High power continuous wave Nd:KGW laser with low quantum defect diode pumping

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Talukder, Rubel Chandra
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Optical society of America
High power diode-pumped solid state (DPSS) lasers are a rapidly growing technology that is attractive for various applications in scientific and industrial fields. DPSS lasers are highly efficient, reliable and durable with superior beam quality when compared to flash-lamp pumped solid state lasers. Double-tungstate crystal of neodymium-doped potassium gadolinium tungstate (Nd:KGW) is one of the most effective active media used in DPSS lasers for generation of continuous wave radiation and ultrashort (i.e. picosecond, 10-12 s) pulses. Unfortunately, the thermal conductivity of KGW host crystals is relatively low (~3 Wm-1K-1). This low thermal conductivity and large quantum defect while pumping with ~808 nm lead to significant thermo-optical distortions. One way to minimize thermo-optical distortions is to reduce the quantum defect. This can be done by pumping at longer wavelengths as compared to conventional 808 nm. In this work we demonstrate what we believe is the first continuous wave Nd:KGW laser with hot band diode pumping at ~910 nm. This pumping wavelength reduced the quantum defect by >46% as compared to the conventional ~808 nm pumping and resulted in significantly lower thermal lensing. The laser produced 2.9 W of average output power at 1067 nm in a diffraction limited beam for an absorbed pump power of 8.3 W. The slope efficiency and optical-to-optical efficiency were found to be 43% and 35%, respectively. Significant reduction of quantum defect offered by this pumping wavelength and availability of suitable high power laser diodes opens an attractive way to further power and efficiency scaling of the Nd:KGW lasers.
Nd:KGW, Quantum defect, Continuous wave
R. C. Talukder, Md Z. E. Halim, T. Waritanant, A. Major, “Multiwatt continuous wave Nd: KGW laser with hot-band diode pumping,” Optics Letters 41, 3810-3812 (2016).
R. C. Talukder, Md Z. E. Halim, T. Waritanant, A. Major, “Multi-Watt Continuous Wave Nd: KGW Laser With Hot Band Diode Pumping,” CLEO: Science and Innovations, 2016.
R. C. Talukder, Md Z. E. Halim, T. Waritanant, A. Major, “Continuous Wave Nd: KGW Laser With Hot Band Diode Pumping,” Photonics North-2016.