Photonic microwave generation in the X- and K-band using integrated soliton microcombs

Liu, Junqiu; Lucas, Erwan; Raja, Arslan S.; He, Jijun; Riemensberger, Johann; Wang, Rui Ning; Karpov, Maxim; Guo, Hairun; Bouchand, Romain; Kippenberg, Tobias J.

doi:10.1038/s41566-020-0617-x

Cited by 355 publications

(247 citation statements)

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“…It shows a phase noise floor of -118 dBc/Hz. Compared with other signal generation experiments based on soliton mcirocombs [25,26,28], our scheme has a 20 dB lower phase noise than these of silica wedge [26] and Si3N4 resonators [28] and a similar performance to MgF2 resonators [25] when scaling these signals to 331 GHz for comparison. We believe that our stable, atomic-clockreferenced THz signal can be used for THz metrology [32] and THz astrophysics [35,36], e.g.…”

Section: Resultsmentioning

confidence: 91%

Terahertz wave generation using a soliton microcomb

et al. 2019

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The Terahertz or millimeter wave frequency band (300 GHz -3 THz) is spectrally located between microwaves and infrared light and has attracted significant interest for applications in broadband wireless communications, space-borne radiometers for Earth remote sensing, astrophysics, and imaging. In particular optically generated THz waves are of high interest for low-noise signal generation. Here, we propose and demonstrate stabilized terahertz wave generation using a microresonator-based frequency comb (microcomb). A unitravellingcarrier photodiode (UTC-PD) converts low-noise optical soliton pulses from the microcomb to a terahertz wave at the soliton's repetition rate (331 GHz). With a free-running microcomb, the Allan deviation of the Terahertz signal is 4.5×10 -9 at 1 s measurement time with a phase noise of -72 dBc/Hz (-118 dBc/Hz) at 10 kHz (10 MHz) offset frequency. By locking the repetition rate to an in-house hydrogen maser, in-loop fractional frequency stabilities of 9.6×10 -15 and 1.9×10 -17 are obtained at averaging times of 1 s and 2000 s respectively, limited by the maser reference signal. Moreover, the terahertz signal is successfully used to perform a proof-ofprinciple demonstration of terahertz imaging of peanuts. Combining the monolithically integrated UTC-PD with an on-chip microcomb, the demonstrated technique could provide a route towards highly stable continuous terahertz wave generation in chip-scale packages for out-of-the-lab applications. In particular, such systems would be useful as compact tools for high-capacity wireless communication, spectroscopy, imaging, remote sensing, and astrophysical applications.

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Section: Resultsmentioning

confidence: 91%

Terahertz wave generation using a soliton microcomb

et al. 2019

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“…of the THz electric field. [4,138] The broadband detection of THz waves in gases has even been extended to THz remote sensing by coherently manipulating the (UV) fluorescence emission from an asymmetrically ionized gas plasma, [159] or even through the THz enhancement of acoustic waves. [160]…”

Section: Thz Sources Based On Laser-filament-induced Plasmasmentioning

confidence: 99%

Laser‐Driven Strong‐Field Terahertz Sources

Fülöp

Tzortzakis

Kampfrath

2019

Advanced Optical Materials

284

147

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reason for this interest relies on the fact that THz radiation can couple resonantly to numerous fundamental motions of ions, electrons, and electron spins in all phases of matter. For example, in solids, the THz range overlaps with the frequency of lattice vibrations (phonons), the collision rates of conduction electrons, the binding energy of bound electron-hole pairs (excitons), and the precession frequency of spin waves (magnons). Consequently, THz radiation, both continuous-wave and pulsed, has been used for characterization of and gaining insight into elementary processes in complex materials. The majority of these studies used relatively weak THz fields and, thus, probed the linear response of the material, without inducing notable material modifications.Only recently, however, completely new avenues in THz science were opened up by triggering nonlinear THz responses of materials. [3][4][5][6][7][8][9][10][11][12][13] Instead of using weak fields to primarily observe selected THz modes such as phonons or magnons, strong fields allow one to actively drive them to unprecedentedly large amplitudes, potentially thereby resulting in novel states of matter. [6,8,11] For example, simulations suggest that exciting matter with intense THz transients may lead to massive modifications of electrically [14] or magnetically [15] ordered domains and enable the acceleration of free ions to ≈1 MeV, [16] and postacceleration to 50-100 MeV energies. [17] Remarkable experimental results such as switching of magnetic order, [18,19] parametric amplification of optical phonons, [20] novel insights into spin-lattice coupling, [21,22] and acceleration of free electrons in a THz linear accelerator [23] were achieved only recently. This progress has been made possible by the development of laser-driven table-top THz sources routinely providing pulses with unprecedented energies and peak electric and magnetic field strengths throughout the entire THz spectral range. Different laser-based THz pulse generation techniques can be used to access different parts of the spectral range extending from 0.1 to 10 THz. Some of the recently developed technologies enable the generation of radiation with even larger bandwidth or tuning range up to 100 THz and beyond, which lead to an extension of what is called the THz spectral range. An overview of the approximate spectral coverage and the achieved highest pulse energies and peak electric-field strengths of various laserdriven technologies is given in Figure 1. ScopeIn this work, the basic principles of femtosecond-laser-driven intense pulsed THz sources and their recent development are reviewed. These sources are capable of delivering peak electric field strengths on the MV cm −1 scale. Corresponding typical THz pulse energies are on the µJ-to-mJ level, depending on A review on the recent development of intense laser-driven terahertz (THz) sources is provided here. The technologies discussed include various types of sources based on optical rectification (OR), spintronic emitters, and laserfilame...

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“…In chip-integrated, planar microresonators, thermal timescales are faster and other approaches are typically required. Fast frequency shifting via single-sideband modulators [14], integrated microheaters with fast response times [15], abrupt changes to the pump power level [16], phase modulation of the pump [17], and an auxiliary laser for providing temperature compensation [18] have all been used, while resonators with sufficiently low optical absorption can obviate the need for such methods [19].…”

mentioning

confidence: 99%

Kerr-Microresonator Soliton Frequency Combs at Cryogenic Temperatures

Moille

Rao

et al. 2019

Phys. Rev. Applied

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We present measurements of silicon nitride nonlinear microresonators and frequency comb generation 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 adiabatic 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 temperatures 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. Finally, we discuss the potential improvement in thermorefractive noise resulting from cryogenic operation. The results of this study open up new directions in advancing chip-scale frequency comb optical clocks and metrology at cryogenic temperatures.Temporal dissipative Kerr soliton pulses generated in nonlinear microresonators are a promising technology for metrological applications of frequency combs [1]. Their ability to cover a spectral region over an octave [2,3] while operating in a low-noise, phase-stable configuration enables new classes of chip-scale photonics components such as optical frequency synthesizers [4,5], optical clocks [6,7], and microwave generators [8,9]. However, reaching soliton states in practice can be challenging. These states lie on the red-detuned side of the microresonator's pump resonance mode [10,11], for which thermo-refractive effects limit stability [12]. This can make accessing soliton states difficult in thermal equilibrium, depending on the properties of the system [2]. Larger scale resonators, such as MgF 2 crystalline devices [10] and SiO 2 microresonators [13], have sufficiently large thermal conductivity and sufficiently slow thermal time constants to enable soliton generation through slow adjustment of the pump laser frequency to the appropriate detuning level. In chip-integrated, planar microresonators, thermal timescales are faster and other approaches are typically required. Fast frequency shifting via single-sideband modulators [14], integrated microheaters with fast response times [15], abrupt changes to the pump power level [16], phase modulation of the pump [17], and an auxiliary laser for providing temperature compensation [18] have all been used, while resonators with sufficiently low optical absorption can obviate the need for such methods [19]. * gmoille@umd.edu † kartik.srinivasan@nist.govHere, we consider another approach, so far unexplored, which is to strongly reduce the thermo-refractive coefficient ∂n ∂T of the resonator, making soliton states accessible with slow frequency tuning of the pump laser ( fig. 1). This is accomplished by operating silicon nitride (Si 3 N 4 ) microresonators at cryogenic temperatures (T ≤ 60 K), where ∂n ∂T drops...

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Photonic microwave generation in the X- and K-band using integrated soliton microcombs

Cited by 355 publications

References 50 publications

Terahertz wave generation using a soliton microcomb

Terahertz wave generation using a soliton microcomb

Laser‐Driven Strong‐Field Terahertz Sources

Kerr-Microresonator Soliton Frequency Combs at Cryogenic Temperatures

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