Diode pumped solid state lasers are particularly attractive for many applications due to the high efficiency and better stability of output beam parameters in comparison with lamp pumped lasers. Low power diode pumped lasers are typically end pumped with the gain medium at one end of a standing wave cavity. A such configuration easily enables operation in fundamental transversal mode [1].

In this paper we report on research and development of a simple, low cost diode pumped Nd:YAG laser with continuous output power of 240 mW. As a pumping source a 1 W laser diode generating on wavelength of 808 nm manufactured by ATC Semiconductors Comp. from Russia was used. The emitting area was 150 um x 1 um and laser package contained built in AR coated cylindrical microlens reducing the divergence of the output beam to 8x10 degrees. In our setup we have used a three mirror folded resonator similar to the astigmatically compensated cavity used in many diode pumped laser systems. The pump radiation from laser diode was focussed using a single uncoated spherical lens with focal length of 50 mm through flat end into the 10 mm long Nd:YAG rod with diameter of 4 mm. The flat end of the rod was high reflection coated for 1.06 um and antireflection coated for 808 nm. The second end of the rod was cut at angle of 88 degrees with respect to the crystal axis and was AR coated at 1.06 um. The rest of the cavity consisted of a high reflecting, 200 mm radius of curvature folding mirror and 10 % transmitting flat output coupler.

In continuous regime, the threshold was 150 mW of absorbed power and the maximum output power was 240 mW for absorbed pump power of 900 mW. The higher efficiency is most probably achievable with optimised focussing of pump radiation. The developed laser modified for generation of picosecond pulses using acousto optic mode-locker will be used for measurement of relaxation times of absorbers for lasers.

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This research has been supported by GAČR grant No.102/97/0580 and by MŠMT grant J04/98:210000022.

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