High efficient, high peak power of 18kW with 4ns pulses of diode pumped passive Q-switched and self Q-switched Nd: yvo4laser at both 1064nm using Cr:YAG and 532 nm using ktp crystals

Abstract

Diode end-pumped solid-state lasers have the potential to yield high quality laser beams with high efficiency for laser range finding and warning receiver applications as well as day and night military laser designation systems. This paper presents theoretical calculations using Advanced Dynamics Professional LASCAD software and experimental studies for a high power pigtailed fiber diode laser module of 8 W operating at 808 nm with a specially designed high efficiency cooling system, end pumped high-efficiency Nd:YVO4 laser of 3×3×10 mm rod and overall cavity length of 44 mm. An optical to optical slope efficiency of around 76%, the final conversion efficiency of 60% and a maximum average output power of 4.11 W at 1064 nm laser were investigated with a high single-mode beam quality factor M2 of < 1.1, and the lowest threshold pumping power of 800 mW was measured, which was in agreement with the theoretical calculations of 776 mW. A high power second harmonic Nd:YVO4 CW laser at 532 nm (green laser) was achieved with an optical to optical slope efficiency of 66% and a final conversion efficiency of 56% using a 5×5×8 mm KTP crystal placed intracavity of the same 1064 nm CW laser with water cooling system. The green laser average output power of 3.38 W at incident diode laser power of 6 W was measured. To the best of our knowledge a self Q-switching effects was generated in Nd:YVO4 laser by changing the cavity dimensions and the position of the intracavity KTP crystal at certain regime of operation for the first time, in which the cavity length is reduced to be 30 mm and the distance between Nd:YVO4 rod and KTP crystal is only 1mm. Self Qswitched laser pulse at 532 nm with high peak power of 96 W, pulse width of 88 ns at FWHM and repetition rate of 400 kHz was achieved. Experimental studies of a passive Q-switched Nd:YVO4 laser using Cr:YAG crystal with three different transmissions of 30%, 40% and 70% were investigated. Passive Q-switched laser pulse at 1064 nm and narrow line width of less than 1.5 nm with highest peak power of nearly 18 kW, short pulse width of less than 4 ns at FWHM and higher repetition rate of 45 kHz using Cr:YAG with transmission of 30% was achieved for the first time. The main application for the investigated effect is generation of an efficient and high repetitive high peak power self Q-switched second harmonic Nd:YVO4 laser system that can be realized without the need of using any of passive Q-switched semiconductor saturable absorber mirror SESAM.