Novel Integrated Waveguide Optical Isolator Based on Nonreciprocal Mode Conversion

Optical feedback into semiconductor lasers can have detrimental effects to laser stability. Optical isolators with high forward transmission and very low return are used to ensure laser stability. Conventional optical isolators including fiber coupled ones consist of a Faraday rotator, a permanent magnet, and other optical components. They work exclusively based on the non-reciprocal Faraday polarization rotation principle. These isolators and their modified waveguide version cannot satisfy monolithic integration requirement with laser array chips owing to the incompatibility of the fabrication processes and packaging (need magnet). New Span Opto-Technology proposes to develop a novel waveguide optical isolator based on nonreciprocal mode conversion rather than using magneto-optical materials. The new waveguide isolator can be fabricated on any waveguide substrate including glass, polymer, and semiconductor materials. The concept of the isolator is supported by the mode conversion theory and has been verified by the beam propagation simulation and our preliminary experiments. The Phase I research will design and develop a prototype waveguide optical isolator. The successful demonstration of the waveguide optical isolator without using Faraday effect will have significant impact to optical science and engineering, and to variety of military and commercial applications using photonic lightwave circuits for computing and communications.