A pulsed Er:YAG laser with resonant in-band diode pumping was demonstrated. Laser pulses with 6.6 mJ energy and 50 ns pulse duration were generated. With an intra-cavity etalon a broad wavelength tuning range from 1643.47 to 1646.78 nm was obtained. A stable dual-wavelength operation was observed by fine tuning of the etalons. The separation of the two wavelengths was 0.78 nm. One of them was located within a methane absorption line and the other was off the line. The frequency stability of the narrow linewidth Er:YAG laser was less than 40 MHz. It is a very compact laser source for methane differential absorption lidar.

High power, high brightness diode lasers are beginning to compete with solid state lasers, i.e. disk and fiber lasers. The core technologies for brightness scaling of diode lasers are optical stacking and dense spectral combining (DSC), as well as improvements of the diode material. Diode lasers have the lowest cost of ownership, highest efficiency and most compact design among all lasers.Multiple Single Emitter (MSE) modules allow highest power and highest brightness diode lasers based on standard broad area diodes. Multiple single emitters, each rated at 12 W, are stacked in the fast axis with a monolithic slow axis collimator (SAC) array. Volume Bragg Gratings (VBG) stabilizes the wavelength and narrow the linewidth to less than 1 nm. Dichroic mirrors are used for dense wavelength multiplexing of 4 channels within 12 nm. Subsequently polarization multiplexing generates 450 W with a beam quality of 4.5 mm*mrad.Fast control electronics and miniaturized switched power supplies enable pulse rise times of less than 10 µs, with pulse widths continuously adjustable from 20 µs to cw. Further power scaling up to multi-kilowatts can be achieved by multiplexing up to 16 channels. The power and brightness of these systems enables the use of direct diode lasers for cutting and welding. The technologies can be transferred to other wavelengths to include 793 nm and 1530 nm. Optimized spectral combining enables further improvements in spectral brightness and power.Keywords: High power diode laser, high brightness diode laser, fiber coupling, spectral combining, narrow bandwidth, wavelength stabilization, short pulses BACKGROUNDHigh power diode lasers find an increasing number of applications in materials processing and pumping of solid state lasers as their brightness increases. Beyond improvements in the design of the diodes themselves -for minimum slow axis divergence, highest power from a given size aperture and improved wall plug efficiency -optical and spectral stacking are deployed to scale power and brightness. Single emitters and minibars allow the highest brightness from the diode aperture. Single emitters typically deliver 12 W from a 100 µm aperture with 11 o slow axis divergence resulting in a similar brightness per emitter as minibars with up to 8 W from the aperture. Minibars require additional optics for beam shaping that can be omitted for single emitters. Single emitters also require low drive currents up to 15 A, which can be easily modulated with more than 100 kHz. Due to the low current cost effective power supplies are available. Furthermore, single emitter chip on submount (COS) is an established component that is available from various suppliers at a variety of different wavelengths and with exceptional ensemble reliabilities of tens of thousands of hours.Optical stacking is state of the art for power scaling, and many different configurations are available for bars and single emitters. Spectral stacking allows scaling of brightness and power. A narrow and stable spectrum of individual diodes is require...

Eye safe laser radiation at 1.6 µm is realized by a resonantly pumped Er:YAG laser operating in cw-and q-switched mode employing high brightness laser diode modules. These modules provide high power and narrow bandwidth emission at 1.5 µm from a 100 µm fibers providing high pump efficiency.

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Laser diodes are efficient and compact devices operating in a wide range of wavelengths. Boosting power by beam combining while maintaining good beam quality has been a long-standing challenge.We discuss various approaches for beam combining with emphasis on solutions pursued at DirectPhotonics. Our design employs single emitter diodes as they exhibit highest brightness and excellent reliability. In a first step, after fast axis collimation, all single emitter diodes on one subunit are stacked side-by-side by a monolithic slow-axis-collimator thus scaling the power without enhancing the brightness.The emissions of all diodes on a subunit are locked by a common Volume Bragg grating (VBG), resulting in a bandwidth < 0.5nm and high wavelength stability. Second, two subunits with identical wavelength are polarization coupled forming one wavelength channel with doubled power and brightness. Third, up to five channels are serially spectrally combined using dichroic filters. The stabilized wavelengths enable dense spectral combining, i.e. narrow channel spacing. This module features over 500W output power within 20nm bandwidth and a beam parameter product better than 3.5mm*mrad x 5mm*mrad (FA x SA) allowing for a 100µm, 0.15NA delivery fiber [1].The small bandwidth of a 500-W-module enables subsequent coarse spectral combining by thin film filters, thus further enhancing the brightness.This potential can only be fully utilized by automated manufacturing ensuring reproducibility and high yield. A precision robotic system handles and aligns the individual fast axis lenses. Similar technologies are deployed for aligning the VBGs and dichroic filters.