Continuous-wave single-mode quantum cascade laser at 5.1 THz based on graded sampled grating design

This is the authors' abstract. We don't add key points for this paper.

We report on the terahertz (THz) quantum cascade lasers in continuous-wave (CW) operation with an emitting frequency above 5 THz. Excellent performance with a smaller leakage current and higher population inversion efficiency is obtained by one-well bridged bound-to-continuum hybrid quantum design at 5 THz. By designing and fabricating a graded metallic sampled distributed feedback grating in the waveguide, the first single-mode THz quantum cascade laser at 5.13 THz in CW operation mode is achieved. The maximum single-mode optical power of ∼ 48 mW is achieved at 15 K with a side-mode suppression ratio above 24 dB. This will draw great interest in the spectroscopy applications above the 5 THz range for THz quantum cascade lasers.