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Dual frequency-comb spectroscopy of chromophores in condensed phases
摘要： Femtosecond time-resolved spectroscopy and frequency-comb spectroscopy have been individually developed to achieve better time and frequency resolutions, respectively. The two spectroscopic techniques have been developed for different systems, even though they use mode-locked laser in common. Recently, there was an interesting merge of the two techniques into a dual frequency-comb (DFC) spectroscopy, resulting in a new femtosecond spectroscopy with simple instrumentation and high data acquisition speed compared to conventional femtosecond spectroscopic techniques. By slightly detuning the repetition rates of two phase-locked frequency-comb lasers, both automatic time-delay scanning and parallel data recording with single point detectors are possible. Thus, we anticipate that the DFC spectroscopy would allow one to expand the application limits of the conventional femtosecond spectroscopic methods. In this Perspective article, we provide reviews of linear and nonlinear DFC spectroscopy theory and applications with a perspective on the development of coherent multidimensional frequency-comb spectroscopy.
关键词： nonlinear spectroscopy,optical frequency-comb,time-resolved spectroscopy,coherent two-dimensional spectroscopy,solvation dynamics,dual comb spectroscopy
更新于2025-09-23 15:22:29
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Broadband molecular spectroscopy with optical frequency combs
摘要： Over the past dozen years, optical frequency combs have evolved into valuable tools for broadband molecular spectroscopy. They have already enabled remarkable advances for the measurement of complicated molecular spectra by improving the resolution, accuracy, sensitivity, and measurement times of spectrometric approaches. In this featured article, we trace some recent developments relevant to high-resolution spectroscopy of molecules, especially in the mid-infrared spectral region. We discuss examples that harness the emerging techniques of cavity-enhanced frequency comb spectroscopy and dual-comb spectroscopy and we conclude with a perspective of forthcoming opportunities and challenges.
关键词： optical frequency combs,molecular spectroscopy,dual-comb spectroscopy,cavity-enhanced frequency comb spectroscopy
更新于2025-09-23 15:21:21
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Mid-infrared dual-comb spectroscopy with room-temperature bi-functional interband cascade lasers and detectors
摘要： Interband cascade (IC) laser structures offer attractive potential for operation at room temperature as both broadband coherent sources of mid-infrared light and fast photodetectors. This makes the realization of extremely compact spectrometers on a monolithic platform possible, and even dual-comb spectroscopy (DCS) configurations. IC comb devices are perfect candidates for this configuration, since they develop near-THz-wide optical frequency comb spectra from a millimeter-sized cavity, using a multi-stage structure that can also function as a very fast photodetector. In this work, we leverage IC photodetectors with a gigahertz bandwidth to demonstrate a self-contained, free-running, room-temperature DCS system in the mid-infrared. The DCS system used detection by the same bi-functional IC device structure to measure 1,1-difluoroethane over (cid:2)600 GHz of optical coverage around 3.6 mm. These results show that the IC platform is suitable for full integration as a broadband, high-resolution on-chip spectrometer in a future chemical sensing system.
关键词： mid-infrared,photodetectors,dual-comb spectroscopy,interband cascade lasers,room-temperature
更新于2025-09-23 15:21:01
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Terahertz Spectroscopy of Gas Mixtures with Dual Quantum Cascade Laser Frequency Combs
摘要： Terahertz laser frequency combs based on quantum cascade lasers provide coherent, broadband, electrically pumped, THz radiation sources for use in future spectroscopic applications. Here, we explore the feasibility of such lasers in a dual-comb spectroscopy configuration for the detection of multiple molecular samples in the gas phase. The lasers span approximately 180 GHz of optical bandwidth, centered at 3.4 THz with sub-milliwatt total optical power. One of the main advantages of dual-comb spectroscopy is its high speed, which opens up the possibility for direct observations of chemical reaction dynamics in the terahertz spectral region. As a proof-of-concept, we recorded continuously evolving spectra from gas mixtures with 1 ms temporal resolution.
关键词： frequency comb,multi-species,Terahertz,real-time,dual-comb spectroscopy,quantum cascade laser
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optical Frequency Comb Generation from Semiconductor Lasers using Optical Injection and Pulsed Gain Switching
摘要： An Optical Frequency Comb (OFC) Generator is a laser source emitting a coherent radiation with an equally spaced group of optical frequencies. OFCs have been used in numerous fields, such as optical communications, RF photonics and infrared spectroscopy. Relatively low repetition rate OFCs (100-1000 MHz) are especially suited for dual comb spectroscopic applications. Low repetition rate OFCs from Gain-Switched (GS) semiconductor lasers using sinusoidal excitation have been reported for spectroscopic applications. On the other hand, the generation of ultra-short optical pulses by pulsed excitation GS has been demonstrated, but as far as we know, it has not been used for OFC generation. In this work, we consider pulsed GS in combination with optical injection (OI) to generate low repetition rate OFCs, and we demonstrate a high performance in terms of noise, flatness and bandwidth. The OFC generator is based on a master-slave configuration. The Slave Laser (SL), a Discrete Mode Laser (DML), is driven in GS operation using a combination of two signals: a bias current and a square signal provided by a pulse pattern generator, with different duty cycles and driving conditions. High-resolution spectra were analyzed with a Brillouin Optical Spectrum Analyzer (BOSA).
关键词： Optical Frequency Comb,Pulsed Gain Switching,Semiconductor Lasers,Dual Comb Spectroscopy,Optical Injection
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Broadband Dual-Comb Spectroscopy of Methane with a Free-Running Erbium Chip Laser
摘要： Dual-comb interferometry enables the identification of a gas through the measure of its unique spectral signature with high resolution and fast acquisition. It has been used here to study the spectroscopic properties of an important greenhouse gas: methane. The environmental influence of methane, as well as its economic impact, have proven the need to study its spectroscopic signature with a high level of accuracy. We report a free-running dual-comb spectrometer which has the potential to fulfil the need for high accuracy portable methane monitoring. The C-band spectrometer reported is now broadened from 1400 nm to 1700nm using fiber amplifiers and highly nonlinear fiber (HNLF). The dual-comb laser originates from two passively mode-locked waveguide lasers integrated into a single Er-doped ZBLAN chip. Free-running combs with high mutual coherence are produced with a repetition rate of 968 MHz and a repetition rate difference of 27 kHz. No phase locks, optical references or self-referencing are required. Through the use of a SESAM mode-locking configuration, the lasers self-start and occupy a volume less than 1.2 L, making it an efficient and compact design.
关键词： methane,free-running laser,dual-comb spectroscopy,spectrometer,erbium chip laser
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Dual-Comb Spectroscopy of Acetylene with a Single, Free-Running MIXSEL Generating two Frequency Combs
摘要： Dual-comb spectroscopy combines the advantages of conventional Fourier transform infrared spectroscopy (FTIR) with the measurement speed, stability and accuracy of multiheterodyne beat note detection. Two optical frequency combs (OFCs) with slightly different line spacing beat on a photodetector and convert the optical spectra down to the more accessible radio frequency (RF) domain. This enables an accurate broadband spectrometer without moving parts featuring short measurement time, however, it also requires two mutually locked OFCs with good noise performance which is challenging. Dual-comb modelocked optically pumped semiconductor disk lasers (SDLs) provide a great simplification. The modelocked integrated external-cavity surface emitting laser (MIXSEL) is a special type of ultrafast SDLs which integrates a semiconductor gain and a saturable absorber in a single epitaxial structure and allows for modelocking in a simple and straight cavity. Most recently we increased the modelocked optical bandwidth above 10 nm with pulse durations below 150 fs. With two intracavity birefringent crystals, the initially unpolarized beam is separated onto two spots on the MIXSEL chip, which can be individually pumped. The dual-comb MIXSEL is a straight linear cavity formed by the two end mirrors (i.e. MIXSEL chip and output coupler (OC) and emits two orthogonally polarized OFCs with a slight difference in line spacing from the same cavity with an intrinsically high mutual coherence. Here, we present dual-comb spectroscopy of acetylene with a single, free-running dual-comb MIXSEL at 1030 nm (290 THz). The laser provides more than 10 nm of optical bandwidth usable for spectroscopic interrogations and with a resolution of 2.73 GHz, we can clearly resolve the individual absorption lines with great precision. Without active stabilization and locking electronics, the overlay of the experimentally acquired dual-comb transmission follows line-by-line the characteristic acetylene transmission envelope as computed from the HITRAN 2016 database after an a posteriori wavelength calibration. Furthermore, the residuals between the observed traces and the HITRAN reference spectrum and its standard deviation of 0.028 attests good transmission intensity precision to our dual-comb spectrometer.
关键词： optical frequency combs,MIXSEL,acetylene,Dual-comb spectroscopy,HITRAN database
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - A Single Free-Running Dual-Comb MIXSEL for Fast and Precise Distance Measurements
摘要： Multiheterodyne techniques in science and technology promise unsurpassed precision in many fields of application such as dual-comb spectroscopy or light detection and ranging (LIDAR). Complexity, performance and cost can be greatly improved with dual-comb semiconductor disk lasers (SDL). Integration of the active semiconductor gain of a vertical external-cavity surface emitting laser (VECSEL) with the saturable absorber of a semiconductor saturable absorber mirror (SESAM) in the same epitaxial structure leads to the modelocked integrated external-cavity surface emitting laser (MIXSEL). The MIXSEL allows modelocking in a simple straight cavity. With two intracavity birefringent crystals, the initially unpolarized cavity beam is separated by polarization. When optically pumping two spots on the semiconductor chip, the dual-comb MIXSEL emits two orthogonally polarized optical frequency combs (OFCs) with a slight difference in pulse repetition rate which can be freely adjusted. The common cavity leads to an intrinsically high mutual coherence between the two OFCs, making the dual-comb MIXSEL the ideal source for dual-comb spectroscopy and other field-deployable multiheterodyne beatnote techniques.
关键词： semiconductor disk lasers,optical frequency combs,Multiheterodyne techniques,dual-comb spectroscopy,MIXSEL,SESAM,VECSEL,LIDAR
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Dual-Comb Spectroscopy using a Single Frequency-Shifting Loop
摘要： Dual-comb spectroscopy (DCS) is a multi-heterodyne interferometric technique that employs two optical frequency combs (OFCs) with different line spacing. When DCS is carried out with a pair of mode-locked OFCs, the need of a tight phase locking between them leads to sophisticated hardware and/or software implementations [1]. A strategy to simplify the DCS architecture, demonstrated with several comb modalities, is the use of a bidirectional laser cavity to produce two counter-propagating combs, each one having different line spacing [2,3]. Alternatively, but offering much more flexibility on the mode separation, electro-optic (EO) frequency combs can also be used for carrying out DCS. In that DCS scheme, both EO combs are fed by a single cw laser, which ensures by default a high degree of mutual coherence between them [4]. In the same vein, but comparatively much less exploited, frequency-shifting loops (FSLs) are also an easily implementable comb platform. Based on the recirculation of light in a loop containing an acousto-optic frequency shifter (AOFS), FSLs are capable of producing spectra with hundreds or even thousands of lines, without resorting to non-linear broadening or optimized fast driving electronics [5]. Recently, we have demonstrated DCS using two different FSLs [6]. However, this system requires the use of a low-bandwidth stabilization system to compensate for the uncorrelated fluctuations between the two combs, a requirement also found in other DCS schemes, and necessary for increasing the acquisition time (and, hence, the measurement signal-to-noise ratio) beyond the ms time scale. To improve the mutual coherence of the two OFCs, we present a bidirectional FSL that generates in the same optical loop two counter-propagating OFCs (called acousto-optic OFCs), with a tunable line spacing difference, as shown in Fig. 1a. The FSL is composed of three bidirectional elements: a frequency shifter that imparts a different frequency shift depending on the light direction, an optical amplifier (EDFA) and a tunable band-pass filter (BPF). The interference between the two acousto-optic OFCs produces a RF comb, whose bandwidth and flatness can be controlled through the parameters of the FSL (Fig. 1b). In order to test our setup, we performed molecular spectroscopy of a HCN absorption line, as can be observed in Fig. 1c. While much simpler, our system performs similarly to the technique that utilizes two different FSLs with a stabilization mechanism [6]. The presented bidirectional FSL is a compact and flexible scheme for DCS. Apart from avoiding duplication of the FSL, it provides common noise rejection between the two generated combs, allowing us to reach acquisition times up to the second scale. In addition, a pair of counter-propagating trains of optical pulses could also be generated by exploiting the temporal Talbot effect [5]. All these features make our system a powerful platform for multi-heterodyne interferometry, including molecular spectroscopy, distance ranging and fiber sensing.
关键词： Dual-comb spectroscopy,multi-heterodyne interferometry,acousto-optic frequency shifter,frequency-shifting loops
更新于2025-09-12 10:27:22
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Computational Doppler-limited dual-comb spectroscopy with a free-running all-fiber laser
摘要： Dual-comb spectroscopy has emerged as an indispensable analytical technique in applications that require high resolution and broadband coverage within short acquisition times. Its experimental realization, however, remains hampered by intricate experimental setups with large power consumption. Here, we demonstrate an ultrasimple free-running dual-comb spectrometer realized in a single all-fiber cavity suitable for the most demanding Doppler-limited measurements. Our dual-comb laser utilizes just a few basic fiber components, allows us to tailor the repetition rate difference, and requires only 350 mW of electrical power for sustained operation over a dozen of hours. As a demonstration, we measure low-pressure hydrogen cyanide within 1.7 THz bandwidth and obtain better than 1% transmittance precision over a terahertz in 200 ms enabled by an all-computational phase retrieval and correction algorithm. The combination of the setup simplicity, comb tooth resolution, and high spectroscopic precision paves the way for proliferation of frequency comb spectroscopy on a larger scale.
关键词： computational phase retrieval,Doppler-limited measurements,hydrogen cyanide,all-fiber laser,Dual-comb spectroscopy
更新于2025-09-12 10:27:22