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Coexisting Frequency Combs Spaced by an Octave in a Monolithic Quantum Cascade Laser by Forrer, Andres; Roesch, Markus; Singleton, Matthew; Beck, Mattias; Faist, Jerome; Scalari, Giacomo is a scholarly article available to read on EtoBox.

What is Coexisting Frequency Combs Spaced by an Octave in a Monolithic Quantum Cascade Laser about?

Quantum cascade lasers are proving to be instrumental in the development of compact frequency comb sources at mid-infrared and terahertz frequencies. Here we demonstrate a heterogeneous terahertz quantum cascade laser with two active regions spaced exactly by one octave. Both active regions are based on a four-quantum well laser design and they emit a combined 3~mW peak power at 15~K in pulsed mode. The two central frequencies are 2.3~THz (bandwidth 300~GHz) and 4.6~THz (bandwidth 270~GHz). The structure is engineered in a way that allows simultaneous operation of the two active regions in the comb regime, serving as a double comb source as well as a test bench structure for all waveguide internal self-referencing techniques. Narrow RF beatnotes ($\sim$ 15~kHz) are recorded showing the simultaneous operation of the two combs, whose free-running coherence properties are investigated by means of beatnote spectroscopy performed both with an external detector and via self-mixing. Comb operation in a highly dispersive region (4.6~THz) relying only on gain bandwidth engineering shows the potential for broad spectral coverage with compact comb sources.

Author

Forrer, Andres; Roesch, Markus; Singleton, Matthew; Beck, Mattias; Faist, Jerome; Scalari, Giacomo

Published

2018

Language

EN