Multiheterodyne spectroscopy using interband cascade lasers

Abstract

Abstract. While midinfrared radiation can be used to identify and quantify numerous chemical species, contemporary broadband midinfrared spectroscopic systems are often hindered by large footprints, moving parts, and high power consumption. In this work, we demonstrate multiheterodyne spectroscopy (MHS) using interband cascade lasers, which combines broadband spectral coverage with high spectral resolution and energy-efficient operation. The lasers generate up to 30 mW of continuous-wave optical power while consuming <0.5 W of electrical power. A computational phase and timing correction algorithm is used to obtain kHz linewidths of the multiheterodyne beat notes and up to 30 dB improvement in signal-to-noise ratio. The versatility of the multiheterodyne technique is demonstrated by performing both rapidly swept absorption and dispersion spectroscopic assessments of low-pressure ethylene (C 2 H 4 ) acquired by extracting a single beat note from the multiheterodyne signal, as well as broadband MHS of methane (CH 4 ) acquired with all available beat notes with microsecond temporal resolution and an instantaneous optical bandwidth of ∼240 GHz. The technology shows excellent potential for portable and high-resolution solid-state spectroscopic chemical sensors operating in the midinfrared.

Stabilized Terahertz Quantum Cascade Laser Dual-Comb Sources with a Hybrid Locking

“…It has to be emphasized that the proposed hybrid locking only locks the RF spectrum, and the optical spectrum partially drifts due to an unlocked offset frequency. In this point of view, the dual-comb system with the hybrid locking method stands between the computationally corrected dual-comb system 26 and the one that is fully referenced to an optically rectified comb. 8 ■ METHODS THz QCL.…”

“…Digital approaches that employ digital mixing, filtering, frequency shifting, etc. analogous to hardware implementations were also applied to various systems for obtaining stable dual-comb signals: THz and mid-infrared QCL frequency combs, interband cascade laser frequency combs, mid-infrared silicon microresonators, and near-infrared waveguide mode-locked lasers. − We also demonstrated that instead of locking four different frequencies of a dual-comb laser system, we can stabilize the dual-comb signal as a whole. For example, by phase locking one of the dual-comb line to a RF synthesizer, all dual-comb lines are much more stabilized .…”

Year in Review

“…The special section papers addressed holographic wavefront printing for 3-D display, 1 real-time reconstruction for holographic 3-D displays, 2 computational photon-counting light detection and ranging (LiDAR) sensor for 3-D imaging, 3 aspheric lens mounting to achieve fine decentration and tilt accuracy, 4 and multi-heterodyne spectroscopy with interband cascade lasers for chemical sensing. 5 The top downloaded paper provided a tutorial on the characterization of Moiré effects that arise in displays, 6 and the two review papers provided state-of-the-art assessments of self-mixing interferometry for mechanical engineering applications, 7 and high-fidelity imaging spectrometer design for airborne and space-based remote sensing. 8 The two regular papers in the top-ten list included a theoretical paper describing a momentum exchange theory for photon diffraction that uses momentum transfer probability distributions as an alternative to classical wave theory, 9 and an applied paper on an underwater laser communications system based on a 680 nm vertical external cavity surface emitting (VECSEL) laser to achieve wider bandwidth than more prevalent blue-green laser systems.…”

Experimental demonstration of a new near-infrared spectroscopy technique based on optical dual-comb: DC-NIRS

“…In many implementations, DCS employs OFC generated using mode-locked lasers 21 , but electro-optical OFC techniques offer a modular solution with configurable resolution and spectral range 22 , 23 . Electro-optic DCS uses a single optical seed to generate both OFCs, which translates into an intrinsic synchronization between the pair of OFCs, hence providing enhanced phase and amplitude stability 24 . Although DCS systems have demonstrated their remarkable capabilities from the visible to the MIR and THz windows in several fields such as metrology, vibrational spectroscopy, or ranging 21 , there is no current demonstration of their usefulness when it comes to dispersive or turbid media, which is the area in which NIRS excels, since scattering seriously damages the coherence needed between the OFC arms of DCS systems.…”