DOCSLIB.ORG

Dual-Comb Interferometry Via Repetition Rate Switching of a Single Frequency Comb

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Dual-Comb Interferometry Via Repetition Rate Switching of a Single Frequency Comb 3614 Vol. 43, No. 15 / 1 August 2018 / Optics Letters Letter Dual-comb interferometry via repetition rate switching of a single frequency comb 1, 1 1,2 1,2 DAVID R. CARLSON, *DANIEL D. HICKSTEIN, DANIEL C. COLE, SCOTT A. DIDDAMS, AND 1,2 SCOTT B. PAPP 1Time and Frequency Division, National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA 2Department of Physics, University of Colorado, 2000 Colorado Ave., Boulder, Colorado 80309, USA *Corresponding author: [email protected] Received 14 June 2018; revised 27 June 2018; accepted 27 June 2018; posted 29 June 2018 (Doc. ID 335008); published 24 July 2018 We experimentally demonstrate a versatile technique for to an ultrafast laser to produce a pulse train whose repetition 0 performing dual-comb interferometry using a single fre- rate periodically alternates between f rep and f rep, resulting in quency comb. By rapid switching of the repetition rate, the creation of a time-multiplexed frequency comb. A fiber the output pulse train can be delayed and heterodyned with splitter then diverts half of the comb power to a delay line itself to produce interferograms. The full speed and resolu- of length Ldelay that is matched to half of the switching rate tion of standard dual-comb interferometry is preserved via L v ∕ 2f , where v is the group velocity of while simultaneously offering a significant experimental delay g mod g the fiber at the comb’s center wavelength. The other half of simplification and cost savings. We show that this approach the comb passes through an acousto-optic modulator is particularly suited for absolute distance metrology due to (AOM) to provide a frequency offset for the photodetected RF an extension of the nonambiguity range as a result of the spectrum, avoiding spectral aliasing at baseband frequencies. continuous repetition rate switching. https://doi.org/10.1364/OL.43.003614 The interference between two mutually coherent optical fre- quency combs with slightly different repetition rates can be used to extract temporal and spectral information from the combs with both high resolution and high speed [1,2]. This technique is known generally as dual-comb interferometry and has been suc- cessfully demonstrated for applications including spectroscopy [3], hyperspectral imaging [4], distance metrology [5], ellipsom- etry [6], and two-way time transfer [7]. The most common im- plementation uses two independent but optically phase-locked combs, though simplifications involving birefringent [8], bidirectional [9], or spatially multiplexed [10] resonators are possible, albeit with limited tunability in the repetition rates. Alternatively, at the cost of acquisition speed or spectral resolu- tion, a single comb can be used to obtain dual-comb interfero- grams through continuous repetition rate sweeping (OSCAT) [11–14], or by using an acousto-optic programmable dispersive Fig. 1. PHIRE concept. (a) An RF source providing the comb rep- filter to continuously shift the delay of a pulse train [15]. etition rate f is periodically modulated to produce two distinct Here we demonstrate a simple and versatile new approach to rep frequencies that alternate at a rate of f mod. The comb output is split dual-comb interferometry, using a single comb laser, that relies and recombined with itself after passing through a fixed length of on rapid switching of the pulse repetition rate to produce optical fiber to produce dual-comb interferograms. An acousto-optic interferograms at the full speed and resolution of standard modulator (AOM) provides a frequency offset for one arm to shift the dual-comb methods. We call this technique parallel heterodyne interferogram carrier frequency away from baseband. (b) An alternate interferometry via rep-rate exchange (PHIRE) and show how it RF configuration using electronic switching to toggle between two dif- can be used for applications including spectroscopy, vibrome- ferent sources for f rep. (c) The modulation f mod is matched to the try, and absolute distance metrology. length of the fiber delay such that the photodetected output produces The fundamental PHIRE concept is illustrated by the interferograms from the two overlapping pulse trains with repetition 0 schematic in Fig. 1(a). A binary modulation f mod is applied rates f rep and f rep. 0146-9592/18/153614-04 Journal © 2018 Optical Society of America Letter Vol. 43, No. 15 / 1 August 2018 / Optics Letters 3615 When these arms are recombined, a sequence of interferograms can be up to 4 orders of magnitude faster than the OSA, while Δ is produced at the difference in repetition rates f rep of the two additionallypffiffiffiffiffi providing an optical signal-to-noise ratio of pulse trains. In comparison, OSCAT, which shares a similar >25 dB∕ N across the comb bandwidth. self-delayed construction, acquires interferograms at the sweep- Increasing the comb bandwidth is possible by undergoing ing speed of f rep, but is practically limited to speeds a few nonlinear spectral broadening before passing through the delay Δ line. In fact, the time multiplexing inherent to PHIRE is ideal orders of magnitude less than the equivalent f rep [11]. If ab- solute calibration of the comb spacing or support for coherent for this type of process because the pulses do not walk across each in the nonlinear medium and thus do not introduce time domain averaging is desired, f mod can alternatively be used to select between two phase-coherent RF sources via a higher-order nonlinearities in the dual-comb interferograms. switch, as shown in Fig. 1(b). However, in both configurations, An example nonlinear PHIRE spectrum is shown in Fig. 2(b), obtained after the comb had been broadened in 4 m of highly the interferograms are reversed every half-cycle of f mod due to Δ the periodic swapping of pulse trains in each arm of the inter- nonlinear fiber. To maintain comb-tooth resolution, f rep was ferometer. Unlike standard dual comb, this means that acquis- reduced to 1 MHz while Ldelay was increased to 3 km. However, ∕ a practical limitation for nonlinear PHIRE using an electro- itions longer than 1 2f mod require extra processing in order to avoid spectral artifacts due to the out-of-phase interfero- optic source is that the two resulting combs have slightly differ- grams. Nevertheless, interferogram sequences shorter than ent spectral bandwidths, and thus a slightly different pulse ∕ chirp is required to optimally compress them [26]. However, 1 2f mod can be digitized and Fourier transformed directly to yield the comb’s full phase and amplitude spectrum. it should be possible to use electronically controlled RF phase The length of the fiber delay determines the optimum shifters to adjust the output pulse chirp synchronously with value of f and thus also limits what values of Δf are sup- f mod to mitigate this effect and allow stronger nonlinear inter- mod rep actions, possibly supporting direct self-referencing [18,27]. ported with full-frequency resolution. For example, when As in other forms of frequency comb spectroscopy, molecu- Δf < 2f , interferograms are acquired at the higher rate rep mod lar absorption measurements can be performed across the comb of 2f mod, though resolution is reduced due to the truncated delay bandwidth. For example, Fig. 2(c) shows several absorption range. This scenario can be useful when acquisition speed takes bands in H14C13N gas, obtained after passing through a 15 cm priority over resolution, but it may be necessary to control the pure gas cell at a pressure of 100 Torr and subtracting the back- relative phase of the RF sources to center the interferogram within ground [28]. To increase the effective resolution of the PHIRE Δ the scan window. On the other hand, when f rep > 2f mod, measurement, we leverage the tunability of the CW pump laser multiple interferograms will be acquired per half-period, with to sweep the entire comb across the absorption features in steps a maximum value limited only by aliasing at the Nyquist-zone of ∼0.01 nm. Absolute calibration of the wavelength in this edges for a given spectral bandwidth. This sequence of multiple case would require self-referencing; however, many applications interferograms can be Fourier transformed to yield a comb- for high-repetition-rate combs do not require such accuracy. resolved spectrum, or processed individually and averaged to improvethesignal-to-noiseratioofasingleinterferogram. While the PHIRE technique can be applied to any type of ultrafast pulse source capable of quickly changing repetition rate, 0 we demonstrate its implementation using an electro-optic modu- -50 lation (EOM) comb. EOM combs are simple and robust sources -100 of pulses that are carved directly from a continuous-wave (CW) Power (dB) laser through cascaded phase and intensity modulation [16–18]. 1546 1548 1550 1552 1554 The result is a highly flexible comb that can support various Wavelength (nm) electronic readout configurations including narrowband self- heterodyne interference spectroscopy [19,20]andOSCAT[21], -40 as well as standard dual-comb interferometry [22–25]. -60 Our EOM comb, implementing the RF configuration from -80 Fig. 1(b) with ∼10 ns switching speed, consists of three phase Power (dB) 1530 1535 1540 1545 1550 1555 1560 1565 1570 modulators followed by one intensity modulator and has a Wavelength (nm) nominal repetition rate of 10.1 GHz. A difference in repetition Δ rates of f rep 3.28 MHz is set by the two phase-coherent 1 RF synthesizers and is chosen to be an integer multiple of ∼ f mod 164 kHz, which is matched to the 600 m single- mode fiber delay. This configuration allows up to 10 interfero- 0.5 Transmittance grams to be acquired during each switching cycle and supports 1548.5 1549 1549.5 1550 1550.5 1551 1551.5 comb-tooth-resolved spectra.
Load more

Recommended publications
  • Fundamentals of Frequency Combs: What They Are and How They Work
    Fundamentals of frequency combs: What they are and how they work Scott Diddams Time and Frequency Division National Institute of Standards and Technology Boulder, CO KISS Worshop: “Optical Frequency Combs for Space Applications” 1 Outline 1. Optical frequency combs in timekeeping • How we got to where we are now…. 2. The multiple faces of an optical frequency comb 3. Classes of frequency combs and their basic operation principles • Mode-locked lasers • Microcombs • Electro-optic frequency combs 4. Challenges and opportunities for frequency combs 2 Timekeeping: The long view Oscillator Freq. f = 1 Hz Rate of improvement f = 10 kHz since 1950: 1.2 decades / 10 years f = 10 GHz “Moore’s Law”: 1.5 decades / 10 years f = 500 THz Gravitational red shift of 10 cm Sr optical clock ? f = 10-100 PHz ?? S. Diddams, et al, Science (2004) Timekeeping: The long view Oscillator Freq. f = 1 Hz f = 10 kHz f = 10 GHz f = 500 THz Gravitational red shift of 10 cm Sr optical clock ? f = 10-100 PHz ?? S. Diddams, et al, Science (2004) Use higher frequencies ! Dividing the second into smaller pieces yields superior frequency standards and metrology tools: 15 νoptical 10 ≈ ≈ 105 νmicrowave 1010 In principle (!), optical standards could surpass their microwave counterparts by up to five orders of magnitude ... but how can one count, control and measure optical frequencies? 5 Optical Atomic Clocks Atom(s) νo Detector At NIST/JILA: Ca, Hg+, Al+, Yb, Sr & Slow Δν Laser Control Atomic Resonance Counter & Laser Read Out Fast Laser (laser frequency comb) Control •Isolated cavity narrows laser linewidth and provides short term timing reference Isolated Optical Cavity •Atoms provide long-term stability and accuracy— now now at 10-18 level! •Laser frequency comb acts as a divider/counter Outline 1.
    [Show full text]
  • Towards On-Chip Self-Referenced Frequency-Comb Sources Based on Semiconductor Mode-Locked Lasers
    micromachines Review Towards On-Chip Self-Referenced Frequency-Comb Sources Based on Semiconductor Mode-Locked Lasers Marcin Malinowski 1,*, Ricardo Bustos-Ramirez 1 , Jean-Etienne Tremblay 2, Guillermo F. Camacho-Gonzalez 1, Ming C. Wu 2 , Peter J. Delfyett 1,3 and Sasan Fathpour 1,3,* 1 CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, FL 32816, USA; [email protected] (R.B.-R.); [email protected] (G.F.C.-G.); [email protected] (P.J.D.) 2 Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA; [email protected] (J.-E.T.); [email protected] (M.C.W.) 3 Department of Electrical and Computer Engineering, University of Central Florida, Orlando, FL 32816, USA * Correspondence: [email protected] (M.M.); [email protected] (S.F.) Received: 14 May 2019; Accepted: 5 June 2019; Published: 11 June 2019 Abstract: Miniaturization of frequency-comb sources could open a host of potential applications in spectroscopy, biomedical monitoring, astronomy, microwave signal generation, and distribution of precise time or frequency across networks. This review article places emphasis on an architecture with a semiconductor mode-locked laser at the heart of the system and subsequent supercontinuum generation and carrier-envelope offset detection and stabilization in nonlinear integrated optics. Keywords: frequency combs; heterogeneous integration; second-harmonic generation; supercontinuum; integrated photonics; silicon photonics; mode-locked lasers; nonlinear optics 1. Introduction The field of integrated photonics aims at harnessing optical waves in submicron-scale devices and circuits, for applications such as transmitting information (communications) and gathering information about the environment (imaging, spectroscopy, etc.).
    [Show full text]
  • Atomic Clocks of the Future: Using the Ultrafast and Ultrastable'
    Atomic clocks of the future: using the ultrafast and ultrastable' Leo Hollberg, Scott Diddanis, Chris Oates, Anne Curtis. SCbastien Bize, and Jim Bergquist National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305 F-mai!: !~ol!ber~~,b~~!der.ni~~.gc\~ *Contribution of NlST not subject Lo copyrigl~t. Abstract. The applicalion of ultrafast mode-locked lasers and nonlinear optics to optical frequency nietrology is revolutionizing the field ofatomic clocks. The basic concepts and applications are reviewed using our recent rcsults with two optical atomic frequency standards based on laser cooled and trapped atoms. In contrast to today's atomic clocks that are based on electronic oscillators locked to microwave transitions in atoms, the nest generation of atomic clocks will ]nos[ likely employ lasers and optical transitions in lasel--cooled atoms and ions. Optical atomic frequency standards use frequency-stabilized CW lasers with good short-term stability that are stabilized to narrow atomic rcsonances using feedback control systems. At NIST we are developing two optical frequency standards, one based on laser cooled and trapped calcium atoms and the other on a single laser cooled trapped Hg+ ion. Similar research is being done at labs around the world. 1\1oving from microwave frequencies, where one cycle corresponds to 100 ps, to optical frequencies where one cycle is a femtosecond long, allows us to divide time into smaller intervals and hence gain frequency stability and timing precision. Steady progress over the past 30 years has improved the performance of optical fiquency standards to the point that they are now competitive with, and even moving beyond.
    [Show full text]
  • Kerr Microresonator Soliton Frequency Combs at Cryogenic Temperatures
    Kerr Microresonator Soliton Frequency Combs at Cryogenic Temperatures Gregory Moille,1, 2, ∗ Xiyuan Lu,1, 2 Ashutosh Rao,1, 2 Qing Li,1, 2, 3 Daron A. Westly,1 Leonardo Ranzani,4 Scott B. Papp,5, 6 Mohammad Soltani,4 and Kartik Srinivasan1, 7, y 1Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA 2Institute for Research in Electronics and Applied Physics and Maryland Nanocenter, University of Maryland,College Park, Maryland 20742, USA 3Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA 4Raytheon BBN Technologies, 10 Moulton Street, Cambridge, MA, 02138, USA 5Time and Frequency Division, National Institute of Standards and Technology, 385 Broadway, Boulder, CO 80305, USA 6Department of Physics, University of Colorado, Boulder, Colorado, 80309, USA 7Joint Quantum Institute, NIST/University of Maryland, College Park, Maryland 20742, USA (Dated: February 19, 2020) We investigate the accessibility and projected low-noise performance of single soliton Kerr fre- quency combs in silicon nitride microresonators enabled by operating at cryogenic temperatures as low as 7 K. The resulting two orders of magnitude reduction in the thermo-refractive coefficient relative to room-temperature enables direct access to single bright Kerr soliton states through adia- batic frequency tuning of the pump laser while remaining in thermal equilibrium. Our experimental results, supported by theoretical modeling, show that single solitons are easily accessible at tem- peratures below 60 K for the microresonator device under study. We further demonstrate that the cryogenic temperature primarily impacts the thermo-refractive coefficient. Other parameters critical to the generation of solitons, such as quality factor, dispersion, and effective nonlinearity, are unaltered.
    [Show full text]
  • Collision of Akhmediev Breathers in Nonlinear Fiber Optics
    PHYSICAL REVIEW X 3, 041032 (2013) Collision of Akhmediev Breathers in Nonlinear Fiber Optics B. Frisquet, B. Kibler,* and G. Millot Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Universite´ de Bourgogne, Dijon, France (Received 1 July 2013; published 19 December 2013) We report here a novel fiber-based test bed using tailored spectral shaping of an optical-frequency comb to excite the formation of two Akhmediev breathers that collide during propagation. We have found specific initial conditions by controlling the phase and velocity differences between breathers that lead, with certainty, to their efficient collision and the appearance of a giant-amplitude wave. Temporal and spectral characteristics of the collision dynamics are in agreement with the corresponding analytical solution. We anticipate that experimental evidence of breather-collision dynamics is of fundamental importance in the understanding of extreme ocean waves and in other disciplines driven by the continuous nonlinear Schro¨dinger equation. DOI: 10.1103/PhysRevX.3.041032 Subject Areas: Interdisciplinary Physics, Nonlinear Dynamics, Optics I. INTRODUCTION randomization inherent to the study of incoherent waves or chaotic states, various numerical works have shown the Nonlinear coherent phenomena in continuous media spontaneous emergence of coherent localized waves (even have been a key subject of research over the last decades rational solutions of the NLSE) from a turbulent environ- in the framework of the nonlinear Schro¨dinger equation ment [7,13–15]. Rogue waves are not just an offshoot of (NLSE), with applications to plasma physics, fluid dynam- breather collisions, but other mechanisms depending on the ics, and nonlinear optics [1]. In particular, much attention physical system must be taken into account in the forma- has been focused on the common solitary wave structures, tion of rogue waves, including the statistical approach, known as solitons, and their interactions in almost conser- when noise is present [16].
    [Show full text]
  • Self-Referencing a CW Laser with Efficient Nonlinear Optics
    Self-referencing a CW laser with efficient nonlinear optics Scott Papp, Katja Beha, Pascal Del’Haye, Daniel Cole, Aurélien Coillet, Scott Diddams Time and Frequency Division, National Institute of Standards and Technology, Boulder, CO 80305 USA [email protected] Abstract: We present self-referencing of a CW laser via nonlinear pulse broadening of a Kerr microcomb and an electro-optic modulation (EOM) comb. Our experiments demonstrate the first phase-coherent optical-to-microwave link via f-2f self-referencing with such combs. OCIS codes: (190.4410) Nonlinear optics, parametric processes; (140.3948) Microcavity devices; (190.4380) Nonlinear optics, four-wave mixing. 1. Overview of experimental results Modelocked-laser frequency combs have revolutionized optical frequency metrology and precision time keeping by providing an equidistant set of absolute reference lines that span in excess of an octave. Their typically sub-GHz repetition frequency and <100 fs optical pulses enable nonlinear broadening for self-referencing, and feature among the highest spectral purity of any oscillator. Such devices have enabled myriad applications from optical clocks (1– 6) to precisely calibrated spectroscopy to quantum information. Moreover, experimental control of carrier-envelope offset phase contributes to ultrafast science. Frequency combs generated from a CW laser via Kerr parametric nonlinear optics in microcavities (Kerr microcombs) (7, 8) and electro-optic modulation (EOM) (9–13) are interesting new platforms for experimenters. The 10’s of GHz or higher repetition frequency and the offset frequency of such combs are tunable to match a fuller range of comb applications in optical communications, metrology, arbitrary waveform generation, and with quantum-based systems.
    [Show full text]
  • Instabilities, Breathers and Rogue Waves in Optics
    Instabilities, breathers and rogue waves in optics John M. Dudley1, Frédéric Dias2, Miro Erkintalo3, Goëry Genty4 1. Institut FEMTO-ST, UMR 6174 CNRS-Université de Franche-Comté, Besançon, France 2. School of Mathematical Sciences, University College Dublin, Belfield, Dublin 4, Ireland 3. Department of Physics, University of Auckland, Auckland, New Zealand 4. Department of Physics, Tampere University of Technology, Tampere, Finland Optical rogue waves are rare yet extreme fluctuations in the value of an optical field. The terminology was first used in the context of an analogy between pulse propagation in optical fibre and wave group propagation on deep water, but has since been generalized to describe many other processes in optics. This paper provides an overview of this field, concentrating primarily on propagation in optical fibre systems that exhibit nonlinear breather and soliton dynamics, but also discussing other optical systems where extreme events have been reported. Although statistical features such as long-tailed probability distributions are often considered the defining feature of rogue waves, we emphasise the underlying physical processes that drive the appearance of extreme optical structures. Many physical systems exhibit behaviour associated with the emergence of high amplitude events that occur with low probability but that have dramatic impact. Perhaps the most celebrated examples of such processes are the giant oceanic “rogue waves” that emerge unexpectedly from the sea with great destructive power [1]. There is general agreement that 1 the emergence of giant waves involves physics different from that generating the usual population of ocean waves, but equally there is a consensus that one unique causative mechanism is unlikely.
    [Show full text]
  • Hyperspectral Terahertz Imaging with Electro-Optic Dual Combs and a FET-Based Detector
    www.nature.com/scientificreports OPEN Hyperspectral terahertz imaging with electro‑optic dual combs and a FET‑based detector Pedro Martín‑Mateos1*, Dovilė Čibiraitė‑Lukenskienė2, Roberto Barreiro1, Cristina de Dios1, Alvydas Lisauskas3,4, Viktor Krozer1,2,5 & Pablo Acedo1 In this paper, a terahertz hyperspectral imaging architecture based on an electro‑optic terahertz dual‑comb source is presented and demonstrated. In contrast to single frequency sources, this multi‑ heterodyne system allows for the characterization of the whole spectral response of the sample in parallel for all the frequency points along the spectral range of the system. This hence provides rapid, highly consistent results and minimizes measurement artifacts. The terahertz illumination signal can be tailored (in spectral coverage and resolution) with high fexibility to meet the requirements of any particular application or experimental scenario while maximizing the signal‑to‑noise ratio of the measurement. Besides this, the system provides absolute frequency accuracy and a very high coherence that allows for direct signal detection without inter‑comb synchronization mechanisms, adaptive acquisition, or post‑processing. Using a feld‑efect transistor‑based terahertz resonant 300 GHz detector and the raster‑scanning method we demonstrate the two‑dimensional hyperspectral imaging of samples of diferent kinds to illustrate the remarkable capabilities of this innovative architecture. A proof‑of‑concept demonstration has been performed in which tree leaves and a complex plastic fragment have been analyzed in the 300 GHz range with a frequency resolution of 10 GHz. Terahertz (THz) spectroscopy and hyperspectral imaging systems are expected to have an important impact in the sorting industries (food, waste management, etc.)1, security2 and non-destructive testing3.
    [Show full text]
  • Microresonator Kerr Frequency Combs with High Conversion Efficiency Xiaoxiao Xue,1,2* Pei-Hsun Wang,2 Yi Xuan,2,3 Minghao Qi,2,3 and Andrew M
    Microresonator Kerr frequency combs with high conversion efficiency Xiaoxiao Xue,1,2* Pei-Hsun Wang,2 Yi Xuan,2,3 Minghao Qi,2,3 and Andrew M. Weiner2,3 1Department of Electronic Engineering, Tsinghua University, Beijing 100084, China 2School of Electrical and Computer Engineering, Purdue University, 465 Northwestern Avenue, West Lafayette, Indiana 47907-2035, USA 3Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907, USA *Corresponding author: [email protected] ABSTRACT: Microresonator-based Kerr frequency comb 1 shows the energy flow chart in microcomb generation. Considering the (microcomb) generation can potentially revolutionize a optical field circulating in the cavity, part of the pump and comb power is variety of applications ranging from telecommunications absorbed (or scattered) due to the intrinsic cavity loss, and part is to optical frequency synthesis. However, phase-locked coupled out of the cavity into the waveguide; meanwhile, a fraction of the microcombs have generally had low conversion efficiency pump power is converted to the other comb lines, effectively resulting in limited to a few percent. Here we report experimental a nonlinear loss to the pump. At the output side of the waveguide, the results that achieve ~30% conversion efficiency (~200 mW residual pump line is the coherent summation of the pump component on-chip comb power excluding the pump) in the fiber coupled from the cavity and the directly transmitted pump; the power present in the other comb lines excluding the pump constitutes the telecommunication band with broadband mode-locked usable comb power. Here we omit any other nonlinear losses possibly dark-pulse combs.
    [Show full text]
  • 20 Years of Developments in Optical Frequency Comb Technology and Applications
    There are amendments to this paper REVIEW ARTICLE https://doi.org/10.1038/s42005-019-0249-y OPEN 20 years of developments in optical frequency comb technology and applications Tara Fortier1,2* & Esther Baumann1,2* 1234567890():,; Optical frequency combs were developed nearly two decades ago to support the world’s most precise atomic clocks. Acting as precision optical synthesizers, frequency combs enable the precise transfer of phase and frequency information from a high-stability reference to hundreds of thousands of tones in the optical domain. This versatility, coupled with near- continuous spectroscopic coverage from microwave frequencies to the extreme ultra-violet, has enabled precision measurement capabilities in both fundamental and applied contexts. This review takes a tutorial approach to illustrate how 20 years of source development and technology has facilitated the journey of optical frequency combs from the lab into the field. he optical frequency comb (OFC) was originally developed to count the cycles from optical atomic clocks. Atoms make ideal frequency references because they are identical, T fi and hence reproducible, with discrete and well-de ned energy levels that are dominated by strong internal forces that naturally isolate them from external perturbations. Consequently, in 1967 the international standard unit of time, the SI second was redefined as 9,192,631,770 oscillations between two hyper-fine states in 133Cs1. While 133Cs microwave clocks provide an astounding 16 digits in frequency/time accuracy, clocks based on optical transitions in atoms are being explored as alternative references because higher transition frequencies permit greater than a 100 times improvement in time/frequency resolution (see “Timing, synchronization, and atomic clock networks”).
    [Show full text]
  • Chip-Based Optical Frequency Combs for High-Capacity Optical
    Nanophotonics 2021; 10(5): 1367–1385 Review Hao Hu* and Leif K. Oxenløwe Chip-based optical frequency combs for high-capacity optical communications https://doi.org/10.1515/nanoph-2020-0561 1 Introduction Received October 7, 2020; accepted December 16, 2020; published online February 3, 2021 An optical frequency comb has an optical spectrum consisting of a series of discrete, equally spaced and Abstract: Current fibre optic communication systems owe phase-locked frequency lines. Frequency combs can be their high-capacity abilities to the wavelength-division generated in several ways, and have many applications, multiplexing (WDM) technique, which combines data and have therefore attracted a lot of attention. In 2005, channels running on different wavelengths, and most often half of the Nobel Prize in physics was awarded to John L. requires many individual lasers. Optical frequency combs, Hall and Theodor W. Hansch for their pioneering work on with equally spaced coherent comb lines derived from a single source, have recently emerged as a potential sub- optical frequency combs for spectroscopy applications. stitute for parallel lasers in WDM systems. Benefits include Since then, optical frequency combs have been widely the stable spacing and broadband phase coherence of investigated for numerous diverse applications, such the comb lines, enabling improved spectral efficiency of as spectroscopy, ranging, atomic clocks, searching for transmission systems, as well as potential energy savings exoplanets, microwave photonics and optical communi- in the WDM transmitters. In this paper, we discuss the re- cations [1–16]. quirements to a frequency comb for use in a high-capacity Current optical communication systems are based on optical communication system in terms of optical line- wavelength-division multiplexing (WDM), which relies on width, per comb line power and optical carrier-to-noise arrays of discrete wavelength laser sources [17].
    [Show full text]
  • Fully Integrated Ultra-Low Power Kerr Comb Generation
    Fully integrated ultra-low power Kerr comb generation Brian Stern1,2, Xingchen Ji1,2, Yoshitomo Okawachi3, Alexander L. Gaeta3, and Michal Lipson2 1School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA 2Department of Electrical Engineering, Columbia University, New York, NY 10027, USA 3Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA Corresponding Author: [email protected] Optical frequency combs are broadband sources that offer mutually-coherent, equidistant spectral lines with unprecedented precision in frequency and timing for an array of applications1•9. Kerr frequency combs in microresonators require a single-frequency pump laser and have offered the promise of highly compact, scalable, and power efficient devices. Here, we realize this promise by demonstrating the first fully integrated Kerr frequency comb source through use of extremely low-loss silicon nitride waveguides that form both the microresonator and an integrated laser cavity. Our device generates low-noise soliton-modelocked combs spanning over 100 nm using only 98 mW of electrical pump power. Our design is based on a novel dual-cavity configuration that demonstrates the flexibility afforded by full integration. The realization of a fully integrated Kerr comb source with ultra-low power consumption brings the possibility of highly portable and robust frequency and timing references, sensors, and signal sources. It also enables new tools to investigate the dynamics of comb and soliton generation through close chip-based integration of microresonators and lasers. Frequency combs based on chip-scale microresonators offer the potential for high- precision photonic devices for time and frequency applications in a highly compact and robust platform.
    [Show full text]