Optical Ring Cavity Research Articles

Tunable all-optical microwave filter with high tuning efficiency.

We propose and experimentally demonstrate a continuously tunable all-optical microwave filter based on a photonic crystal (PC) L3 cavity. Due to the small cavity mode volume and prominent optical properties, the required power to arouse the cavity nonlinear effects is low as microwatt level. Moreover, the cavity resonance could be continuously shifted by finely adjusting the input powers. Therefore, under optical single sideband modulation, the frequency interval between the optical carrier and cavity resonance could be controllable. In this case, the central frequency of the microwave photonic filter (MPF) could be continuously tuned with low power consumption. To the best of our knowledge, the experimental tuning efficiency of 101.45 GHz/mW is a record for on-chip tunable all-optical microwave filters. With dominant features of all-optical control, ultra-high tuning efficiency (101.45 GHz/mW), large rejection ratios (48 dB) and compact footprint (100 µm2), the proposed silicon nanocavity is competent to process microwave signals, which has many useful applications in on-chip energy-efficient microwave photonic systems.

DANCE: Dark matter Axion search with riNg Cavity Experiment

We have proposed a new approach to search for axion dark matter with an optical ring cavity [Phys. Rev. Lett. 121, 161301 (2018)]. The coupling of photons to axions or axion-like particles makes a modulated difference in the phase velocity between left- and righthanded photons. Our method is to measure this phase velocity difference with a ring cavity, by measuring the resonant frequency difference between two circular polarizations. Our estimation shows that the sensitivity to axion-photon coupling constant g aγ for axion mass m ≲ 10−10 eV can be improved by several orders of magnitude compared with the current best limits. In this paper, we present the principles of the Dark matter Axion search with riNg Cavity Experiment (DANCE) and the status of the prototype experiment, DANCE Act-1.

Study of the influence of dopant precursor on the growth and properties of Li-doped ZnO

Lithium-doped ZnO structures with sizes in the micro- and nano-scale and different morphologies were obtained by vapor–solid growth method. Two different precursors, lithium oxide and lithium carbonate, were used as the lithium source in order to study the influence on the morphology and optical properties of the obtained structures. Scanning electron microscopy, cathodoluminescence, photoluminescence, X-ray diffraction, energy dispersive X-ray microanalysis and Raman spectroscopy were used to characterize their structure, morphology, composition and optical properties. Depending on the lithium content present, changes in the crystalline quality and the luminescent intensity of the samples were observed. Optical resonant cavity behavior was also observed in some of the nano-structures.

Cavity-enhanced and long-lived optical memories for two orthogonal polarizations in cold atoms.

The storage and retrieval efficiency (SRE) and lifetime of optical quantum memories are two key performance indicators for scaling up quantum information processing. Here, we experimentally demonstrate a cavity-enhanced long-lived optical memory for two polarizations in a cold atomic ensemble. Using electromagnetically induced-transparency (EIT) dynamics, we demonstrate the storages of left-circularly and right-circularly polarized signal light pulses in the atoms, respectively. By making the signal and control beams collinearly pass through the atoms and storing the two polarizations of the signal light as two magnetic-field-insensitive spin waves, we achieve a long-lived (3.5 ms) memory. By placing a low-finesse optical ring cavity around the cold atoms, the coupling between the signal light and the atoms is enhanced, which leads to an increase in SRE. The presented cavity-enhanced storage shows that the SRE is ∼30%, corresponding to an intrinsic SRE of ∼45%.

Optically contorting into new dimensions

Topological Optics Creating synthetic dimensions has generated interest in many branches of science, ranging from ultracold atomic physics to photonics. The ability to do so provides a versatile platform for realizing effective gauge potentials and novel topological physics that might be difficult or impossible to realize in real systems. Dutt et al. show that a structured optical ring cavity can sustain more than one synthetic dimension. Under modulation, coupling the different degrees of freedom within the resonator is used synthesize two additional dimensions. The authors are then able to emulate many complex physical phenomena usually associated with condensed matter systems. Science , this issue p. [59][1] [1]: /lookup/doi/10.1126/science.aaz3071

Mode locking in an optomechanical cavity

We experimentally study a fiber-based optical ring cavity integrated with a mechanical resonator mirror and an optical amplifier. The device exhibits a variety of intriguing nonlinear effects including synchronization and self-excited oscillation. Passively generated optical pulses are observed when the frequency of the optical ring cavity is tuned very close to the mechanical frequency of the suspended mirror. The optical power at the threshold of this process of mechanical mode locking is found to be related to quantum noise of the optical amplifier.

Research on a Novel GaN-Based Converted Mini-LED Backlight Module via a Spectrum-Decouple System

Owing to the development of modern display technology, micro- and mini-light-emitting diodes (LEDs) have affected technological advancements in the display industry. The structure of mini-LEDs is completely different than that of traditional LED backlights because the former employs a display technology with an LED array structure, optical resonant cavity, and color conversion layer. Display backlight technology encounters difficulty in achieving a truly effective energy-loss mechanism when designing or measuring mini-LED performance. The present study proposes three major mini-LED energy loss mechanisms: cross-talk, resonant, and quantum conversion losses. Herein, the spectrum was obtained through the integrating sphere system, and the calculation mechanism was formed by the down-conversion theorem as the decoupling principle, which successfully calculated the independent energy-loss efficiency of each mechanism and effectively deduced the brightness and color saturation performance of this design combination.

Ultrasensitive velocity estimation via cyclic weak measurement

The weak-value-amplification technique has been shown to be advantageous for precision metrology. Previous weak-value-based applications have used only a small fraction of data while discarding the rest during post-selection. Here we consider the use of the power-recycling technique to improve the sensitivity of an interferometric weak-value-based velocity measurement scheme. We discuss ways to realize this idea by introducing a power recycling mirror to make the Michelson interferometer a resonant optical cavity. In our analysis, the signal is well enhanced by the cavity and corresponding SNR is also improved although the temporal walk-off effect exits.

Circular dichroism mode splitting and bounds to its enhancement with cavity-plasmon-polaritons

Abstract Geometrical chirality is a widespread phenomenon that has fundamental implications for discriminating enantiomers of biomolecules. In order to enhance the chiral response of the medium, it has been suggested to couple chiral molecules to resonant optical cavities in order to enhance the circular dichroism (CD) signal at the resonant frequency of the cavity. Here, we studied a distinctly different regime of chiral light-matter interaction, wherein the CD signal of a chiral medium splits into polaritonic modes by reaching the strong coupling regime with an optical microcavity. Specifically, we show that by strongly coupling chiral plasmonic nanoparticles to a non-chiral Fabry-Pérot microcavity one can imprint the mode splitting on the CD spectrum of the coupled system and thereby effectively shift the initial chiral resonance to a different energy. We first examined the effect with the use of analytical transfer-matrix method as well as numerical finite-difference time-domain (FDTD) simulations. Furthermore, we confirmed the validity of theoretical predictions in a proof-of-principle experiment involving chiral plasmonic nanoparticles coupled to a Fabry-Pérot microcavity.

A single photonic cavity with two independent physical synthetic dimensions.

The concept of synthetic dimensions has generated interest in many branches of science, ranging from ultracold atomic physics to photonics, as it provides a versatile platform for realizing effective gauge potentials and topological physics. Previous experiments have augmented the real-space dimensionality by one additional physical synthetic dimension. In this study, we endow a single ring resonator with two independent physical synthetic dimensions. Our system consists of a temporally modulated ring resonator with spatial coupling between the clockwise and counterclockwise modes, creating a synthetic Hall ladder along the frequency and pseudospin degrees of freedom for photons propagating in the ring. We observe a wide variety of physics, including effective spin-orbit coupling, magnetic fields, spin-momentum locking, a Meissner-to-vortex phase transition, and signatures of topological chiral one-way edge currents, completely in synthetic dimensions. Our experiments demonstrate that higher-dimensional physics can be studied in simple systems by leveraging the concept of multiple simultaneous synthetic dimensions.

Quantum entanglement via a controllable four-wave-mixing mechanism in an optomechanical system

We propose an approach to generate strong quantum entanglement by the controllable four wave mixing mechanism in a single cavity, weak coupling optomechanical system. The optomechanical system is driven by a strong two tone pump field and a weak signal field, simultaneously. The two tone pump field consists of a lower and an upper sideband, which couple with the optical cavity and mechanical resonator, and generate the beam splitter and two mode squeezing interactions under the rotating wave approximation. This interaction mechanism modifies the effective susceptibility of the optomechanical cavity and optomechanically induces a four wave mixing process. Strong quantum entanglement can be generated between the signal and four wave mixing fields with an entangled degree over 16 dB in realistic optomechanical systems. The generation scheme of the quantum entanglement is quite robust against thermal mechanical noise, and entanglement above 3 dB can persist at room temperature in the weak coupling regime.

Pulse Delay Time Statistics in a Superradiant Laser with Calcium Atoms.

Cold samples of calcium atoms are prepared in the metastable ^{3}P_{1} state inside an optical cavity resonant with the narrow band (375Hz) ^{1}S_{0}→^{3}P_{1} intercombination line at 657nm. We observe a superradiant emission of hyperbolic secant shaped pulses into the cavity with an intensity proportional to the square of the atom number, a duration much shorter than the natural lifetime of the ^{3}P_{1} state, and a delay time fluctuating from shot to shot in excellent agreement with theoretical predictions. Our incoherent pumping scheme to produce inversion on the ^{1}S_{0}→^{3}P_{1} transition should be extendable to allow for continuous wave laser operation.

Experimental near infrared absorption enhancement of graphene layers in an optical resonant cavity

Graphene has recently emerged as a promising candidate for a wide range of photonic and optoelectronic applications, with a high application potential in devices using infrared radiation. The optical absorption of 2D materials and graphene can be uniquely enhanced when they are embedded in optical resonant cavities, since optically-thin atomic-thickness absorbers do not perturb the cavity itself. Despite the many theoretical studies, experimental validation is still lagging behind. Here, large near infrared (NIR) absorption of unpatterned chemical vapor deposition graphene is experimentally demonstrated for the first time in a large area (1 inch) passive optical device by exploiting the enhancement of the electric field at the center of a Fabry–Perot cavity. Test devices were fabricated with single layer, double layer and five layers graphene, sandwiched between two almost symmetric Bragg mirrors deposited by radio frequency sputtering and consisting of alternate layers of Si and SiO2. A thin evaporated MgF2 overlayer was used to reduce sputtering induced damage on graphene layers. Measured absorption values, in the range of 37%–45%, were found in very good accordance with simulated ones. A maximum absorption of 45% was measured at 2345 nm for the double-layer graphene.

High-accuracy and wide dynamic range frequency-based dispersion spectroscopy in an optical cavity.

A spectroscopic method free from systematic errors is desired for many challenging applications of gas detection. Although existing cavity-enhanced techniques exhibit very high precision, their accuracy strongly depends on propagation of the light amplitude through an optical system and its detection. Here, we demonstrate that the frequency-based molecular dispersion spectroscopy, involving sub-Hz-level precision in frequency measurements of optical cavity resonances, leads to sub-per-mille accuracy and a wide dynamic range, both previously unattainable by any other spectroscopic technique. The method offers great sensitivity of 5×10-11 cm-1, high speed, limited only by the fundamental response time of the cavity, and traceability of both axes of the spectrum to the primary frequency standard. All these features are necessary for convenient realization of comprehensive molecular spectroscopy from Doppler up to collisional regime without changing the spectroscopic method and modification of the experimental setup. Moreover, the presented approach does not require linear, high-bandwidth nor phase-sensitive detectors and can be directly implemented in existing cavity-enhanced spectrometers utilizing either continuous-wave or coherent broadband radiation. We experimentally prove the predominance of frequency-based spectroscopy over intensity-based one. Our results motivate replacement of intensity-based absorption spectroscopy with a pure frequency-based dispersion one in applications where the highest accuracy is required.

Microwave to optical conversion with atoms on a superconducting chip

We describe a scheme to coherently convert a microwave photon of a superconducting co-planar waveguide resonator to an optical photon emitted into a well-defined temporal and spatial mode. The conversion is realized by a cold atomic ensemble trapped close the surface of the superconducting atom chip, near the antinode of the microwave cavity. The microwave photon couples to a strong Rydberg transition of the atoms that are also driven by a pair of laser fields with appropriate frequencies and wavevectors for an efficient wave-mixing process. With only several thousand atoms in an ensemble of moderate density, the microwave photon can be completely converted into an optical photon emitted with high probability into the phase matched direction and, e.g. fed into a fiber waveguide. This scheme operates in a free-space configuration, without requiring strong coupling of the atoms to a resonant optical cavity.

Quantum Phase Properties in Collective Three-Level V-Type System with Diamagnetic Term

In this paper, we present a rigorous investigation of the quantum phase transitions (QPTs) for a model which describes the degenerate collective regime of a three-level V-configuration atoms Bose-Einstein condensate (BEC). We consider that the three-level atoms of a BEC coupled to an optical resonator (cavity) with high finesse in the presence of a diamagnetic term, i. e., a system of N-identical three-level atoms interacting with a one-mode quantized electromagnetic cavity field. Also, the different components of this system are labeled by the different phase factors. By using the Glauber’s coherent states for the field, we calculate the free energy and study the finite-temperature phase transition for this model in the thermodynamic limit (N → ∞). Also, the potential energy surfaces constructed by taking the expectation value with respect to the direct product for a test state a direct product of coherent Heisenberg-Weyl HW(1)-states (for the electromagnetic field ), and U(3) (for the atomic field, i. e., matter contribution) coherent states. Moreover, the scaled ground-state energy is obtained by taking the expectation value of an effective Hamiltonian in the framework of the mean-field approach. In the thermodynamic limit, the energy surface takes a simple form for a direct description of the phase transitions. The relation between the QPTs and the symmetry physics are established and the QPTs for this model are investigated numerically. The properties of both stability and the equilibrium are calculated using the catastrophe theory. We notice that the second-order phase transitions (superradiant (SR)) with multi-level systems might be achievable in a wide range of physical systems, especially those where it is possible to engineer the spec-tra and oscillator strengths.

Quantum coherence transfer between an optical cavity and mechanical resonators

This study highlights the theoretical investigation ofquantum coherence in mechanical oscillators and its transfer between the cavityand mechanical modes of an optomechanical system comprising an optical cavity and twomechanical oscillators that, in this study, were simultaneously coupled tothe optical cavity at different optomechanical coupling strengths. The quantumcoherence transfer between the optical and mechanical modes is found to dependstrongly on the relative magnitude of the two optomechanical couplings.The laser power, decay rates of the cavity and mechanical oscillators,environmental temperature, and frequency of the mechanical oscillator areobserved to significantly influence the investigated quantum coherences.Moreover, quantum coherence generation in the optomechanical system is restrictedby the systems stability condition, which helps sustain high and stablequantum coherence in the optomechanical system.

Angular dependence of the optical reflectance in two-dimensional Si-ZnO photonic crystals

In this work, we present an experimental study of the angular dependence of the optical reflectance in two 2-dimensional photonic structures, built on a silicon substrate coated with a ZnO thin film. Photonic structures studied describe a regular square lattice with a lattice constant a = 1.05 μm and circular air holes with a radius r = 0.63a. Additionally, one of these photonic structures contains a pattern of nine quasi-circular micro-cavities embedded in a regular square lattice photonic crystal, describing a secondary square lattice. A comparison of the optical reflectance of the two photonic structures as a function of the incidence angle for transverse magnetic polarization mode in the visible (Vis) and near-infrared (NIR) ranges of the electromagnetic spectrum was accomplished. Results obtained revealed a strong angular dependence of the reflective optical properties of the two 2-dimensional photonic structures on the illumination incidence angle. The photonic structure with the array of resonant optical cavities presented a very unusual behavior regarding the reflectance of the substrate, this because its reflectance described specific modulations dependent on the incidence angle of illumination.

Super-efficient temporal solitons in mutually coupled optical cavities

A coherently driven Kerr optical cavity is able to convert a continuous-wave laser to a sequence of ultrashort soliton pulses, enabling the generation of broadband and mode-locked frequency combs. Kerr cavity solitons are balanced through an energy exchange with the driving pump field. Improving the energy conversion efficiency from the pump to the soliton is of great significance for practical applications, but remains an outstanding challenge due to a limited temporal overlap between the soliton and the pump. Here, we report the discovery of temporal Kerr solitons in mutually coupled cavities instead of a traditional single cavity. We propose a strategy for breaking the limitation of pump-to-soliton energy conversion, and connect the underlying mechanism to impedance matching in radiofrequency electronic circuits. With macro optical fiber ring cavities which share the same physical model as miniature optical microresonators, we demonstrate nearly one-order improvement of the efficiency. The results pave the way towards super-efficient soliton microcombs based on optical microresonators with ultra-high quality factors.

Supersolid-Based Gravimeter in a Ring Cavity.

We propose a novel type of composite light-matter interferometer based on a supersolidlike phase of a driven Bose-Einstein condensate coupled to a pair of degenerate counterpropagating electromagnetic modes of an optical ring cavity. The supersolidlike condensate under the influence of the gravity drags the cavity optical potential with itself, thereby changing the relative phase of the two cavity electromagnetic fields. Monitoring the phase evolution of the cavity output fields thus allows for a nondestructive measurement of the gravitational acceleration. We show that the sensitivity of the proposed gravimeter exhibits Heisenberg-like scaling with respect to the atom number. As the relative phase of the cavity fields is insensitive to photon losses, the gravimeter is robust against these deleterious effects. For state-of-the-art experimental parameters, the relative sensitivity Δg/g of such a gravimeter could be of the order of 10^{-10}-10^{-8} for a condensate of a half a million atoms and interrogation time of the order of a few seconds.