Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator

Abstract

Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology.

HBN-Encapsulated, Graphene-based, Room-temperature Terahertz Receivers, with High Speed and Low Noise

“…Finally, we evaluate the bandwidth (BW) of our terahertz PD by taking advantage of the employed QCL. When the QCL is driven with high-voltage pulses ( V QCL > 29 V), it enters the so-called negative differential resistance (NDR) regime . From an electrical point of view, this corresponds to a very unstable high field domain regime, in which the driving current fluctuates randomly under increased applied bias.…”

“…When the QCL is driven with high-voltage pulses (V QCL > 29 V), it enters the so-called negative differential resistance (NDR) regime. 66 From an electrical point of view, this corresponds to a very unstable high field domain regime, in which the driving current fluctuates randomly under increased applied bias. From an optical point of view, the QCL average output power progressively decreases when increasing the voltage, due to the increased overall temperature of the laser lattice, which, in turn, reduces the population inversion.…”

Dispersion dynamics of quantum cascade lasers

“…Quantum cascade lasers (QCLs) are a semiconductor source of coherent radiation in the mid-infrared and terahertz (THz) [1], and their high powers and large nonlinearities have led to several interesting devices exploiting nonlinear effects. For example, impressive results have been obtained in generating Thz radiation from mid-infrared structures via differencefrequency generation [2][3][4], active mode locking has been achieved [5][6][7], and as of late there has been an explosion in research in using QCLs to generate frequency combs [8][9][10][11][12]. Mid-infrared difference-frequency generation can be used to generate continuous wave THz radiation without the need for cryocoolers, and frequency combs can be used to perform coherent broadband spectroscopy [13][14][15] or to perform broadband tomography [16].…”

Terahertz Radiation Modulates Neuronal Morphology and Dynamics Properties

“…Terahertz sources based on avalanche diodes are widely used due to their relatively high linear output power and compact design. They generally operate at frequencies below 1 THz and can achieve output powers of up to 100 mW [ 63 ].…”