High Power RF Photodiodes
Abstract
For both analog and digital optical transmission systems, high-power photodetectors are becoming increasingly important. Analog communications systems for antenna remoting, phased array antennas, and photonic analog-to-digital converter systems require high fi delity with large dynamic range. To build optical links for these systems means that the optical to electrical converters (i.e., the photodetectors) must be able to operate at high photocurrent levels to minimize noise fi gure while providing the required dynamic range. In the digital domain, fi ber optic systems are rapidly being developed for next-generation ethernet and secure communication systems. One approach to producing high-performance systems is to increase the optical power incident on the widebandwidth photodetectors so that the photogenerated RF output power (voltage swing) can directly drive the digital logic circuits. Th is approach eliminates the complications and expense of postdetection, widebandwidth, fl at-phase RF amplifi ers but requires higher performance photodiodes. Two factors limit a photodiode?s output power: space-charge screening of the intrinsic region electric fi eld, and thermal considerations.1 Space charge screening arises from the spatial distribution of photogenerated carriers as they transit the photodetectors depletion region. Th ese charge carriers create an electric fi eld that opposes the external-bias electric fi eld. At sufficiently high optical power levels, the space-charge-induced electric field is strong enough to collapse the bias electric field, resulting in loss of the RF signal. Thermal limitations are the result of the geometry and thermal conductivity of the photodiode layers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2005
- Accession Number
- ADA525697
Entities
People
- D. A. Tulchinsky
- K. J. Williams
Organizations
- United States Naval Research Laboratory