Micro-combs: A novel generation of optical sources

By Alessia Pasquazi, Marco Peccianti, Luca Razzari, David J. Moss, Stephane Coen, Miro Erkintalo, Yanne K. Chembo, Tobias Hansson, Stefan Wabnitz, P. Del’Haye and 3 more. 2017

748 citations recorded by the source corpus.

Abstract The quest towards the integration of ultra-fast, high-precision optical clocks is reflected in the large number of high-impact papers on the topic published in the last few years. This interest has been catalysed by the impact that high-precision optical frequency combs (OFCs) have had on metrology and spectroscopy in the last decade [ [1] , [2] , [3] , [4] , [5] ]. OFCs are often referred to as optical rulers: their spectra consist of a precise sequence of discrete and equally-spaced spectral lines that represent precise marks in frequency. Their importance was recognised worldwide with the 2005 Nobel Prize being awarded to T.W. Hansch and J. Hall for their breakthrough in OFC science [ 5 ]. They demonstrated that a coherent OFC source with a large spectrum – covering at least one octave – can be stabilised with a self-referenced approach, where the frequency and the phase do not vary and are completely determined by the source physical parameters. These fully stabilised OFCs solved the challenge of directly measuring optical frequencies and are now exploited as the most accurate time references available, ready to replace the current standard for time. Very recent advancements in the fabrication technology of optical micro-cavities [ 6 ] are contributing to the development of OFC sources. These efforts may open up the way to realise ultra-fast and stable optical clocks and pulsed sources with extremely high repetition-rates, in the form of compact and integrated devices. Indeed, the fabrication of high-quality factor (high-Q) micro-resonators, capable of dramatically amplifying the optical field, can be considered a photonics breakthrough that has boosted not only the scientific investigation of OFC sources [ [8] , [13] , [11] , [12] , [10] , [7] , [9] ] but also of optical sensors and compact light modulators [ [14] , [6] ]. In this framework, the demonstration of planar high-Q resonators, compatible with silicon technology [ [14] , [13] , [11] , [12] , [10] ], has opened up a unique opportunity for these devices to provide entirely new capabilities for photonic-integrated technologies. Indeed, it is well acknowledged by the electronics industry that future generations of computer processing chips will inevitably require an extremely high density of copper-based interconnections, significantly increasing the chip power dissipation to beyond practical levels [ [15] , [16] , [17] ]; hence, conventional approaches to chip design must undergo radical changes. On-chip optical networks, or optical interconnects, can offer high speed and low energy per-transferred-bit, and micro-resonators are widely seen as a key component to interface the electronic world with photonics. Many information technology industries have recently focused on the development of integrated ring resonators to be employed for electrically-controlled light modulators [ [14] , [15] , [16] , [17] ], greatly advancing the maturity of micro-resonator technology as a whole. Recently [ [13] , [11] , [12] ], the demonstration of OFC sources in micro-resonators fabricated in electronic (i.e. in complementary metal oxide semiconductor (CMOS)) compatible platforms has given micro-cavities an additional appeal, with the possibility of exploiting them as light sources in microchips. This scenario is creating fierce competition in developing highly efficient OFC generators based on micro-cavities which can radically change the nature of information transport and processing. Even in telecommunications, perhaps a more conventional environment for optical technologies, novel time-division multiplexed optical systems will require extremely stable optical clocks at ultra-high pulse repetition-rates towards the THz scale. Furthermore, arbitrary pulse generators based on OFC [ [18] , [19] ] are seen as one of the most promising solutions for this next generation of high-capacity optical coherent communication systems. This review will summarise the recent exciting achievements in the field of micro-combs, namely optical frequency combs based on high-Q micro-resonators, with a perspective on both the potential of this technology, as well as the open questions and challenges that remain.

Subfields: Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/aff860f7a0dadbea061a7ae9abcbe608ebdd1354

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Citations in the corpus

Optical data transmission at 44Tb/s and 10 bits/s/Hz over the C-band with standard fibre and a single micro-comb source (2020, methodology): “Micro-combs [1-4] - optical frequency combs generated by integrated micro-cavity resonators – offer the full potential of their bulk counterparts [5,6], but in an integrated footprint.”
Photonic RF Phase-Encoded Signal Generation With a Microcomb Source (2020, methodology): “Soliton crystals are recently discovered coherent and stable solutions of the Lugiato-Lefever equation [33], which governs the nonlinear dynamics of integrated Kerr comb optical”
Broadband RF Channelizer Based on an Integrated Optical Frequency Kerr Comb Source (2018, methodology): “Integrated micro-comb sources [27]–[31], particularly those based on CMOS-compatible plat-”
Microcomb-Based Photonic RF Signal Processing (2019, background): “First, the coherent nature of the soliton states [17] will enable more advanced RF functions such as wideband frequency conversion and clock generation.”
RF Photonics: An Optical Microcombs’ Perspective (2018, background): “As discussed in detail elsewhere [47], [49], [54], [117], when the detuning Δ is adiabatically ramped along the tilted cavity response (mir-”
Photonic RF Arbitrary Waveform Generator Based on a Soliton Crystal Micro-Comb Source (2020, background): “for micro-comb generation [22], such as silica, magnesium fluoride, silicon nitride, and doped silica glass.”
Broadband Photonic RF Channelizer With 92 Channels Based on a Soliton Crystal Microcomb (2020, background): “Recently, microcombs [27]–[31], particularly those based on CMOS-compatible platforms [32]–[40], came into focus since”