Injection-seeded pulsed alexandrite laser for differential absorption lidar application.

Area of Science:

• Laser Physics and Spectroscopy
• Atmospheric Remote Sensing
• Optical Engineering

Background:

• Differential absorption lidar (DIAL) requires highly frequency-stabilized lasers for accurate atmospheric measurements.
• Previous laser systems faced limitations in meeting the stringent frequency stability demands for simultaneous humidity, pressure, and temperature profiling.
• The need for a robust laser source capable of locking to specific atmospheric absorption lines is critical for advanced remote sensing applications.

Purpose of the Study:

• To develop and characterize a Q-switched alexandrite laser system injection-seeded by a continuous-wave (cw) single-mode titanium-sapphire laser.
• To demonstrate the system's capability to achieve the frequency stabilization necessary for differential absorption lidar (DIAL) measurements.
• To validate the laser system's performance for simultaneous, high-precision atmospheric profiling of humidity, pressure, and temperature.

Main Methods:

• Injection seeding of a Q-switched alexandrite laser with a cw single-mode titanium-sapphire master oscillator.
• Utilizing a servoloop with derivative spectroscopy to lock the titanium-sapphire laser emission to a targeted atmospheric absorption line.
• Characterization of the alexandrite laser's pulse energy, duration, spectral linewidth, and long-term spectral position stability.

Main Results:

• The cw titanium-sapphire laser's spectral position was stabilized within ±3.5 × 10⁻⁴ cm⁻¹ (10 MHz) of the absorption line peak over 1 hour.
• The Q-switched alexandrite laser produced pulses with 30 mJ energy and 500 ns duration, featuring a spectral linewidth of approximately 3.3 × 10⁻³ cm⁻¹ (100 MHz).
• The centroid of the alexandrite laser's emitted spectrum exhibited a standard deviation of 6 × 10⁻⁴ cm⁻¹ (18 MHz) and remained within ±1.3 × 10⁻³ cm⁻¹ (40 MHz) of the absorption line peak over 1 hour.

Conclusions:

• The developed injection-seeded Q-switched alexandrite laser system achieves the required frequency stabilization for differential absorption lidar (DIAL) applications.
• The system demonstrates excellent long-term spectral stability, making it suitable for precise atmospheric measurements of key environmental parameters.
• This laser technology advances the capabilities of remote sensing for meteorological and climate monitoring.