Photonic Crystal Microcavity Research Articles

Benchmarking five numerical simulation techniques for computing resonance wavelengths and quality factors in photonic crystal membrane line defect cavities.

We present numerical studies of two photonic crystal membrane microcavities, a short line-defect cavity with a relatively low quality (Q) factor and a longer cavity with a high Q. We use five state-of-the-art numerical simulation techniques to compute the cavity Q factor and the resonance wavelength λ for the fundamental cavity mode in both structures. For each method, the relevant computational parameters are systematically varied to estimate the computational uncertainty. We show that some methods are more suitable than others for treating these challenging geometries.

Spatially selective hydrogen irradiation of dilute nitride semiconductors: a brief review

We provide a brief survey of the most recent results obtained by performing spatially selective hydrogen irradiation of dilute nitride semiconductors. The striking effects of the formation of stable N–H complexes in these compounds—coupled to the ultrasharp diffusion profile of H therein—can be exploited to tailor the structural (lattice constant) and optoelectronic (energy gap, refractive index, electron effective mass) properties of the material in the growth plane, with a spatial resolution of a few nm. This can be applied to the fabrication of site-controlled quantum dots (QDs) and wires, but also to the realization of the optical elements required for the on-chip manipulation and routing of qubits in fully integrated photonic circuits. The fabricated QDs—which have shown the ability to emit single photons—can also be deterministically coupled with photonic crystal microcavities, proving their inherent suitability to act as integrated light sources in complex nanophotonic devices.

Experimental observation of wave localization at the Dirac frequency in a two-dimensional photonic crystal microcavity.

Trapping light within cavities or waveguides in photonic crystals is an effective technology in modern integrated optics. Traditionally, cavities rely on total internal reflection or a photonic bandgap to achieve field confinement. Recent investigations have examined new localized modes that occur at a Dirac frequency that is beyond any complete photonic bandgap. We design Al2O3 dielectric cylinders placed on a triangular lattice in air, and change the central rod size to form a photonic crystal microcavity. It is predicted that waves can be localized at the Dirac frequency in this device without photonic bandgaps or total internal reflections. We perform a theoretical analysis of this new wave localization and verify it experimentally. This work paves the way for exploring localized defect modes at the Dirac point in the visible and infrared bands, with potential applicability to new optical devices.

Effect of thickness deviation on the absorption of graphene in photonic crystal microcavity

The effect of thickness deviation on the optical properties of graphene-based optical microstructure was studied by using the transfer matrix method. Machining errors led to inconsistencies in the thicknesses of different parts and resulted in an offset of absorption peak, thus significantly reducing the average light absorption. The 3-nm deviation decreased the light absorption of graphene-optical microstructure by approximately 3.5 times. However, if the machining error is included in the design, then a relatively small Q value will help reduce the effect of machining error and the light absorption can be enhanced by about 32%.

Photonic coherent perfect transmission, absorption, and synthesis in a bimodal cavity quantum electrodynamics system

In this paper, we investigate an optical hybrid system in which a single quantum emitter is coupled to both modes of a bimodal optical microcavity, and propose a scheme for coherent perfect transmission, coherent perfect absorption, and coherent perfect synthesis of optical photons by utilizing such a bimodal cavity quantum electrodynamics (QED) system. In the present scheme, each mode of the bimodal microcavity can be coherently driven by an external monochromatic continuous-wave driving laser and the two cavity modes are not directly coupled to each other due to their orthogonal polarizations. It is found that three important phenomena, i.e., photonic coherent perfect transmission, absorption, and synthesis can be achieved in the optical hybrid system under appropriate conditions. We discuss in detail the theoretical model and present results of numerical simulation of the system in the steady state with experimentally achievable system parameters. Also, the possible experimental realization of the scheme in a solid-state approach is analyzed based on the semiconductor quantum dot and the photonic crystal defect microcavity. This study may provide further insight into the understanding of bimodal cavity QED system and find potential applications in quantum information processing and future quantum networks.

Broad-spectrum enhanced absorption of graphene-molybdenum disulfide photovoltaic cells in metal-mirror microcavity

The optical absorption of graphene-molybdenum disulfide photovoltaic cells (GM-PVc) in wedge-shaped metal-mirror microcavities (w-MMCs) combined with a spectrum-splitting structure was studied. Results showed that the combination of spectrum-splitting structure and w-MMC can enable the light absorption of GM-PVcs to reach about 65% in the broad spectrum. The influence of processing errors on the absorption of GM-PVcs in w-MMCs was 3–14 times lower than that of GM-PVcs in wedge photonic crystal microcavities. The light absorption of GM-PVcs reached 60% in the broad spectrum, even with the processing errors. The proposed structure is easy to implement and may have potentially important applications in the development of ultra-thin and high-efficiency solar cells and optoelectronic devices.

Ultralow-power on-chip all-optical Fano diode based on uncoupled nonlinear photonic-crystal nanocavities

We achieved an ultralow-power Fano-like diode in integrated photonic circuits through two cascaded and uncoupled photonic-crystal microcavities, coated with a nonlinear layer constructed from polycrystalline indium-tin oxide doped with gold nanoparticles. The multicomponent nanocomposite layer helps to obtain an extremely large nonlinearity enhancement on account of the quantum confinement effect, hot-electron injection, and local-field enhancement effect. Thus, the strong nonlinearity enhancement, asymmetric Fano-like spectrum lineshape, and asymmetric light confinement for the forward and backward incidence cases guarantee the nonreciprocal transmission of signal light. A compact size of 7 μm is maintained for the photonic-crystal microcavities and the transmission contrast reached 15 dB. Besides, we achieved 1.5 kW cm−2 operating threshold intensity (cut down by a thousand times). This work assists chip-integrated optical computing on the basis of nonlinear photonic-crystal microcavities.

Micro-force Sensor Based on Photonic Crystal Micro-cavity and Fiber Loop Ring-Down

Micro-force Sensor Based on Photonic Crystal Micro-cavity and Fiber Loop Ring-Down

Optical transmission characteristics of multi-band triangular-lattice photonic crystal coupling cavity waveguide based on annular microcavity

The light localization characteristics of the near-infrared triangular-lattice photonic crystal annular microcavity are studied theoretically in this paper. The photonic crystal has a lattice constant of <i>a</i>=540 and it is composed of silicon rods each with a radius of <i>r</i>=135 immersed in air background. The two kinds of annular microcavities are obtained by removing 12 silicon rods which are located respectively at a distance of 2a and at a distance of √<span style="border-top:1px solid; padding-top:0px;">3</span><i>a</i> to the central rod. Five resonant wavelengths and the corresponding eigen mode profiles of the microcavity are studied. A coupled resonant optical waveguide is formed by integrating the microcavities with a periodic length of 7<i>a</i> in space. The group velocity of light beam propagation within multiple guiding bands are analyzed by the tight-binding approximation method. The maximum and minimum velocity of 0.0028<i>c</i> and 0.00082<i>c</i> are obtained, where <i>c</i> is the light velocity in vacuum. The light transmittance values and spatial steady distributions of the electric field's amplitude through the structure at several wavelengths within the guiding bands are studied by the finite-difference time-domain method. The results are consistent with that calculated by the plane wave expand method. Interleaving circular microcavities perpendicular to the direction of optical transmission at a lateral distance of 2√<span style="border-top:1px solid; padding-top:0px;">3</span><i>a</i>, the coupling region between the adjacent microcavities is changed, the difference in group velocity between guiding bands apparently decreases and the transmittance values of two frequency bands are enhanced.<br/>Keeping the size of silicon rods unchanged, two kinds of microcavities are constructed by removing the six rods with the distances of 2<i>a</i> and √<span style="border-top:1px solid; padding-top:0px;">3</span><i>a</i> from the center of the central silicon rod, respectively. The resonant wavelengths supported by the above two microcavities are studied. Two coupled-resonant optical waveguides with a periodic length of 7<i>a</i> are proposed. Connecting these two coupled cavity optical waveguides with the W1-typed input/output waveguides, the selecting and sharing function of guiding band are finally achieved for wavelengths within different frequency bands. Keeping the group velocity slowing down, a maximum value of one guiding band reaches 0.00047<i>c</i>.

Design optimization of a compact photonic crystal microcavity based on slow light and dispersion engineering for the miniaturization of integrated mode-locked lasers

We exploit slow light (high ng) modes in planar photonic crystals in order to design a compact cavity, which provides an attractive path towards the miniaturization of near-infrared integrated fast pulsed lasers. By applying dispersion engineering techniques, we can design structures with a low dispersion, as needed by mode-locking operation. Our basic InP SiO2 heterostructure is robust and well suited to integrated laser applications. We show that an optimized 30 μm long cavity design yields 9 frequency-equidistant modes with a FSR of 178 GHz within a 11.5 nm bandwidth, which could potentially sustain the generation of optical pulses shorter than 700 fs. In addition, the numerically calculated quality factors of these modes are all above 10,000, making them suitable for reaching laser operation. Thanks to the use of a high group index (28), this cavity design is almost one order of magnitude shorter than standard rib-waveguide based mode-locked lasers. The use of slow light modes in planar photonic crystal based cavities thus relaxes the usual constraints that tightly link the device size and the quality (peak power, repetition rate) of the pulsed laser signal.

Two-dimensional fivefold photonic crystal microcavity

Fivefold photonic crystal (PC) structure is originally presented with theoretical investigation about its photonic band gap through transmission spectrum calculated by finite-difference time-domain methods. The existence of PC band gap makes it possible for defect structures with high-quality factor. Two types of fivefold PC microcavity are proposed of which the quality factor, normalized frequency, and electromagnetic field profile have been simulated. With some preliminary structural parameters optimization, monopole mode in one-defect fivefold PC microcavity with a high-Q factor (∼2212) and whispering gallery mode in six-defect fivefold PC microcavity with a high-Q factor (∼13,300) are obtained.

Optical interaction between one-dimensional fiber photonic crystal microcavity and gold nanorod**Project supported by the National Basic Research Program of China (Grant No. 2013CB632704) and the National Natural Science Foundation of China (Grant No. 11434017).

Localized surface plasmon resonance (LSPR) has demonstrated its promising capability for biochemical sensing and surface-enhanced spectroscopy applications. However, harnessing LSPR for remote sensing and spectroscopy applications remains a challenge due to the difficulty in realizing a configuration compatible with the current optical communication system. Here, we propose and theoretically investigate a hybrid plasmonic-photonic device comprised of a single gold nanorod and an optical fiber-based one-dimensional photonic crystal microcavity, which can be integrated with the optical communication system without insertion loss. The line width of the LSPR, as a crucial indicator that determines the performances for various applications, is narrowed by the cavity–plasmon coupling in our device. Our device provides a promising alternative to exploit the LSPR for high-performance remote sensing and spectroscopy applications.

Abnormal mode splitting in photonic crystals micro-cavity containing highly dispersive metamaterials

We theoretically study abnormal mode splitting in a one-dimensional photonic crystals (PhCs) micro-cavity composed of highly dispersive metamaterials and dielectric. In particular, the abnormal split peaks can be posited in normal and anomalous dispersion regions, respectively. The normal split modes in conventional all-dielectric PhCs are always blue shifted owing to the propagating phases in two kinds of dielectrics decrease with incident angle. Here, based on the phase variation compensation between anomalous dispersion metamaterials and the dielectric, the dispersion of the split mode can be offset and thus red shift abnormal modes splitting can be realized. Moreover, such abnormal splitting modes can be either tuned by the optical properties of the PhCs, but also by the dispersion characteristics of the material. The abnormal splitting modes will possess potential applications for angle-tuned etalon filters, angle-dependent optical sensor, nonlinear optical devices, and so on.

Observations of cavity polaritons in one-dimensional photonic crystals containing a liquid-crystalline semiconductor based on perylene bisimide units.

We investigated the optical transmission properties of one-dimensional photonic crystal (1D-PC) microcavity structures containing the liquid-crystalline (LC) perylene tetracarboxylic bisimide (PTCBI) derivative. We fabricated the microcavity structures for this study by two different methods and observed the cavity polaritons successfully in both samples. For one sample, since the PTCBI molecules were aligned in the cavity layer of the 1D-PC by utilizing a friction transfer method, vacuum Rabi splitting energy was strongly dependent on the polarization of the incident light produced by the peculiar optical features of the LC organic semiconductor. For the other sample, we did not utilize the friction transfer method and did not observe such polarization dependence. However, we did observe a relatively large Rabi splitting energy of 187 meV, probably due to the improvement of optical confinement effect.

Dye concentration dependence of spectral triplet in one-dimensional photonic crystal with cyanine dye J-aggregate in strong coupling regime

We report on the dye concentration dependence of nonlinear transmission properties of one-dimensional photonic crystal microcavities containing cyanine dye J-aggregates. Using femtosecond nonlinear transmission spectroscopy, we observed a transition from a polariton doublet state to a spectral triplet state over the whole tested concentration range, even at room temperature. In these samples, changes in the dye concentration affected the Rabi splitting energy in the linear transmission measurements; however, we found that changes in the concentration did not greatly affect the triplet formation.

Study of photonic crystal microcavities coupled with waveguide for biosensing applications

In this paper, we propose a two-dimensional photonic crystal biosensor implemented by waveguide and microcavity. The optical sensing characteristics of the structure are analyzed by using two-dimensional finite difference time domain method. Biomolecules, e.g., DNAs, trapped in selected holes cause resonant wavelength shifting at the output terminal. The quality factor and the sensitivity of the proposed structure are about 6776 and 3.4 nm/fg, respectively, with a minimum detectable biomolecule weight in a sensing hole of 0.029 fg. We have also investigated the structure for use in bulk refractive index sensing. A sensitivity and detection limit of 210 nm/RIU and 8.92 × 10−5 were obtained respectively. Furthermore, to overcome the single purpose capacity of the sensor, a multichannel optofluidic sensor has been designed. The structure is made up of three microcavities connected in series and coupled to a waveguide. Simulation results indicate that the response of each detection unit to the refractive index variation (from 1.330 to 1.371) was completely independent. These features make the designed device a promising element for performing label-free multiplexed detection in monolithic substrate for medical diagnostics and environmental monitoring.

Quantum many-body simulation using monolayer exciton-polaritons in coupled-cavities

Quantum simulation is a promising approach to understanding complex strongly correlated many-body systems using relatively simple and tractable systems. Photon-based quantum simulators have great advantages due to the possibility of direct measurements of multi-particle correlations and ease of simulating non-equilibrium physics. However, interparticle interaction in existing photonic systems is often too weak, limiting the potential for quantum simulation. Here we propose an approach to enhance the interparticle interaction using exciton-polaritons in MoS2 monolayer quantum dots embedded in 2D photonic crystal microcavities. Realistic calculation yields optimal repulsive interaction in the range of 1–10 meV—more than an order of magnitude greater than the state-of-the-art value. Such strong repulsive interaction is found to emerge neither in the photon-blockade regime for small quantum dot nor in the polariton-blockade regime for large quantum dot, but in the crossover between the two regimes with a moderate quantum-dot radius around 20 nm. The optimal repulsive interaction is found to be largest in MoS2 among commonly used optoelectronic materials. Quantum simulation of strongly correlated many-body systems in a finite chain of coupled cavities and its experimental signature are studied via the exact diagonalization of the many-body Hamiltonian. A method to simulate 1D superlattices for interacting exciton-polariton gases in serially coupled cavities is also proposed. Realistic considerations on experimental realizations reveal advantages of transition metal dichalcogenide monolayer quantum dots over conventional semiconductor quantum emitters.

Specific Detection of Antibiotics by Silicon-on-Chip Photonic Crystal Biosensor Arrays

Photonic crystal (PC) microcavities formed by 2-D air holes on silicon-on-insulator substrates were utilized as biosensors to detect antibiotics with high specificity. The antibiotic, gentamicin, with molecular weight of only 478 g/mol, was successfully detected via its binding to corresponding antibody pre-immobilized on the sensor surface. Detection range (in concentration) was extended by combining different types of PC biosensors on a single silicon chip, covering from 0.1 nM to 1 $\mu \text{M}$ . Specificity of detection was also verified on the studied antibiotic.

Facile design and stabilization of a novel one-dimensional silicon-based photonic crystal microcavity

A novel silicon-based optical microcavity composed of a defect layer sandwiched between two parallel rugate mirrors is created by the electrochemical anodization of silicon in a hydrofluoric acid-based electrolyte using a precisely controlled current density profile. The profile consists of two sinusoidally modulated current waveforms separated by a fixed current that is applied to produce a defect layer between the mirrors. The spectral response of the rugate-based microcavity is simulated using the transfer matrix method and compared to the conventional Bragg-based microcavity. It is found that the resonance position of both microcavities is unchanged. However, the rugate-based microcavity exhibits a distinct reduction of the sidebands' intensity. Further attenuation of the sidebands' intensity is obtained by creating refractive index matching layers with optimized thickness at the bottom and top of the rugate-based microcavity. In order to stabilize the produced microcavity against natural oxidation, atomic layer deposition of an ultra-thin titanium dioxide layer on the pore wall is carried out followed by thermal annealing. The microcavity resonance position shows an observable sensitivity to the deposition and annealing processes.

Linear and nonlinear microwave responses of a microwave photonic filter based on a photonic crystal microcavity

We propose and demonstrate an ultracompact bandpass microwave photonic filter (MPF) based on a silicon photonic crystal (PhC) microcavity. Taking the fabricated PhC microcavity as an example, we comprehensively investigate both the linear and nonlinear microwave responses of the MPF based on silicon waveguide devices. Two cases are discussed in the experiment, i.e., the optical carrier wavelength is located on the left or right side of the notch resonant wavelength of the PhC microcavity. The experimental results agree well with the theoretical analyses. For the former case, the central frequency of MPF increases monotonically when fixing the optical carrier wavelength and increasing the optical carrier power. For the latter case, the nonlinear response at a fixed optical carrier wavelength shows a decrease first and then an increase in the central frequency of MPF when increasing the optical carrier power. A jump of the response is observed in the switching process. Moreover, we also observe an interesting bistable microwave response in the experiment under an optical carrier power of around −2.6 dBm in the latter case.