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An optical angle sensor based on chromatic dispersion with a mode-locked laser source
摘要： This paper proposes a new optical angle sensor, in which a mode-locked laser is employed as the light source, and chromatic dispersion of a collimator objective is utilized to detect the angular displacement of a target of interest. In the proposed method, each of the optical modes in the femtosecond laser beam reflected from the reflector mounted on a target of interest is separated from the others by chromatic dispersion of a collimator objective to generate a group of focused laser beams that can be utilized as the scale for measurement of an angular displacement of the target. By detecting the change in peak frequency in optical spectra obtained by the photodetector, a small angular displacement can be measured. In this paper, as the first step of research, a prototype optical setup is developed, and some basic experiments are carried out to demonstrate the feasibility of the proposed method for measurement of angular displacement.
关键词： Chromatic dispersion,Angular displacement,Angle measurement,Optical frequency comb,Laser autocollimation
更新于2025-11-28 14:24:03
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Absolute distance measurement based on spectral interferometry using femtosecond optical frequency comb
摘要： We demonstrated an absolute distance measurement method based on the frequency folding e?ect using the spectral interferometry of femtosecond optical frequency comb. And the investigation was carried out on the ranging accuracy in?uence of the phase noise in the traditional complicated phase unwrapping method via band-pass ?lter and Fourier Transform. To reduce the e?ects of the phase noise, we proposed the non-?ltered and di?erential envelop phase demodulation method, and its robustness was illustrated with a standard deviation of 75 nm for the stability of single point measurements. Further, through the extension of the non-ambiguity range, we achieved a resolution of better than 30 ??m in a long distance measurements range of 70 m, yielding a relative precision of 3.1 × 10 ? 7.
关键词： Spectral interferometry,Optical frequency comb,Absolute distance measurement
更新于2025-11-28 14:23:57
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Uncertainty evaluation of an 171Yb optical lattice clock at NMIJ
摘要： We report an uncertainty evaluation of an 171Yb optical lattice clock with a total fractional uncertainty of 3.6 × 10^{-16}, which is mainly limited by the lattice-induced light shift and the blackbody radiation shift. Our evaluation of the lattice-induced light shift, the density shift, and the second-order Zeeman shift is based on an interleaved measurement where we measure the frequency shift using the alternating stabilization of a clock laser to the 6s2 1S0–6s6p 3P0 clock transition with two different experimental parameters. In the present evaluation, the uncertainties of two sensitivity coefficients for the lattice-induced hyperpolarizability shift d incorporated in a widely used light shift model by RIKEN and the second-order Zeeman shift aZ are improved compared with the uncertainties of previous coefficients. The hyperpolarizability coefficient d is determined by investigating the trap potential depth and the light shifts at the lattice frequencies near the two-photon transitions 6s6p3P0–6s8p3P0, 6s8p3P2, and 6s5f3F2. The obtained values are d = ?1.1(4) μHz and aZ = ?6.6(3) Hz/mT2. These improved coefficients should reduce the total systematic uncertainties of Yb lattice clocks at other institutes.
关键词： precise measurement,optical lattice clock,optical frequency comb,Frequency standards,SI second
更新于2025-09-23 15:23:52
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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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Calculating the Effective Center Wavelength for Heterodyne Interferometry of an Optical Frequency Comb
摘要： Heterodyne interferometry based on an optical frequency comb (OFC) is a powerful tool for distance measurement. In this paper, a method to calculate the effective center wavelength of wide spectrum heterodyne interference signal was explored though both simulation and experiment. Results showed that the effective center wavelength is a function of the spectra of the two interfered beams and time-delay of the two overlapped pulses. If the product of the spectra from two arms is symmetric, the effective center wavelength does not change with time-delay of the two pulses. The relative difference between the simulation and experiment was less than 0.06%.
关键词： center wavelength,optical frequency comb,heterodyne interferometry
更新于2025-09-23 15:22:29
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Tunable optical frequency comb from a compact and robust Er:fiber laser
摘要： We report on a compact and robust self-referenced optical frequency comb with a tunable repetition rate, generated by an all-polarization-maintaining (PM) mode-locked Er-doped fiber laser. The spacing between comb teeth can be tuned above 300 kHz at a repetition rate of 101 MHz. The repetition rate and the carrier–envelope offset of the laser are stabilized separately, and the relative residual phase noises are determined to be 336 μrad and 713 mrad (1 Hz–1 MHz). The accurate frequency characteristics and the stable structure show great potential for the use of such a comb in applications of precision measurements.
关键词： fiber laser,optical frequency comb,all-polarization-maintaining,mode-locking
更新于2025-09-23 15:21:01
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Tuneable Optical Frequency Comb Generator for THz Spectroscopy
摘要： We present an optical frequency comb generator with a record span of 3.8 THz suitable for high resolution THz spectroscopy, based on a single phase modulator system. The line spacing, exactly referenced to a microwave synthesizer, can be continuously tuned from 17.5 GHz to 20 GHz overcoming the limitation otherwise imposed by the free spectral range of the fibre loop, making the system capable of generating a continuously tuneable electrical signal from 122.5 GHz to >2.7 THz. The system noise has been measured up to a record frequency of 300 GHz, and shown to be limited by the multiplied phase noise of the reference synthesizer.
关键词： THz spectroscopy,tuneable,heterodyne signal,phase modulator,optical frequency comb generator
更新于2025-09-23 15:21:01
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Transmission characteristics of 24.5??Gb/s atmospheric laser communication based on optical frequency comb
摘要： Through cascading Mach–Zehnder intensity modulator (MZIM) and phase modulator (PM), an optical frequency comb (OFC) with 7 flat comb teeth is produced. The frequency interval of the OFC is 25 GHz and the flatness is less than 1.5 dB. The 7 channels of the OFC are used as the carrier source of the one-to-many free-space optical (FSO) communication system, and the atmospheric turbulence simulation pool is used to simulate the turbulence intensity in the real atmosphere to verify its feasibility for FSO communication. In the experiment, the bit error rate (BER) and eye diagram are measured under the back-to-back (BTB) conditions, and the temperature difference of atmospheric turbulence simulation pool are 80 ?C, 150 ?C and 220 ?C. Each channel of the system can stably transmit the on–off keying (OOK) signal of 3.5 Gb/s, and the 7 channels can stably transmit the OOK signal of 24.5 Gb/s. Thereby, the OFC can be used in place of multiple lasers or laser arrays as a carrier source for a one-to-many FSO communication system.
关键词： Wavelength division multiplexing,Optical frequency comb,Atmospheric turbulence,Free-space optical communication
更新于2025-09-23 15:19:57
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Laser optical frequency combs and their applications in optical fibre communication systems and astrophysics
摘要： This paper examines the generation and applications of laser optical frequency combs (LOFCs). The unique properties of LOFCs are widely used in spectroscopy and metrology, in particular for making ultra-accurate optical clocks. The use of LOFCs contributes to advances in optical fibre communication systems and studies pertaining to fundamental problems of astrophysics, such as the search for and investigation of exoplanets and verification of the hypothesis that physical constants vary with time.
关键词： exoplanets,optical frequency comb,calibration of astronomical spectrographs,multiplexing,Doppler spectroscopy
更新于2025-09-23 15:19:57
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Ultra-Wide and Flattened Optical Frequency Comb Generation Based on Cascaded Phase Modulator and LiNbO3-MZM Offering Terahertz Bandwidth
摘要： In this paper, a new technique for generation of ultra-wide and flattened optical frequency comb (OFC) based on serial cascading of a phase modulator and dual-driven Lithium-Niobate Mach Zehnder modulator (DD-LiNbO3-MZM) is proposed. Over 60 carriers were generated by carefully adjusting the RF switching voltage (RFSV) of the DD-LiNbO3-MZM and the signal frequency of the sinusoidal wave (RF) source. A low power amplified RF source with a signal driving power of ~16.9dBm is applied, and the power of CW laser is kept at 3dBm. The frequency spacing (FS) is kept at 20GHz for generating the maximum number of carriers. Nonetheless, the scheme is also tested for the FSs of 64GHz, and 32GHz. Each scenario is examined in simulation environment and the main outcomes are highlighted. The proposed scheme is comparatively simple and the FS varies with the applied RF source on the modulators. The achieved OFC lines have a tone-to-noise ratio (TNR) of over ~45dB with an undesired side mode suppression ratio of approximately 20dB. The comb lines are almost flat with a varying power deviation of around 0dB-6dB which is optimized to nearly ~0.12dB. Furthermore, the impact of the RFSV on the generated number of carriers is studied in detail. The scheme is analyzed in terms of cost efficiency, power deviations, TNR, optical signal to noise ratio, and number of achieved comb lines.
关键词： Optical Frequency Comb,Mach-Zehnder modulator,Phase modulator,Intensity modulation
更新于2025-09-23 15:19:57