Broad-gain (Δλ/λ0</~0.4), temperature-insensitive (T<0~510K) quantum cascade lasers

Area of Science:

• Quantum engineering
• Semiconductor lasers
• Mid-infrared optoelectronics

Background:

• Quantum cascade lasers (QCLs) are semiconductor devices emitting light via intersubband transitions.
• Achieving broad gain bandwidth and stable room-temperature operation are key challenges in QCL development.
• Previous designs often struggle with temperature sensitivity and limited spectral width.

Purpose of the Study:

• To report broad-gain operation in quantum cascade lasers (QCLs) at ~8.7 μm.
• To investigate the temperature and voltage insensitivity of electroluminescence spectra.
• To demonstrate stable room-temperature continuous wave (CW) operation.

Main Methods:

• Utilizing a dual-upper-state to multiple-lower-state transition design for QCLs.
• Characterizing electroluminescence spectra and laser performance over varying temperatures and voltages.
• Fabricating buried heterostructure devices for CW operation.

Main Results:

• Achieved ~500 cm(-1) wide electroluminescence spectra, insensitive to voltage and temperature above room temperature.
• Demonstrated an extremely weak temperature dependence of laser performance with a T0-value of 510 K.
• Attained a room-temperature threshold current density of 2.6 kA/cm2.
• Successfully achieved room-temperature CW operation despite broad gain spectra.

Conclusions:

• The novel QCL design enables exceptionally broad and stable gain operation.
• The temperature-insensitivity of the electroluminescence spectra directly translates to robust laser performance.
• These findings pave the way for high-performance, stable mid-infrared QCLs for various applications.