Efficiency enhancement of high energy, actively Q-switched Nd:YAG Laser

Roi Alterman

M.Sc. student under the supervision of Prof. Shlomo Ruschin

11 May 2021, 15:00 
Efficiency enhancement of high energy, actively Q-switched Nd:YAG Laser




Diode-pumped solid-state (DPSS) lasers are widely used on account of their compactness and high efficiency.

The Q-switched 1.06µm Nd:YAG laser studied in this thesis is presumably the most prominent DPSS. In recent years, interest in high-efficiency lasers has increased, especially for harsh environment applications where power resources and volume are limited, such as military space and metrology applications. High-efficiency lasers are essential for several reasons: the higher the efficiency of the laser, the less the unwanted thermal effects, therefore improving birefringence, polarization-dependent loss, cavity stability, and beam quality while reducing the dependency on working conditions.

Several methods and techniques for achieving high efficiency using direct pumping at 885 nm were carefully examined. Different laser rod dopings were tested, analyzing the effects of Nd concentration levels on laser performance.

Various aspects of this performance, such as beam quality efficiency and maximum internal intensity, were studied. Throughout all the study stages, starting with the design considerations and including the experiments, great emphasis was placed on developing analytical and numerical predictive models.
The various results and insights achieved were incorporated into constructing a compact efficiency enhanced high energy laser. The Q-switched laser operated at a 5 Hz pulse repetition rate (PRF) with a 128 mJ/pulse output and light-to-light conversion efficiency of 33.6%; to our knowledge, it is the most efficient DPSS Nd:YAG laser of its type and class.
To compensate for the pulse width’s reduction caused by the short cavity, a pulse-stretching technique based on an electro-optical modulator was demonstrated. This technique allowed QS pulse temporal shape adjustment.

















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