Optical sideband generation up to room temperature with mid-infrared quantum cascade lasers

Area of Science:

• Quantum optics
• Semiconductor lasers
• Nonlinear optics

Background:

• Quantum cascade lasers (QCLs) are semiconductor devices emitting in the mid-infrared (MIR) spectrum.
• Nonlinear optical effects in QCLs are crucial for frequency conversion and advanced photonic applications.
• Generating MIR light from NIR sources offers new possibilities for spectroscopy and sensing.

Purpose of the Study:

• To demonstrate mid-infrared (MIR) sideband generation using a near-infrared (NIR) optical carrier within a quantum cascade laser (QCL).
• To enhance the nonlinear susceptibility of the QCL through resonant injection of an NIR beam.
• To investigate the temperature dependence of the generated sideband for practical applications.

Main Methods:

• Utilizing a GaAs-based MIR QCL with an aluminum-reinforced waveguide.
• Injecting an external NIR beam resonant with the QCL's interband transitions.
• Aligning NIR and MIR modes within the QCL's active region to maximize nonlinear interaction.

Main Results:

• Achieved efficient frequency mixing and sideband generation by enhancing nonlinear susceptibility.
• Observed a resonant behavior of the difference sideband (E(NIR) - E(QCL)) with respect to the NIR pump wavelength.
• Obtained a maximum second-order nonlinear susceptibility (χ((2))) of approximately 1 nm/V.
• Demonstrated that sideband intensity is largely independent of QCL operating temperature.

Conclusions:

• Successful demonstration of MIR sideband generation on a NIR optical carrier within a QCL.
• The resonant injection technique significantly enhances nonlinear optical processes in QCLs.
• The room-temperature operation capability makes this method highly practical for various applications.