Application of upconversion detection to pulsed C0(2) lidar.

Area of Science:

• Optics and Photonics
• Atmospheric Science
• Laser Technology

Background:

• Pulsed carbon dioxide (CO(2)) lidar systems are crucial for atmospheric monitoring.
• Traditional direct detection diodes in lidar systems face limitations in sensitivity and background noise.
• Heterodyne detection methods in lidar are susceptible to speckle noise.

Purpose of the Study:

• To investigate the application of an upconversion detector for pulsed CO(2) lidar.
• To evaluate methods for rejecting thermal background radiation in upconversion detectors.
• To assess the sensitivity improvements offered by upconversion detectors compared to existing technologies.

Main Methods:

• Utilizing a nonlinear infrared (IR) crystal to convert 10-microm lidar radiation to the visible spectrum.
• Employing a narrowband filter for the up-converted signal or a cold filter front end for background radiation rejection.
• Detection of the up-converted visible signal using a photomultiplier tube.

Main Results:

• Upconversion detectors offer improved sensitivity, estimated to be 2 orders of magnitude better than direct detection diodes when using a narrowband visible filter.
• A cold filter front end can enhance upconversion detection performance close to the signal-shot noise limit.
• Upconversion detectors are not affected by speckle noise, unlike pulsed heterodyne detectors.

Conclusions:

• Upconversion detectors represent a significant advancement for pulsed CO(2) lidar systems.
• These detectors provide enhanced sensitivity and noise reduction capabilities.
• The technology offers a promising alternative for lidar applications requiring high performance and reliability.