en تخصصي Special كاربردي Applicable 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 E_p up to 0.8 J, the mode structure remained intact. Further increasing of E_p, 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. Ce:Nd:YAG laser, Cr:YAG passive Q-switch, LED-pumping, laser free-running. 75 84 http://ijop.ir/browse.php?a_code=A-10-678-1&slc_lang=en&sid=1 Mostafa Tarkashvand tarkash1@yahoo.com 10031947532846003156 10031947532846003156 No Department of plasma and nuclear fusion, Nuclear science technology research institute, North Kargar, Tehran, Iran, Payame Noor University, P.O. Box 19395-3697, Tehran, Iran Amir Hossein Farahbod afarahbod@aeoi.org.ir 10031947532846003157 10031947532846003157 Yes Department of plasma and nuclear fusion, Nuclear science technology research institute, North Kargar, Tehran, Iran Seyed Ali Hashemizadeh ahashemizadeh@yahoo.com 10031947532846003158 10031947532846003158 No Department of Physics, Payame Noor University, P.O. Box 19395-3697, Tehran, Iran