Abstract

The internal quantum efficiency for conversion of light to photo-electrons in silicon can be near unity.^1,2 The quantum efficiency of silicon diode detectors is thus primarily limited by reflection at the high refractive index detector surface. Well designed devices with suitable antireflection coatings can achieve efficiencies approaching 90% over a reasonable bandwidth. The major source of loss remains reflection from the diode front surface. In this design we use two diodes connected in parallel and positioned so as to capture the reflected beams (Fig. 1). The light then has three chances of being transmitted through the semiconductor surface and reflection losses can fall to 0.1%. Small area (2.5-mm diameter) pin diodes are used to give low dark current and moderate bandwidth for quantum optics application.³

© 1994 IEEE