Dual-comb spectroscopy based on quantum-cascade-laser frequency combs

Abstract

Dual-comb spectroscopy performed in the mid-infrared-where molecules have their strongest rotovibrational absorption lines-offers the promise of high spectral resolution broadband spectroscopy with very short acquisition times (ms) and no moving parts. Recently, we demonstrated frequency comb operation of a quantum-cascade-laser. We now use that device in a compact, dual-comb spectrometer. The noise properties of the heterodyne beat are close to the shot noise limit. Broadband (15 cm À 1 ) high-resolution (80 MHz) absorption spectroscopy of both a GaAs etalon and water vapour is demonstrated, showing the potential of quantum-cascade-laser frequency combs as the basis for a compact, all solid-state, broadband chemical sensor.

Single-mode instability in standing-wave lasers: The quantum cascade laser as a self-pumped parametric oscillator

“…In the last few years, comb generation in a QCL on adjacent FP modes has been demonstrated [37][38][39], and the importance of parametric mode coupling is known [40,41]. (These devices all had multistage inhomogeneously broadened active regions, which distinguishes them from the devices in our work.)…”

Optimizing the active region of interband cascade lasers for passive mode-locking

“…So far, in the literature there is an intense discussion about the fundamental mode-locking of quantum cascade lasers (QCLs), which has been a challenge for the last one and a half decades, but has already been demonstrated. [19][20][21] Another possible implementation could be a mode-locked interband cascade laser (ICL), of which the first demonstration at 3 µm has just been announced. 22 The ICLs have been well established in the 3-6 µm range, and even beyond 2,23 which could potentially allow for construction of mode-locked devices, which however have additional requirements, including also the respective modification and optimization of the active region to allow for a large enough transition rate difference between the absorber and gain sections.…”

On-chip dual-comb based on quantum cascade laser frequency combs

“…As the comb formation takes place directly in the QCL active region, QCL frequency combs (QCL-combs) offer the unique possibility of a completely integrated chipbased system capable of performing broadband highresolution spectroscopy. In the meantime, a theoretical description of the comb formation has already been developed 21,22 , dispersion compensation of QCL-combs was investigated 18,23 and dual-comb spectroscopy using QCL-combs has been demonstrated 24 . In this letter, we demonstrate an on-chip dual-comb source based on MIR QCL-combs.…”

“…Further control of the comb parameters is demonstrated by measuring the radio frequency (RF) spectrum of the laser current 24 . The RF spectrum contains the beatnotes at the roundtrip frequency of the two combs f rep,1 and f rep,2 , as they are biased in parallel by a unique current driver.…”

“…In order to demonstrate the advantage of an on-chip system compared to a system where both combs would be totally independent, we measure this coefficient by using our previously demonstrated dual-comb spectrometer 24 , where the two combs consist of two different devices. In this case, a temperature fluctuation of one comb will directly translate into a temperature drift of the multi-heterodyne beatnotes.…”