A Method and Apparatus for a Monolithic Tunable Terahertz Radiation Source using Nonlinear Frequency Mixing in Quantum Cascade Lasers
Physical Sciences : Electrical
Available for licensing
- Mikhail Belkin, Ph.D. , Electrical and Computer Engineering
- Seungyong Jung , Electrical & Computer Engineering
- Karun Vijayraghavan , ATX Photonics LLC
Terahertz radiation occupies a middle ground between microwaves and infrared light waves known as the terahertz gap. Technology for its generation and manipulation is in its infancy. It represents the region in the electromagnetic spectrum where the frequency of electromagnetic radiation becomes too high to be measured digitally via electronic counters, so must be measured by proxy using the properties of wavelength and energy. Similarly, the generation and modulation of coherent electromagnetic signals in this frequency range ceases to be possible by the conventional electronic devices used to generate radio waves and microwaves, requiring the development of new devices and techniques.
Photon energy in the THz range is less than band-gap of nonmetallic materials, and thus THz beam can traverse through such materials. The transmitted THz beam is used for material characterization, layer inspection, and developing transmission images.
Researchers at The University of Texas at Austin have developed a novel method of generating single-mode, tunable terahertz radiation in a monolithic, electrically-pumped source based on THz difference-frequency generation (DFG) quantum cascade laser (QCL). The source is fabricated with two single-period Bragg gratings. The gratings are etched into separated sections of the device waveguide, electrically isolated from one another, and biased independently. Tuning is achieved by locally changing the temperature of one of the grating sections with respect to the other via application of a DC current.
- All-monolithic construction is cheaper to manufacture, rugged, and compact
- Generates single THz radiation that is highly desired for frequency-domain spectroscopy
- Room temperature operation, which is an advantage over cryogenically cooled solutions
- Demonstration of tunable THz emission between 3.44 and 4.02 THz (580 GHz bandwidth)
- Potential for operation of sources in the 0.5 to 10 THz range with an equivalent tuning range
- Electrically pumped and completely monolithic (i.e., it requires no moving parts)
This type of source is expected to find numerous applications in field of THz spectroscopy, chemical/biological sensing, explosives detection, security screening, medical imaging, and high-speed telecommunications.