- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Increased multiplexing of superconducting microresonator arrays by post-characterization adaptation of the on-chip capacitors
摘要： We present an interdigitated capacitor trimming technique for fine-tuning the resonance frequency of superconducting microresonators and increasing the multiplexing factor. We first measure the optical response of the array with a beam mapping system to link all resonances to their physical resonators. Then, a new set of resonance frequencies with uniform spacing and higher multiplexing factor is designed. We use simulations to deduce the lengths that we should trim from the capacitor fingers in order to shift the resonances to the desired frequencies. The sample is then modified using contact lithography and re-measured using the same setup. We demonstrate this technique on a 112-pixel aluminum lumped-element kinetic-inductance detector array. Before trimming, the resonance frequency deviation of this array is investigated. The variation of the inductor width plays the main role for the deviation. After trimming, the mean fractional frequency error for identified resonators is (cid:1)6.4 (cid:2) 10(cid:1)4, with a standard deviation of 1.8 (cid:2) 10(cid:1)4. The final optical yield is increased from 70.5% to 96.7% with no observable crosstalk beyond (cid:1)15 dB during mapping. This technique could be applied to other photon-sensitive superconducting microresonator arrays for increasing the yield and multiplexing factor.
关键词： interdigitated capacitor trimming,lumped-element kinetic-inductance detector,superconducting microresonators,multiplexing factor,resonance frequency tuning
更新于2025-09-23 15:21:01
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Observation of Arnold Tongues in Coupled Soliton Kerr Frequency Combs
摘要： We demonstrate various regimes of synchronization in systems of two coupled cavity soliton-based Kerr frequency combs. We show subharmonic, harmonic, and harmonic-ratio synchronization of coupled microresonators, and reveal their dynamics in the form of Arnold tongues, structures that are ubiquitous in nonlinear dynamical systems. Our experimental results are well corroborated by numerical simulations based on coupled Lugiato-Lefever equations. This Letter illustrates the newfound degree of flexibility in synchronizing Kerr combs across a wide range of comb spacings and could find applications in time and frequency metrology, spectroscopy, microwave photonics, optical communications, and astronomy.
关键词： synchronization,nonlinear dynamics,Arnold tongues,Kerr frequency combs,microresonators
更新于2025-09-19 17:13:59
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Improving photon antibunching with two dipole-coupled atoms in whispering-gallery-mode microresonators
摘要： In the two-atom or multiatom system, the atoms can interact with each other through exchange of virtual photon. This kind of energy exchange is often referred as the dipole-dipole interaction (DDI). Here we consider this DDI system consisting of a pair of two-level atoms strongly coupled with a bimodal whispering-gallery-mode (WGM) microresonator which is driven by an external laser field. Our aim is to explore the photon correlation characteristics of the proposed architecture using realistic experimental parameter values. We compare in detail the quality of photon antibunching (i.e., the smallness of the second-order correlation function) from three involved configurations in cavity quantum electrodynamics (QED): (i) only one two-level atom, (ii) two far apart two-level atoms without DDI, and (iii) two DDI (dipole-coupled) two-level atoms are respectively coupled to the driven WGM microresonator through the evanescent field. We clearly show that the DDI between both atoms can distinctly enhance the photon antibunching even in the weak-coupling regime in configuration (iii) with feature-rich line shapes. We also find that the photon antibunching can be modulated by properly adjusting the atom-cavity coupling strength. In addition, we display that this strong photon antibunching is robust against the cooperative atomic decay. Our DDI-based cavity QED scheme may provide an alternative way to the construction of integrated on-chip single-photon sources.
关键词： photon antibunching,whispering-gallery-mode microresonators,single-photon sources,dipole-dipole interaction,cavity quantum electrodynamics
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Switching Dynamics of Dark Solitons in Kerr Microresonators
摘要： Dissipative Kerr solitons (DKS) are localized structures in optical resonators that arise from a double balance between dispersion and Kerr effect, and linear loss and parametric gain [1]. The periodic nature of DKS corresponds to frequency combs. DKS can be generated in high-Q microresonators for diverse applications, from coherent communications to precision frequency synthesis [1]. Most studies of DKS have focused on microresonator cavities operating in the anomalous dispersion regime, where the waveforms correspond to bright soliton pulses. Coherent microresonator combs can also be formed in the normal dispersion regime [2]. The time-domain waveform corresponds to a localized dark-pulse structure, interpreted as two interlocked switching waves connecting the two branches of the bi-stability curve in continuous-wave-pumped Kerr resonators [2,3]. Each switching wave connects the two branches following an oscillating behavior. These type of Kerr combs are relevant for practical applications because they display unusually high power-conversion efficiency [4,5], but their physical dynamics remain largely unexplored. Here, we report the discovery of deterministic switching of dark pulse Kerr combs, where the number of oscillations that appear between the switching waves can be either increased or decreased one at a time. The switching dynamics observed here have intriguing similarities to the switching behavior of bright temporal solitons in anomalous dispersion microresonators [6], and they indicate that dark pulse Kerr combs arise as a complex interplay of dark solitons circulating in the cavity.
关键词： microresonators,switching dynamics,dark pulse Kerr combs,Dissipative Kerr solitons
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Frequency Comb Generation and Conversion in Non-Centrosymmetric Optical Microresonators
摘要： Optical frequency combs have become the key technology in optical precision measurements [1], bear a high potential for broadband, high-resolution molecular spectroscopy [2] and are promising to advance future optical clocks [3]. For low-power, compact and mobile applications, high-repetition-rate combs such as continuous-wave-pumped Kerr combs [4] and soliton frequency combs based on a third-order nonlinearity [5] have turned out to be especially useful. Thus far, most of these frequency combs operate in the near-infrared (NIR) spectral regime around 1550 nm for reasons such as chromatic material dispersion. Many applications ranging from astronomical spectroscopy, optical clocks and quantum physics all the way to molecular sensing, however, require the frequency combs to be centered in the ultraviolet (UV), visible (VIS) and mid-infrared (MIR) spectral regimes [3,6-8]. In this contribution, we present pathways towards achieving this goal. In a first approach [9], synchronously pumped high-Q whispering gallery-mode resonators with a second-order nonlinearity are employed to convert a high-repetition-rate (21 GHz) NIR comb into the VIS and UV wavelength regimes at the same time (see Fig. 1(a)), using an engineered quasi-phase-matching structure. Furthermore, via degenerate optical parametric oscillation (OPO) the sub-harmonic of the initial comb in the MIR can be generated; non-degenerate OPO even allows for wavelength-tunable signal and idler combs. These results pave the way towards a phase-coherent link of frequency combs across the UV, VIS, NIR and MIR spectral regions in a single microresonator. This could allow for low-power self-referenced frequency combs without the need for octave-spanning spectra (e.g. via 3f-4f-interferometry). Additionally, we show first results towards achieving frequency combs purely based on second-order nonlinearities in few-mode optical microresonators (see Fig. 1(b)). This type of combs not only allows to potentially access wavelength regimes different from the NIR, but they also come with the opportunity to use fast electro-optic tuning, a method that is very weak for Kerr microcombs.
关键词： optical frequency combs,nonlinear optics,microresonators,frequency conversion
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Femtosecond-Driven Up-Conversion in a Radially Poled LiNbO <sub/>3</sub> Microresonator
摘要： Nowadays, there are plenty of different techniques developed for the generation of Optical Frequency Combs (OFCs), but Mode Locked Laser (MLL) OFC is still the most commonly used and commercially available one [1]. Although MLLs are capable of producing very high-peak power OFCs with femtosecond pulse durations, it is sometimes challenging to apply them directly for a number of reasons. First, MLLs typically produce OFCs with repetition frequencies (fr) below 1 GHz, so additional filtering of the unwanted modes is required for the applications in telecommunications, astrocombs etc. Second, many spectral regions – namely mid-infrared, visible and ultraviolet – are difficult to access by MLLs, which implies the use of external parametric up- and down-conversion. One promising platform for such spectral transfer is high Q-factor optical microresonators based on second order (χ(2)) nonlinear crystals, since not only do they provide the desired spectral transfer, but also open up opportunities for the miniaturization of the system. In addition, such microresonators support whispering gallery modes that possess very low mode volumes, making it possible to enhance nonlinear (χ(2)) processes. This is a significant advantage over the already existing bulk analogs.
关键词： Mode Locked Laser,microresonators,second harmonic generation,femtosecond pulses,Optical Frequency Combs
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Optical Switching in Microresonators using the Kerr Nonreciprocity
摘要： Photonic circuits are spreading as a viable alternative to conventional electronic circuits. Electro-optic modulators (EOMs) are currently used as switches in telecommunications thanks to their simplicity and speed, however they are driven electrically. Several approaches have been demonstrated to realise all-optical switches such as ring lasers in which the lasing direction is controlled by an input seed, however these devices still require additional electrical or optical pumping. An alternative approach is to exploit the change in resonant frequency of nonlinear resonators with the input power. This has been successfully demonstrated in semiconductor resonators, where the nonlinearity is provided by the carrier generation from two-photon absorption, and in dielectric resonators governed by the Kerr effect. However, this approach needs the input to be in a narrow range of power and detuning from the cavity resonance and is adversely affected by the cavity’s thermal drift due to the high circulating powers. We demonstrate a device that works in a different regime of the Kerr effect. In our case the bistability arises from the twofold contribution of the cross-phase modulation with respect to the self-phase modulation to the refractive index change, Δni ∝ n2(Ii + 2 I j), where i, j are the two possible directions [1,2]. As a consequence, above a threshold power, Pth, light of a given frequency can circulate in just one direction inside the resonator and the switching between the two corresponding states exhibits hysteresis. This regime can be accessed in a much broader range of input powers, from Pth to ～ 5Pth, and the frequency of the laser can drift by up to about 10 GHz thanks to thermal locking [3].
关键词： Kerr nonreciprocity,microresonators,photonic circuits,all-optical switching
更新于2025-09-12 10:27:22
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Folded chaotic whispering-gallery modes in nonconvex, waveguide-coupled planar optical microresonators
摘要： Chaotic whispering-gallery modes have significance both for optical applications and for our understanding of the interplay between wave phenomena and the classical ray limit in the presence of chaotic dynamics and openness. In strongly nonconvex geometries, a theorem by Mather rules out the existence of invariant curves in phase space corresponding to rays circulating in whispering-gallery patterns, so that no corresponding modes of this type are expected. Here, we discuss numerical computations of the electromagnetic fields in planar dielectric cavities that are strongly nonconvex because they are coupled to waveguides. We find a family of special states which retains many features of the chaotic whispering-gallery modes known from convex shapes: An intensity pattern corresponding to near-grazing incidence along extended parts of the boundary, and comparatively high-cavity Q factors. The modes are folded into a figure-eight pattern, so overlap with the boundary is reduced in the region of self-intersection. The modes combine the phenomenology of chaotic whispering-gallery modes with an important technological advantage: The ability to directly attach waveguides without spoiling the Q factor of the folded mode. Using both a boundary-integral method and the finite-difference time-domain technique, we explore the dependence of the phenomenon on wavelength in relation to cavity size, refractive-index contrast to the surrounding medium, and the degree of shape deformation. A feature that distinguishes folded from regular whispering-gallery modes is that a given shape will support high-Q folded chaotic whispering-gallery modes only in certain wavelength windows.
关键词： chaotic whispering-gallery modes,finite-difference time-domain technique,nonconvex geometries,waveguide-coupled planar optical microresonators,boundary-integral method
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Hot-Cavity Spectroscopy of Dark Pulse Kerr Combs in Microresonators
摘要： Kerr frequency combs are generated through cascaded four-wave mixing in high-Q microresonators [1]. These devices are pumped with a continuous-wave laser and modulational instability (MI) is responsible for the growth of the initial comb lines. Since it is easier to satisfy the MI phase matching condition in the anomalous dispersion regime, most studies on Kerr combs have focused on anomalous dispersion microresonators. However, coherent microresonator combs can also take place in the normal dispersion regime. In these combs, phase matching is attained with the aid of the mode coupling between transverse modes of the microresonator [2]. One particularly interesting comb state that operates in the normal dispersion regime is the dark pulse Kerr comb [3]. The time domain pulses of these combs arise as interlocking switching waves that connect the upper and lower homogenous steady state solutions of the bi-stability curve in the continuous-wave-driven Kerr cavity [see Fig. (a)] [3]. These combs are of high interest as most nonlinear materials suitable for fabricating microresonators display normal dispersion in the visible and near infrared ranges. Moreover, these combs provide a much higher power conversion efficiency compared to bright-soliton combs, which makes them particularly useful for telecommunications [4]. Nevertheless, the formation of dark-pulse combs and their dynamics remain largely unexplored. In this work, we provide a better physical understanding of the formation of this type of combs by measuring the system’s response as the pump laser is tuned into resonance. We discover that the formation of the dark pulse Kerr combs is associated with the appearance of an extra resonance, in striking similarity to recent observations made for bright temporal solitons in the anomalous dispersion regime [5], and explain the findings based on cross-phase modulation (XPM) induced by the two homogeneous steady state solutions of the Kerr cavity.
关键词： dark pulse Kerr comb,microresonators,normal dispersion regime,Kerr frequency combs,telecommunications
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Saturable Absorption with CNT Coupled WGM and Fabrication of Er-Doped Microresonator for on-Chip Mode-Locked Laser
摘要： Mode-locked (ML) fiber lasers are becoming key components in industry, because they provide high performance while being relatively inexpensive. The generation of high-repetition rate pulses is gaining interest but it remains a challenge to achieve a GHz repetition rate with fiber lasers. On the other hand, whispering-gallery-mode (WGM) microresonators allow the strong confinement of light and miniaturizing an ML laser into a WGM microresonator will enable us to achieve a high pulse repetition rate, a small footprint and on-chip integrability. In this work, we explore the possibility of a passive ML laser with the system shown in Fig. 1(a). There are two key technologies involved; one is saturable absorption (SA) and the other is laser gain in a microresonator. First, we verified numerically that we could realize an ML laser with our proposed carbon nanotube (CNT) coupled erbium (Er) doped microresonator, and the result is shown in Fig. 1(b). We modelled our system with a nonlinear Schr?dinger equation, where we took gain and SA (also loss (Q), Kerr effect, and dispersion) into account [2]. The result shows that a self-starting ML is possible with microresonator parameters. Next, encouraged by the numerical result, we experimentally demonstrated SA in a microtoroid. We grew CNTs selectively on a silica microtoroid by chemical vapor deposition and investigated the SA behavior (Fig. 1(c)). By performing a pump-probe like experiment we successfully characterized the SA behavior in a microresonator system. This is the first demonstration of SA in a WGM microcavity system [1]. We then fabricated an Er-doped active microtoroid by using the sol-gel method. The sol-gel method is one way of forming silica from a metal alkoxide precursor. Although sol-gel has been widely used, it is still a challenge to fabricate high-quality defect-free film on a Si wafer that allows us to fabricate an ultrahigh-Q WGM microresonator. Figure 1(d)-(f) shows the fabricated films. We found optimum parameters and obtained a clean film as shown in Fig. 1(g). By using this film, we fabricated an Er-doped WGM microresonator, where the Q was 1.2×106 at 1480 nm (Fig. 1(h)). We obtained clear up-conversion luminescence when we pumped the cavity at 1480 nm, which constitutes the first step towards ML lasing in such a WGM microresonator. In summary, these results provide a promising approach for realizing an on-chip high repetition rate ML WGM microresonator.
关键词： saturable absorption,sol-gel method,carbon nanotube,whispering-gallery-mode microresonators,erbium-doped microresonator,Mode-locked fiber lasers
更新于2025-09-11 14:15:04