Nonlinear optical effects in active matrix diode pumped

Selectively pumping rare earth-doped solid state lasers show important differences between broad-band frequency lamp pumping and monochromatic diode pumping, demonstrate the importance of completely characterizing the pumping dynamics including the effects of up-conversion and excited state absorption. Experiments in room temperature were carried out to study the higher order processes that produced the orange, yellow, green and blue fluorescence (visible often by the naked eye) in diode pumped solid state lasers and microlasers with the high pump power density up to 30 kW/cm2. These higher order processes were energy transfer up-conversion and excited state absorption of both pump and laser radiation. This type of processes may be an important loss mechanism for monochromatic pumping of laser. Energy transfer up-conversion reduces the population of the upper laser level, effectively shortening its lifetime. Additional heat deposition increase strongly under nonlasing conditions. Attributed to up-conversion and ESA there is a significant difference in thermal lens power between lasing and nonlasing conditions. Generation of heat in the laser medium is a fundamental problem which ultimately sets limits on the maximum operating power. (author)