Optical Detector for Improved Signal Amplification

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Perspective view of an embodiment of a sensor including a plurality of vertical-cavity surface-emitting lasers (VCSELs)
Aravinda Kar, Ph.D.
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Raju Nagaiah
Research Associate 407.882.0593
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Optical signal amplification

US Patent 9,601,902

A new method of signal amplification has been developed by a UCF researcher to offer improved signal amplification utilizing optical gain rather than traditional gain in the detector. The novel approach to optical signal amplification does not require active electronic elements, avoiding problems such as thermal run away that can cause a detector to become inoperative in harsh environments. Additionally, the technology includes embodiments requiring no power, allowing the sensor to operate for an indefinite period of time. Applications of this sensor include detection of neutrons, control and monitoring of nuclear reactors and fuel processing, characterization of nuclear fuel rods, and detection of concealed fissile and radioactive materials.

Technical Details

This method of optical signal amplification detects incident photons through absorption, increasing the carrier concentration, thereby modulating the index of refraction and the reflectivity of the semiconductor in a way that can be monitored externally. By operating without the need for other active electronic elements on the photodetector, the device eliminates the concern over active elements’ risk of operational problems compared to passive elements. It enhances detection of weak electromagnetic (EM) signals by amplifying the signal optically instead of traditional electrical amplification. Operating on the principle of photoexcitation, it transfers electrons from the dopant energy level to the conduction band or from the valance band to the dopant energy level, for n- and p-type dopants, respectively. When paired with a laser beam on the semiconductor surface from a diode laser or other source, the device changes the electron density in the conduction of valence bands, which then changes both the refractive index and the semiconductor's reflectivity, resulting in an amplified signal output.


  • Optical signal amplification
  • Improved sensitivity


  • Nuclear reactors and fuel processing
  • Characterization of nuclear fuel rods
  • Detection of concealed fissile and radioactive materials
  • Medical and military imaging systems
  • Communication devices