Study On The Operating Properties Of Directly Pumped Solid-state Intracavity Raman Laser At 1.5μm

Solid-sate Raman lasers have recently become a research focus in the fields of diode-pumped solid-state lasers and nonlinear optics. Though the stimulated Raman scattering(SRS) effect and by using different pump wavelengths and different Raman medium, the solid-state Raman lasers can generate emissions from ultraviolet to the near-infrared spectra region. Compared with other nonlinear optical frequency conversion techniques, solid-state Raman lasers possess the merits of without phase-matching, narrow pulse width, good beam quality, etc., and also can be used to generate 1.5μ m eye-safe laser output. In this thesis, the 880nm-diode-pumped solid-state intracavity Raman laser at 1525 nm was theoretically and experimentally studied in detail.The theoretical work includes four aspects. Firstly, by using the coupled-wave equations and the classical harmonic oscillator model, the gain coefficient expressions for the steady state SRS and the transient SRS were deduced. The Raman gain coefficients at different wavelengths were calculated under the given parameters. Secondly, by employing the rate-equation theory for the actively Q-switched Raman lasers, the time evolution behaviors of the inverted population density and intracavity photon density were simulated, and the building and attenuating processes of the Raman laser pulses were discussed. Thirdly, based on the matrix optical theory and by using the Matlab software, the variations of the fundamental spot radius and cavity stability factor with cavity lengths at different cavity configurations were simulated. The fundamental spot radius at different positions in the laser cavity was also calculated. Lastly, the thermal lensing effects of the laser and Raman crystals, and also the corresponding impacts on the performances of the Raman laser were simulated and analyzed.The experimental work was focus on the first Stokes effect based YVO4 Raman laser at 1525 nm, driven by an 880 nm LD directly pumped Nd:YVO4 laser at 1342 nm. By adopting three different cavity configurations, the impacts of the pump power and repetition rate on the average output power, pulse width and shape, beam quality, etc., were investigated. At the diode pump power of 15.9W and pulse repetition rate of 30 k Hz, the average output power at 1525 nm as high as 530 m W was obtained. Besides, at the pulse repetition rate of 10 k Hz, the diode pump threshold as low as 2.6W was achieved. When the pump power was higher than 9.1W(@10k Hz repetition rate), the pulse duration at 1525 nm was stabilized around 5ns which was compressed effectively compared with the fundamental pulses.