Microsecond fiber laser pumped, single-frequency optical parametric oscillator for trace gas detection.

Area of Science:

• Laser physics
• Nonlinear optics
• Spectroscopy

Background:

• Optical parametric oscillators (OPOs) are crucial for generating tunable laser light.
• Doubly resonant OPOs offer lower thresholds but typically suffer from multimode operation.
• Microsecond pulse durations are relevant for certain sensing applications.

Purpose of the Study:

• To report the first microsecond doubly resonant optical parametric oscillator (OPO).
• To demonstrate single longitudinal mode operation and low threshold in a nested cavity OPO.
• To showcase its potential for trace gas sensing.

Main Methods:

• Utilized a nested cavity optical parametric oscillator (OPO) architecture.
• Employed a master oscillator-power amplifier fiber laser as the pump source.
• Demonstrated tunable output in the 3.3-3.5 μm range.
• Measured adjustable pulse repetition rates from 40 to 100 kHz.
• Utilized photoacoustic spectroscopy for trace gas detection.

Main Results:

• Achieved single longitudinal mode operation with a low oscillation threshold (few microjoules).
• Generated widely tunable idler radiation in the 3.3-3.5 μm range.
• Obtained high duty cycle (~10^-2) and mean output power (up to 25 mW).
• Successfully demonstrated photoacoustic detection of atmospheric methane.

Conclusions:

• The developed microsecond doubly resonant OPO is a versatile and efficient tunable light source.
• The nested cavity design enables single mode operation and low threshold.
• The system shows significant potential for sensitive trace gas sensing applications.