Transmission/reflection filter for double sideband IR waveguide modulators
Abstract
For 10.6-micron laser radar systems which utilize a double sideband modulator as a local oscillator frequency shifter in the receiver section, it is necessary to remove the carrier signal and the unwanted sideband signal prior to routing the frequency-shifted radiation to the heterodyne detector. This paper discusses the use of a reflective-mode Fabry-Perot etalon in conjunction with an optical duplexer to remove the carrier signal. The duplexer is a thin-film polarizer together with a quarter-wave plate. Since the sideband-to-carrier power out of the modulator is typically a few percent, it is imperative that mirror surface error and finite coating reflectivity be properly accounted for in order to achieve an adequate filter design. A rejection ratio corresponding to 20 dB between the laser carrier and the sideband was measured for the present design.
- Publication:
-
Laser radar III
- Pub Date:
- June 1989
- DOI:
- 10.1117/12.960224
- Bibcode:
- 1989SPIE..999...56B
- Keywords:
-
- Double Sideband Transmission;
- Frequency Shift;
- Light Modulation;
- Optical Filters;
- Optical Radar;
- Fabry-Perot Interferometers;
- Infrared Filters;
- Optical Heterodyning;
- Optical Waveguides;
- Transfer Functions;
- Electronics and Electrical Engineering