Study of the Spatiotemporal Behavior of LED-Pumped Ce:Nd:YAG Laser

In this paper, the mode structure and time behavior of a LED-pumped Ce:Nd:YAG laser have been studied. Four blue LED bars with total 128 LEDs at 460 nm are utilized to pump a 3 mm diameter laser rod. Using a Cr4+:YAG passive optical switch with 96% initial transmission, and a low loss stable optical resonator and 0.7 J pumping energy, a single 17 micro-joules Q-switched laser pulse with 240 ns pulse-width and nearly TEM00 mode profile was produced. By increasing the pumping energy Ep up to 0.8 J, the mode structure remained intact. Further increasing of Ep, the laser mode changed to TEM10. Numerical calculations show that the central high gain area of the laser rod and saturation mechanism of the passive Q-switch behaves like as a soft aperture to enforce the laser resonator to oscillate on a low order transverse mode. For laser free-running, the TEM00 mode has not been achieved and the optical resonator produced high order transverse mode patterns.