Terahertz quantum cascade lasers operating up to ∼ 200 K with optimized oscillator strength and improved injection tunneling

Abstract

630-631 (2008). 27. For the density matrix calculations, the electron temperature was chosen 90 K higher than lattice. Pure dephasing time constants of tunneling τ * = 0.35 ps, and of optical intersubband transition τ * ul = 1.1 ps were used. Intrawell intersubband scatterings by LO phonon, e-impurities and interface roughness were considered. The momentum dependance of scattering is averaged over the assumed Maxwell-Boltzmann distribution of carriers in the subbands. 28.

Broadly tunable terahertz generation in mid-infrared quantum cascade lasers

“…THz quantum cascade lasers (QCLs) are a promising technology for the 1-5 THz spectral range; however, they still require cryogenic cooling to operate [3][4][5][6][7][8] and their tuning range is limited 9 . An alternative approach to generate THz radiation in QCLs are sources based on intracavity difference-frequency generation (DFG) in dual-wavelength mid-infrared (l ¼ 3-15 mm) QCLs designed to have giant optical non-linearity in the active region [10][11][12][13][14] .…”

Distributed feedback terahertz frequency quantum cascade lasers with dual periodicity gratings

“…Terahertz (THz) frequency quantum cascade lasers (QCLs) have undergone rapid development in performance since their first demonstration, 1 finding potential application in a number of fields including astronomy, security screening, biomedicine, and cultural heritage, inter alia. 2,3 Operating across the 1.2-5 THz range, QCLs can provide high peak output powers (1 W), 4 a high spectral purity, 5,6 frequency, phase and amplitude stability, 7-9 and an ultrabroadband gain spanning an octave in frequency 10,11 at temperatures 199 K. 12 Most of the mentioned applications require sources with a low divergent spatial profile in the far-field as well as a fine spectral control of the emitted radiation. However, the double-metal waveguides conventionally employed to maximize the THz QCL operating temperature 12 suffer from a lack of efficient extraction and a poor collimation of the output radiation, 13 owing to the sub-wavelength dimensions of the resonant cavities.…”

“…12 We engineered our gratings by employing the following refractive index modulation: nðzÞ ¼ n 1 þ ðn 2 À n 1 Þf ðz; k f b ; k e ðaÞÞ; where n 1 and…”

“…12 We engineered our gratings by employing the following refractive index modulation: nðzÞ ¼ n 1 þ ðn 2 À n 1 Þf ðz; n 2 are the minimum and maximum values of the refractive index, respectively, and the function f, which varies between 0 and 1, contains periodic functions oscillating at the feedback wavevector k fb and the extraction wavevector k e (a). The latter is, in turn, a function of the desired beam steering angle a.…”

Broadly tunable monolithic room-temperature terahertz quantum cascade laser sources

“…Besides p-doped germanium lasers that require strong magnetic fields and low-temperature cryogenic cooling for operation 3,4 , quantum cascade lasers (QCLs) are the only electrically pumped semiconductor sources that demonstrated operation in this entire spectral range. Narrowband THz emission has been demonstrated in both THz QCLs [5][6][7][8] and THz sources based on intracavity difference-frequency generation (DFG) in midinfrared QCLs (THz DFG-QCLs) 9,10 . The latter is the only technology that results in electrically pumped monolithic semiconductor sources operable at room temperature in the entire 1-5 THz range [10][11][12][13] .…”