Operation of terahertz quantum-cascade lasers at 164 K in pulsed mode and at 117 K in continuous-wave mode

Abstract

We combine photonic crystal and quantum cascade band engineering to create an in-plane laser at terahertz frequency. We demonstrate that such photonic crystal lasers strongly improve the performances of terahertz quantum cascade material in terms of threshold current, waveguide losses, emission mode selection, tunability and maximum operation temperature. The laser operates in a slow-light regime between the M saddle point and K band-edge in reciprocal lattice. Coarse frequency control of half of a terahertz is achieved by lithographically tuning the photonic crystal period. Thanks to field assisted gain shift and cavity pulling, the single mode emission is continuously tuned over 30 GHz.

Beam patterns of terahertz quantum cascade lasers with subwavelength cavity dimensions

“…2͒ and 1.9 THz ͑Ref. 3͒ ͑ Ϸ 160 m͒ and for temperatures up to 117 K. 4 These sources are very promising as local oscillators for heterodyne detection 5,6 and for general terahertz imaging applications. 7 The terahertz QCLs which have achieved the highest temperature performance are based on the so-called "metal-metal waveguides" of subwavelength dimensions.…”

Leaky and bound modes in terahertz metasurfaces made of transmission-line metamaterials

“…Metal-metal waveguides are fabricated by sandwiching the semiconductor intersubband gain medium between two metal cladding layers using wafer bonding. 3,4 The resulting ridge waveguides are similar in form to parallel plate or microstrip transmission lines (TLs), which are known to support a quasi-TEM mode without a low frequency cutoff. A major challenge for THz QC-laser design is the efficient out-coupling of laser power into a directive beam from a cavity with subwavelength dimensions.…”

Active terahertz quantum-cascade composite right/left-handed metamaterial

“…7,8 Under this condition, a single narrow beam with FWHM $10 is observed at about À63 from broadside direction. The measured frequency and angle of the directive beam are well within the left-handed (backward wave) bandwidth of the CRLH antenna and consistent with the calculated dispersion relation.…”

“…[3][4][5] The most suitable platform for active THz CRLH metamaterial implementation is THz QClaser metal-metal waveguide, 6 which is similar in form to microstrip transmission line. Because it provides good modal confinement and low loss in a structure with sub-wavelength transverse dimensions, metal-metal waveguide offers the best high-temperature laser operation ($200 K pulsed, 7 117 K cw 8 ). The application of CRLH metamaterial concepts can offer terahertz QC-lasers new functionality by leveraging microwave antenna concepts, such as the use of leakywave antennas for beam steering.…”

“…The active material was a four-well resonant-phonon depopulation design similar to that described in Ref. 8, except modified to operate in the range of 2.4-2.9 THz. The GaAs/Al 0.15 Ga 0.85 As quantum well heterostructure was grown by molecular beam epitaxy with 86 cascaded modules to form a 5 lm thick active region.…”