Blue-green diode lasers New Evolution

Blue-green diode lasers New Evolution
High power edge emitting diode lasers are the most efficient coherent light sources available. They feature small physical size combined with high reliability. Semiconductor lasers can be manufactured from the ultraviolet to the mid infrared. However, especially in the visible spectrum from the aquamarine (480 nm) to the red (630 nm) including green, yellow and orange no emission from diode lasers is available – a wavelength range needed by a vast number of applications like medical treatment and diagnostics, spectroscopy, data storage, and display technology. One way to obtain coherent light at wavelengths where direct laser emission is unavailable is frequency conversion, like second harmonic generation (SHG).

Andreas Jechow and his co-authors from the University of Potsdam and the Ferdinand Braun Institut für Höchstfrequenztechnik, Berlin, Germany give a review on SHG using edge emitting diode lasers and nonlinear crystals to obtain laser radiation in the blue-green spectral range. They focus on the advances made with single pass SHG using bulk and waveguide crystals utilizing diode lasers as pump sources.

Frequency doubling of diode laser emission has become an alternative to diode pumped solid state laser and optically pumped semiconductor laser systems and it promises the realization of blue-green laser devices with high wall plug efficiency. This is feasible because of the availability of highly efficient nonlinear materials based on quasi phasematching and the recent advances in manufacturing high brilliance edge emitting diode lasers. Single pass and resonant SHG schemes that can deliver up to 1.5 W of optical output power in the visible spectrum have been demonstrated. Furthermore, single pass conversion efficiencies as high as 50% have become possible with channel waveguide quasi phase-matched devices and low power diode lasers.
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