Optical parametric oscillators and precision optical frequency measurements

We report experimental results of frequency tuning, stabilization, and beat-note phase noise measurements of a type-II phase-matched potassium titanyl phosphate (KTP) doubly resonant optical parametric oscillator (OPO). Three types of OPO cavity design were constructed and experimented for their mechanical stability and frequency tunability. Four tuning elements were employed in our 2-element and 3-element OPOs to control their stability and output frequencies. Discrete frequency tuning of over a range of -3 THz was obtained by crystal angle tuning and cavity-length scanning. We achieved continuous frequency tuning over a 0.5-GHz range through the use of temperature and electro-optic tuning of the KTP crystal. Using these frequencycontrol techniques, we phase locked the signal-idler beat frequency to an external microwave frequency source near the frequency degenerate point and at 665 GHz with the use of an optical frequency comb generator. The power spectral density of the residual phase noise of the phase-locked signal-idler beat note was measured to be 0.3 mrad/viRz. With the ability to tightly phase lock the beat-note frequency, the quadrature spectra of the signal-idler beat-note were experimentally measured for the first time. By amplitude modulating the input pump beam, the pump intensity to quadrature-phase transfer functions were also measured. A linearized quantum mechanical calculation for the OPO beat-note spectra was performed to facilitate a better understanding of the experimental observation. As a foundation for future experiments, we have also constructed and investigated the tuning properties of a dual-cavity OPO (DCOPO). The signal and idler fields were separated internally to resonate in their own respective cavities, thus providing independent cavity-length controls. The DCOPO was continuously tunable over a range of -1 GHz that was limited by the weak pump resonance. A theoretical model was developed to explain and predict the tuning behavior of our DCOPO. Thesis Supervisor: Ngai Chuen Wong Title: Research Scientist, Research Laboratory of Electronics Thesis Supervisor: Daniel Kleppner Title: Professor, Department of Physics