The paper deals with optical excitations arising in a one-dimensional chain of identical spheres due optical coupling of whispering gallery modes (WGM). The band structure of these excitations depends significantly on the inter-mixing between WGMs characterized by different values of angular quantum number, $l$. We develop a general theory of the photonic band structure of these excitations taking these effects into account and applied it to several cases of recent experimental interest. In the case of bands originating from WQMs with the angular quantum number of the same parity, the calculated dispersion laws are in good qualitative agreement with recent experiment results. Bands resulting from hybridization of excitations resulting from whispering gallery modes with different parity of $l$ exhibits anomalous dispersion properties characterized by a gap in the allowed values of \emph{wave numbers} and divergence of group velocity.
The use of an optically thick slab may provide versatile solutions for the realization of a current injection type laser using photonic crystals. Here, we show that a transversely higher-order defect mode can be designed to be confined by a photonic band gap in such a thick slab. Using simulations, we show that a high-Q of 10^5 is possible from a finely tuned second-order hexapole mode. Experimentally, we achieve optically pumped pulsed lasing at 1347 nm from the second-order hexapole mode with a peak threshold pump power of 88 uW.
We show that, taking a two-dimensional photonic-crystal slab system as an example, surprisingly high quality factors (Q) over 10^5 are achievable, even in the absence of a rigorous photonic-band-gap. We find that the density of in-plane Bloch modes can be controlled by creating additional photon feedback from a finite-size photonic-crystal boundary that serves as a low-Q resonator. This mechanism enables significant reduction in the coupling strength between the bound state and the extended Bloch modes by more than a factor of 40.
A photonic crystal (PhC) nanocavity formed in an optically very thick slab can support reasonably high-Q modes for lasing. Experimentally, we demonstrate room-temperature pulsed lasing operation from the PhC dipole mode emitting at 1324 nm, which is fabricated in an InGaAsP slab with thickness (T) of 606 nm. Numerical simulation reveals that, when T > 800 nm, over 90% of the laser output power couples to the PhC slab modes, suggesting a new route towards an efficient in-plane laser for photonic integrated circuits.
Through periodic index modulation, we create two different types of photonic structures in a heated rubidium vapor for controlled reflection, transmission and diffraction of light. The modulation is achieved through the use of the AC Stark effect resulting from a standing-wave control field. The periodic intensity structures create translationally invariant index profiles analogous to photonic crystals in spectral regions of steep dispersion. Experimental results are consistent with modeling.
We discuss soliton control in reconfigurable optically-induced photonic lattices created by three interfering beams. We reveal novel dynamical regimes for strongly localized solitons, including binary switching and soliton revivals through resonant wave mixing.
Topological photonic insulators pave the way toward efficient integrated photonic devices with minimized scattering losses. Optical properties of the majority of topological structures proposed to date are fixed by design such that no changes to their performance can be made once the device has been fabricated. However, tunability is important for many applications, including modulators, switches, or optical buffers. Therefore, we propose a straightforward way for the dynamic control of transmission in a silicon-based topological photonic crystal enabled by all-optical free-carrier excitation …
We demonstrate that graphene-based photonic superlattices provide a versatile platform for electrical and all-optical control of photonic beams with deep-subwavelength accuracy. Specifically, by inserting graphene sheets into periodic metallo-dielectric structures one can design optical superlattices that posses photonic Dirac points (DPs) at frequencies at which the spatial average of the permittivity of the superlattice, $\bar{ \varepsilon}$, vanishes. Similar to the well-known zero-$\bar{n}$ bandgaps, we show that these zero-$\bar{\varepsilon}$ DPs are highly robust against structural disor…
This paper discusses free carrier generation by pulsed laser fields as a mechanism to switch the optical properties of semiconductor photonic crystals and bulk semiconductors on an ultrafast time scale. Requirements are set for the switching magnitude, the time-scale, the induced absorption as well as the spatial homogeneity, in particular for silicon at lambda= 1550 nm. Using a nonlinear absorption model, we calculate carrier depth profiles and define a homogeneity length l_hom. Homogeneity length contours are visualized in a plane spanned by the linear and two-photon absorption coefficients.…
Controlling the optical response of a medium through suitably tuned coherent electromagnetic fields is highly relevant in a number of potential applications, from all-optical modulators to optical storage devices. In particular, electromagnetically induced transparency (EIT) is an established phenomenon in which destructive quantum interference creates a transparency window over a narrow spectral range around an absorption line, which, in turn, allows to slow and ultimately stop light due to the anomalous refractive index dispersion. Here we report on the observation of a new form of either in…
Due to strong absorption of the incident light, the media with high refractive index are considered restrictive for applications in photonic crystals (PhCs). The possibility to resolve this problem by optical saturation effectively minimizing the absorption of the PhC medium is discussed. Such approach might be promising for the significant broadening of the photonic band-gap.
The realization of optical non-reciprocity is crucial for many device applications, and also of fundamental importance for manipulating and protecting the photons with desired time-reversal symmetry. Recently, various new mechanisms of magnetic-free non-reciprocity have been proposed and implemented, avoiding the limitation of the strong magnetic field imposed by the Faraday effect. However, due to the difficulties in suppressing the drive and its induced noises, these devices exhibit limited isolation performances and leave the quantum noise properties rarely studied. Here, we demonstrate a n…
We show the possibility to periodically modulate refractive index in atomic medium in space or/and time while simultaneously keeping vanishing absorption/gain. Such modulation is based on periodic resonant enhancement of refractive index, controlled by an external optical field, and opens a way to produce coherently controllable photonic structures. We suggest possible implementation of the proposed scheme in rare-earth doped crystals with excited state absorption.
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, College of Engineering and Applied Sciences, School of Physics, Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University（南京大学）；Key Laboratory of Semiconductor Display Materials and Chips, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences（中国科学院苏州纳米技术与纳米仿生研究所）；Nanzhi Institute of Advanced Optoelectronic Integration（南智先进光电子集成研究院）；State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University（中山大学）；Purple Mountain Laboratories（紫金山实验室）
We report on the frst experimental observation of discrete vortex solitons in two-dimensional optically-induced photonic lattices. We demonstrate strong stabilization of an optical vortex by the lattice in a self-focusing nonlinear medium and study the generation of the discrete vortices from a broad class of singular beams.
The ability to tune the wavelength of light emission on a silicon chip is important for scalable photonic networks, distributed photonic sensor networks and next generation computer architectures. Here we demonstrate light emission in a chip-scale optomechanical device, with wide tunablity provided by a combination of radiation pressure and photothermal effects. To achieve this, we develop an optically active double-disk optomechanical system through implantation of erbium ions. We observe frequency tuning of photoluminescence in the telecommunications band with a wavelength range of 520 pm, g…
We study tunable refraction of light in one-dimensional periodic lattices induced optically in a photorefractive crystal. We observe experimentally both positive and negative refraction of beams which selectively excite the first or second spectral bands of the periodic lattice, and demonstrate tunability of the output beam position by dynamically adjusting the lattice depth. At higher laser intensities, the beam broadening due to diffraction can be suppressed through nonlinear self-focusing while preserving the general steering properties.
A method for designing physically path length matched, three-dimensional photonic circuits is described. We focus specifically on the case where all the waveguides are uniquely routed from the input to output; a problem which has not been addressed to date and allows for the waveguides to be used in interferometric measurements. Circuit elements were fabricated via the femtosecond laser direct-write technique. We demonstrate via interferometric methods that the fabricated circuits were indeed optically path length matched to within 45 um which is within the coherence length required for many a…
Optoelectronic components with adjustable parameters, from variable-focal-length lenses to spectral filters that can change functionality upon stimulation, have enormous technological importance. Tuning of such components is conventionally achieved by either micro- or nano-mechanical actuation of their consitutive parts, stretching or application of thermal stimuli. Here we report a new dielectric metasurface platform for reconfigurable optical components that are created with light in a non-volatile and reversible fashion. Such components are written, erased and re-written as two-dimensional …
In this work, we report the first demonstration of a solution processable, optically switchable 1D photonic crystal by implementing phototunable doped metal oxide nanocrystals. The resulting device structure shows bi-photonic response with the photonic bandgap covering the visible spectral range and the plasmon resonance of the doped metal oxide the near infrared. By means of a facile photodoping process, we tuned the plasmonic response and switched effectively the optical properties of the photonic crystal, translating the effect from the near infrared to the visible. The ultrafast bandgap pu…
Bringing efficient second-order nonlinear effects in integrated photonics is an important task motivated by the prospect of enabling all possible optical functionalities on chip. Such task has proved particularly challenging in silicon photonics, as materials best suited for photonic integration lack second-order susceptibility ($χ^{(2)}$). Methods for inducing effective $χ^{(2)}$ in such materials have recently opened new opportunities. Here, we present optically reconfigurable quasi-phase-matching in large radius Si$_3$N$_4$ microresonators resulting in mW level on-chip second-harmonic gener…
Optical activity (OA), also called circular birefringence, is known for two hundred years, but its applications for topological photonics remain unexplored. Unlike the Faraday effect, OA provokes rotation of the linear polarization of light without magnetic effects, thus preserving the time-reversal symmetry. Here, we report a direct measurement of the Berry curvature and quantum metric of the photonic modes of a planar cavity containing an optically active organic microcrystal (perylene). Photonic spin-orbit-coupling induced by the cavity results in the action of a non-Abelian gauge field on …
The engineering of localised modes in photonic structures is one of the main targets of modern photonics. An efficient strategy to design these modes is to use the interplay of constructive and destructive interference in periodic photonic lattices. This mechanism is at the origin of defect modes in photonic bandgaps, bound states in the continuum and compact localised states in flat bands. Here we show that in lattices of lossy resonators, the addition of external optical drives with controlled phase enlarges the possibilities of manipulating interference effects and allows designing novel ty…
This paper presents a novel microwave photonic (MWP) radar scheme that is capable of optically generating and processing broadband linear frequency-modulated (LFM) microwave signals without using any radio-frequency (RF) sources. In the transmitter, a broadband LFM microwave signal is generated by controlling the period-one (P1) oscillation of an optically injected semiconductor laser. After targets reflection, photonic de-chirping is implemented based on a dual-drive Mach-Zehnder modulator (DMZM), which is followed by a low-speed analog-to-digital converter (ADC) and digital signal processer …
In this article, localized linear defect modes due to bandgap guidance in two-dimensional photonic lattices with localized or non-localized defects are investigated theoretically. First, when the defect is localized and weak, eigenvalues of defect modes bifurcated from edges of Bloch bands are derived analytically. It is shown that in an attractive (repulsive) defect, defect modes bifurcate out from Bloch-band edges with normal (anomalous) diffraction coefficients. Furthermore, distances between defect-mode eigenvalues and Bloch-band edges are exponentially small functions of the defect streng…
We study thermal radiation from nonlinear ($χ^{(3)}$) photonic cavities coupled to external channels and subject to incident monochromatic light. Our work extends related work on nonlinear mechanical oscillators [Phys. Rev. Lett. 97, 110602 (2006)] to the problem of thermal radiation, demonstrating that bistability can enhance thermal radiation by orders of magnitude and result in strong lineshape alternations, including "super-narrow spectral peaks" occurring at the onset of kinetic phase transitions. We show that when the cavities are designed so as to have perfect linear absorptivity (rate …
We report polariton lasing in localised gap states in a honeycomb lattice of coupled micropillars. Localisation of the modes is induced by the optical potential created by the excitation beam, requiring no additional engineering of the otherwise homogeneous polariton lattice. The spatial shape of the gap states arises from the interplay of the orbital angular momentum eigenmodes of the cylindrical potential created by the excitation beam and the hexagonal symmetry of the underlying lattice. Our results provide insights into the engineering of defect states in two-dimensional lattices.
High-Q Lithium Niobate Microring Resonator with Electro-Optically Reconfigurable Coupling Strength
Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）；State Key Laboratory of Precision Spectroscopy, East China Normal University（精密光谱学国家重点实验室，华东师范大学）；The Extreme Optoelectromechanics Laboratory (XXL), School of Physics, East China Normal University（极端光机电实验室（XXL），物理学院，华东师范大学）；WLSA Shanghai Academy（WLSA上海学院）；Hefei National Laboratory（合肥国家实验室）；Collaborative Innovation Center of Extreme Optics, Shanxi University（极端光学协同创新中心，山西大学）
We demonstrate experimentally all-optical beam steering in modulated photonic lattices induced optically by three beam interference in a biased photorefractive crystal. We identify and characterize the key physical parameters governing the beam steering, and show that the spatial resolution can be enhanced by the additional effect of nonlinear beam self-localization.
We report on the experimental observation of weak localization in an optically induced disordered (2+1)-dimensional photonic structure. Our flexible method of optical induction is applied with a nondiffracting random intensity distribution. We focus on the analysis of a statistical output spectrum for many probe events with variance of the incoming beam's transverse spatial frequency. For particular spatial frequencies we find considerable signatures of transverse coherent backscattering.
Flying particle sensors in hollow-core photonic crystal fibers require accurate localization of the optically trapped microparticles. We report position measurement to micrometer-resolution, using optical frequency domain reflectometry, of two 1.65-$μ$m-diameter polystyrene particles.
Birefringent magnetophotonic crystals are found to exhibit degeneracy breaking for asymmetric contradirectional coupling in planar waveguides. Fundamental to high-order local normal mode coupling leads to partially overlapping gyrotropic bandgaps inside the Brillouin zone and partial suppression of Bloch mode propagation. A large magneto-optically active reorientation in polarization state is found for allowed Bloch modes at bandgap edges.
Nonlinear topological photonics has been attracting increasing research interest, as it provides an exciting photonic platform that combines the advantages of active all-optical control offered by nonlinear optics with the unique features of topological photonic systems, such as topologically-protected defect-immune light propagation. In this paper, we demonstrate that topological interface modes and trivial edge modes of a specially designed graphene metasurface can be coupled in a tunable and optically controllable manner, thus providing an efficient approach to transfer optical power to top…
Scattering immune propagation of light in topological photonic systems may revolutionarize the design of integrated photonic circuits for information processing and communications. In optics, various photonic topological circuits have been developed, which were based on classical emulation of either quantum spin Hall effect or quantum valley Hall effect. On the other hand, the combination of both the valley and spin degrees of freedom can lead to a new kind of topological transport phenomenon, dubbed quantum spin valley Hall effect (QSVH), which can further expand the number of topologically p…
Photonic molecules, named by analogy with chemical molecules, are clusters of closely located electromagnetically interacting microcavities or "photonic atoms". As two or several microcavities are brought close together, their optical modes interact, and a rich spectrum of photonic molecule supermodes emerges, which depends both on geometrical and material properties of individual cavities and on their mutual interactions. Here, we discuss ways of controllable manipulation of photonic molecule supermodes, which improve or add new functionalities to microcavity-based optical components. We pres…
We implement a cold damping scheme to cool one mode of the center-of-mass motion of an optically levitated nanoparticle in ultrahigh vacuum from room temperature to a record-low temperature of 100 micro-Kelvin. The measured temperature dependence on feedback gain and thermal decoherence rate is in excellent agreement with a parameter-free model. We determine the imprecision-backaction product for our system and provide a roadmap towards ground-state cooling of optically levitated nanoparticles.
Harnessing nonlinear optical effects in a photonic chip scale has been proven useful for a number of key applications in optical communications. Microwave photonics can also benefit from the adoption of such a technology, creating a new concept of nonlinear integrated microwave photonics. Here, we discuss the potential of on-chip nonlinear processing towards the creation of robust and multifunctional microwave photonic (MWP) processors. We also highlight key recent results in the field, including frequency agile MWP filters and ultra-wideband signal generators.
Electromagnetically induced transparency has the unique ability to optically control transparency windows with low light in atomic systems. However, its practical applications in quantum physics and information science are limited due to rigid experimental requirements. Here, we demonstrate a new mechanism of optically induced transparency in a micro-cavity by introducing a four-wave mixing gain to nonlinearly couple two separated resonances of the micro-cavity in an ambient environment. A signature Fano-like resonance was observed owing to the nonlinear interference of the two coupled resonan…
As light localization becomes increasingly pronounced in photonic systems with less order, we investigate optically induced two-dimensional Fibonacci structures which are supposed to be amongst the most ordered realizations of deterministic aperiodic patterns. For the generation of corresponding refractive index structures, we implement a recently developed incremental induction method using nondiffracting Bessel beams as waveguide formation entities. Even though Fibonacci structures present slightly reduced order, we show that transverse light transport is significantly hampered here in compa…
We introduce a universal method to optically induce multiperiodic photonic complex superstructures bearing two-dimensional (2D) refractive index modulations over several centimeters of elongation. These superstructures result from the accomplished superposition of 2D fundamental periodic structures. To find the specific sets of fundamentals, we combine particular spatial frequencies of the respective Fourier series expansions, which enables us to use nondiffracting beams in the experiment showing periodic 2D intensity modulation in order to successively develop the desired multiperiodic struct…
Two-photon photopolymerization of UV curing resins is an attractive method for the fabrication of microscopic transparent objects with size in the tens of micrometers range. We have been using this method to produce three-dimensional structures for optical micromanipulation, in an optical system based on a femtosecond laser. By carefully adjusting the laser power and the exposure time we were able to create micro-objects with well-defined 3D features and with resolution below the diffraction limit of light. We discuss the performance and capabilities of a microfabrication system, with some exa…
We introduce a class of optical media based on adiabatically modulated, dielectric-only, and potentially extremely low-loss, photonic crystals. The media we describe represent a generalization of the eikonal limit of transformation optics (TO). The foundation of the concept is the possibility to fit frequency isosurfaces in the k-space of photonic crystals with elliptic surfaces, allowing them to mimic the dispersion relation of light in anisotropic effective media. Photonic crystal cloaks and other TO devices operating at visible wavelengths can be constructed from optically transparent subst…
Ordinary metallic photonic crystals (PCs) have photonic band gaps in which the density of states (DOS) is strongly modified. Thermal emission of photons can be suppressed and enhanced accordingly. We consider the thermal emission characteristics of a metallic photonic crystal slab with a tunable thickness which in the thick limit approaches that of a photonic crystal and in the thin limit approaches that of a textured surface. We find that a thick photonic crystal suppresses emission in a specific range while a thin slab suppresses low frequency emission.
The photonic modes mediated absorption dynamics at femtosecond time scales along with the control of spontaneous emission tunability are investigated all-dielectric optical microcavity having BaTiO3 (BTO) as defect layer. The cavity-enhanced transient absorption reveals the dominant excited state absorption (ESA) of both photonic and electronic modes due to strong third-order optical nonlinearity influence. Photoluminescence of BTO is found to be guided and tuned by the photonic cavity mode. Such active photonic structures can be envisaged as a potential candidate in nonlinear optics and photo…
We propose the use of an optically trapped, dye doped polystyrene microsphere for spatial probing of the refractive index at any position in a fluid. We demonstrate the use of the dye embedded in the microsphere as an internal broadband excitation source, thus eliminating the need for a tunable excitation source. We measured the full width at half maximum of the TE and TM resonances, and their frequency spacing as a function of the refractive index of the immersion fluid. From these relations we obtained an absolute sensitivity of 5e-4 in local refractive index, even when the exact size of the…
We designed an on-chip transformative optic system of a metalens-photonic crystal resonator metasystem on a foundry compatible silicon photonic platform. By adjusting the on-chip metalens' focusing length and mode dimension, the insertion loss between the metalens and the photonic crystal resonator and waveguide structures are minimized through mode-matching. The micro-system does not involve any single mode silicon nanowire waveguide, and thus mechanically robust without any oxide claddings. The proposed microsystem is ideal for miniaturized chemical and biosensors operating in air or solutio…
Random surface texturing of an optically-thick film to increase the path length of scattered light rays, first proposed nearly thirty years ago, has thus far remained the most effective approach for photon absorption over the widest set of conditions. Here using recent advances in computational electrodynamics we describe a general strategy for the design of a silicon thin film applicable to photovoltaic cells based on a quasi-resonant approach to light trapping where two partially-disordered photonic-crystal slabs, stacked vertically on top of each other, have large absorption that surpasses …
Optically-Induced Modulation and Programming of Diamond Photonic Cavities
Institute of Physics, Swiss Federal Institute of Technology Lausanne (EPFL)（洛桑联邦理工学院物理研究所）；Center of Quantum Science and Engineering, Swiss Federal Institute of Technology Lausanne (EPFL)（洛桑联邦理工学院量子科学与工程中心）；Photonics Research Group, Department of Information Technology (INTEC), Ghent University - IMEC（根特大学信息技朮系光子研究组（与IMEC联合））；University of Stuttgart（斯图加特大学）
Optical vortex beams carry orbital angular momentum and thus exert torque on illuminated objects. A dielectric microtool - a microbarbell - is used in a two-laser optical tweezers to measure the torque of a focused optical vortex. The tool was either freely rotating due to the applied torque or set into oscillations by the counteracting force. Four different trapping configurations provided different ways of sensing the torque and gave consistent results. The value of torque was determined by confronting the experimental results with numerical and analytical models.
Third-order nonlinear optical effects in photonic microcavities are studied. Significant light defocusing in the thin nonlinear microcavity spacer was observed. The polarization self-action effect was detected, when the large nonlinear polarization rotation angle arises when exciting the microcavity mode, being proportional to the radiation intensity.
Using only electro-optic modulators, we generate a 41-line 10-GHz Gaussian-shaped optical frequency comb. We use this comb to demonstrate apodized microwave photonic filters with greater than 43-dB sidelobe suppression without the need for a pulse shaper.
We study, both theoretically and experimentally, the Bragg scattering of light in optically-induced photonic lattices and reveal the key physical mechanisms which govern nonlinear self-action of narrow beams under the combined effects of Bragg scattering and wave diffraction, allowing for selecting bands with different effective dispersion.
A single-mode all-silica photonic crystal fiber with an effective area of 600 square-micron and low bending loss is demonstrated. The fiber is characterized in terms of attenuation, chromatic dispersion and modal properties.
Using a 3D fully-vectorial nonlinear time-domain analysis we numerically investigate the generation of terahertz radiation by pumping a photonic crystal microcavity out of resonance. High quality factors and a quadratic susceptibility lead to few-cycle terahertz pulses via optical rectification. Material dispersion as well as linear and nonlinear anisotropy is fully accounted for.
