Optical frequency comb technology: from ground to space

Optical frequency combs,as powerful tools for precision spectroscopy and research into optical frequency standards,have driven continuous progress and significant breakthroughs in applications such as time-frequency transfer,measurement of fundamental physical constants,and high-precision ranging,achieving a series of milestone results in ground-based environments.With the continuous maturation and evolution of femtosecond lasers and related technologies,optical frequency combs are moving from ground-based applications to astronomical and space-based applications,playing an increasingly important role in atomic clocks,exoplanet observations,gravitational wave measurements,and other areas.This paper,focusing on astronomical and space-based applications,reviews research progress on astronomical frequency combs,optical clock time-frequency networks,gravitational waves,dark matter measurement,dual-comb large-scale absolute ranging,and high-resolution atmospheric spectroscopy.With enhanced performance and their gradual application in the field of space-based research,optical frequency combs will undoubtedly provide more powerful support for astronomical science and cosmic exploration in the future.

Frequency-modulated continuous-wave multiplexed gas sensingbased on optical frequency comb calibration

Laser absorption spectroscopy has proven to be an effective approach for gas sensing, which plays an important rolein the fields of military, industry, medicine and basic research. This paper presents a multiplexed gas sensing system basedon optical frequency comb (OFC) calibrated frequency-modulated continuous-wave (FMCW) tuning nonlinearity. Thesystem can be used for multi-parameter synchronous measurement of gas absorption spectrum and multiplexed opticalpath. Multi-channel parallel detection is realized by combining wavelength division multiplexing (WDM) and frequencydivision multiplexing (FDM) techniques. By introducing nonlinear optical crystals, broadband spectrum detection is simultaneouslyachieved over a bandwidth of hundreds of nanometers. An OFC with ultra-high frequency stability is used asthe frequency calibration source, which guarantees the measurement accuracy. The test samples involve H13C14N, C_(2)H_(2)and Rb vapor cells of varying densities and 5 parallel measurement experiments are designed. The results show that themeasurement accuracies of spectral absorption line and the optical path are 150 MHz and 20 m, respectively. The schemeoffers the advantages of multiplexed, multi-parameter, wide spectrum and high resolution detection, which can realize theidentification of multi-gas components and the high-precision inversion of absorption lines under different environments.The proposed sensor demonstrates great potential in the field of high-resolution absorption spectrum measurement for gassensing applications.

Mid-infrared Optical Frequency Comb-based Fourier Transform Spectrometer for Broadband Molecular Spectroscopy

Optical frequency combbased Fourier transform spectroscopy has the features of broad spectral bandwidth,high sensitivity,andmultiplexed trace gas detection,which has valuable application potential in the fields of precision spectroscopy and trace gas detection.Here,we report the development of a mid-infrared Fourier transform spectrometer based on an optical frequency comb combined with a Herriott-type multipass cell.Using this instrument,the broadband absorption spectra of several important molecules,including methane,acetylene,water molecules and nitrous oxide,are measured by near real-time data acquisition in the 2800-3500 cm^(-1)spectral region.The achieved minimum detectable absorption of the instrument is 4.4×10^(-8)cm^(-1)·Hz^(-1/2)per spectral element.Broadband spectra of H_(2)0 are fited using the Voigt profile multispectral fitting technique and the consistency of the concentration inversion is 1%.Our system also enables precise spectroscopic measurements,and it allows the determination of the spectral line positions and upper state constants of N_(2)O in the(0002)-(1000)band,with results in good agreement with those reported by Toth[Appl.Opt.30,5289(1991)].

Phase-coherence dynamics of frequency-comb emission via high-order harmonic generation in few-cycle pulse trains

Frequency-comb emission via high-order harmonic generation(HHG)provides an alternative method for the coherent vacuum ultraviolet(VUV)and extreme ultraviolet(XUV)radiation at ultrahigh repetition rates.In particular,the temporal and spectral features of the HHG were shown to carry profound insight into frequency-comb emission dynamics.Here we present an ab initio investigation of the temporal and spectral coherence of the frequency comb emitted in HHG of He atom driven by few-cycle pulse trains.We find that the emission of frequency combs features a destructive and constructive coherences caused by the phase interference of HHG,leading to suppression and enhancement of frequency-comb emission.The results reveal intriguing and substantially different nonlinear optical response behaviors for frequency-comb emission via HHG.The dynamical origin of frequency-comb emission is clarified by analyzing the phase coherence in HHG processes in detail.Our results provide fresh insight into the experimental realization of selective enhancement of frequency comb in the VUV–XUV regimes.

Comb-Based Filter Design Using Sharpening Technique and Certain Palindromic Polynomial

This paper presents a novel approach to improve aliasing rejection in comb-based decimation filters. The method is established on certain palindromic polynomials with all zeros on the unit circle and the sharpening technique. As a result, aliasing rejection and the passband characteristic are improved. The method is illustrated with various examples and compared with the methods from the literature. .

一种改进的Fixed-base Comb安全快速算法

本文从分析椭圆曲线上Fixed-baseComb算法出发,根据其特点,利用牺牲乘法操作以降低求逆操作的方法,分别用2kP、2P+Q的快速算法对Fixed-baseComb算法的预计算阶段和赋值阶段进行改进,极大地提高了计算效率:在素数域上预计算阶段提高70%～80%,而赋值阶段提高38%～43%,同时,改进算法通过对k的预处理,使得算法能够抵抗边际信道攻击.

Sub-femtometer-resolution absolute spectroscopy with sweeping electro-optic combs

Optical frequency comb with evenly spaced lines over a broad bandwidth has revolutionized the fields of optical metrology and spectroscopy.Here,we propose a fast interleaved dual-comb spectroscopy with sub-femtometer-resolution and absolute frequency,in which two electro-optic frequency combs are swept.Electrically-modulated stabilized laser enables ultrahigh resolution of 0.16 fm(or 20 k Hz in optical frequency)and single-shot measurement in 90 ms.Total 20 million points are recorded spanning 3.2 nm(or 400 GHz)bandwidth,corresponding to a spectral sampling rate of 2.5×10^(8)points/s under Nyquist-limitation.Besides,considering the trade-off between the measurement time and spectral resolution,a fast single-shot measurement is also realized in 1.6 ms with 8 fm(or 1 MHz)resolution.We demonstrate the 25-averaged result with 30.6 d B spectral measurement signal-to-noise ratio(SNR)by reducing the filter bandwidth in demodulation.The results show great prospect for precise measurement with flexibly fast refresh time,high spectral resolution,and high SNR.

Ultrasonic Sound Hot Extract—Ultraviolet Spectrophotometric Determination of Total Flavone in Comb Honey

[Objective] The aim was to establish a rapid method for the determination of the content of total flavonoids in the honey comb. [Method] The content of total flavonoids weas determined based on samples including comb honey, propolis, royal jelly, linden tree honey, with a polyamide column chromatography by spectrophotometry at 360 nm wavelength. [Result] The recovery rate of the method was above 90%, and the variation coefficient was lower than 2%. Compared with the traditional method, this method has less reagent consumption, simple operation and so on.[Conclusion] The content of total flavonoids in comb honey was 14.97 mg/100 g, although is only 0.87% of the total flavone content in propolis. The contained total flavonoids at least doubled than that of others and comb honey is more valuable in the content of flavonoids.

Influence of Dropping scales of E7/6 Comber on Process Performance

The dropping scales is an important parameter for comber noil and combing quality. Because the rocking of the nipper shaft makes the nippers move backward and forward through a series of links, the original position of nipper frame is altered when changing the dropping scales, the other parameters of combing are changed accordingly. In this paper, the timing of opening-closing on nipper, the timing of cylinder’s combing, the timing of detaching-lapping and variation of nip pressure are calculated and their effects on combing are analyzed in different dropping scales on E7/6 comber.

无移位操作的快速comb乘法算法

有限域GF(2n)上乘法运算是影响GF(2n)上椭圆曲线密码实现效率的关键运算之一。基于窗口技术的comb乘法算法,被认为是目前有限域GF(2n)上乘法运算最快的算法之一。但是,它仍然使用了移位操作,而移位操作恰好又是域GF(2n)乘法运算中很耗时的操作。提出并实现了一种新的基于窗口技术的快速comb乘法算法,该算法避免了移位操作,且不增加异或运算次数。理论分析和实验结果表明,新算法有很好的实现效率,适合于有限域GF(2n)上椭圆曲线密码算法的软件实现。

一种基于折半运算的Comb标量乘算法

通过将折半运算应用于Comb算法,提出了一种新的Comb标量乘算法,它可以提高域F2^m上的椭圆曲线标量乘法的效率.在预计算阶段和赋值阶段,新算法分别用高效的折半运算取代倍点运算.对新算法运行时间进行分析,并与传统的Comb算法进行比较,当窗口宽度w=4时,新算法效率提高58%-63%.

On design of efficient comb decimator with improved response

A three-part comb decimator is presented in this paper, for the applications with severe requirements of circuit performance and frequency response. Based on the modified prime factorization method and multistage polyphase decomposition, an efficient non-recursive structure for the cascaded integrator-comb （CIC） decimation filter is derived. Utilizing this structure as the core part, the proposed comb decimator can not only loosen the decimation ratio＇s limitation, but also balance the tradeoff among the overall power consumption, circuit area and maximum speed. Further, to improve the frequency response of the comb decimator, a cos-prefilter is introduced as the preprocessing part for increasing the aliasing rejection, and an optimum sin-based filter is used as the compensation part for decreasing the passband droop.

抗SPA攻击的固定基comb标量乘算法

简单能量分析攻击(SPA)是椭圆曲线密码体制中比较常见的一种攻击方式。基于Mohamed提出的优化固定基comb标量乘算法,提出一种优化的标量编码算法,使得编码后标量中所有的项均不为零;并在此基础上提出一种能够抵抗SPA攻击的固定基comb算法,在保证算法性能的基础上提高算法的安全性。最终OCTEON平台上实验结果表明,对比能够抗SPA攻击的Joye-Tunstall算法,本文提出的算法在需要存储预计算点数量相同的情况下,计算性能得到了大幅度的提高。

“战斗力”能译成“combativeness”吗?

新华网英文版在一篇报道中把军事术语"战斗力"译成了"combativeness"。通过分析十四部英汉词典中"combativeness"的释义、八部汉英词典给出的"战斗力"的译法以及基于问卷调查的结果,作者指出了新华网这一译法的错误,补充了汉英词典未收录的"战斗力"的两种译法,并强调加强外宣翻译中政治意识的重要性。

梳形聚合物comb-1的溶液性能对比评价

通过试验手段对比梳形聚合物comb-1与大庆生产的HPAM和日本三菱公司生产的MO-4000的溶液性能,主要包括溶液粘度对浓度的依赖性、剪切稳定性、抗盐性及粘度对温度依赖性的研究。试验表明,在实验室自来水中和在盐水中梳形聚合物comb-1的剪切稳定性、抗盐性、高温粘度保持性等均优于日本MO-4000和大庆HPAM。日本MO-4000和大庆HPAM是目前油田应用的较为普遍的聚丙烯酰胺,通过对比研究,说明梳形聚合物comb-1的性能更好,有望成为聚丙烯酰胺的替代品。

A long-term frequency-stabilized erbium-fiber-laser-based optical frequency comb with an intra-cavity electro-optic modulator

We demonstrate an optical frequency comb based on an erbium-doped-fiber femtosecond laser with the nonlinear polarization evolution scheme. The repetition rate of the laser is about 209 MHz. By controlling an intra-cavity electro- optic modulator and a piezo-transducer, the repetition rate can be stabilized with a high-bandwidth servo in a frequency range of 3 kHz, enabling long-term repetition rate phase-locking. The in-loop frequency stability of repetition rate is about 1.6× 10-13 in an integration time of 1 s, limited by the measurement system; and it is inversely proportional to integration time in the short term. Furthermore, using a common path f-2f interferometer, the carrier envelope offset frequency of the comb is obtained with a signal-to-noise ratio of 40 dB in a 3-MHz resolution bandwidth. Stabilized cartier envelope offset frequency exhibits a deviation of 0.6 mHz in an integration time of 1 s.

梳形聚合物comb-1的结构表征

对实验室合成梳形聚合物comb-1的化学结构、形貌特征及抗盐性能进行了研究.通过FT-IR傅立叶变换红外光谱和Inova-600型核磁共振波谱分析得出梳形聚合物comb-1的化学结构是丙烯酰胺与单体B的共聚物;通过Nanoscope IIIa型多功能原子力显微镜观察该梳形聚合物形貌,发现该聚合物确实是梳形结构;利用Quanta-200型扫描电镜对梳形聚合物comb-1进行观察,发现其抗盐性能较好,并且在模拟南阳油田水质条件下,相比日本三菱公司生产的MO-4000而言,梳形聚合物comb-1确实具有更好的抗盐能力.

A 23.75-GHz frequency comb with two low-finesse filtering cavities in series for high resolution spectroscopy

A laser frequency comb with several tens GHz level is demonstrated,based on a Yb-doped femtosecond fiber laser and two low-finesse Fabry-Perot cavities（FPCs） in series.The original 250-MHz mode-line-spacing of the source comb is filtered to 4.75 GHz and 23.75 GHz,respectively.According to the multi-beam interferences theory of FPC,the side-mode suppression rate of FPC schemes is in good agreement with our own theoretical results from 27 dB of a single FPC to43 dB of paired FPCs.To maintain long-term stable operation and determine the absolute frequency mode number in the23.75-GHz comb,the Pound-Drever-Hall（PDH） locking technology is utilized.Such stable tens GHz frequency combs have important applications in calibrating astronomical spectrographs with high resolution.

基于奇系数Comb的椭圆曲线密码抗功耗攻击方案

针对资源受限的密码芯片在抵抗功耗攻击中存在效率和安全两个方面的矛盾。通过将标量采用奇系数梳状算法进行编码,然后结合预计算表将椭圆曲线标量乘法运算转化为一组小标量乘法运算,并利用基点掩码技术实施抗功耗攻击,提出一种基于奇系数Comb的椭圆曲线密码抗功耗攻击方案。算法性能分析结果表明:与传统的抗功耗攻击方案相比,给出的抗功耗攻击方案不仅可以抵抗简单功耗攻击、差分功耗攻击、零值寄存器功耗攻击和零值点功耗攻击,并且能够在存储空间和主循环运算量基本保持不变的情况下具有更高效的运算效率,在各种资源受限的应用系统中具有较好的实际应用价值。

Review of low timing jitter mode-locked fiber lasers and applications in dual-comb absolute distance measurement

Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperature is considerably below one femtosecond at high Fourier frequency. The ultrashort pulse train with ultralow timing jitter enables absolute time-of-flight measurements based on a dual-comb implementation, which is typically composed of a pair of optical frequency combs generated by femtosecond lasers. Dead-zone-free absolute distance measurement with sub-micrometer precision and kHz update rate has been routinely achieved with a dual-comb configuration, which is promising for a number of precision manufacturing applications, from large step-structure measurements prevalent in microelectronic profilometry to three coordinate measurements in large-scale aerospace manufacturing and shipbuilding. In this paper, we first review the sub-femtosecond precision timing jitter characterization methods and approaches for ultralow timing jitter mode-locked fiber laser design. Then, we provide an overview of the state-of-the-art dual-comb absolute ranging technology in terms of working principles, experimental implementations, and measurement precisions. Finally, we discuss the impact of quantum-limited timing jitter on the dual-comb ranging precision at a high update rate. The route to highprecision dual-comb range finder design based on ultralow jitter femtosecond fiber lasers is proposed.