To address NASA's need for miniature optical isolators in atom interferometry applications, Physical Optics Corporation (POC) proposes to develop a miniature optical isolation technology based on magnetic photonic crystals optimized at wavelengths in the visible and NIR range. The proposed optical isolator design is based on enhanced magneto-optical effects in photonic crystals. With the proper lattice parameter and magneto-optical material, high optical transmission and large Faraday rotation can be achieved simultaneously at a target wavelength. A proposed device, occupying <0.1 cc, is expected to achieve high optical transmittance (forward loss <2 dB) and excellent optical isolation (extinction >40 dB); therefore, it is suitable for applications in various compact atom interferometers. In Phase I, POC will demonstrate the feasibility of the proposed technology in the visible spectral range and provide a Phase II prototype design. In Phase II, the technology will be further optimized and tested in operational environments.