Waveguide integration of a >4.7-THz quantum-cascade laser (original) (raw)

THz quantum cascade lasers with wafer bonded active regions

Optics Express, 2012

We demonstrate terahertz quantum-cascade lasers with a 30 µm thick double-metal waveguide, which are fabricated by stacking two 15 µm thick active regions using a wafer bonding process. By increasing the active region thickness more optical power is generated inside the cavity, the waveguide losses are decreased and the far-field is improved due to a larger facet aperture. In this way the output power is increased by significantly more than a factor of 2 without reducing the maximum operating temperature and without increasing the threshold current.

High performance THz quantum cascade laser with different optical waveguide configurations

Quantum Sensing and Nanophotonic Devices IV, 2007

We report on the fabrication of THz quantum cascade lasers (QCLs) based on different optical waveguide configurations and compare the thermal properties of THz devices fabricated with metal-metal optical waveguides based on Au/Au or In/Au wafer bonding. In particular, we show how the careful choice of the metal sequence used for the reactive bonding may lead to a considerable improvement of the device thermal performance. This information was obtained from the analysis of microprobe band-to-band photoluminescence spectra measured on devices operating in continuous wave (cw). The experimental normalized thermal resistances (R L * ), show that the use of Au/Au wafer bonding optimizes the heat dissipation. An extensive comparison with a set of surface-plasmon based THz QCLs, demonstrate that the use of metal-metal wafer bonding can allow cw operation at progressively higher temperatures. Finally, we present the experimental results obtained on a bound-to-continuum QCLs (2.84 THz) emitting 77 mW peak power at 4K, fabricated from an MBE wafers acquired by a commercial provider.

Photonic bandstructure engineering of THz quantum-cascade lasers

Applied Physics Letters, 2011

We present the design and realization of active photonic crystal (PhC) terahertz (THz) lasers operating in higher photonic bands. The structure consists of an array of isolated pillars fabricated from a THz quantum-cascade laser and embedded in a double-metal waveguide. The PhC geometry is adopted to achieve lasing in the first and second photonic bands. Thereby, the optical mode is pushed from the active pillars into the surrounding. The sensitivity of local sensors can be increased by almost one order of magnitude compared to designs operating in the lowest photonic band.

3.5 THz quantum-cascade laser emission from dual diagonal feedhorns

International Journal of Microwave and Wireless Technologies, 2019

Antenna-pattern measurements obtained from a double-metal supra-terahertz-frequency (supra-THz) quantum cascade laser (QCL) are presented. The QCL is mounted within a mechanically micro-machined waveguide cavity containing dual diagonal feedhorns. Operating in continuous-wave mode at 3.5 THz, and at an ambient temperature of ~60 K, QCL emission has been directed via the feedhorns to a supra-THz detector mounted on a multi-axis linear scanner. Comparison of simulated and measured far-field antenna patterns shows an excellent degree of correlation between beamwidth (full-width-half-maximum) and sidelobe content and a very substantial improvement when compared with unmounted devices. Additionally, a single output has been used to successfully illuminate and demonstrate an optical breadboard arrangement associated with a future supra-THz Earth observation space-borne payload. Our novel device has therefore provided a valuable demonstration of the effectiveness of supra-THz diagonal feed...

Physics and technology of Terahertz quantum cascade lasers

Advances in Physics: X

Even though already in the seventies, right after the invention of the quantum cascade laser (QCL) concept, it was argued that this device could be operated in the THz (far-infrared) range of the electromagnetic spectrum, it was only in 2002 that the first working THz QCL was demonstrated. Soon afterwards, the progress was very rapid; in the space of 2-3 years, operating temperatures were raised, single-mode DFB devices were produced, applications as local oscillators in heterodyne transceivers were implemented, frequency coverage was extended to the whole 1-5 THz region. In the last few years, technological advancement has continued to improve performances: the maximum operating temperature has now reached about 250 K and about 1 W peak output power has been demonstrated. Several beam engineering techniques have been implemented, with the scope of enhancing spectral purity, improving beam quality and achieving vertical emission. In parallel, various approaches have been devised that allow frequency tunability of the emitted light, with the most efficient schemes achieving a tuning range of about 10% of the central emission frequency. Even the generation of frequency combs directly from THz QCLs has been obtained, by employing dispersion compensated waveguides and an intrinsic material non-linearity. This manuscript reviews the physics underlying the operation of THz QCLs, the technology developed to advance laser performances, and highlights the latest most promising progresses in this fascinating area of opto-electronics.

Thermal properties of THz quantum cascade lasers based on different optical waveguide configurations

Applied Physics Letters, 2006

We compare the thermal properties of THz quantum cascade lasers ͑QCLs͒ fabricated with metal-metal optical waveguides based on Au/ Au or In/ Au wafer bonding. This information was obtained from the analysis of microprobe band-to-band photoluminescence spectra measured on devices operating in continuous wave ͑cw͒. The experimental normalized thermal resistances ͑R L * ͒, show that the use of Au/ Au wafer bonding optimizes the heat dissipation. Comparison with surface-plasmon based THz QCLs, demonstrates that the use of metal-metal wafer bonding can allow cw operation at progressively higher temperatures.

Active region designs and mounting schemes of THz quantum-cascade laser

Materials Today: Proceedings, 2020

THz quantum cascade-lasers (QCLs) are the best sources for generating efficient THz radiations, which are fabricated by the semiconductor heterostructure. The layers of GaAs quantum wells and AlGaAs barriers are formed with different thicknesses to design the heterostructure. In the present paper, we review different designs of THz QCLs active regions which are followed by a comparison between epitaxy-up and down processing techniques of the fabricated wafers. The present review should be helpful for the scientific community working in the scientific area of the THz radiation field and, in particular, for the researchers interested to switch from the epitaxy-up processing of the wafers to epitaxy-down mounting to make possible an increase of the operating temperature of the THz QCLs in the continuous wave operation mode.

High power terahertz quantum cascade lasers with symmetric wafer bonded active regions

Applied Physics Letters, 2013

We increased the active region/waveguide thickness of terahertz quantum cascade lasers with semi-insulating surface plasmon waveguides by stacking two symmetric active regions on top of each other, via a direct wafer bonding technique. In this way, we enhance the generated optical power in the cavity and the mode confinement. We achieved 470 mW peak output power in pulsed mode from a single facet at a heat sink temperature of 5 K and a maximum operation temperature of 122 K. Furthermore, the devices show a broad band emission spectrum over a range of 420 GHz, centered around 3.9 THz. V