Passive Q-switched cw diode-pumped Nd-doped YAG and YVO 4 lasers

Abstract

ABSTRACT cw diode pumped solid state lasers have sought for various scientific, medical and military applications, where compactreliable, stable, and highly efficient sources are desirable. There are several applications such as fiber-optic sensing or rangefinding which require short bursts of high peak power densities at multi-kilohertz repetition rates, and with a good beam quality. An extensive research on the properties of passively Q-switched, CW diode-pumped, ND-lasers has been conducted. We have used various pumping schemes to diode pump the Q-switched Nd:YAG and Nd:YVO4 laser crystals.Such schemes are transverse pumping by a cylindrical microlens—coupled diode array or longitudinally pumping by afiber-coupled diode array. The passive Q-switching elements were Cr:YAG (polished, uncoated) and Cr4:GGG (polished,coated), which were inserted inside the laser resonator. The I .06 tm laser emission shows a repetitive modulation in thekHz frequency domain, and temporal bandwidth, full width at half maximum, (FWHM) in the range of 50-600 nsec. Themodulation frequency and bandwidth depend on the characteristics of the Q-switching material (e.g. Cr44 concentration,sample thickness) and on the input power level of the diode array used. We shall report design parameters and performanceof various types of passively Q-switched and free-running diode pumped Nd-lasers. We shall present and discuss methodsto increase the efficiency of Q-switched solid state lasers.Diode pumping, passive Q-switching, transverse pumping, longitudinal pumping.