This PDF file contains the front matter associated with SPIE Proceedings Volume 11667, including the Title Page, Copyright information, and Table of Contents.

A new type of laser diode bar offering over 1000W peak power at near-infrared wavelengths (770nm to 1100nm) has been developed. Multi-bar arrays with bar-to-bar pitches as low as 350μm are assembled creating individual units with over 50kW peak power. Data will be presented showing performance at various operating conditions and pulse modes. Scaled assemblies with common electrical and thermal manifolds offering over 1MW of peak optical power within a 58mm x 63mm emission area will also be shown. The impact of beam shaping and beam conditioning with micro-optics will be presented. To power these devices, a new breed of drive and pulser electronics have been developed to operate over 1,000A with the voltage necessary to drive 1MW-class scaled assemblies. This presentation will show how an integrated approach to mating drive electronics and the diode arrays lead to optimal performance and significant size, weight, and cost advantages.

The high-power diode-laser industry is dependent on highly qualified production output for fast axis collimation (FAC) lenses in scalable quantities. Not only controlled production processes but also the optical qualification of the final FAC product contribute to this goal. The product qualification approach chosen is based on diode laser collimation by active alignment and automated positioning of the FAC in collimation for the fast axis and imaging in the slow axis, allowing to evaluate the collimation performance with a specific and installed diode laser on individual emitter intensity profiles. We present the automated setup with results for corresponding sensitivity and repeatability analysis for the measurement of residual divergence.

PLX was founded in 1955 as Precision Lapping and Optical Company, producing highly accurate optical domes, lenses, prisms, and mirrors. In the 1970’s the invention of the hollow retroreflector by PLX enabled work on mission-critical projects for military and space applications. PLX’s proprietary technologies and manufacturing capabilities with highperformance optical systems are renowned for performing under the harshest environmental conditions such as extreme temperature, combat and deep space while maintaining near-perfect accuracy over time. In 2000 PLX invented the Monolithic Optical Structure Technology™ (M.O.S.T.™). M.O.S.T is a unique optical innovation that combines all the elements of a complex optical design into a single monolithic unit - creating superb optical and thermal stability as well as unsurpassed shock and vibration resistance. Today, PLX continues to push the boundaries of boresighting and targeting. With their exceptional stability, PLX’s boresighting systems have been repeatedly proven in the field. This presentation will expand upon the M.O.S.T.™ solution with case studies of M.O.S.T.™ designs and results for specific applications, such as laser delay line systems, boresighting, and telescope alignment systems. Other applications can utilize this novel technology, such as spectroscopy, interferometry, LIDAR, free space optics, laser tracking, laser cavities, satellites, targeting sights, laser beam steering systems, alignment, or sensors.

We developed a fast wavelength switchable external cavity diode laser (ECDL) using a DMD as a seed laser for an injection-seeded terahertz (THz) wave parametric generator (is-TPG). Generally, the wavelength of an ECDL is selected by the angle of the mirror or grating; however, in this case, a DMD is used as the wavelength selector. A power output of 300 mW and a tunable range of 26 nm were obtained. Furthermore, high-rate modulation at 6.55kHz was realized. This laser makes it possible to switch the THz wavelengths of is-TPG rapidly to match the absorption spectrum of a reagent.

In order to optimize the output parameters of 808nm array of high-power microchannel heat sink package, the fluid thermodynamic characteristics of 50 × 10 array were simulated. The thermal distribution of the simulation results was used to guide the array assembly. The spectral characteristics of each bar in the stacked array were observed by near-field fiber scanning probe. The simulation results show that the flow rate of the stacked bar decreases gradually from bottom to top, the temperature of the bar increases gradually, and the flow rate of each stacked bar decreases slowly as it is far away from the water outlet. When the flow rate at the entrance of the stack array is 10 L/min, the temperature difference between the bottom and top bar of a single stack array is 13.1 °C, the flow rate difference is 0.24 L/min, and the FWHM width of the stack array spectrum can reach 4.5nm. The temperature of the active region is calculated by measuring the wavelength shift of each bar in a single stacked array, and the results are consistent with the simulation results. The spectral characteristics of the array can be effectively improved by assembling the array according to the temperature distribution.

Red-emitting lasers with longitudinal and lateral single mode emission are currently required for non-destructive spectroscopy methods based on quantum mechanical effects (e.g. MID-IR quantum-OCT). So far, the size of currently used solid state lasers prevents effective miniaturization, which is required for successful out-of-the lab usage. To address this challenge the FBH developed specialized ridge waveguide lasers (RWL) near 660 nm with an integrated fourth order distributed Bragg reflector (DBR) surface grating, requiring only a single epitaxy step. The DBR-RWLs feature a diffraction limited output beam with a stabilized emission linewidth below 10 MHz. An optical output power of more than 50 mW and lifetimes of more than 10,000 h at 20 mW could be demonstrated. Furthermore, we used tapered diode amplifiers (TPA) to boost the optical output power to more than 500 mW in an all - semiconductor master-oscillator power-amplifier (MOPA) configuration. The TPA has a total length of 2.5 mm and was mounted p-side-down on structured CVD-diamonds, allowing optimal cooling and separate currents for the RW and taper sections. The MOPA setup did not degrade the linewidth properties. The side mode suppression rate exceeds 40 dB. However, the spatial beam quality in the slow axis degraded somewhat to an M²_1/e² of 1.8 (M²₄₀ = 3.1). As a next step we are working towards miniaturization of the MOPA setup to about matchbox size to make it a suitable candidate for a pump source in a portable MID-IR quantum-OCT scanner system.

We present a CO2-laser based machining process for the manufacturing of all-fiber components. A CO2-laser beam is used to perform multiple steps of the manufacturing chain. The first step is the removal of the fiber’s polymer coating, followed by the removal of large parts of the glass cladding to access buried waveguides of the fiber. Excellent surface quality (Ra <10 nm) and process control for precision cladding removal are demonstrated, thus enabling the manufacturing of fiber components. A low loss evanescent field coupler (0.13 dB) was manufactured and coupling between two cores was achieved by fusing two altered fibers together.

We investigate hollow-core fibers for fiber delivery of high power ultrashort laser pulses. We have benchmarked 3 types of hollow-core fiber, respectively photonic bandgap, nested, and kagome fibers. nested and Kagome reach the 100W average power level, and are characterized experimentally for the delivery of 300 fs- 10 ps pulse range . Systematic experimental study of limitations in terms of beam quality, depointing, non linear effects, polarization or fiber coiling is reported.

Pockels cell is one of the major components limiting the pulse repetition rate of high-power laser sources. The birefringence of the electro-optical crystal is controlled by the electric voltage which allows high-frequency modulation of intracavity losses, thus unlocking the MHz frequency band for pulse repetition rate. The purpose of this work was to investigate the influence of the piezoelectric ringing on the polarisation contrast of the potassium rubidium titanyl phosphate (KRTP) based electro-optical modulator in the frequency range up to 10 MHz. This was done by complex impedance and polarisation contrast measurements, as well as comparison to numerically identified fundamental frequencies of the crystal. The behaviour and dominant mechanism behind the effects of piezoelectric ringing were found to be distinct in three modulation frequency ranges: up to 2 MHz, above 2 MHz, and above 6.3 MHz. In particular, above 6.3 MHz, no piezoelectric-ringing-induced depolarisation was observed. These findings make KRTP based Pockels cells attractive for high-repetition-rate pulse picking applications.

Thermal effects of critical passive and active kilowatt-splices in all fiber master-oscillator power amplifier (MOPA) are investigated. Proper designs for cooling apparatus are proposed and demonstrated experimentally, for the purpose of minimizing splice heating which is critical for the reliability of high power operation. By using these optimized methods, we have demonstrated numerically and experimentally for standard 125 µm, 200 µm and 400 µm Yb fibers temperature rise of critical active splice < 0,1 K/W.

We present the development of an all-fiber side-fused signal-pump-combiner based on an integrated 3C R feedthrough fiber. This specialty fiber uses a 34 μm single-mode core and shows great potential to enable further output power scaling while maintaining high beam quality. The side-fusing technique has the advantage of an uninterrupted signal core and can be used in co- and counter-pumped fiber lasers and amplifiers. The signal-pump-combiner was operated up to an input power of 600W from four pump fibers and coupling efficiencies of 79% were achieved. The component was additionally investigated by computer tomography imaging, which revealed that the cladding structure of this specialty fiber prevented the required level of glass fusion of the 3C R fiber with the pump fibers. The investigation will help to further increase the pump coupling efficiency of the signal-pump-combiners. This represents the first step of developing all-fiber and high power capable laser systems based on the 3C R fiber.

A beam delivery system (BDS) fibered with hollow core photonic crystal fibre (HC-PCF) has been identified as very promising for ultra-short pulse (USP) laser micromachining for it allows flexible, secured and robust laser beam delivery to the work piece. These features are of paramount importance for vertical markets such as automotive or consumer electronics. We report on a system that integrates a BDS, a laser beam pointing stabilization module and a 50 W power, 250 fs pulsewidth Yb-based USP laser. The BDS comprises a low loss, low dispersion and high damage threshold Inhibited-Coupling (IC) HC-PCF. The latter is ruggedized with a semi-rigid industrial cable with ends attached respectively to an injection head for ease of laser beam coupling, and to an output connector for beam delivery to the work piece. The injection head is aligned with a special module for laser beam jitter stabilization and beam-shape control and monitoring. Also, it exhibits the necessary gas and thermal handling to minimize parasitic optical nonlinear effect or photoionization and power induced heating. To test the endurance of this fibered-USP laser system, it was continuously run over 17 hours. The results show exceptional integrity in the power transmission (86 ±1%), spectral and temporal structure and beam quality (M²~1.1). The BDS output beam shows a pointing stability of only 0.7±0.1 μrad. These results represent an important milestone towards the industrialization of fiber delivered USP laser-based machines.

An advantage of using additive manufacturing (AM) processes as opposed to conventional fabrication methods is that the additional degrees of freedom in design allow compact and at the same time lightweight components to be manufactured. In addition, AM reduces the material consumption, resulting in a more cost efficient production. Among others, the field of laser development benefits from the progressive implementation of AM-related opportunities. However, this integration is mostly limited to single components. In contrast, we present a compact, lightweight solid-state laser oscillator system for low-power applications based on additively manufactured optomechanical components via Fused Filament Fabrication (FFF). The laser system is based on a Nd:YVO₄-crystal pumped externally with a fiber-coupled laser diode at a wavelength of 808nm and a maximum output power of 3 W. The commercial optical components, such as lenses and the crystal, are firmly embedded via FFF in quasi-monolithic optomechanics. Thereby, they are fixed at their position and thus secured against misalignment. Furthermore, sensor technology for temperature monitoring is implemented into the structure. The possibility of the FFF process to work with different materials in parallel is used here. This multi-material printing approach enables the use of the appropriate polymer for the individual mechanical and thermal requirements for any structural part. The thermal stability of the printed structures is evaluated to ensure damage-free operation of the 3D-printed polymer optomechanics. Furthermore, output power, optical-to-optical efficiency, beam pointing, and spatial beam profile of the laser system are measured for several on- and off-switching cycles as well as for long-term operation.