Synchronous upconversion of quantum cascade lasers in AgGaS₂.

Area of Science:

• Optics and Photonics
• Laser Physics
• Nonlinear Optics

Background:

• Quantum cascade lasers (QCLs) are crucial for mid-infrared (mid-IR) spectroscopy.
• Synchronous upconversion is a valuable technique for detecting weak mid-IR signals.

Purpose of the Study:

• To investigate the synchronous upconversion of a pulsed, tunable QCL in the 5.4–10.2 µm range.
• To evaluate the upconversion quantum efficiency and noise properties of the system.
• To assess the suitability of this technique for spectral analysis of highly absorbing samples.

Main Methods:

• Utilized a pulsed, tunable quantum cascade laser (QCL) operating in the 5.4–10.2 µm range.
• Employed a 30 kHz, Q-switched, 1064 nm laser for synchronous pumping.
• Used a 10 mm-long AgGaS₂ crystal for the upconversion process.
• Investigated pulse-to-pulse energy stability and timing jitter.

Main Results:

• Achieved an upconversion quantum efficiency of 16% due to good temporal overlap between the QCL and the pump laser.
• Demonstrated upconverted pulse-to-pulse stability of approximately 1.75% for QCL pulses in the 30–70 ns range.
• The system exhibits broad tunability and high signal-to-noise ratio.

Conclusions:

• The demonstrated synchronous upconversion system offers efficient and stable mid-IR signal generation.
• The combination of tunability and high signal quality makes it ideal for spectral analysis of challenging, highly absorbing samples.
• This technique advances mid-IR spectroscopic capabilities.