The Studies Of Novel Solid-state Lasers Based On Optical Parametric Oscillation And Stimulated Raman Scattering

Nonlinear frequency conversion technology has established itself as a reliable and efficient way to obtain diverse and versatile laser sources with novel and valuable wavelengths. It has been one important aspect and one of the focus topics in optics. In the past several decades, all kinds of nonlinear optical effects have been researched deeply and widely. For example, the second order nonlinear optical effects such as second harmonic generation, sum frequency generation, differential frequency generation, and optical parametric oscillation, etc, and the third order nonlinear optical effects such as four wave mixing, stimulated Raman scattering, and stimulated Brillouin scattering, etc. In all kinds of nonlinear optical effects, we focus on optical parametric oscillation and stimulated Raman scattering. Both of them all efficient nonlinear optical processes and from them high output power can be generated. Sometimes, all these nonlinear conversion methods can’t satisfy people’s need. Hence the researchers combined two or even three of them together.In this dissertation, we studied both the signal-resonant and idler resonate intracavity KTiOAsO4(KTA) optical parametric oscillator (OPO), and through theoretical simulations and analyses based on rate-equation model, we made reasonable explanations to the experimental results. Based on novel Raman crystal BaTeMo2O9(BTM), we studied its spontaneous Raman spectra and studied its relative Rman scattering cross section. And we also realize the1179nm and1531nm intracavity Raman laser. We realized a novel frequency conversion system that using Raman laser to pump OPO. In order to improve the conversion efficiencies of the nonlinear optical processes, the properties of the fundamental laser was investigated by taking an side-pumped Nd:YAG laser as an example. The main contents of this dissertation are as follows:1. A diode-end pumped actively Q-switched YVO4/Nd:YVO4KTA OPO has been studied experimentally. The signal wave was resonate while the idler wave not. With an incident diode power of25.9W, up to1.18W output of3.47μn idler wave was obtained. The signal power was obtained to be3.77W at1535.0nm simultaneously. We found the signal pulse width was wider than that of the idler. At the highest output power, the result was3.8ns and2.9ns for the signal and idler, respectively. The beam quality factors were2.1±0.1and2.0±0.1for the signal, while9.5±0.5and8.8±0.5for the idler.2. Novel theoretical model based on rate equations was set up in order to simultaneously deal with the output characteristics of both the signal and idler waves in intracavity singly resonated OPO. This model has been used to analyze the performance of the above KTA-OPO. The average output power and the pulse width were simulated for both signal and idler waves. The results agreed with the experiment ones. Both the theory and experiment have shown a phenomenon:In a signal-resonate singly resonant OPO, the idler pulse width is shorter than the signal pulse width under a same incident diode power.3. We have realized what are to our knowledge the first experimental results of idler-resonant KTA-OPO. With a diode pump power of15.4W, the idler output power was obtained to be105mW at3467nm and the signal output power was obtained to be720mW at1535nm. The conversion efficiency from diode to total OPO output power was5.4%. During the experiment we found the pulse widths of the idler laser were wider than that of the signal laser. Moreover, a significant improvement of the beam quality was observed for the idler wave.4. The spontaneous Raman scattering spectra of new crystal BaTeMoaO9(BTM) was given in detail. And the relative Raman scattering cross section for BTM with respect to YVO4was measured.5. A diode end-pumped actively Q-switched Nd:YAG/BaTeMo2O9laser at1179nm has been demonstrated with a intracavity configuration for the first time. The maximum output power of625mW was achieved at a repetition rate of10kHz and a pump power of8.6W, corresponding to optical-to-optical conversion efficiency of7.3%. The pulse width was9.9ns and the peak power was6.3kW.6. A diode-end-pumped acousto-optically Q-switched NdiYVO4/BTM intracavity Raman laser has been demonstrated. A19mm-long Z-cut BTM crystal successfully shifted the1342-nm fundamental laser to1531-nm first-Stokes laser. With a pump power of10.8W, a first-Stokes power of0.83W was obtained at a pulse repetition rate of25kHz. The pulse width was11ns and the peak power was3.0kW.7. We realized an intracavity KTP-OPO pumped by an acousto-optically Q-switched Nd:YAG/BaWO4Raman laser. The device has realized three steps of conversion:from a laser diode wavelength of808nm to the fundamental wavelength of1064nm; next, to the Stokes wavelength of1180nm; and finally to the OPO signal wavelength of1810nm. With a pump power of7.2W and a pulse repetition rate of15kHz, we obtained690mW of1810nm laser. The corresponding optical-to-optical (diode-to-signal laser) conversion efficiency was6.8%.8. Theoretical model based on rate equations was set up to analyze the performance of the Raman pumping OPO system. The results agreed with the experiment ones.9. Laser properties of diode-side-pumped Nd:YAG laser operating at1123nm were demonstrated. Both radial and tangential thermal focal lengths of this side-pumped Nd:YAG rod are determined under the1123nm and1064nm lasing condition. Laser output performances in terms of stability, output power and beam quality influenced by pump power were also discussed.The main innovations of this dissertation are as follows:1. For the first time, the output power of the3.5μm laser from diode-end pumped KTA OPO was scaled up to watt level. By selecting the Diffusion bonded crystal as the laser medium and optimizing the cavity design, the output power of idler wave was up to1.18W at the condition of25.9W-pumping power and50kHz-pulse repetition rate.2. For the first time, the idler-resonate KTA-OPO was demonstrated. The beam quality of the3.5μm laser was improved. Moreover, this experiment verified that the pulse width of the signal and the idler were not the same. The resonant one had the wider pulse width.3. Novel theoretical model based on rate equations was set up for singly resonant OPOs by adding the expression of the idler photon density. Then the rate equation model can simultaneously deal with the output characteristics of both the signal and idler waves in intracavity singly resonated OPO.4. For the first time, we proposed and realized a novel nonlinear frequency conversion system that using a Raman laser to pump an OPO. By emplying the NdiYAG/BaWO4/KTP scheme, we realized three steps of conversion:from a laser diode wavelength of808nm to the fundamental wavelength of1064nm; next, to the Stokes wavelength of1180nm; and finally to the OPO signal wavelength of1810nm.5. We realized the first BTM Raman laser emitting at the eye-safe wavelength. By employing Nd:YVO4as the laser medium and the using acousto-optically Q switch, the1342nm fundamental laser successfully shifted to1531nm eye-safe laser.6. For the first time, we measured both the radial and tangential thermal focal lengths of the diode side-pumped Nd:YAG rod under the1123nm lasing condition.