Abstract

Widely-tunable room-temperature, electrically-pumped semiconductor sources in 1-5 THz spectral range are highly desired for spectroscopy and imaging application. THz sources based on intra-cavity difference-frequency generation (DFG) in dual wavelength mid-infrared quantum cascade lasers (QCLs) [1-3] with Cherenkov phase-matching [4] are currently the only monolithic room-temperature semiconductor devices that can operate and provide widely-tunable output in this entire spectral range and beyond [5-7]. We will present our latest results on the development of broadly-tunable THz systems based on this technology. Both monolithic and external cavity configurations are explored. In our external-cavity systems we fix one mid-IR pump frequency by a distributed feedback grating etched into the QCL waveguide and tune the second mid-IR pump frequency with an external grating in a Littrow-type configuration. Due to strong spatial hole burning in QCLs, gain competition between the two mid-infrared pumps is reduced and, with careful balancing of the feedback for the mid-infrared pumps, simultaneous two-color emission can be achieved experimentally. External-cavity THz DFG-QCL systems demonstrate continuous tuning at room temperature from 1.2 THz to 5.9 THz with THz peak power output varying between 5 and 90 W, depending on the operating frequency [5,6]. Beam steering of terahertz Cherenkov emission with frequency is suppressed by bonding devices onto high-resistivity silicon substrates that have virtually no refractive index dispersion and vanishingly-small optical loss in 1-6 THz range. To reduce the size and avoid mechanical complexity of external cavity tuners, we also demonstrate monolithic room-temperature THz DFG-QCL tuners with a tuning range from 3.44 THz to 4.02 THz, which corresponds to 15% of their center frequency. Devices are based on a single ridge-waveguide DFG-QCL source with electrically-separated distributed feedback section and distributed Bragg reflector sections that are used to select and tune the frequencies of the two mid-infrared pumps [7]. We have also fabricated an array of 10 of such monolithic THz DFG-QCL tuners that provide continuous tunability between 2 and 4 THz at room temperature with up to 100 μW of peak THz power output.

© 2015 IEEE

PDF Article
More Like This
Broadly-Tunable Room-Temperature Monolithic Terahertz Quantum Cascade Laser Sources

Aiting Jiang, Seungyong Jung, Yifan Jiang, Karun Vijayraghavan, Jaehyun Kim, and Mikhail Belkin
SM1H.3 CLEO: Science and Innovations (CLEO_SI) 2015

Broadly Tunable Room Temperature Monolithic Terahertz Quantum Cascade Laser Sources

Seungyong Jung, Aiting Jiang, Yifan Jiang, Karun Vijayraghavan, Xiaojun Wang, Mariano Troccoli, Frederic Demmerle, Gerhard Boehm, Markus-Christian Amann, and Mikhail A. Belkin
SeTh2D.4 Optical Sensors (Sensors) 2014

Broadly tunable room temperature terahertz quantum cascade laser sources

Mikhail A. Belkin, Yifan Jiang, Karun Vijayraghavan, Seungyong Jung, Frederic Demmerle, Gerhard Boehm, and Markus C. Amann
MTh4B.4 Mid-Infrared Coherent Sources (MICS) 2013

References

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription