Properties and frequency conversion of high-brightness diode-laser systems

An overview of recent developments in the field of high-power, high-brightn ess diode-lasers, and the optically nonlinear conversion of their output in to other wavelength ranges, is given. We describe the generation of continu ous-wave (CW) laser beams at power levels of several hundreds of milliwatts to several watts with near-perfect spatial and spectral properties using b laster-Oscillator Power-Amplifier (MOPA) systems. With single- or double-st age systems, using amplifiers of tapered or rectangular geometry, up to 2.8 5 W high-brightness radiation is generated at wavelengths around 810 nm wit h AlGaAs diodes. Even higher powers, up to 5.2 W of single-frequency and hi gh spatial quality beams at 925 nm, are obtained with InGaAS diodes. We des cribe the basic properties of the oscillators and amplifiers used. A strict proof-of-quality for the diode radiation is provided by direct and efficie nt nonlinear optical conversion of the diode MOPA output into other wavelen gth ranges. We review recent experiments with the highest power levels obta ined so far by direct frequency doubling of diode radiation. In these exper iments, 100 mW single-frequency ultraviolet light at 403 nm was generated, as well as 1 W of single-frequency blue radiation at 465 nm. Nonlinear conv ersion of diode radiation into widely tunable infrared radiation has recent ly yielded record values. We review the efficient generation of widely tuna ble single-frequency radiation in the infrared with diode-pumped Optical Pa rametric Oscillators (OPOs). With this system, single-frequency output radi ation with powers of more than 0.5 W was generated, widely tunable around w avelengths of 2.1 mum and 1.65 mum and with excellent spectral and spatial quality. These developments are clear indicators of recent advances in the field of high-brightness diode-MOPA systems, and may emphasize their future central importance for applications within a vast range of optical wavelen gths.