off individual lasers of a matrix-grating DFB laser array. The laser array consists of 16 DFB lasers, which are arranged as a 4-by-4 matrix. Besides, the REC technique is used to simplify the fabrication of the grating and precisely control the grating phase. 16 channels with 2.4-nm-spacing are obtained and the SMSRs of all the 16 channels are above 40 dB, indicating good single mode operation. A high-speed driving circuit is designed to supply stable direct current for the DFB laser array and to control the switching process. The experimental result shows that the switching time between 2 channels is less than 100 nanoseconds.

A tunable V-cavity laser based on half-wave multimode interference reflector (MIR-VCL) which operates in O-band is purposed and experimentally demonstrated. The superior side mode suppression ratio (SMSR) is achieved by the halfwave MIR, which is analyzed through the theory of multimode interference coupler. The laser is fabricated on the five quantum wells (QWs) InGaAlAs/InP wafer whose PL peak is about 1300 nm and has a compact device size of 500 µm × 350 µm. With the injection current on the gain electrode and short cavity electrode fixed, 27 channels with a spacing of about 100 GHz are obtained by tuning the injection current on the long cavity electrode. Experimental results show that among the whole tuning range, the SMSR ranges from 35 dB to 41.5 dB. By controlling the injection current on gain electrode and the TEC temperature, 51-channel wavelength tuning from 1288 nm to 1318 nm is obtained. The laser reaches its threshold when the total injection current is 65 mA. The tunable MIR-VCL in O-band has good potential for applications in 5G front-haul and datacenter networks.

The effect of equalization enhanced phase noise (EEPN) will be introduced in digital signal processing (DSP) based coherent optical communication systems. The EEPN will seriously degrade the transmission performance of a highcapacity optical transmission system. In this work, the influence of EEPN on the performance of dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) optical transmission system using the electrical dispersion compensation (EDC), the single-channel digital back-propagation (DBP), the partial-bandwidth DBP and the full-field DBP (FF-DBP) were comparatively evaluated with and without considering distortions from the EEPN. Deteriorations on achievable information rates (AIRs) and modulation error ratios (MERs) of optical communication systems due to EEPN have also been assessed. Numerical results indicate that the transmission performance of coherent optical systems can be significantly degraded by the EEPN, especially when FF-DBP is used for the nonlinearity compensation. The larger the linewidth of the local oscillator (LO) laser is, the more serious the degradation caused by EEPN is. This deterioration leads to a decrease in optimal launch powers, AIRs and MERs in the long-haul optical communication systems. In the DP-16QAM transmission system, because of the interference of the EEPN generated by the LO laser with a linewidth of 1 MHz, the degradations on the AIR and MER are 0.15 Tbit/s and 4.15 dB in the case of FF-DBP, respectively. It can also be concluded that, for coherent optical systems with long transmission distances and high symbol rates, the compensation bandwidth and the computational complexity of MC-DBP in the DSP module can be significantly reduced by using narrower-linewidth LO lasers

Photonic generation of frequency-modulated continuous wave (FMCW) based on period-one (P1) oscillation of an optically injected semiconductor laser (OISL) is numerically investigated. A modulated optical injection can drive an OISL into P1 oscillation for generating an FMCW signal, and an optical feedback is further introduced to reduce the phase noise of the generated signal. The influences of operation parameters on the performance of the generated FMCW signal are discussed. The numerical results show that under proper operating conditions, a photonic FMCW signal with a sweep range of 12.41 GHz can be obtained. After adopting optical feedback, the frequency comb contrast can be increased to a level more than 30 dB.

In this work, we propose and experimentally demonstrate a scheme for generating fast physical random bits (PRBs). For such a scheme, the chaotic signal output from an optoelectronic delay loop (OEDL) pumped by a semiconductor laser (SL) under modulated optical feedback is utilized as the chaotic entropy resource, and the m least significant bits (m-LSBs) extraction and local XOR operation are selected as the post-processing methods. Firstly, through analyzing the influences of some typical parameters on the properties of the chaotic signal, the optimized parameter regions for achieving high quality chaotic signals with weak time-delay signatures and broad bandwidths are determined. Secondly, a high quality chaotic signal under optimized parameters is selected as a chaotic entropy resource, which is sampled and transferred to an original digital bit sequence by an 8-bit analog-to-digital converter (ADC) at a rate of 80 GS/s. Finally, through adopting the m least significant bits (m-LSBs) extraction and logical exclusive OR (XOR) operation to process the original digital bit sequence, a PRB at a rate up to 400 Gbits/s can be generated, which has passed all the NIST tests.

Based on a slave vertical-cavity surface-emitting laser (S-VCSEL) simultaneously driven by dual chaotic optical injection (DCOI) from two master VCSELs (M-VCSELs) with double optical feedback (DOF), an unpredictability-enhanced broadband chaotic signal generation scheme is proposed and numerically investigated. The unpredictability degree (UD) and bandwidth of chaotic signals are evaluated by the peak value (σ) of self-correlation function (SF) at the feedback time and the effective bandwidth (EBW), respectively. The results show that, M-VCSEL with DOF can generate chaos signals with lower time delay signature (TDS) than that with single optical feedback (SOF). Under suitable injection strength and frequency detuning, both two orthogonal polarization components (X-PC and Y-PC) of the S-VCSEL can be driven to generate unpredictability-enhanced broadband chaotic signals with suppressed TDS (σ < 0.1) and wide EBW (EBW < 50GHz). Moreover, a relatively large parameter space to achieve this high-quality chaos signals can be determined.

Mid-infrared semiconductor lasers have a wide range of applications in gas sensing, environmental monitoring, medical diagnosis and other fields. The V-coupled cavity laser (VCCL) approach has been successfully applied in the communication band to achieve single-mode operation with a wide tuning range because of its advantages of no grating, compact structure and simple wavelength control. In this paper, the concept of V-coupled cavity is introduced to the interband cascaded lasers, and a monolithically integrated mid-infrared widely tunable single-mode laser is developed. In addition, we experimentally demonstrated a simple and general algorithm for wavelength tuning controlled by two electrodes synchronously, and realized quasi-continuous tuning of single-mode wavelength in mid-infrared interband cascade laser based on the V-coupled cavity configuration for the first time. In the tuning process, the injection current of the short cavity remains unchanged, and the stepped increase of the long cavity current is equivalent to the realization of discrete tuning with the channel spacing of 1.1 nm determined by the short cavity. With the increase of the injection current of the coupler electrode while fixing the long cavity current, the thermo-optic effect caused by the coupler current will cause the refractive index of the two FP cavities to change together, thus realizing the fine tuning of the laser wavelength. A total tuning range of 53.2 nm has been achieved, from 2.8244 μm to 2.8776 μm, with the temperature adjusted from 110K to 120K.

Optical frequency combs in dissipative Kerr soliton state can exist stably in a high Q-factor nonlinear cavity when a continuous wave pump laser is coupled to the microresonator as long as the double balance between anomalous cavity dispersion and kerr nonlinearity, and cavity loss and parametric gain is realized. However, due to the thermal instability of the microresonator, the generation and survival of the DKS requires keeping the pump at effective red-detuned regime. In this paper, in order to overcome the thermal instability when the intracavity power changes as the pump wavelength swept from blue-detuned to red-detuned with respect to a resonance of the microresonator, we adopt the thermal-assisted method, using an additional stable narrow linewidth laser as an assisted laser. We have studied the different mechanism of Optical frequency combs generation based on an opposite-directional pump configuration, According to the experimental results, two different initial comb states observed in the Si₃N₄ microresonator, but only one initial state can lead to stable Optical frequency comb generation. By adjusting the input power and stopping wavelength of the assisted laser and the pump laser respectively and properly, we observe the “step-like” transmission in our Si₃N₄ microresonator.

Interferometric fiber optic gyroscopes driven by lasers are new hotspots in recent years at home and abroad. Semiconductor lasers are considered to be an alternative to traditional broadband light sources due to their high commercial maturity, good average wavelength stability, and low intensity noise. However, the semiconductor laser is a highly coherent light source with a narrow linewidth. When it is used in an interferometric fiber optic gyroscope, it will reintroduce non-ideal characteristics such as Rayleigh scattering, Kerr effect, polarization cross-coupling and so on, which will affect the accuracy of the gyroscope. The linewidth of the semiconductor laser is widened before use. Based on the OptiSystem simulation platform, the article builds a semiconductor laser linewidth widening model, and analyzes and evaluates several different phase modulation broadening techniques and their effects. It has certain guiding significance for the experimental design and engineering application of semiconductor laser linewidth broadening.

The output linewidth and the electrical-to-optical power conversion efficiency of a grating-feedback external-cavity diode laser are directly related to the coupled optical power which is fed back into the laser cavity by the diffraction grating. This coupled power not only relies on the first-order grating reflectivity but also on the back-coupling efficiency which ultimately determines how much feedback optical power can couple into the diode laser cavity. It is qualitatively shown that the change in the collimating lens position could contribute significantly to the output linewidth in experiment. In this paper, the influence of the misaligned collimating lens on the back-coupling efficiency is numerically simulated and analyzed based on the beam coupling theory and ray transfer matrix theory. The results indicate that the distance from the lens to grating has little effect on the back-coupling efficiency, and the back-coupling efficiency reaches the maximum value when the diode laser front-facet is separated from the lens by the lens focal length. Meanwhile, it is found the back-coupling efficiency remains almost unchanged while the lens is tilted with respect to the axis perpendicular to opitcal aixs at small angle. Beside, the relationship between the coupling efficiency and the lens lateral displacement is also analysized and discussed.

A high peak power annularly-stacked laser diode pump has been designed and manufactured for a solid state laser (SSL), which is constructed by 12 single annular stacks composed of 3-bar laser diode (LD) submodules. High peak power and high wavelength uniformity have been considered. Macro channel cooling has been used during the operation of the annular stacks, at typical coolant flow rate of 2L/min. Heat dissipation and stress of a single annular stack have been simulated by finite element software, which shows high temperature uniformity of 3-bar submodules (plus or minus 0.5℃) and low package stress (11.8MP). The peak power of the annularly stacked laser diode pump has reached 234kW at a peak current of 450A or less. A high uniformity of centroid wavelength (802 plus or minus1nm) with a full width at half maximum (FWHM) of 4nm has been measured. More than 24 million shots have been verified for the 3-bar LD submodules.

Quantum cascade laser (QCL) emitting in the mid-wave infrared atmospheric windows (3μm to 5 μm) will be of immediate use to several civilian applications, including airborne self-defense protection system and trace gas sensing and free space optical communications. In this work, an experimental study of laser coupling in fiber-optic waveguide with small-bore diameters of d =105 μm. The output beam quality of QCL transmission out of the fiber is analyzed. The output laser nearfield and the farfiled of a QCL with nearly 500 mW continuous wave power at room temperature is measured by a two-dimensional beam quality analyzer. Results show that the output nearfield and farfield is nearly super-Gaussian distributed after tansmition from the multimode fiber.

In this paper, we propose and numerically investigate a novel scheme to optically generate microwave signal based on mutual injection locking. A twin-stripe semiconductor laser is driven into mutual injection locking state with two phase-locked wavelengths. Microwave signals with low phase noise are achieved. The frequency of the demonstrated microwave signals can be tuned by adjusting detuning frequency between the twin lasers. The results show that our proposed scheme is featured with not only lower phase noise but also better noise tolerance compared with typical master-slave injection configuration.

The combination of solid-state laser technology and semiconductor laser technology bloomed the technology of vertical external cavity lasers (VECSELs). This technology has developed rapidly and is attracting more and more scientists’ attention in the last few years. Recently, VECSELs in the wavelength range of 1040nm-1200nm which can achieve green to yellow light emission by double frequency generation are realized in our group. A series of VECSEL gain chip structures are deposited using MOCVD. Based on the analyze of band gap and resonant periodic gain (RPG) structure, the quantum wells of the gain chip are placed at the loops of the resonant stand wave to obtain maximum optical gain. After the removal of substrate, the gain chips are tested in the flat concave short cavity with 2% output mirror. The maximum output power of 1064nm laser is 1.6W at a pump power of 10W and the best optical to optical conversion efficiency is 32%. Using the gain chip, we also obtain the double frequency laser emitting at 530nm-580nm, including 532nm, 566nm, 569nm, and 572nm et al., which is in the range of yellow green of visible spectrum. The 532nm green laser can reach a 24mW continuous output power and the other yellow green laser can reach at least 5mW continuous output power. By the optimization of the gain chip and laser cavity design, this technology can be used in the field of laser projection, nonlinear microimaging, laser therapy and atomic or molecular physics.

Semiconductor diode sided pumped Nd: YAG solid laser can achieve higher power output. However, because of the characteristic of semiconductor and crystal, we need temperature controlling and active cooling system. And those systems cause it is hard to minimize the volume, weight and power dissipation. In this article, we use two absorption peak, 796 and 808nm, of Nd: YAG crystal to compose multiwavelength cooling-free array with three different wavelength diodes. It can be used in wide temperature range and solve those problem effectively. Use Matlab to calculate the result with two different conditions. One condition is that the average power absorption efficiency is higher than 40%, the temperature is from -55 to 60°C and the variance is lower than 4%. This condition is calculated for wide temperature range. The other condition is that the average power absorption efficiency is higher than 50%, the temperature is from -30 to 30°C and the variance is lower than 7%. This condition is prepared for higher absorption. For each group, choose three best wavelength automatically, then change the wavelength difference between middle wavelength and others. By doing those calculation, we can simulate the process tolerance in production and get the best result. Finally, we use GaAsP/InGaP/InGaAlP strain quantum well material of light and electron limited respectively, and 1mm cavity length with high fill factor. Besides, we also use different coatings to change center wavelength lightly and package with high efficient cooling to make sure the uniformity. As a result, we get an array pumped source of multiwavelength and temperature control-free which has difference of center wavelength lower than ±0.8nm, and its FWHM (full width half maximum ) is 3.5±0.5nm. Simulation results of spectrum is conformed to the actual test results. The best wide temperature range has three wavelength combinations of 786nm, 805nm and 811nm @25°C. The variance of hole temperature is 3.92% and the average power absorption is 41.99%. Besides, the best higher power absorption result is three different wavelength of 806, 811, 815nm @25°C. The variance of hole temperature is 4.78% and the highest power absorption is 52.68%. Those two simulations agree with the actual test result and get good feedback from users.