Antenna-coupled polycrystalline silicon air-bridge thermal detector for mid-infrared radiation

Polycrystalline silicon (polysilicon) airbridges coupled to log-periodic and bow-tie planar antennas have been fabricated for mid-infrared radiation detection. The detectors in thermocouple and bolometer modes exhibit a higher electrical responsivity than previously reported metal based antenna-coupled thermal detectors. Measurements made at 10.2 μm wavelength indicate that the linearly polarized antennas have an on-axis cross-polarization ratio of about −4.5 dB and the pattern in the free-space side has a directivity of approximately 5–9 dB. The coupling efficiency is about 15%. Frequency responses for modulated optical signals agree with thermal transport models.