Hybrid laser modules for the green spectral region with high output powers and high conversion efficiency
Fig. 1: Visible power dependence on near-infrared power during frequency doubling of diode lasers in bulk crystals, planar waveguides and channel waveguides.
Fig. 2: Visible spectrum at maximum output power of 1.07 W.
Compact, robust and efficient laser light sources emitting in the green spectral region are required for many application fields. Depending on the maximum output power, they are used in biotechnology, display technology and as pump lasers for Ti:Sapphire solid-state lasers. Such modules can be realized by means of frequency doubling of near-infrared GaAs diode lasers in nonlinear crystals. Compared to GaN diode lasers, they reach significantly improved beam quality and efficiencies at higher output powers. Furthermore, the presented concept can be easily transferred to other wavelengths, as for example the yellow spectral region.
At the Ferdinand-Braun-Institut, frequency doubling of diode lasers in bulk crystals, planar waveguides and channel waveguides is systematically examined. In channel waveguides, a very high conversion efficiency of 40% can be reached, but this concept allows only moderate power levels in the range of 200 mW (Fig. 1 - blue triangles). Whereas in bulk crystals the situation is reversed and very high powers of 1.8 W are generated (Fig. 1 - yellow squares), however, at a relatively low conversion efficiency of 22%. Planar waveguides, in contrast, enable to generate high power levels in the Watt range and feature high conversion efficiencies. In a laboratory setup, an output power of 1.1 W at an opto-optical conversion efficiency of 26% was reached with this concept (Fig. 1 - green circles). A corresponding electro-optical conversion efficiency of 8.4% was measured. Hence, frequency doubling of diode lasers in planar waveguides is currently the solution of choice to realize compact visible diode laser modules with output powers of several Watt and an electro-optical conversion efficiency of more than 10%. Furthermore, the green light generated during the experiment feature a spectral linewidth of 0.8 pm full width at half maximum (FWHM) and a side mode suppression ratio (SMSR) of 20 dB (Fig. 2).
Publications:
D. Jedrzejczyk, R. Güther, K. Paschke, B. Eppich, G. Erbert, "<link /fileadmin/fbh-berlin/english/ver10/pub55.htm _blank>200 mW at 488 nm From a ppMgO:LN Ridge Waveguide by Frequency Doubling of a Laser Diode Module", IEEE Photon. Technol. Lett. 22, pp. 1282–1284 (2010).
K. Paschke, Ch. Fiebig, D. Jedrzejczyk, "Kompakte Laser für Medizintechnik und Displays", Optik & Photonik 3 - Oktober 2010, Wiley-VCH Verlag, pp. 43-46 (2010).
D. Jedrzejczyk, R. Güther, K. Paschke, W.-J. Jeong, H.-Y. Lee, G. Erbert, "<link /fileadmin/fbh-berlin/english/ver11/pub14.htm _blank>Efficient high-power frequency doubling of DBR tapered laser radiation in a ppMgO:LN planar waveguide", Opt. Lett. 36, pp. 367-369 (2011).
D. Jedrzejczyk, R. Güther, K. Paschke, G. Erbert, "<link /fileadmin/fbh-berlin/english/ver11/pub16.htm _blank>1 W at 531 nm generated in a ppMgO:LN planar waveguide by means of frequency doubling of a DBR tapered diode laser", SPIE Proc. 7917-2, pp. 80710N-1 - 80710N-7 (2011).
FBH research: 06.06.2011