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...

We report on the development of compact and frequency-stable Er:YAG laser systems emitting in the eye-safe spectral region. Resonant cw diode pumping provides 4.5 W output power in cw operation and 2.2 mJ in Q-switched operation with pulse duration of about 140 ns. The application of intra-cavity etalons allows for wavelength tuning from 1645.22 to 1646.33 nm while the frequency stability accounts for less than 50 MHz. The potential of the erbium laser sources in terms of methane detection was evaluated under laboratory conditions by absorption measurements employing a multi-pass absorption cell. The experimental investigations were accompanied by theoretical studies on the influence of pressure broadening on the absorption behavior of methane.

Active remote sensing represents a promising technology to accurately measure the atmospheric concentration of the climate-relevant trace gases carbon dioxide and methane. For this application, frequency stabilized laser sources with high pulse energy emitting at specific absorption lines around 1.6 µm wavelength are required. While Raman frequency conversion of high power solid-state laser systems provides sources suitable for CO 2 detection, compact resonantly pumped Er:YAG lasers are demonstrated to be feasible for CH 4 absorption measurements.

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.