To address NASA's need for compact optical isolators, Physical Optics Corporation (POC) proposes to continue the development of a new Miniature Optical Isolator (MOI). The novel optical isolator design is based on enhanced magneto-optical (MO) effects in magnetic photonic crystals. The innovation in the technology is its capacity to engineer MO effects not only by choosing the right material but also by adjusting the lattice parameters of 1 dimensional photonic crystals. While occupying a very small volume (~0.1 cm^3), a MOI device will achieve high optical transmission (2 dB or less forward loss) and excellent optical isolation (40 dB) at target wavelengths at a low cost. Therefore, the MOI technology directly addresses NASA's requirements for a compact, robust optical isolator for applications in cold atom systems. In Phase I, POC demonstrated the feasibility of the MOI technology through modeling and analysis, as well as fabrication of a proof-of-concept prototype with basic performance parameters characterized. In Phase II, POC will further optimize the device and fabricate prototypes for validation of key performance metrics, as well as evaluate life cycle and environmental performance.