Photonic Crystal Microresonators Research Articles

Magneto-Optical Faraday Effect in Quasicrystalline and Aperiodic Microresonator Structures

We theoretically and numerically investigate magnetophotonic microresonators formed by a magnetic layer sandwiched between two reflective multilayers with different layer arrangements. Quasicrystals with the Fibonacci layer sequence and aperiodic structures with the Thue–Morse sequence are all compared to the conventional photonic crystal Bragg microresonators. The magneto-optical spectral properties of such magnetophotonic structures are completely different from each other and from a uniform magnetic film. In multilayered structures of various order types, microresonator modes are excited. The feature of multilayered structures with arrangements different from a periodic one is that they support the excitation of the multiple microresonator modes in a limited visible and near-infrared spectral range. The wavelengths of the two microresonator modes in a regular photonic crystal differ by more than one octave. This feature of the quasi-crystalline and aperiodic microresonators is important for applications in devices based on the Faraday effect.

Inverse design of a high‐quality factor multi‐purpose optical biosensor

This paper investigates a high-quality and multi-purposed biosensor with maximum stable output transmittance numerically by using the inverse design method. The proposed biosensor utilises particle swarm optimisation for inverse design which will be a helpful way of designing different kinds of precise sensors in the future. In this research, some parameters are introduced to the optimiser to find the best cavity parameters for developing a high-quality sensor to sense different targets. Many previous studies were on single-goal biosensors, or their quality factor and output spectrum were very low. The proposed sensor can sense different parts of blood components, the amount of glucose in the urine, and tear's glucose for the first time just in one device to the best of our knowledge. Compared to previous works, this structure detects the differences between refractive indexes analytes with a high-quality factor and a high and stable output transmittance spectrum. This structure contains two-dimensional photonic crystal microresonators to provide resonance frequencies in the photonic bandgap. The device works on a window of 1.55 μm with a quality factor equal to 24,000, the sensitivity is 500 nm/RIU (refractive index unit), and the resolution is equal to 4 × 10−5. In this paper, the scaling method, particle swarm optimisation, two-dimensional finite-difference dime domain, and Plane-Wave Expansion methods are utilised.

Hybrid InGaP nanobeam on silicon photonics for efficient four wave mixing

Abstract

Four-port SNAP microresonator device.

It is well known from quantum mechanics that the transmission amplitude of a symmetric double-barrier structure can approach unity at the resonance condition. A similar phenomenon is observed in optics for light which propagates between two waveguides weakly coupled through a microresonator. Examples of microresonators used for this purpose include ring, photonic crystal, toroidal, and bottle microresonators. However, ring and photonic crystal photonic circuits, once fabricated, cannot be finely tuned to arrive at the mentioned resonant condition. In turn, it is challenging to predictably adjust coupling to toroidal and bottle microresonators by translating the input-output microfibers, since the modes of these resonators are difficult to separate spatially. Here we experimentally demonstrate a four-port micro-device based on a SNAP microresonator introduced at the surface of an optical fiber. The eigenmodes and corresponding eigenwavelengths of this resonator are clearly identified for both polarization states by the spectrograms measured along the length of the fiber. This allows us to choose the resonant wavelength and simultaneously determine the positions of the input-output microfiber tapers to arrive at the required resonance condition.

Cavity-enhanced harmonic generation in silicon rich nitride photonic crystal microresonators

We report second and third harmonic generation in photonic crystal cavities fabricated in a suspended silicon-rich nitride membrane under resonant continuous-wave excitation at telecom wavelength. Two-dimensional photonic crystal cavities with a far-field optimized line-width modulated design were employed. A quality factor at fundamental wavelength as high as Q = 1.3 × 104 and a coupling efficiency ηc ≈ 30% enabled us to exploit the cavity field enhancement to achieve the generation efficiencies ρSH = (4.7 ± 0.2) × 10−7 W−1 and ρTH = (5.9 ± 0.3) × 10−5 W−2. The absence of saturation effects at high power and the transparency of the device at the second harmonic wavelength suggest the absence of two-photon absorption and related detrimental effects.

2D Material Microcavity Light Emitters: To Lase or Not to Lase?

AbstractAtomically thin layers of transition metal dichalcogenides (TMDs) are of great interest to the photonics community because of their unique optical properties. For example, in conjunction with microring or photonic crystal microresonators, they readily form microcavity light emitters. A number of configurations are now presented that apparently meet the conditions for lasing, yet there is considerable debate in the community as to whether lasing is actually achieved. By employing a very comprehensive set of assessment criteria, herein is shown that none of the TMD devices meet all the conditions for lasing, despite some very convincing data being presented. These findings are examined in the context of microcavity lasers based on III–V gain materials. Applications of TMD light emitters in the areas of quantum information and biosensing are also discussed to highlight areas where lasing action is not necessarily required.

WGM Micro-Fluidic-Channel Based on Reflection Type Fiber-Tip-Coupled Hollow-Core PCFs

A micro-fluidic-channel is proposed based on a fiber-tip-excited hollow-core photonic crystal fiber microresonator. The reflection conical fiber tip is fabricated based on electric arc fusion technique. A quality factor up to $8.65 \times 10^{\mathrm { {4}}}$ has been experimentally acquired at $\sim 1557.75$ nm. Theoretical simulation results indicate that the refractive index sensitivity of the whispering-gallery-mode resonance wavelength reaches 1259.9211 nm/RIU for biocompatible low refractive index range. The proposed microfluidic detection platform has a few desirable merits, such as ease of fabrication, low-cost, and structure robustness, which ensures its applicability for practical use in chemical as well as biological sensing applications.

Mono- to few-layered graphene oxide embedded randomness assisted microcavity amplified spontaneous emission source

The realization of optoelectronic devices using two-dimensional materials such as graphene and its intermediate product graphene oxide (GO) is extremely challenging owing to the zero band gap of the former. Here, a novel amplified spontaneous emission (ASE) system based on a GO-embedded all-dielectric one-dimensional photonic crystal (1DPhC) micro-resonator is presented. The mono- to few-layered GO sheet is inserted within a microcavity formed by two 5-bilayered SiO2/SnO2 Bragg reflectors. Significantly enhanced photoluminescence (PL) emission of GO embedded in 1DPhC is explicated by studying the electric field confined within the micro-resonator using the transfer matrix method. The inherent randomness, due to fabrication limitations, in the on-average periodic 1DPhC is exploited to further enhance the PL of the optically active micro-resonator. The 1DPhC and randomness assisted field confinement reduces the ASE threshold of the mono- to few-layered weak emitter making the realization of an ASE source feasible. Consequently, ASE at the microcavity resonance and at the low-frequency band-edge of photonic stop-band is demonstrated. Variation of the detection angle from 5° to 30°, with respect to the sample surface normal allows reallocation of the defect mode ASE peak over a spectral range of 558–542 nm, making the GO-incorporated 1DPhC a novel and attractive system for integrated optic applications.

Sculpting narrowband Fano resonances inherent in the large-area mid-infrared photonic crystal microresonators for spectroscopic imaging.

Fourier transform infrared (FT-IR) imaging spectrometers are almost universally used to record microspectroscopic imaging data in the mid-infrared (mid-IR) spectral region. While the commercial standard, interferometry necessitates collection of large spectral regions, requires a large data handling overhead for microscopic imaging and is slow. Here we demonstrate an approach for mid-IR spectroscopic imaging at selected discrete wavelengths using narrowband resonant filtering of a broadband thermal source, enabled by high-performance guided-mode Fano resonances in one-layer, large-area mid-IR photonic crystals on a glass substrate. The microresonant devices enable discrete frequency IR (DF-IR), in which a limited number of wavelengths that are of interest are recorded using a mechanically robust instrument. This considerably simplifies instrumentation as well as overhead of data acquisition, storage and analysis for large format imaging with array detectors. To demonstrate the approach, we perform DF-IR spectral imaging of a polymer USAF resolution target and human tissue in the C-H stretching region (2600-3300 cm(-1)). DF-IR spectroscopy and imaging can be generalized to other IR spectral regions and can serve as an analytical tool for environmental and biomedical applications.

High-Q CMOS-integrated photonic crystal microcavity devices

Integrated optical resonators are necessary or beneficial in realizations of various functions in scaled photonic platforms, including filtering, modulation, and detection in classical communication systems, optical sensing, as well as addressing and control of solid state emitters for quantum technologies. Although photonic crystal (PhC) microresonators can be advantageous to the more commonly used microring devices due to the former's low mode volumes, fabrication of PhC cavities has typically relied on electron-beam lithography, which precludes integration with large-scale and reproducible CMOS fabrication. Here, we demonstrate wavelength-scale polycrystalline silicon (pSi) PhC microresonators with Qs up to 60,000 fabricated within a bulk CMOS process. Quasi-1D resonators in lateral p-i-n structures allow for resonant defect-state photodetection in all-silicon devices, exhibiting voltage-dependent quantum efficiencies in the range of a few 10 s of %, few-GHz bandwidths, and low dark currents, in devices with loaded Qs in the range of 4,300–9,300; one device, for example, exhibited a loaded Q of 4,300, 25% quantum efficiency (corresponding to a responsivity of 0.31 A/W), 3 GHz bandwidth, and 30 nA dark current at a reverse bias of 30 V. This work demonstrates the possibility for practical integration of PhC microresonators with active electro-optic capability into large-scale silicon photonic systems.

Fano line shapes in transmission spectra of silicon photonic crystal resonators

Transmission measurements on symmetrically waveguide-loaded one-dimensional silicon photonic crystal microresonators are observed to exhibit Fano line shapes, which we find to be due to the interference between the resonant transmission and a leaky second-order quasi-transverse-electric mode partially guided through the photonic crystal. The line shape is tunable by varying the exciting fiber position, the material index, and via the cavity nonlinearity. This two-mode interference method applied to a one-dimensional silicon photonic crystal cavity represents a compact and tunable approach to obtaining such line shapes in integrated optical devices, with implications for efficient modulation of optical signals and nonlinear all-optical switching.

Pattern-integrated interference [Invited

Pattern-integrated interference (PII) is described as a logical progression starting from the primary precursors of interference and holography. PII produces, in a single-exposure step, a periodic interference pattern with preselected periods absent. These blocked periods, for example, can form the nonperiodic functional elements of a photonic-crystal device or the circuit elements in a periodic-layout-design semiconductor chip. Various possible system configurations for PII are presented and compared. Example PII-produced intensity patterns for a photonic-crystal microresonator filter and an optical switch are simulated and discussed.

Analyzing the Modality of Two-Dimensional Photonic Crystal Fiber Optical Micro-Resonators by Equivalent Refractive Index Mode

This paper analyzes the modality of two-dimensional photonic crystal micro-resonators by adopting equivalent refractive index mode. In this paper, it controls the optical field distribution only through altering the thickness of light guide layer, while the parameter like resonator structure and crystal lattice arrangement remain stable. It discusses that it would arrive at a satisfactory photon locality while the refractive index of light guide layer material is gallium nitride , the thickness of light guide layer is and its equivalent refractive index is 2.1.This reveals the influence of micro-resonator light guide layer’s thickness towards the modality, providing a preferable pre-estimate method for the actual research of micro-resonators with higher quality.

Optical Microcavities Clad by Low-Absorption Electrode Media

Four types of high-Q optical microcavities - disk, 1-D photonic crystal nanobeam, 2-D photonic crystal slab, and 3-D photonic crystal optical microresonators - clad by low-optical-loss electrode media such as indium tin oxide are designed and evaluated by the perturbation theory and 3-D finite-difference time-domain (FDTD) method. The quality (Q) factor is obtained via perturbation theory in which the imaginary part of the cladding material is regarded as a perturbation and confirmed to agree with results from the 3-D FDTD method. Although the studied designs preserve the high-Q factor, they provide the placement of low-loss conductive electrode material proximate to high-Q microcavity modes. Further enhancement of the Q factor is possible by a reduction of the electrode volume. Microlasers based on this study would provide an excellent heat sink and efficient carrier injection into a microcavity mode, thereby resulting in the realization of continuous-wave, room-temperature microlasers with low threshold.

Two-dimensionally relocatable microfiber-coupled photonic crystal resonator

A photonic crystal microresonator is proposed in this study that is relocatable in two dimensions. A wavelength-scale resonator with high Q-factor (26,000) and high collection efficiency (80%) is formed and repositioned by simply placing and relocating a curved-microfiber to a new position on the surface of a two-dimensional square lattice photonic crystal slab. The formation of the resonator was confirmed by observing lasing of resonators. Infrared microscope images showed that the lasing site is two-dimensionally relocated in-situ. Spectral tuning was demonstrated by modifying the curvature of the microfiber. Functionalities, such as the two-dimensional relocation, spectral tuning and efficient extraction, which the curved-microfiber coupling offers, may provide an alternative way of coupling with a single quantum dot.

Impedance matching in photonic crystal microcavities for second-harmonic generation

By numerically integrating the three-dimensional Maxwell equations in the time domain with reference to a dispersive quadratically nonlinear material, we study second-harmonic generation in planar photonic crystal microresonators. The proposed scheme allows efficient coupling of the pump radiation to the defect resonant mode. The outcoupled generated second harmonic is maximized by impedance matching the photonic crystal cavity to the output waveguide.

Hybrid Single-Nanowire Photonic Crystal and Microresonator Structures

We report a hybrid approach for photonic systems that combines chemically synthesized single nanowire emitters with lithographically defined photonic crystal and racetrack microresonator structures. Finite-difference time-domain calculations were used to design nanowire photonic crystal structures where the photonic band gap overlaps the electronic band gap of the nanowire. Photoluminescence (PL) images of cadmium sulfide (CdS) nanowire photonic crystal structures designed in this way demonstrate localized emission from engineered defects and light suppression in regions of the photonic crystal. PL spectroscopy studies of defect-free nanowire photonic crystal structures further demonstrate the photonic band gap or stop band that spans most of the CdS band edge emission spectrum. In addition, single CdS nanowire-racetrack microresonator structures were fabricated, and PL imaging and spectroscopy measurements show good coupling of the nanowire to the microcavity including efficient feedback and amplified spontaneous emission. These hybrid structures exploit unique strengths of bottom-up and top-down approaches and thereby open new opportunities in nanophotonics from efficient and localized light sources to integrated optical processing.

Photonic crystal wires for optical parametric oscillators in isotropic media

We investigate four wave mixing in photonic crystal wire microresonators realized in an isotropic medium. One-dimensional optical parametric oscillators are numerically analyzed by solving Maxwell’s equations in all dimensions and including material dispersion as well as nonlinear polarization.

Near-field visualization of light confinement in a photonic crystal microresonator.

By using scanning near-field optical microscopy, we directly map the subwavelength confinement of light around a point defect in a two-dimensional photonic crystal microresonator. Comparison of our results with the outcome of three-dimensional finite-difference time domain calculations allows us to identify small imperfections in the structure that result in the spatial modification of the intensity distribution.

Direct spectroscopy of a deep two-dimensional photonic crystal microresonator

Photonic crystals based on macroporous silicon with fundamental band gaps in the middle infrared region 3.4‐5.8 mm were fabricated. Scanning probe optical microscopy and laser spectroscopy were combined to examine a deep two-dimensional photonic crystal microresonator based on a single point defect. Two sharp resonances were recorded in the band gap, in excellent agreement with the results of numerical simulations. Such a microresonator with high-quality factors and a subwavelength mode extension could be used for a range of applications including integrated optical gas sensors.