Double-metal waveguide terahertz difference-frequency generation quantum cascade lasers with surface grating outcouplers

Abstract

We report terahertz quantum cascade laser (QCL) sources based on intra-cavity difference-frequency generation processed into double-metal waveguides with surface-grating outcouplers. This configuration enables high confinement of the terahertz mode in the device active region and efficient surface extraction of terahertz radiation along the entire length of the waveguide. The devices operate at room temperature at 1.9 THz and produce over 110 lW of peak power output with the mid-infrared-to-terahertz conversion of 150 lW/W 2. The results represent at least a factor of 2 improvement in the performance compared to the best Cherenkov difference-frequency generation QCL devices operating below 2 THz.

Roadmap of Terahertz Imaging 2021

“…Finally, it is worth noting the spectral tunability of these devices. As it was already mentioned, room temperature THz difference-frequency generation scheme QCLs operates slightly below 2 THz [53], while conventional THz QCLs design at the highest reported temperature-250 K at 4 THz [49]. The issue to shift to lower frequencies the red wing in emission still remains unsolved and challenging; thus, probable alternative to cover subTHz frequencies can be electronic devices, like Schottky barrier-based frequency multipliers [56,57], CMOS technology-based oscillators [58][59][60][61][62], heterojunction bipolar transistors [63][64][65], or semiconductor superlattices [66][67][68].…”

“…The peak powers, for instance, at 3.6 THz can be scaled up to 1.4 mW using the distributed-feedback waveguide withČerenkov phase-matching scheme [52]. THz QCLs processed into double-metal waveguides with surface-grating outcouplers allow to shift the red side of the emission below 2 THz and reach rather effective mid-infrared-to-terahertz conversion with peak power output over 110 µW at 1.9 THz [53].…”

“…The considered devices are plotted with respect to the emitting power in sources section (left) and the noise equivalent power (NEP) in sensors one (right). Taken data references: Schottky diodes multipliers[87,439] CMOS-based and SiGe-based electronic emitters[62]; CMOS and SiGe detectors parameters[159], parameters of Schottky detectors [440], microbolometers values[167], conventional THz QCL[41]; frequency-difference THz QCLs (FD THz QCLs) parameters-from publications by M. Razeghi[51,52] and M. Belkin's[53] groups. Optoelectronic THz systems (denoted as red solid lines) are attributed for the emitters section only.…”

Lens-coupled sub-THz and THz quantum cascade laser sources based on intra-cavity frequency mixing

“…In order to achieve higher output power in the THz frequency, a more efficient THz extraction scheme is required since lower frequency THz generation is inherently difficult. Actually, recent studies have shown that the THz output of nonlinear THz-QCLs can be significantly improved by employing efficient THz out couplers [39,40].…”

Room temperature, single-mode 1.0 THz semiconductor source based on long-wavelength infrared quantum-cascade laser

“…In addition, the temperature dependence of the device was investigated in a temperature range from 210 to 293 K, and stable single mode operation was achieved. In the near future, further improvements in performance may be achieved via the adoption of further efficient THz extraction schemes, 30,31) with the aim of producing THz sub-mW output power at room temperature. These high-performance THz NL-QCLs will open up new opportunities for many THz applications.…”