Spectroscopic Study of Terahertz Generation in Mid-Infrared Quantum Cascade Lasers

Yifan Jiang, Karun Vijayraghavan, Seungyong Jung, Aiting Jiang, Jae Hyun Kim, Frederic Demmerle, Gerhard Boehm, Markus C. Amann, Mikhail A. Belkin

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

Terahertz quantum cascade laser sources based on intra-cavity difference-frequency generation are currently the only room-temperature mass-producible diode-laser-like emitters of coherent 1-6 THz radiation. Device performance has improved dramatically over the past few years to reach milliwatt-level power output and broad tuning from 1.2 to 5.9 THz, all at room-temperature. Terahertz output in these sources originates from intersubband optical nonlinearity in the laser active region. Here we report the first comprehensive spectroscopic study of the optical nonlinearity and investigate its dependence on the mid-infrared pump frequencies. Our work shows that the terahertz generation efficiency can vary by a factor of 2 or greater depending on the spectral position of the mid-infrared pumps for a fixed THz difference-frequency. We have also measured for the first time the linewidth for transitions between the lower quantum cascade laser states, which is critical for determining terahertz nonlinearity and predicting optical loss in quantum cascade laser waveguides.

Original languageEnglish
Article number21169
JournalScientific Reports
Volume6
DOIs
StatePublished - 16 Feb 2016

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