Continuous wave vertical emission from terahertz microcavity lasers with a dual injection scheme

Area of Science:

• Optics and Photonics
• Quantum Electronics
• Terahertz Science

Background:

• Terahertz (THz) frequencies are crucial for various applications.
• Compact THz sources, like quantum cascade lasers (QCLs), require improved continuous wave (CW) efficiency for widespread use.
• Current QCL designs face limitations in power output and operational efficiency.

Purpose of the Study:

• To demonstrate a highly efficient microcavity laser for THz emission.
• To enhance the CW operation efficiency of THz quantum cascade lasers (QCLs).
• To explore a novel laser design for improved THz generation and out-coupling.

Main Methods:

• Fabrication of a subwavelength microcavity laser using evanescently coupled whispering gallery microdisk resonators.
• Implementation of a dual injection scheme for the laser cavity.
• Utilizing a suspended gold bridge to enhance vertical out-coupling efficiency.
• Characterization of laser performance, including threshold current, slope efficiency, and emitted power.

Main Results:

• Achieved single-mode CW vertical emission at 3.3 THz at 10 K.
• Obtained a low threshold current of 6.4 mA and a high slope efficiency of 145 mW/A.
• Measured up to 320 μW emitted power in quasi-CW mode.
• Demonstrated tunable emission directionality by varying pumping strength.
• Significantly enhanced vertical out-coupling efficiency via the gold bridge.

Conclusions:

• The proposed microcavity laser design offers high brightness and low power consumption for CW THz QCLs.
• This design enables efficient THz generation and out-coupling, suitable for massive parallelization.
• The advancements contribute to the realization of high-performance, practical THz QCL systems.