Micro-integrated optical isolators for visible wavelengths for space application

Optical isolators are essential components for highly demanding applications, enabling the use of single frequency lasers. With their capability to design micro-integrated laser systems, the availability of single frequency laser diodes in the visible wavelength region, led to a demand for suitable micro-integrated optical isolators for visible wavelength, e.g. for micro-integrated ECDL laser and MOPA modules. Unlike for the near infrared, micro-integrated optical isolators for the wavelength region between 680 and 1000 nm are not available so far, limiting or even hindering use of micro-integrated laser sources for space mission with photonic, spectroscopic and quantum-technological mission payloads. To overcome this issue, a micro-optical isolator for space application for visible wavelengths has been developed. The design specifically features a low stress crystal mount with a symmetric heat removal essential for good isolation, the avoidance of beam deflection, and a large allowable temperature range. Moreover, the high homogeneity of the magnetic field enables at least 40dB single stage isolation, limited by polarizers and crystal properties. Structural and thermo-elastic analyses have been performed to ensure a space qualifiable design. The properties of the CdMnTe crystals, such as Verdet constant, transmission, optical loss, and polarization, around the generic wavelength of 780 nm have been measured. At 1064 and 780 nm an optical and thermal characterization of the CdMnTe crystals at high power (up to 1.4 W) has been carried out. The isolator design as well as the measurement results will be presented.