The mechanism research of the Cr⁴⁺Nd³⁺:YAG laser

The 946nm diode-pump microchip self-Q-switched laser of a chromium and neodymium codoped yttrium aluminum garnet crystal material (Cr^4+Nd^3+:YAG) is studied, especially about its physical mechanism of operation. The ^4F_3/2→^4I_9/2 transition of Nd^3+ ion is beneficial to achieving laser oscillation in a quasi-three-level system based on coating the cavity mirrors of the microchip with films that suppress the 1064nm operation and enhance the 946nm laser. The Cr^4+ ion is a saturable absorber. The initial loss N_\rm t1 is high, which acts as the threshold for laser oscillation. The stable loss N_\rm t2 is low because the Cr^4+ ion is acceleratively bleached by the fast enhancement of the oscillating laser. The high N_\rm t1, small N_\rm t2 and fast progresses permit the oscillating laser of the Cr^4+Nd^3+:YAG to have a good self-Q-switched property whose full width at half maximum is about 4.2ns. Its highest laser power is about 5.7mW. Its peak power is about 150W. Its good fundamental transverse TEM_00 mode results from the absorption bleaching established by both the pump and oscillating lasers, which suppress other transverse mode and allow the oscillation only in the fundamental transverse TEM_00 mode.