In modern communication and sensing devices, such as radios, cell phones, computers, and radar, phase-locked loop (PLL) technology is widely applied to enable coherent detection, which has a higher sensitivity and data capacity compared to traditional envelope detection. However, historically the idea of extending this PLL concept into the optical domain has proved difficult. The fundamental difficulty of building an optical phase-locked loop (OPLL) is due to the limited loop bandwidth relative to the laser linewidth and wavelength stability. In order to solve this problem, photonic and electronic integration needs to be applied along with novel system designs.

In this Ph.D. dissertation, homodyne and heterodyne OPLLs are designed, fabricated, and implemented based on advanced InGaAsP/InP photonic integration technology, as well as electronic integration. All the optic components needed in the OPLL are integrated monolithically, including a slave laser, a 90-degree hybrid, four high-speed photodetectors, and microstrip transmission lines, optical amplifiers and interconnecting optical waveguides.

The integration technology enables stable OPLLs with advanced functionalities. OPLL closed-loop bandwidth has been improved to around 1.1 GHz, and based on this OPLL, a synchronized homodyne receiver is achieved, with a data rate up to 40 Gbit/s. Error free (bit error rate < 10-12) is realized up to 35 Gbit/s. As for sensing and synthesis applications, two lasers are phase locked to each other with an offset frequency range of 40 GHz, and phase-locked frequency sweeping has been achieved. The residual phase noise is smaller than 0.03 rad2 integrating from 100 Hz to 10 GHz.

Utilizing the OPLLs demonstrated in this thesis, there are many potential applications. In the area of coherent communication, especially in short or mid distance range, where dispersion is not serious, OPLL-based homodyne receiver has advantages of highest sensitivity, lower power consumption, smaller size and lower cost. In the area of optical sensing and synthesis, many novel coherent optical system can be established by using this OPLL as the key building block, including, but not limited to, light detection and ranging (LIDAR), fiber sensing, optical synthesis, optical tomography and terahertz wave generation.