1.3 μLD Module with Optical Isolator Using YIG Crystals by the Floating Zone Method

This paper reports on fabrication of an LD (laser diode) module with an optical isolator using YIG crystals in which the optical parts are fixed by soldering and YAG laser welding. The LD to single-mode fiber coupling efficiency was less than -4.6 dB, and the isolator insertion loss was 0.1 dB. Output variation in the 0 to 50°C temperature range was as low as 0.4 dB and after heat treatment, coupling loss variation was less than 0.25 dB, a very stable value. This seems to be due to the fact that the optical fiber and the lens were fixed by the metal fixing methods. Laser output noise induced by the reflected laser beam from the far end of the single-mode fiber is reduced by the optical isolator. Using YIG made by the FZ method and fabricating the module using the metal fixing methods realizes high isolation ratio and high reliability.