Single-frequency mid-infrared optical parametric oscillator source for coherent laser radar.

Area of Science:

• Optics and Photonics
• Laser Physics
• Infrared Technology

Background:

• Coherent mid-infrared (mid-IR) light sources are crucial for high-resolution spectroscopy and sensing.
• Existing sources often struggle with stability and coherence, limiting their application range.
• Optical parametric oscillators (OPOs) offer tunability but require careful design for high coherence.

Purpose of the Study:

• To design and characterize a highly coherent single-frequency mid-IR source.
• To evaluate the noise properties (frequency and amplitude) of the developed source.
• To demonstrate the source's utility in coherent laser radar (lidar) applications.

Main Methods:

• Utilized a single-frequency optical parametric oscillator (OPO) design.
• Measured detailed frequency and amplitude noise spectra over a defined bandwidth.
• Applied the source to measure micro-Doppler spectra from vibrating targets for lidar demonstration.

Main Results:

• Achieved a highly coherent mid-IR source operating at 3.57 µm.
• Quantified low root-mean-square (rms) intensity noise of 0.03% (1.2–1000 Hz).
• Observed a low rms frequency drift of 8 kHz within a 1 ms interval.
• Successfully demonstrated coherent laser radar capabilities by measuring micro-Doppler signatures.

Conclusions:

• The developed single-frequency OPO provides a stable and coherent mid-IR light source.
• The characterized low noise performance is suitable for demanding applications.
• The demonstrated lidar capability highlights the source's potential for target velocity and vibration analysis.