Analytical model for design criteria of passively Q-switched lasers

Abstract

A general and straightforward model was developed for the design of passively -switched lasers. With the secondthreshold criterion and using a numerically fitting procedure, the output pulse energy was expressed as an analytical function of the initial transmission of the saturable absorber and the reflectivity of the output coupler. An analytical expression for the optimal output reflectivity was also obtained for maximizing the output pulse energy of a passively -switched laser with a given initial transmission of the saturable absorber. Excellent agreement was studied between the present results and detailed theoretical computations. A Nd:YAG laser with Cr 4+ :YAG as a saturable absorber was performed to illustrate the use of the present model. Index Terms-Passively -switched laser, saturable absorber, solid-state laser, Cr 4+ :YAG.

Analyzing the Intracavity Frequency Doubling of the Simultaneous Q-Switched Mode-Locked Diode-Pumped Pulsed Nd3+Laser with Cr4+:YAG as a Polarized Saturable Absorber

“…The problem of passively Q-switched lasers with simultaneous mode-locking has been treated experimentally and theoretically in many references [1][2][3][4][5][6][8][9][10] with, and without the existence of the IFD. None of the mentioned references discusses the impact of the polarization process on the characteristics of the output laser pulse.…”

“…By assuming that the excited state lifetime of the absorber is larger than the laser pulse width, the instantaneous population inversion density of the uniform--pumped gain medium, in each period of pulse build-up, can be written in the following reduced form [2,3,5,6,9]:…”

“…The time evolution of instantaneous population inversion density of the ground level of polarized isotropic Cr 4+ :YAG saturable absorber, neglecting the different relaxation process, is [2,3,5,6,9]:…”

Efficient dual-wavelength Nd:LuLiF_4 laser

“…The effective laser-beam area in the Nd:LLF crystal and in the SA was in a ratio (A∕A s ) of about 2.8. These conditions facilitate the second threshold condition being easily satisfied [21]. Initial experiments indicated that the PQS operation of the Nd:LLF laser was relatively sensitive to the position of V 3 :YAG, and the PQS characteristics were recorded when the V 3 :YAG was placed 5 mm away from the OC.…”

“…It can be found that the pulse width varies only slightly with P abs , and the 3% OC cavity provides narrower pulse width than that of 8% OC at identical P abs . Based on the analysis of coupled rate equations [21,22], the population inversion of the Nd:LLF depleted in a very short time, and the pulse width saturated; thus the pump power has little influence on the pulse width. The average pulse widths were roughly to be 120.1 ns with 3% OC and 129.7 ns with 8% OC.…”