Wolfgang Reill

8-W high-efficiency continuous-wave semiconductor disk laser at 1000 nm

We demonstrate more than 8-W continuous-wave output power with good beam quality (M2<1.8) from an optically pumped semiconductor disk laser. The combination of low threshold density of 470 W/cm2 and high differential efficiency of 60% results in an optical-to-optical conversion efficiency of 46% for this high output level. Good epitaxial quality and low thermal resistance allow the scaling of output power with pump spot area.

Scaling brilliance of high power laser diodes

New direct diode laser systems and fiber lasers require brilliant fiber coupled laser diodes for efficient operation. In the German funded project HEMILAS different laser bar designs are investigated with tailored beam parameter products adapted for efficient fiber coupling. In this paper we demonstrate results on 9xx and 1020nm bars suitable for coupling into 200μm fibers. With special facet technology and optimised epitaxial structure COD-free laser bars were fabricated with maximum efficiency above 66%. For short bars consisting of five 100μm wide emitters 75W CW maximum output power was reached. In QCW-mode up to 140W are demonstrated. The 10% fill factor bars with 4mm cavity are mounted with hard solder. Lifetime tests in long pulse mode with 35W output power exceed 5000 hours of testing without degradation or spontaneous failures. Slow axis divergence stays below 7° up to power levels of 40W and is suitable for simple fiber coupling into 200μm NA 0.22 fibers with SAC and FAC lenses. For fiber coupling based on beam rearrangement with step mirrors, bars with higher fill factor of 50% were fabricated and tested. The 4mm cavity short bars reach efficiencies above 60%. Lifetime tests at accelerated powers were performed. Finally fiber coupling results with output powers of up to 2.4 kW and beam quality of 30 mm mrad are demonstrated.

Green semiconductor disk laser with 0.7W cw output power

We demonstrate 0.7W cw output power at 520nm from an intracavity frequency doubled optically pumped semiconductor disk laser at room temperature. High beam quality and optical conversion efficiency of 10% has been achieved.

0.7 W CW output power from a green semiconductor disk laser

We demonstrate 0.7 W cw output power at 520 nm from an intracavity frequency doubled Optically Pumped Semiconductor Disk Laser at room temperature. High beam quality and optical conversion efficiency of 10% has been achieved.

52.4: High Speed Green Frequency Converted Semiconductor Laser for Projection Displays

Recent progress on compact green laser for projection applications based on frequency doubled semiconductor structures will be presented. Avoiding external acousto- or electro-optical modulation for scanning laser displays, the green laser prototypes can be directly modulated in the 20–40MHz range.

Multiwatt semiconductor disk lasers for near-infrared wavelengths

Optically-pumped semiconductor disk lasers offer high output power in combination with good beam quality. By optimizing epitaxial quality as well as thermal resistance, we have demonstrated more than 8W of continuous-wave, room-temperature emission at 1000nm. These high power-levels are tied to high optical-conversion efficiencies of more than 40%. Whereas available wavelengths for solid-state disk lasers are restricted to a set of atomic transitions, semiconductor disk lasers can be conveniently tailored to meet almost any wavelength. Building upon the high-power results at 1000nm, we have extended the emission range towards 900nm as well as 1100nm. Two prominent examples are devices realized at 920nm and 1040nm, in each case demonstrating several Watts of laser output.

0.7W Green Frequency Doubled Semiconductor Disk Laser

We demonstrate 0.7W cw output power at 520nm from an intracavity frequency doubled Optically Pumped Semiconductor Disk Laser at room temperature. High beam quality and optical conversion efficiency of 10% has been achieved.

High Power Semiconductor Disk Lasers

We present high-power emission from semiconductor disk lasers. By intra-cavity frequency-doubling of multi-Watt infra-red emission, more than 0.6 W of blue and green have been generated. 200 mW have been achieved directly for red emitters.

High power semiconductor disk lasers

Results on high-power optically pumped semiconductor disk lasers are reviewed. Multi-Watt emission with differential efficiencies larger than 40% and power-densities up to 15 kW/cm2 is demonstrated in the near-infrared wavelength range of 920-1050 nm

Diode laser modules based on new developments in tapered and broad area diode laser bars

In the last few years an increasing demand for high-brightness diode laser sources is observable, which is mainly driven by applications for fiber laser pumping and materials processing. A number of different approaches have been investigated in the past for the realization of such systems. In this paper we compare different concepts for high-brightness, high-power diode laser modules that are based on the new generation of tapered diode laser bars and new developments in broad area diode laser bars, respectively. One of the main advantages of tapered diode laser bars is the good beam quality in the slow-axis direction, which allows the design of high-power laser systems with a symmetric beam profile without the necessity of using sophisticated beam shaping systems. Such laser modules with multiple bars aiming for kilowatt output power can be realized with different incoherent coupling principles, including spatial multiplexing, polarization multiplexing and wavelength multiplexing. On the other hand, modules with a single or only a few tapered diode laser bars aim for very high brightness suitable for fiber coupling with fiber diameters down to 50 μm with a numerical aperture (NA) of 0.22. In this paper we present a detailed characterization of the new generation of tapered diode laser bars, including typical electro-optical data, measurements of beam quality and lifetime data. Tapered diode laser bars typically suffer from a broad spectrum which is extremely obstructive for pumping applications with small absorption bandwidths. To overcome this disadvantage we used volume bragg gratings (VBG) to improve the spectral quality of tapered diode laser bars. In addition to further improve the brightness of such diode laser systems we investigated external phaseplates to correct for smile and lens aberrations.