**8. References**

[1] Atlas User's Manual (2011) Device Simulation Software, Silvaco Inc.

[2] Sentaurus Device User Guide (2009) Synopsys Inc., v. C-2009.06.

[3] Colinge J-P (2008) FinFETs and Other MOSFET Multi-Gate Transistors, Springer.

	- [4] Gimenez S P, Bellodi M (2010) Diamond SOI MOSFET. PI0802745-5 A2, Publication Date: 03/23/2010, (RPI 2046).

**Chapter 14** 

© 2012 Lăncrănjan et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

**Numerical Simulation of Passively** 

**Q-Switched Solid State Lasers** 

I. Lăncrănjan, R. Savastru, D. Savastru and S. Micloş

Short laser light pulses have a large number of applications in many civilian and military applications [1-10]. To a large percentage these short laser pulses are generated by solid state lasers using various active media types (crystals, glasses or ceramic) operated in Qswitching and/or mode-locking techniques [1-10]. Among the short light pulses laser generators, those operated in Q-switching regime and emitting pulses of nanosecond FWHM duration occupy a large part of civilian (material processing - for example: nanomaterials formation by using ablation technique [3,7]) and military (projectile guidance over long distances and range finding) applications. Basically, Q-switching operation relies on a fast switching of laser resonator quality factor Q from a low value (corresponding to large optical losses) to a high one (representing low radiation losses). Depending on the proposed application, two main Q-switching techniques are used: active, based on electrical (in some cases operation with high voltages up to about 1 kV being necessary) or mechanical (spinning speeds up to about 1 kHz being used) actions on an optical component at least, coming from the outside of the laser resonator, and passive relying entirely on internal to

the laser resonator induced variation of one optical component transmittance.

Figure 1 displays a general schematic of electronic energy levels of laser active centers embedded in an active medium and of saturable absorption centers embedded into solid state passive optical Q-switch cell laser oscillator operated in passive optical Q-switching regime [11-18,26]. As laser active centers, rare earth (RE) triple ions included by substitution into crystalline or poly micro-crystalline structure of the solid state active medium are used to a large extent. The four electronic energy levels of a laser active center can be observed together with the transitions between them, transitions which constitute the laser emission

and reproduction in any medium, provided the original work is properly cited.

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/47812

**1. Introduction** 

**2. Theory** 

