scholarly journals Spectroscopic Imaging with an Ultra-Broadband (1–4 THz) Compact Terahertz Difference-Frequency Generation Source

Electronics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 336
Author(s):  
Atsushi Nakanishi ◽  
Shohei Hayashi ◽  
Hiroshi Satozono ◽  
Kazuue Fujita
Keyword(s):  
Imaging Technique ◽  
Spectroscopic Imaging ◽  
Difference Frequency Generation ◽  
Difference Frequency ◽  
Quality Monitoring ◽  
Terahertz Emission ◽  
Mid Infrared ◽  
Quantum Cascade ◽  
Frequency Generation ◽  
Multi Mode

We demonstrate spectroscopic imaging using a compact ultra-broadband terahertz semiconductor source with a high-power, mid-infrared quantum cascade laser. The electrically pumped monolithic source is based on intra-cavity difference-frequency generation and can be designed to achieve an ultra-broadband multi-mode terahertz emission spectrum extending from 1–4 THz without any external optical setup. Spectroscopic imaging was performed with three frequency bands, 2.0 THz, 2.5 THz and 3.0 THz, and as a result, this imaging technique clearly identified three different tablet components (polyethylene, D-histidine and DL-histidine). This method may be highly suitable for quality monitoring of pharmaceutical materials.

Mid-infrared multi-mode absorption spectroscopy, MUMAS, using difference frequency generation

2014 ◽  
Vol 118 (3) ◽  
pp. 343-351 ◽  
Author(s):  
Henry Northern ◽  
Seamus O’Hagan ◽  
Michelle L. Hamilton ◽  
Paul Ewart
Keyword(s):  
Absorption Spectroscopy ◽  
Difference Frequency Generation ◽  
Difference Frequency ◽  
Mid Infrared ◽  
Frequency Generation ◽  
Multi Mode

scholarly journals Optical external efficiency of terahertz quantum cascade laser based on Čerenkov difference frequency generation

2019 ◽  
Vol 28 (04) ◽  
pp. 1950036
Author(s):  
A. Hamadou ◽  
J.-L. Thobel ◽  
S. Lamari
Keyword(s):  
Quantum Cascade Laser ◽  
Quantum Cascade Lasers ◽  
Difference Frequency Generation ◽  
Terahertz Wave ◽  
Difference Frequency ◽  
Infrared Transmission ◽  
Mid Infrared ◽  
Quantum Cascade ◽  
Frequency Generation ◽  
External Efficiency

In this paper, we consider terahertz sources based on Čerenkov difference frequency generation in a dual-wavelength mid-infrared quantum cascade laser and calculate analytically the optical external efficiency of the out-going terahertz wave. The mid-infrared pumps operate simultaneously and have a common upper level. For short cavity lengths and low terahertz losses in the substrate, we find that implementation of the Čerenkov emission scheme in terahertz difference frequency generation quantum cascade lasers improves the optical external efficiency dramatically. The maximum value of the latter is close to 19%, but is only attainable if the laser exhibits negligible mid-infrared transmission losses.

scholarly journals Recent progress in terahertz difference-frequency quantum cascade laser sources

Nanophotonics ◽  
2018 ◽  
Vol 7 (11) ◽  
pp. 1795-1817 ◽  
Author(s):  
Kazuue Fujita ◽  
Seungyong Jung ◽  
Yifan Jiang ◽  
Jae Hyun Kim ◽  
Atsushi Nakanishi ◽  
...  
Keyword(s):  
Active Region ◽  
Quantum Cascade Laser ◽  
Continuous Wave ◽  
Difference Frequency Generation ◽  
Difference Frequency ◽  
High Resistivity ◽  
Dramatic Improvement ◽  
Terahertz Emission ◽  
Quantum Cascade ◽  
Frequency Generation

AbstractTerahertz quantum cascade laser (QCL) sources based on intra-cavity difference frequency generation are currently the only electrically pumped monolithic semiconductor light sources operating at room temperature in the 1–6-THz spectral range. Relying on the active regions with the giant second-order nonlinear susceptibility and the Cherenkov phase-matching scheme, these devices demonstrated drastic improvements in performance in the past several years and can now produce narrow-linewidth single-mode terahertz emission that is tunable from 1 to 6 THz with power output sufficient for imaging and spectroscopic applications. This paper reviews the progress of this technology. Recent efforts in wave function engineering using a new active region design based on a dual-upper-state concept led to a significant enhancement of the optical nonlinearity of the active region for efficient terahertz generation. The transfer of Cherenkov devices from their native semi-insulating InP substrates to high-resistivity silicon substrates resulted in a dramatic improvement in the outcoupling efficiency of terahertz radiation. Cherenkov terahertz QCL sources based on the dual-upper-state design have also been shown to exhibit ultra-broadband comb-like terahertz emission spectra with more than one octave of terahertz frequency span. The broadband terahertz QCL sources operating in continuous-wave mode produces the narrow inter-mode beat-note linewidth of 287 Hz, which indicates frequency comb operation of mid-infrared pumps and thus supports potential terahertz comb operation. Finally, we report the high-quality terahertz imaging obtained by a THz imaging system using terahertz QCL sources based on intra-cavity difference frequency generation.

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