Abstract: A dual-comb spectrometer comprising two lasers outputting respective frequency combs having a frequency offset between their intermode beat frequencies. One laser acts as a master and the other as a follower. Although the master laser is driven nominally with a DC drive signal, the current on its drive input line nevertheless oscillates with an AC component that follows the beating of the intermode comb lines lasing in the driven master laser. This effect is exploited by tapping off this AC component and mixing it with a reference frequency to provide the required frequency offset, the mixed signal then being supplied to the follower laser as the AC component of its drive signal. The respective frequency combs in the optical domain are thus phase-locked relative to each other in one degree of freedom, so that the electrical signals obtained by multi-heterodyning the two optical signals are frequency stabilized.

Abstract: A dual-comb spectrometer comprising two lasers outputting respective frequency combs having a frequency offset between their intermode beat frequencies. One laser acts as a master and the other as a follower. Although the master laser is driven nominally with a DC drive signal, the current on its drive input line nevertheless oscillates with an AC component that follows the beating of the intermode comb lines lasing in the driven master laser. This effect is exploited by tapping off this AC component and mixing it with a reference frequency to provide the required frequency offset, the mixed signal then being supplied to the follower laser as the AC component of its drive signal. The respective frequency combs in the optical domain are thus phase-locked relative to each other in one degree of freedom, so that the electrical signals obtained by multi-heterodyning the two optical signals are frequency stabilized.

Abstract: A dual-comb spectrometer comprising two lasers outputting respective frequency combs having a frequency offset between their intermode beat frequencies. One laser acts as a master and the other as a follower. Although the master laser is driven nominally with a DC drive signal, the current on its drive input line nevertheless oscillates with an AC component that follows the beating of the intermode comb lines lasing in the driven master laser. This effect is exploited by tapping off this AC component and mixing it with a reference frequency to provide the required frequency offset, the mixed signal then being supplied to the follower laser as the AC component of its drive signal. The respective frequency combs in the optical domain are thus phase-locked relative to each other in one degree of freedom, so that the electrical signals obtained by multi-heterodyning the two optical signals are frequency stabilized.

Abstract: A vibrational circular dichroism (VCD) spectroscopy method and apparatus that can significantly reduce the measurement time needed to acquire a differential absorption spectrum compared to known approaches. A dual-comb is generated by superimposing the outputs from two quantum cascade laser sources, thus providing a third comb interferogram with beat frequencies higher than the polarization modulation frequency. Consequently, for each of the left and right circularly polarized light, the measurement signal measures transmission through the sample across the full wavelength range of interest during each period of the polarization modulation. A complete vibrational spectrum is thus acquired in each modulation of a polarization modulator, instead of only acquiring data for a single wavelength during each modulation of the polarization, as in dispersive or tunable laser VCD, or only a single Fourier component of the spectrum, as in Fourier transform VCD.

Abstract: A dual-comb spectrometer 5 with two lasers 10, 12 serving as a local oscillator and an interrogator. The lasers output light beams with respective frequency combs C1, C2 of defined free spectral range, FSR. A detector 30 can detect heterodyne mixing of the combined beams to detect an RF frequency comb C3. Respective control signals are supplied to the lasers which have functional forms configured to cause the frequencies of the lasers' frequency combs C1, C2 to tune over a defined fraction of their FSR. This enables a reduction of the effective spectral sampling period by a factor equal to the ratio of the FSR to the spectral resolution of the spectrometer, which will typically be several orders of magnitude, so that the spectral sampling period can be reduced from the GHz to the MHz range, which in turn enables a gapless spectrum to be obtained in a short time.

Abstract: A heterodyne detection spectrometer setup comprises an optical path with at least a first cavity able to emit a first laser beam; a second cavity able to emit a second laser beam; and at least one combining and/or reflecting element. The cavities are connected to current drivers for stimulating laser emission, which shows increased signal-to-noise ratios of the heterodyne signal and an increased dynamic range. This can be reached if at least the second cavity comprises an active medium connected to a heterodyne signal extraction element and a (multi-) heterodyne signal processing unit, which is simultaneously usable for laser light generation and as detector element, comprising an active medium introduced in the optical path in order that the first and/or second laser beam can enter the respective other cavity. At least one reference path is established between the two cavities in the optical path with at least two combining and/or reflecting elements.

Abstract: A heterodyne detection spectrometer setup comprises an optical path with at least a first cavity able to emit a first laser beam; a second cavity able to emit a second laser beam; and at least one combining and/or reflecting element. The cavities are connected to current drivers for stimulating laser emission, which shows increased signal-to-noise ratios of the heterodyne signal and an increased dynamic range. This can be reached if at least the second cavity comprises an active medium connected to a heterodyne signal extraction element and a (multi-) heterodyne signal processing unit, which is simultaneously usable for laser light generation and as detector element, comprising an active medium introduced in the optical path in order that the first and/or second laser beam can enter the respective other cavity. At least one reference path is established between the two cavities in the optical path with at least two combining and/or reflecting elements.

Abstract: An optical frequency comb setup including a semiconductor cascade laser drivable by a laser driver, emitting a laser beam through an end facet of the semiconductor cascade laser with a frequency comb with at least two given individual emission frequencies, repetition frequency, carrier envelope offset frequency shows improved comb stability and/or comb formation and/or comb bandwidth. This is achieved by an external cavity added outside of the cavity of the semiconductor cascade laser, having a reflective element with a mirror surface reflecting the at least two individual emission frequencies being arranged in a relative distance to the end facet allowing to adapt repetition frequency and/or carrier envelope offset frequency and/or the dispersion seen by the light in the optical frequency comb setup.