This PDF file contains the front matter associated with SPIE Proceedings Volume 12867, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Lidar sensors provide perception pipelines with low-latency, three-dimensional point clouds, giving geometrically accurate data for the detection of objects, vehicles and pedestrians. In autonomous vehicles, sensor design needs to consider the challenges associated with cities and highways, solar background, as well as adverse weather conditions. We consider the advantages and limitations of different lidar technologies with a concentration on pulsed-time-of-flight lidar. Recent advances in Single Photon Avalanche Diode (SPAD) technology have increased photon-detection efficiency and reduced sources of noise. We review improvements in edge-emitting lasers and VCSELS, showing trends in power and Beam Parameter Product (BPP). For edge-emitting lasers, we review the performance of gain-guided versus index-guided lasers and resulting BPP. For VCSELs, we consider trends with larger diameters, more junctions, and back-side emission. Finally, we offer an overview of lidar technology for autonomous vehicles and suggest a roadmap for improved lasers and sensors.

We present weakly tapered ridge waveguide distributed Bragg reflector lasers with three active regions epitaxially stacked in a common waveguide emitting nanosecond pulses around 905nm for LIDAR. The vertical structure is optimized for pulsed operation and implementation of a surface Bragg grating for emission in the 2nd order vertical mode. 6mm long diode lasers with a 25μm output aperture, integrated in an inhouse high pulse current electronic driver, provide a pulse power ⪆20W, a beam propagation ratio M²~4.5, and a brightness of ~16W(mm mrad). The emission spectrum features a spectral bandwidth of ⪅0.3nm and a temperature-related shift of ⪅70pm/K.

Currently, in systems using Photonic Integrated Circuits (PIC), not many integrated options for lasers on-chip are available. So generally, off-chip devices (pig-tailed lasers, etc.) or underperforming on-chip devices are used. From both price and performance point of view, this is an undesirable situation. Especially, for automotive-grade solid-state FMCW LiDAR systems, the elephant in the room is generally ignored; the optical output power generated by the laser is too low, and/or the mode-hop free tuning is too little and too slow. In this presentation, we will show designs and expected results that offer a customized laser suitable for FMCW LiDAR, with powers only limited by nonlinear effects in the PIC platform, wavelength tuning ranges of over 100 nm and Lorentzian linewidths appropriate to that of a distance measurement of 300 m (source to target). Our current hybrid integration solution is targeted at c-band, but the approach is valid for all wavelengths for which the PIC platform is transparent.

LiDAR (light detection and ranging) technology has gained significant importance in various fields, including autonomous vehicles, environmental monitoring, and remote sensing. 905nm pulsed laser diodes are an essential component of a LiDAR system, which performance relies heavily on the laser power level and the characteristics of its emitted light beam. While the fabrication of high-power pulsed laser diodes is already mature, reliably combining a high-power level and a concentration of the laser beam (⪆90%) within a limited emitting width is an ongoing challenge. Another major concern is the development of facet coatings capable of withstanding the high-power density generated by these lasers. Facet degradation due to the excessive optical power leads to a reduced laser efficiency and a risk of increased failure rates. Here, we have devised novel optical waveguide designs for triple junction 905nm lasers with optimized mode profiles and an effective confinement structure. This enables lasers to have a power density that is four (4) times higher than the traditional ones and, to confine most of the beam energy within an emitting width of less than 60 µm. Furthermore, our research explores innovative approaches to facet coatings that enhance facet durability and minimize power-induced degradation. This results in exceptionally reliable lasers, as demonstrated by a thousand hours of life test data. Through this work, we have achieved significant advancements in design and fabrication of high-power laser diodes for LiDAR applications. Experimental results demonstrate improved power efficiency, reliable facet coatings, and effective energy confinement within the desired emitting width.

High brightness semiconductor diode lasers can provide tremendous system-level advantages for many applications. Recent advancements in InP-based edge-emitting diode lasers operating in the 1500 – 1600 nm wavelength band could enable compact, direct diode solutions with performance metrics that previously could only be met by fiber-based lasers or solid-state laser systems. We report on high power, high beam quality diode lasers at 1550 nm based on a tapered chip architecture. We have demonstrated ⪆5 W of continuous wave output power at room temperature, with a slow axis beam propagation factor M2 of 1.1, corresponding to a slow axis linear brightness of 9.2 W mm^-1 mrad^-1. We have also demonstrated a fully packaged watt-class single mode fiber-coupled Semiconductor Optical Amplifier (SOA) based on this technology. This package delivers ⪆30 dBm (1.2 W) ex-fiber saturation output power, ten times higher saturation power than the prior state-of-the-art. This result is achieved with an input seed power of 30 mW (approximately 15 dBm), corresponding to an overall gain of approximately 16 dB. To demonstrate the functionality of the SOA, we have carried out linewidth measurements and data transmission measurements. These tapered lasers and amplifiers offer great potential benefit for many pumping and direct use applications.

The micro-fabrication process for advanced GaAs-based Pulsed Laser Diodes (PLDs) necessitates the precise etching of trenches for patterning waveguides. Traditionally, we employed wet etching in our approach, which, unfortunately, does not allow for precise engineering of waveguide trench geometry. The isotropic nature of wet etching results in a sidewall angle of approximately 45°. To enhance device performance, achieving a steeper angle without compromising other process steps dry etching is preferable. Ideally, trenches with sidewall angles ranging from 60° to 70° would strike an optimal balance. In pursuit of this goal, we initiated a Design of Experiment (DoE) to optimize the etching by Inductively Coupled Plasma - Reactive Ion Etching (ICP-RIE). Through this experimentation, we identified an ICP-RIE recipe capable of producing trenches with sidewall angles within the desired range (60° to 70°), exhibiting low roughness and attaining a depth of 17 μm. After this optimization, we applied the new ICP-RIE process to fabricate PLDs and conducted a comparative analysis against devices produced using our conventional wet etching method. The PLDs etched with ICP-RIE showcased slightly superior performance compared to those etched with wet etching. The implementation of ICP-RIE not only enhances device performance but also allows for a reduction in footprint per device. Consequently, this optimization contributes to an increased yield of devices per wafer, thus demonstrating the potential for scalability and improved efficiency in our micro-fabrication process.

We present novel 1550 nm InGaAsP MQW based broad area single emitters with 100 μm stripe width showing 4.9 W CW output power at 20 °C operation temperature and a maximum wall plug efficiency of 40%. An optimized low loss large optical cavity design has been used, allowing for a narrow optical far-field of 25° x 15°FHWM. Furthermore respective wavelength stabilized lasers have been realized.

Development of high brightness blue lasers that can process copper materials has been increasingly expected to implement a highly efficient processing and downsizing that help to achieve Green Transformation (GX). In order to meet this expectation, the high brightness blue laser oscillator has been developed. Based on the Direct Diode Laser (DDL) method which uses a semiconductor blue laser as a direct light source and our unique Wavelength Beam Combining (WBC) technology, it has achieved 2.1 (kW) of an output power, 3.2 (mm mrad) of Beam Parameter Product (BPP) indicating the beam quality. This laser oscillator can establish a penetration welding of the copper materials with over 2 (mm) in thickness. Development of the pulse power circuit has helped to produce a high current pulse power supply which provides 10 (kHz) of the frequency, 4.8 (μsec) of the rise time, and 0.8 (μsec) of the fall time. Furthermore, the copper plate welding experiment conducted with the pulse power has demonstrated a 3.5-fold higher precision processing compared to the continuous wave driving processing in terms of the aspect ratio which shows the relationship between the welding width and depth.

Copper is widely used in many industries due to high electrical conductivity and with the recent acceleration of EV shift, the needs for copper material processing are rapidly increasing. High power near-infrared (NIR) fiber lasers have been used in laser processing since high electric-optic conversion efficiency and excellent laser beam quality. However, copper welding with NIR fiber lasers is challenging. The absorption of copper is low in the NIR, and copper with high thermal conductivity diffuses the heat rapidly at welding spots. Previously we reported the hybrid laser system with 1- kW blue laser and 3-kW NIR fiber laser for copper welding. Blue laser with high absorption of copper generates stable molten pool at welding spots and assists NIR fiber laser processing for uniform welding and less spattering. In this paper, we present the improvements of blue laser. The first one is high power 2-kW with 300-μm core diameter and the second one is high brightness 1-kW with 200-μm. These are achieved by high power laser diode module, which has 500-W output power with 110-μm core diameter, and fiber-bundled beam combiner. Copper welding characteristics using this improved blue laser and NIR fiber laser would also be discussed.

Blue lasers are promising light source candidates for laser metal processing such as copper welding and heating, because copper has a high optical absorption coefficient in the blue spectral region. We have jointly developed 250 W blue Laser Diode (LD) modules including multiple LD chips with Furukawa Electric Co., Ltd. Their hybrid laser system consisting of an infrared fiber laser and the blue LD modules has already been commercialized. In this study, we report on the development progress for higher optical output power of the blue LD module used in the hybrid laser system. Specifically, we have achieved the output power for the LD module over 500 W from the fiber with a 110µm core diameter by increasing the output power of the constituent blue LD chip from 13 W to 16 W and the number of the installed LDs from 24 pcs to 36 pcs. The luminance is more than 5 MW/cm2 and the Beam Point Parameter (BPP) is almost 9 mm-mrad.

The paper presents the stabilization of blue multi-emitter modules using fiber Bragg gratings as external reflectors. The gratings are directly written into the large mode area delivery fiber with a femtosecond laser. Different writing techniques are considered and discussed. The effectiveness of the proposed stabilization approach is experimentally demonstrated.

The blue semiconductor laser with a wavelength range of 450nm has developed rapidly in recent years. For high-reflective and high-thermal conductive materials represented by copper, gold and high-strength aluminum, the absorption rate of blue laser is 5-10 times than infrared lasers. Blue laser can achieve high-quality and consistent welding results, stable melt pools and no spatter. With the development of blue semiconductor laser technology, there is a growing demand for higher brightness and reliability. Based on the practical application background, we have designed and implemented a stable high-brightness blue laser. Through BPP theory and ZEMAX simulation calculation, 48pcs TO-packaged 5.5W blue lasers are coupled into a 105μm core diameter 0.22NA fiber using polarization and optical fiber coupling technology. More than 250W output power is obtained with coupling efficiency exceeds 90% and electro-optical efficiency exceeds 35%. The high brightness blue laser has passed various reliability tests including accelerated aging for 7000 hours, 85°C high temperature storage, -40°C low temperature storage, -20°C to approximately 70°C temperature cycling test, vibration and mechanical shock test. The stable high-brightness blue laser finds significant applications in medical, 3D printing and welding.

The effect of oxygen defects on the gradual degradation rates of power and nonradiative carrier recombination in ~800 nm laser diodes was studied experimentally. While intentional introduction of oxygen at low levels (<5×10^15 cm^-3) was observed to degrade lasing performance prior to aging, no variation in gradual degradation rate of lasing power was observed. This suggests that degradation in these devices is not due to nonradiative recombination at low levels of point defects. Simulation of our data indicates that the power degradation may arise from increased intracavity absorption.

The increased performance requirements for high-power Edge Emitting Laser Diodes (EELD) present serious challenges for laser manufacturing processes and quality. One of the primary failure mechanisms limiting the performance and reliability of GaAs and AlGaAs-based laser diodes is related to Catastrophic Optical Mirror Damage (COMD), which occurs at the output facet when the laser is operated at high power levels. The main cause of COMD is oxidation-related atomic-level defects at the laser diode facet, which act as sites for absorption and heating. This paper demonstrates that by tailoring the III-V material surface with a novel crystalline oxide process prior to mirror coatings, the EELD performance can be substantially increased. A dedicated high-performance laser passivation equipment is developed and tested on surface-sensitive quantum well test structures and ultimately on high aluminum content edge-emitting laser bar diodes.

Using a high sensitivity infrared camera, we image the optical cavity of an operating high-power diode laser through a window etched in the substrate and observe weak IR emission from the waveguide core region. The IR intensity maps show dark spots in the cavity that subsequently grow into line defects (all oriented in the same direction) as the laser ages. This technique holds promise as a nondestructive, in situ approach to study the formation and evolution of defects in an operating device. We also use CCD-based thermoreflectance to generate high-resolution facet temperature profiles of the same lasers during aging, with the results suggesting that the slow degradation of optical power that occurs prior to laser failure relates more to cavity defect formation than facet defect (hotspot) formation.

Semiconductor Laser Diodes (LDs) generate high output powers with high power conversion efficiencies. While broad-area LDs are favored for high-power applications, narrow-waveguide LDs are in demand for their single-mode characteristics. However, LDs suffer from device failures caused by Catastrophic Optical Damage (COD) due to elevated self-heating at high operating currents. It is critical to understand the COD mechanism in these devices to enhance their reliability and operating output power. In this study, we investigated the self-heating and temperature characteristics of LDs with varying waveguide widths to uncover the cause of their failure mechanism. We assessed the performance, junction, and facet temperatures of the narrow (W=7 μm) and broad waveguide (W=100 μm) LDs. The narrower waveguide LDs achieved and operated at higher output power densities but, surprisingly, maintained lower junction and facet temperatures. Additionally, we employed a thermal simulation model to analyze heat transport characteristics versus LD waveguide widths. The simulation results showed that narrower waveguide LDs exhibit improved three-dimensional heat dissipation, resulting in reduced junction and facet temperatures and, thus, enhanced reliability. Our simulations align well with the experimental data. The findings demonstrate a transition in heat dissipation characteristics from broad to narrow waveguide behavior at approximately 50 μm width. These results clarify the fundamental reasons behind the superior reliability of narrower waveguide LDs and provide valuable guidance for LD thermal management.

High-power broad-area lasers are critical components for space satellite communications systems. Broad-area lasers with InGaAs-AlGaAs strained Quantum Well (QW) active regions are currently used in space satellite systems. These QW lasers have shown excellent power and efficiency characteristics, but these lasers are still susceptible to COD (catastrophic optical damage) leading to catastrophic and sudden degradation. Thus, their long-term reliability in space environments is a major concern. Furthermore, our group has shown that these lasers predominantly degrade by a new failure mode due to Catastrophic Optical Bulk Damage (COBD). The 3-D confinement of carriers in InAs-GaAs Quantum Dot (QD) active region has a potential to suppress nonradiative recombination of carriers at growth or radiation induced defect sites. This feature makes the QD lasers attractive for space applications. For the present study, we employed time-resolved analysis techniques including time-resolved electroluminescence (TR-EL) and time-resolved photoluminescence (TR-PL) techniques to investigate degradation in high-power broad-area lasers. We studied broad-area lasers with two different types of active regions – strained InGaAs-AlGaAs single QW layer and ten stacks of InAs-GaAs QD layers. TR-EL techniques were employed for time-resolved analysis of degradation processes in QW and QD lasers to study the sequence of critical events including the formation and propagation of dark line defects in ⪅110⪆, ⪅11̅0⪆, and ⪅100⪆ directions during accelerated life-tests. TR-PL techniques were employed to measure carrier lifetimes in QW laser wafer. Lastly, we report our understanding on degradation mechanisms in broad-area lasers with QW and QD active regions.

The efficiency and reliability of high power (multi-kW) fiber lasers has revolutionized material processing and other applications. However, diode lasers offer the promise of even higher efficiency, yet scaling to high power while maintaining good beam quality remains a significant challenge. We discuss the challenges, advances, and potential future of this technology.

In this paper, we will show reliable lasing performance of distributed Bragg reflector tapered diode lasers (DBR-TPLs) emitting at 1180 nm more than 7 W in continuous wave operation for 3,000 h without failure. The devices feature an epitaxial layer structure with an optimized strained double quantum well in a newly developed asymmetric large optical cavity resulting in a small vertical far field emission of 16° (FWHM). The DBR-TPLs consist of a 4 mm long tapered gain-guided section and a 2 mm long ridge waveguide section containing a 1 mm long DBR-grating. Owing to the integrated DBR-grating the investigated devices show predominantly longitudinal single mode emission between mode hops and an excellent beam quality with a power content of more than 75% in the central lobe at 8 W. Therefore, DBR-TPLs emitting at 1180 nm have become a highly efficient and narrowband light source, which can be used for efficient frequency doubling and enable various applications. In this paper epitaxial, device and emission characteristics will be discussed in detail.

Innovation in diode laser design and technology, assembly techniques and optical design are used to realize high-brightness pump modules for application in pumping of fiber lasers. In a first demonstration, monolithically grating-stabilized diode lasers with wavelength around 970 nm are integrated into prototype modules that deliver 500 W of continuous wave TE-polarized optical power at a conversion efficiency ⪆ 55% within a spectral width of 1.2 nm (95% power) in a narrow beam, suitable for low-loss coupling into a 200-µm core fiber. An especially simple opto-mechanical configuration is developed, without need for external volume Bragg gratings.

There is a need for high-power narrow-linewidth, small footprint, highly coherent diode lasers at various wavelengths (400-1800 nm) that can be utilized in many areas of photonics including fiber laser seeding, remote sensing, biomedical imaging, atomic clocks, quantum computing, THz spectroscopy, Raman spectroscopy, optical trapping, etc. Volume Bragg Grating (VBG) stabilized Fabry-Perot (FP) semiconductor lasers offer a versatile and robust platform for these applications. A Scanning Fabry-Perot Interferometer (FPI) is implemented for in-situ VBG alignment for these hybrid external cavity lasers (HECLs) in high volume production. Utilizing this method, it is possible to isolate a Single Longitudinal Mode (SLM) of a single spatial mode semiconductor laser with very narrow linewidth. The typical laser linewidth during the production process is measured to be 0.01 nm with an Optical Spectrum Analyzer (OSA) and a few MHz with the FPI, both of which were limited by the resolution of the instrument. However, the actual linewidth of these high-power lasers (up to 450 mW fiber-coupled and 600 mW free space) are measured in final testing using the heterodyne beat note method. These measurements show that these VBG-locked single spatial mode FP lasers have Lorentzian linewidth of less than 100 kHz. The result of narrower laser linewidth is achieved due to the effect on the external cavity feedback and the increased cavity length. The linewidths of these wavelength stabilized lasers between 633 nm and 1064 nm are presented here and the input of the isolator, laser driver electronics and temperature controller on linewidth are studied and discussed as a function of optical power, laser temperature, and wavelength.

In recent digital coherent transmission systems, it is necessary to improve the received Optical Signal to Noise Ratio (OSNR) after fiber transmission in order to achieve higher transmission capacity. Fiber Raman Amplifiers (FRAs) are well-known techniques for improving OSNR, especially backward FRAs, which are widely applied in high-capacity digital coherent transmission systems. However, pump lasers having higher output and lower power consumption are required since the Raman gain is small in the FRAs. As a means to realize these characteristics, a laser waveguide structure with a small optical confinement coefficient of the LD chip (low-Γ structure) is very effective. Especially, this makes Inter-Valence Band Absorption (IVBA) could be reduced by distributing an electric field toward the substrate side, and internal loss could be reduced to improve the slope efficiency. We have proposed a novel low-Γ structure consisting of a GaInAsP/InP electric field-controlled layer, which has an advantage of mass production. In this paper, we demonstrate 1W fiber output operation at 35 °C of Fiber-Bragg grating laser modules (FBG-lasers) for Fiber Raman Amplifier using a GaInAsP laser chip with electric field control layer for the first time. In order to realize high power at high temperature operation of 35 °C of laser chip temperature at a case temperature of 70 °C, we optimize the design of a laser chip waveguide keeping a single transverse mode to reduce the series resistance. With an operating current of 2.7 A, FBG-laser exhibits 7.8W of power consumption with 775mW of fiber output.

In the first part of this paper, we report on a fiber-coupled wavelength-stabilized high power diode laser system with an optical output power of more than 4 kW at a wavelength of 969 nm. The spectrum is locked over the entire working range with a FWHM of less than 0.5 nm. More than 90% power is encircled within 0.7 nm. The radiation is coupled into a fiber with a core diameter of 1000 μm. Additionally, we show the way for further power scaling up to 8 kW by using diode laser bars that enable higher injection current and output power. In the second part of this paper, we report on the impact of external back-reflections on the diode laser either by long term operation with VBGs or by short term operation in an experimental set-up based on a partially reflective mirror. For our standard set-up with VBG, we do not observe any feedback induced failures or degradation for operating times up to 3,000 hours. However, as expected, we do observe failures with increased feedback. In accordance with the literature, misalignment towards the p-clad can be very critical at wavelengths greater than 960 nm. The feedback-induced failure-rate increases exponentially with the injection current which make high power diode laser bars with high filling factors a very robust solution for external wavelength stabilization.

Yb-doped fiber laser and amplifiers are strong contenders as combinable sources used in power-scalable spectral beam combined and coherent beam combined High Energy Laser (HEL) systems. Power levels well beyond 300kW is anticipated for HEL systems for DoD applications. Pumping these fiber amplifiers at 976 nm has become an imperative. Furthermore, technology demonstrations of HELs have resorted to slow turn-on time. This needs to change for fieldable HEL systems. The need for an “instant-on” of HEL beam on demand cannot be over emphasized. Pumping a fiber laser/amplifier on this strong absorption peak also leads to a reduction in cost due to the shorter fiber and higher threshold power for nonlinear effects such as Stimulated Raman Scattering (SRS) and Stimulated Brillouin Scattering (SBS). But the absorption band of Yb-doped fiber is very narrow (<5 nm) and very sharp drop-off occurs around the peak near 976 nm. nLIGHT has developed high-efficiency, OSL technology by incorporating into the semiconductor laser chip, a wavelength-selective element which forces the laser to operate only at the desired wavelength over all operating current (output power) and a wide range of operating temperature. Although wavelength-stabilization in semiconductor laser pumps have been done in the past using external Volume Bragg Gratings (VBGs) they are not as efficient for HEL application. Furthermore, VBG adds cost, mass and volume to the pump package. We have demonstrated nearly penalty-free wavelength-stabilized high power, high efficiency chips. These chips can be readily introduced into a fiber-coupled package without needing any modification to the opto-mechanical design of the package – a drop-in replacement to the current pump packages. We have packaged them in a low SWaP fiber-coupled packages to produce ⪆550W with 55% at 25C and ⪆530W with ⪆52% at 50C using wavelength-locked diodes with a narrow spectral bandwidth ⪅0.4 nm at FWHM. The center wavelength shifts at 0.065 nm/K. The full power-in-the-band (within ±2nm of Yb-absorption peak) can be achieved in millisecond time scale enabling instant-on capability for HEL systems. Wavelength-stabilized pumps will be an imperative in fielded HEL systems because these pumps will enable high efficiency, high fiber amplifier channel power, low SWAP, low cost and “instant on” over a wide operating temperature range.

With the development of fiber lasers, the weight, power and brightness of fiber coupled semiconductor lasers are increasingly required. Low SWAP (low size and weight and power-efficient) laser diode has been a major focus of research. This paper mainly introduces the latest development of BWT low-SWaP products. In 2023, BWT introduces products with a power to mass ratio of 2.3W/g. By optimizing the optical path, increasing the power of the single chip, optimizing the structural design, and changing the material, BWT has introduced a higher brightness low-SWaP wavelength stabilized pumps. relying on a proprietary architecture of spatial and polarization multiplexing with multi-emitters.

Diode laser pumps are a critical technology for advanced accelerators based on laser plasma accelerators, and essential system components when higher repetition rate operation is needed. They are also a significant cost element in larger systems. An overview of progress in research and industry is presented, summarizing status of the technology, focusing on efforts to economically scale peak and average power and to enable new options in plasma acceleration, for example the use of thulium-doped gain media with its pumping wavelength at 780 nm. Development needs to support the accelerator community will be collected, covering topics such as efforts to lower cost in €/W by raising the diode laser output power, to increase repetition rates to 100 Hz and even up to 1 kHz, to scale TRL of emerging diode laser technologies, and to ensure low-failure-rate operation of large systems.

We report progress in the development of GaAs-based laser diodes with ultra-wide stripe widths of W = 1200 μm emitting at a wavelength of λ = 915 nm. In order to restrict ring oscillations and higher order modes in these ultra-wide devices we utilise periodic current structuring with a period of 29 μm and width of 20 μm. We compare the performance of a device with current structuring realised through contact layer implantation of the device after epitaxial growth, termed a 'Contact Implant' laser, and a device with buried current structuring close to the active region of the device realised using two step epitaxial regrowth and Buried-Regrown-Implant-Structure (BRIS) technology, termed a 'BRIS' laser. Quasi-Continuous Wave (QCW) measurement of the devices show that both the 'Contact Implant' and 'BRIS' laser achieve a very high peak output power of Popt = 200 W at a power conversion efficiency of ηE = 59% and ηE = 52%, respectively, with a peak efficiency of around 70%. QCW beam-quality measurements show that the 'BRIS' laser has a much reduced 95% power content far-field angle of 9°, compared to 12.7° for the 'contact implant' laser, at a power of P_opt = 100 W. Under Continuous Wave (CW) operation the 'contact implant' laser reaches an output power of P_opt = 68 W at ηE = 57% and the 'BRIS' laser reaches P_opt = 53 W at ηE = 50%, but with a reduced far-field angle of 11.9° at P_opt = 40 W for the 'BRIS' laser.

We present a passively mode-locked monolithic diode laser operating at 780 nm. It features a tapered gain section serving as a power booster and generates ultrashort pulses (~8 ps) with a peak power of approximately 45 W and a repetition rate of 6.6 GHz. The estimated beam propagation ratio is less than 1.3. This diode laser is intended as a compact and cost-efficient alternative to Ti:sapphire lasers for use in two-photon-polymerization-based 3D-printing systems.

Numerous next-generation quantum and spectroscopic sensing applications are emerging from the lab into portable commercial products. Next-generation spectroscopic sensors are used in applications including drug and compound identification in industrial analysis and quality control, non-invasive medical applications such as blood flow and glucose monitoring, as well as environmental sensing and monitoring. Quantum sensing applications include precision Positioning, Navigation, and Timing (PNT) instruments for use in GPS denied environments, as well as precision magnetometers and gravimeters for both ground and space-borne mission capability. The key component for each of these portable applications is a robust single frequency laser source. To minimize the laser power requirements, Photodigm has developed high operating temperature (HOT™) Distributed Bragg Reflector (DBR) lasers in the GaAs/ AlGaAs materials system for operation at key Near-Infrared (NIR) wavelengths. The HOT™ DBR reduces overall packaged device power consumption by operating at elevated temperatures by operating on wavelength without the need for Peltier cooling. The HOT™ DBR device eliminates the need for thermoelectric cooling by relying on a combination of laser self-heating and resistive heating to maintain a stable operating wavelength needed to probe or maintain lock to a spectroscopic transition. Fabrication of the HOT™ DBR lasers requires an optimized multi-quantum well structure and DBR grating designed to achieve the desired spectroscopic wavelength at temperatures up to 75-85 °C. This report describes progress to date including performance and lifetime data for HOT™T DBR lasers for applications at several alkali atom and related wavelengths for portable quantum sensing and spectroscopic applications requiring minimum laser package power consumption.

Industrial material processing represents a significant application for lasers. In this paper, we present our work on high power Diode Laser (DL) modules for the high brightness fiber laser pumping and direct diode laser integration. Together with state-of-the-art 915 nm and 976 nm Laser Diode (LD) single emitters from Coherent, we have realized an optical power 1200 W DL output (26 A driving current) with a 135 μm core-diameter fiber with a Numerical Aperture (NA) of 0.22 (power ratio of NA 0.19/0.22 ⪆95%). A dual wavelength combining technique was employed, yielding an fiber output brightness of 74 MW/(cm²•str). The fiber was end-capped to decrease the energy density on the optical coating. By adopting the same fiber end-capping optical coupling and wavelength combining techniques, a higher power DL module coupling 1800 W optical power into a 220 μm end-capped fiber was successfully fabricated. The module achieved a favorable balance between power and brightness, and its direct application potential was certified through spot welding of thin stainless-steel plates.

Our primary goal is to significantly enhance the output power of broad-area Laser Diodes (LDs) for improved cost-effectiveness of laser systems and broaden their applications in various fields. To achieve this, we implemented an epitaxial design with low internal optical loss and high internal efficiency in agreement with our simulations. We present comprehensive results of high-power single-emitter and bar LDs spanning wavelengths from 915 to 1064 nm. To demonstrate power scaling in single emitter LDs, we utilized waveguide widths from 100 to 500 µm, achieving a Continuous-Wave (CW) maximum output power of 74 W at 976 nm under room temperature conditions, limited by the heatsink temperature control. We also build fiber-coupled modules with single-emitters operating at 1.6 kW. Employing the same epitaxial structure in 1-cm wide laser bars, we demonstrated 976 nm laser bars operated at 100 A CW with 113 W output and a high efficiency of 72.9% at room temperature. Additionally, we achieved 500 W room-temperature CW laser bars at 940 nm. For long wavelength designs at 1064 nm, 500 W output was obtained in Quasi-Continuous-Wave (QCW) operating laser bars. Our results represent significant advancements in obtaining high power and efficient LDs across a broad wavelength range and configuration.

Handheld fiber laser welding is increasingly replacing arc welding as the technology of choice, driving strong demand for components that enable cost-efficient designs. In a first step, this trend has driven the development of multi-mode edge-emitting laser diodes in the 9xx nm wavelength range that, depending on emitter width, nowadays routinely achieve output power levels in the range of 35-45 W. We report on our recent developments of even more powerful single emitter laser diodes at Coherent Corp. to support novel and even more cost-efficient fiber laser architectures. Our newest generation of edge-emitting devices provides reliable output power levels in CW operation of up to 65 W from a 320 μm-wide emitter.

Laser displays require red, green, and blue Broad Area Laser Diodes (BA-LDs) for their light sources. The requirements for the LDs are high output with high wall plug efficiency (W.P.E.) Blue and green LDs consist of AlInGaN/GaN. The former has been reported with W.P.E. above 50%. The latter has low one around 24%, but the luminosity of the green light is quite high compared to blue and red, so the W.P.E doesn’t become a big problem so far. The red color shows lower luminosity as the wavelength gets longer. Therefore, short wavelengths such as 638 nm are chosen for red LD for the display. The highest one of 42% at CW operation, 25°C, was reported by other two researchers so far in this wavelength BA-LDs. We developed the 638-nm BA-LD. The LD chip had a similar stripe geometry to the reported one with a cavity length of 1.5 mm and dual stripe geometry with a stripe width of 75 μm each. A window-mirror structure was also implemented, and the chip was mounted on a Φ9 TO-can in a junction-down configuration. As a result, the peak W.P.E of 42.3% was achieved, 0.3 points higher than the previous report. The power dissipation related to the threshold current accounts for a large part of the total dissipation. Each stripe width of 60 μm was chosen to reduce the threshold current, and the LD showed the world’s highest of 44.9% under this condition. This value was approximately 7% (2.9 points) higher than the reported value.

Individually addressable laser diode arrays (IAB) have been first demonstrated in near-infrared wavelengths, 8xx nm and 9xx nm, being mostly utilized in the digital printing industry. When moving towards visible wavelengths, other applications emerge. Examples of these are various display applications, including AR/VR products and head-up-displays. In addition, novel applications for narrow linewidth lasers have emerged in the field of quantum computing. In this paper, we present our latest single-mode visible array results in 650 nm region, showing up to three times improvement in brightness. In addition, we demonstrate faster stabilization of the device during life-test and reach stabler operating power of the devices. Life-tests have been run with Automatic Current Control (ACC) mode with two different operating currents, showing only minor change in output power. High stability and reliable operation combined with our IAB design are enablers for further miniaturization of device design, scalable to 100 emitters and beyond, reaching e.g. higher resolution for printing and display applications. Additionally, such design and scalability can be integrated with on-chip gratings reaching DBR and DFB operation, which enables new capabilities in quantum applications.

We report a selective injection design for GaAs-based Photonic-Crystal Surface-Emitting Lasers (PCSELs). COMSOL and FDTD simulations are carried out to design the injection electrode size to achieve largest gain overlapping factors with optical mode and lowest gain threshold. The PCSEL devices are fabricated with GaAs-based Multiple Quantum Well (MQW) wafer. Devices with surface area of 250×250 μm2 are fabricated with different injection electrode sizes. Testing results show that the best beam properties and an output power of 750 mW were achieved with a 150 μm p-electrode design, demonstrating selective injection impact to PCSEL beam profile.

We developed a new generation of high-power laser modules for laser drying in battery electrode fabrication. Low power densities and homogeneous heating with full system efficiencies ⪆50% is within the record system efficiencies offered today. Moreover, simple scalability of the illumination profile and highly standardized fabrication techniques are the game changer benefits from using VCSELs as light source.

The size and weight of a fiber laser source are important metrics. The diodes used to pump this device and the cooling associated with it are the largest contributors to the size and weight of the fiber laser source. A bar-based approach has the potential for a lighter more compact diode since the source heat removal is done from a more compact heat sink. In this paper we describe results obtained from the development of a bar-based fiber coupled diode source, resulting in over 500 W of power out of the fiber, with 49% efficiency, wavelength locked at 976 nm, from a 231 μm core 0.22 NA fiber. The resulting volume metric is 0.25 cm³ /W and the weight metric is 0.36 g/W, which includes the diode heatsink.

We report a novel approach for the assembly of monolithic diode laser stacks with up to 56 laser diode bars at 0.48mm pitch. These stacks are based on 940nm laser bars AuSn soldered on CuW-submounts. By joining the 56 bar-on-submounts (BoS) using an electrically conductive material the complete continuous stack is formed. A robot is used to load these BoS into fixtures for the bonding process. We show the attachment of this monolithic stack to an insulated micro-channel cooler using electrically insulating bonding material to complete the laser module. Use of the novel bonding materials at lower joining temperatures, compared to conventional soldering processes, results in a stack assembly with lower induced stress which allows monolithic stacks with higher number of elements. We demonstrate peak power above 500W per bar at 0.3% duty cycle and 500A peak current with an average junction temperature of 45°C, with over 29kW total peak power. Analysis of the dynamic temperature behavior within the pulses is presented using fast spectral measurements and simulation along with initial reliability test results.

We will present our latest innovations on high-power diode lasers and discuss their application in quantum technologies. We show that these laser sources are key not only to explore the magic world of quantum physics, but also to drive the commercialization of exciting new applications coming along with the second quantum revolution, such as quantum computers, -sensing, -metrology and optical clocks. Compared to other laser sources such as gas- or solid-state lasers, diode lasers offer key advantages for these applications, e.g. their compactness, low weight, low energy consumption and low cost of ownership.

This talk will span a wide range of quantum applications involving lasers, with a focus on emerging, compelling, and scalable photonic-based solutions.

Photonic quantum technology is based on photonic packages that combine active semiconductors generating single frequency radiation and photodetectors with Photonic Integrated Circuits (PIC) for routing the photons and active components for modulating the photons. Typically, tens of individual single mode channels must be precisely controlled for constant optical path length and sensitive, high frequency feedback loops are deployed. Integrated photonic packages must be designed for properly managing the temperature distribution between passive and active optical elements as well as proper heat dissipation. The routing of electrical DC and RF drive current as well as sensitive RF sense currents must be laid out for minimal interference. Consistent high optical coupling efficiency and very low losses of all optical channels is vital for performance.

This study explores the efficacy of Wireless Optical Power Transfer (WOPT) for secure long-range wireless power transmission, particularly at extended wavelengths. A novel approach, infrared wireless charging, leverages retroreflectors for simplified alignment. The presented WOPT system incorporates an Erbium-Doped Fiber Amplifier (EDFA) operating at 1550 nm. The reflectivity and transmissivity of a spherical ball lens retroreflector are summarized and compared to optimize power transfer. Achieving resonant cavities between the transmitter and receiver requires precise beam alignment, yielding 750 mW at 1 meter and 500 mW over 30 meters at an Amplified Spontaneous Emission (ASE) output power of 1 W. A power loss budget analysis highlights challenges in power transmission, mitigated by adjusting the beam spot size. Examination of incidence angles reveals limitations, with optimal performance up to a 60° angle. These findings emphasize the safety, efficiency, and limitations of the proposed RBC system, offering insights for advancing long-range Wireless Optical Power Transfer (WOPT) systems.