The Research On Quasi-Phase-Matched Mid-Infrared Optical Parametric Oscillator And Intracavity Optical Parametric Generator

The optical parametric conversion which includes optical parametric oscillator (OPO) and optical parametric generator (OPG), plays an important role in realizing tunable laser source, at the same time, the quasi-phase-matching (QPM) technology can make use of the maximum nonlinear coefficient to increase the conversion efficiency, avoid the walk-off effect, and may apply the whole transmission range of the crystal. So the QPM technology has become a developing focus in nonlinear optics. The optical parametric conversion based on the QPM technology has many applications in infrared countermeasures, optic communication system, remote sensing and spectroscopy. This thesis focus on mid-infrared QPM OPO with important value and QPM intracavity optical parametric generator (IOPG) which is less researched. The main content and key innovative points of this dissertation are as follows:1. A summary of methods to produce the mid-infrared laser is given. Characters of several nonlinear crystals valid in the mid-infrared laser are compared. And the development of mid-infrared QPM OPO in improving the output power and reducing the threshold are introduced in detail.2. The theory of QPM OPO is investigated, and the theory of temperature tuning is analyzed. From the three-wave interaction equation, the problem how to reduce the threshold and realize the temperature-dependent tuning is solved.3. A mid-infrared QPM OPO is demonstrated, in which a monolithic periodically poled MgO-doped lithium niobate (PPMgLN) crystal is pumped by a high-repetition all solid state Nd:YVO4 laser to realize the mid-infrared QPM OPO. The wavelength range of 3330.6³624.1nm is obtained, and when the average pump power is 4.3W, the average mid-infrared output power reaches 563mW.4. The theory of QPM IOPG is investigated and the cavity is optimized. And then we experimentally demonstrate the QPM IOPG, in which a four-mirror ring cavity is selected, The IOPG is based on periodically poled lithium niobate (PPLN) internal to the cavity as the nonlinear material, which is pumped by a diode-end-pumped Nd:YVO₄ ring laser. A signal wavelength ranging from 1497nm to 1517nm is obtained by turning the temperature of PPLN, and a maximum average output power is 440mW.