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All-polarization-maintaining dual-wavelength mode-locked fiber laser based on Sagnac loop filter
摘要： We demonstrate an all polarization-maintaining (PM) fiber based dual-wavelength mode-locked Er-fiber laser. A nonlinear amplifying loop mirror (NALM) with an intracavity nonreciprocal phase shifter is used for self-started mode-locking. A short segment of PM fiber is angle-spliced to the NALM, functioning as a PM Sagnac loop filter, thus enabling dual-wavelength mode-locking. The wavelength separation is solely determined by the angle-spliced PM fiber length. Stable dual-wavelength mode-locking operation is switchable between 1570/1581 nm and 1581/1594 nm. The two-color pulse trains oscillating in the same cavity have an inherent offset repetition rate of ~1 kHz owing to cavity dispersion, allowing future high precision dual-comb applications with a simple and robust configuration.
关键词： polarization-maintaining fiber,dual-comb applications,dual-wavelength mode-locked fiber laser,Sagnac loop filter
更新于2025-11-28 14:24:03
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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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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Performance of Bi-Directional Mode-Locked Fiber Laser at 2 ??m
摘要： Bidirectional mode-locking pulse laser has attracted great attentions because of its simplicity and compactness for free-running dual-comb spectroscopy. In this paper, we developed an all-polarization-maintaining, bi-directional Tm-doped fiber laser at 2 μm with a single-wall carbon nanotube (SWNT) presented absorber mode-locking mechanism. By manipulating the polarization controller, changing the pump power and shortening the cavity length, we successfully obtain bidirectional mode-locking operations at different repetition frequencies, namely 35 MHz and 122 MHz. Besides, the repetition rate difference between clockwise and counterclockwise pulse trains is adaptable, varying from 764 Hz to 1.01 KHz at 35 MHz and 540 Hz to 1.8 KHz at 122 MHz.
关键词： repetition rate,dual-comb mode-locking,repetition rate difference
更新于2025-09-23 15:21:01
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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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Dual-comb-based asynchronous pump-probe measurement with an ultrawide temporal dynamic range for characterization of photo-excited InAs quantum dots
摘要： A dual-comb-based asynchronous optical sampling (ASOPS) pump-probe measurement system is demonstrated for characterizing the relaxation dynamics in a photo-excited self-assembled InAs quantum dot (QD) semiconductor. Although the photo-excited QD material has multiple complex relaxation processes, the transient transmittance responses (from femtoseconds to nanoseconds) are successfully obtained within a sub-second short acquisition time by using the ASOPS system. This is achieved with high stability and an extremely wide temporal dynamic range of approximately 105. The utility of the developed system is demonstrated as a powerful and easy-to-use measurement tool for studying the complex photo-excited dynamics of QD materials.
关键词： dual-comb,asynchronous optical sampling,InAs quantum dots,pump-probe measurement,relaxation dynamics
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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A Traceable High-Accuracy Velocity Measurement by Electro-Optic Dual-Comb Interferometry
摘要： An electro-optic dual-comb Doppler velocimeter for high-accuracy velocity measurement is presented in this paper. The velocity information of the object can be accurately extracted from the change of repetition frequency, which is in the microwave frequency domain and can be locked to an atomic clock. We generate two optical combs by electro-optic phase modulators and trace their repetition frequencies to the rubidium clock. One functions as the measurement laser and the other the reference. Experimentally, we verify its high accuracy in the range of 100–300 mm/s with a maximum deviation of 0.44 mm/s. The proposed velocimeter combines the merits of high accuracy and wide range. In addition, since the repetition frequency used for the measurement is traceable to the rubidium clock, its potential superiority in traceability can be utilized in velocity metrology.
关键词： electro-optic dual-comb interferometry,Traceability,laser Doppler velocimetry
更新于2025-09-12 10:27:22