Study On The Characteristics Of Passively Q-switched Laser Using AlGaInAs As The Saturable Absorber

High power diode-pumped all-solid-state lasers have attracted much attention for their unique merits, such as long lifetime, compact structure, high stability and optical-optical conversion efficiency, etc. The lasers employ diode laser as the pump source instead of conventional Helium or Xenon flashlamp, leading to a significant improvement of efficiency, reliability and beam quality, and thus called the revolution of the laser history.With the Q-Switching technology, we can get stable and reliable laser pulses, which can be widely used in the fields of pulse distance measurements, communication systems, remote sensors, high speed holography, military, and medical diagnostics, etc. Diode-pumped passively Q-switched solid-state lasers that use saturable absorbers have attracted significant attention because of their compactness and simplicity in operation. Based on some kinds of material's strong nonlinear absorption to the incident light, the saturable absorbers are used as loss devices to modulate the Q quality of the resonant cavity. Saturable absorbers are widely used to generate nanosecond, and high repetition rate pulse because it has such advantages as low costs, small volume, and convenient operation, etc. AlGaInAs is a new kind of saturable absorber material, which can be easily grown and fabricated. Besides, its performance can parallel the results of Cr⁴⁺-doped crystals, which are the most used saturable absorbers nowadays.In this dissertation, by using the fiber-coupled laser-diode as the pump source, Nd:YVO₄/YVO₄ bonding crystal as the gain medium, we studied the Q-switching characteristics of the semiconductor saturable absorber AlGaInAs. Meanwhile, the coupling wave rate equations are used to analyze the properties of the above-mentioned Q-switched lasers theoretically. The main contents can be outlined as follows:(1)The history and development of the all-solid-state lasers are introduced, thedevelopment of Q-switching technology is introduced, the development of the technology of bonding crystals is presented, and the history and the applications of semiconductor materials in laser physics are introduced.(2)The performance of the AlGaInAs is researched: by using a fiber-coupledlaser-diode as the pump source, a Nd:YVO₄/YVO₄ bonding crystal as the gainmedium, AlGAInAs as the saturable absorber, a passive Q-switched laser wasrealized. The dependences of the pulse energy, pulse width, pulse repetition rate onthe pumping power were measured.(3)Using the rate equations of passively Q-switched lasers, the theoretical resultsfor the pulse energy, pulse width, pulse repetition rate were obtained, and theyshowed agreement with the experimental result on the whole.By the theoretical and experimental research, we have a better understanding for the Q-switching material: AlGaInAs semiconductor saturable absorber. And there are some instructional significance and application values for the AlGaInAs passively Q-switched lasers.