Extended cavity quantum cascade laser with cavity resonator integrated grating filter

Area of Science:

• Physics
• Quantum Optics
• Laser Technology

Background:

• Quantum cascade lasers (QCLs) are crucial semiconductor lasers.
• Achieving stable, single-mode emission and wide tunability in QCLs remains a challenge.

Purpose of the Study:

• To report on a novel extended cavity quantum cascade laser design.
• To demonstrate the functionality of a cavity resonator integrated grating filter (CRIGF) as a combined end-reflector and spectral selector.

Main Methods:

• Fabrication of an extended cavity quantum cascade laser incorporating a CRIGF.
• Characterization of the laser's emission properties, including mode stability, spectral output, and threshold current.
• Investigation of frequency tuning capabilities by altering the CRIGF periodicity.

Main Results:

• Stable, mode-hop-free, single-mode emission was achieved around 2150 cm^-1.
• The laser exhibited stable operation over a broad injection current range (>50 mA) with a low threshold current (~290 mA).
• Digital frequency tuning exceeding 65 cm^-1 was demonstrated by adjusting the CRIGF's grating periodicity.

Conclusions:

• The CRIGF is an effective component for achieving single-mode operation and spectral selectivity in extended cavity QCLs.
• The demonstrated digital frequency tuning offers a new method for precise wavelength control in QCLs.
• This laser design shows significant potential for applications requiring stable, tunable single-mode mid-infrared emission.