Photonic Crystal Nanobeam Cavities Research Articles

Using photonic crystal nanobeam cavities for integration of optical signal

In this paper we propose and numerically investigate an all-optical temporal integrator based on a photonic crystal cavity. We show that an array of photonic crystal cavities enables high-order temporal integration. The effect of the value of the cavity’s free spectral range on the accuracy of the integration is considered. The influence of the coupling coefficients in the resonator array on the integration accuracy is demonstrated. A compact integrator based on a photonic crystal nanobeam cavity is designed, which allows high-precision integration of optical pulses of subpicosecond duration.

Slotted photonic crystal nanobeam cavity with an ultrahigh quality factor-to-mode volume ratio

We describe the design, fabrication, and characterization of a 1-dimensional silicon photonic crystal cavity with a quality factor-to-mode volume ratio greater than 10(7), which exceeds the highest previous values by an order of magnitude. The maximum of the electric field is outside the silicon in a void formed by a central slot. An extremely small calculated mode volume of 0.0096 (λvac/n)(3) is achieved through the abrupt change of the electric field in the slot, despite which a high quality factor of 8.2 × 10(5) is predicted by simulation. Quality factors up to 1.4 × 10(5) are measured in actual devices. The observation of pronounced thermo-optic bistability is consistent with the strong confinement of light in these cavities.

Single particle detection in CMOS compatible photonic crystal nanobeam cavities

We report the label-free detection of single particles using photonic crystal nanobeam cavities fabricated in silicon-on-insulator platform, and embedded inside microfluidic channels fabricated in poly-dimethylsiloxane (PDMS). Our system operates in the telecommunication wavelength band, thus leveraging the widely available, robust and tunable telecom laser sources. Using this approach, we demonstrated the detection of polystyrene nanoparticles with dimensions down to 12.5nm in radius. Furthermore, binding events of a single streptavidin molecule have been observed.

Scalable photonic crystal chips for high sensitivity protein detection

Scalable microfabrication technology has enabled semiconductor and microelectronics industries, among other fields. Meanwhile, rapid and sensitive bio-molecule detection is increasingly important for drug discovery and biomedical diagnostics. In this work, we designed and demonstrated that photonic crystal sensor chips have high sensitivity for protein detection and can be mass-produced with scalable deep-UV lithography. We demonstrated label-free detection of carcinoembryonic antigen from pg/mL to μg/mL, with high quality factor photonic crystal nanobeam cavities.

Ultrasensitive Gas-Phase Chemical Sensing Based on Functionalized Photonic Crystal Nanobeam Cavities

Photonic crystal nanobeam cavities with high-quality factors are very sensitive to the changes of the dielectric properties of their surroundings. Utilizing this high sensitivity and by applying chemical functionalization, an ultrasensitive chemical sensor for gases based on a nanobeam cavity was demonstrated. A limit of detection of 1.5 parts-per-billion (ppb) in ambient conditions, determined from the noise level of the system, was achieved for nerve agent simulant methyl salicylate. The nanobeam cavity's nonlinear thermo-optical bistability is also utilized to realize a threshold detector for cumulative chemical exposure.

Slotted Photonic Crystal Single Nanobeam Cavity

Photonic crystal (PhC) nanobeam cavities have attracted considerable interest due to their compact mechanical structure, ultra-high Q-factors and low mode volumes (V approx. (l/n)3).

Spontaneous emission enhancement and saturable absorption of colloidal quantum dots coupled to photonic crystal cavity

We demonstrate spontaneous emission rate enhancement and saturable absorption of cadmium selenide colloidal quantum dots coupled to a nanobeam photonic crystal cavity. We perform time-resolved lifetime measurements and observe an average enhancement of 4.6 for the spontaneous emission rate of quantum dots located at the cavity as compared to those located on an unpatterned surface. We also demonstrate that the cavity linewidth narrows with increasing pump intensity due to quantum dot saturable absorption.

Slotted photonic crystal nanobeam cavity with parabolic modulated width stack for refractive index sensing

We present the design, fabrication, and the characterization of high-Q slotted 1D photonic crystal (PhC) cavities with parabolic-width stack. Their peculiar geometry enables the location of the resonating mode close to the air-band. The majority of optical field distributes in the slotted low-index area and the light matter interaction with the analytes has been enhanced. Cavities with measured Q-factors ~10(4) have been demonstrated. The refractive index sensing measurement for NaCl solutions with different concentrations shows a sensitivity around 410. Both the achieved Q-factor and the sensitivity are higher than the one reported recently by using 2D slotted PhC cavities. The total size for the sensing part of the present device is reduced to 16.8 × 2.5 μm(2).

Horizontally slotted photonic crystal nanobeam cavity with embedded active nanopillars for ultrafast direct modulation

A horizontally slotted photonic crystal nanobeam cavity with an embedded active nanopillar structure is proposed for ultrafast direct modulation. By designing the thicknesses of both the nanobeam and the horizontal slot layer, the quality factor (Q factor) and the mode volume (Vn) of the proposed cavity can be engineered independently. As a result, the spontaneous emission (SpE) rate is enhanced with a small Vn of 2.4 while the SpE rate and the cavity photon lifetime have an optimal Q factor of ∼ 1000. In our simulation, the modulation bandwidth could be enhanced up to 170 GHz with different emission linewidths of the active nanopillar.

Fano resonances in ultracompact waveguide Fabry-Perot resonator side-coupled lossy nanobeam cavities

We propose and demonstrate experimentally an ultracompact resonant system exhibiting sharp asymmetric Fano-resonance, in which a tiny photonic crystal nanobeam cavity is laterally coupled to a waveguide Fabry-Perot resonator. Under the presence of cavity intrinsic loss, we find that the system produces sharper and higher extinction ratio Fano resonance spectra only if appropriate phase is selected. The whole device (∼6 μm2) is implemented on silicon on insulator platform, and experimentally we observe steep-slope Fano resonance with extinction ratio of 7.3 dB, slope above 5 dB/nm, and average insertion loss less than 1.8 dB.

Optical design of split-beam photonic crystal nanocavities

We design high-quality-factor photonic crystal nanobeam cavities formed by two mechanically isolated cantilevers. These "split-beam" cavities have a physical gap at the center, allowing mechanical excitations of one or both of the cavity halves. They are designed by analyzing the optical band structures and mode profiles of waveguides perforated by elliptical holes and rectangular gaps and are predicted to support optical resonances with quality factors exceeding 10(6) at wavelengths of ~1.6 μm.

Slow-Light-Enhanced Nonlinear Characteristics in Slot Waveguides Composed of Photonic Crystal Nanobeam Cavities

We investigate slow-light-enhanced nonlinear characteristics in slot waveguides composed of photonic crystal (PC) nanobeam cavities. To evaluate the effective nonlinear coefficient, numerical simulations are performed by using 3-D vector finite-element method for periodic waveguide analysis. Results show that the maximum nonlinear coefficient of 11 600 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> is obtained by optimizing waveguide width and height. This high optical nonlinearity is realized owing to strong light confinement at slotted geometry and small group velocity in PC nanobeam cavities. Also, we show that there exists tradeoff between the effective nonlinear coefficient and the bandwidth in the case of changing one-period length of the proposed structure.

Ultracompact, Reflection-Free and High-Efficiency Channel Drop Filters Based on Photonic Crystal Nanobeam Cavities

We propose an ultracompact channel drop filter (CDF) based on photonic crystal nanobeam cavities. The conditions for implementing such an ideal CDF are derived from the temporal coupled-mode equations governing the operation of the CDF. By considering the intercoupling of the two involved nanobeam cavities, some ambiguities of the previous equivalent circuit model analysis are cleared up. Practical configurations on silicon-on-insulator (SOI) for the proposed CDF are suggested with a typical length less than 15 μm. Finite difference time domain (FDTD) method calculations show that the proposed filter can achieve drop efficiency higher than 99% without any reflection. Compared to the λ/4-shifted Bragg grating resonators based CDF, the proposed CDF is more compact, high-efficient and reflection-free. It is also easy to implement a low-power tunable filter due to the ultrahigh quality factor Q and ultrasmall modal volume V of the involved photonic crystal nanobeam cavities.

Photonic Crystal Nanobeam Cavities for Tunable Filter and Router Applications

We investigate the suitability of photonic crystal nanobeam cavities for interconnect applications. Owing to their small footprint, exactly the same as that of an optical waveguide, as well as ultrahigh quality factor resonances that they support, nanobeam cavities are attractive candidates for realization of densely integrated on-chip optical networks. We discus tunability of these filters using thermo-optic, electromechanic, and optomechanic effects, and we compare different reconfiguration strategies in terms of tuning hold power, tuning efficiency, and maximum operating frequency.

Electro-Mechanical Q Factor Control of Photonic Crystal Nanobeam Cavity

We design and demonstrate a photonic crystal nanobeam cavity with a Q factor controllable by a micro-electro-mechanical system (MEMS). The cavity is evanescently coupled to an adjacent nanobeam waveguide, and its Q factor is controlled by electro-mechanically adjusting the gap distance between them. We experimentally demonstrate control of the Q factor from 2,250 to 2,750, by applying voltage from 0 to 11 V.

Single-cell photonic nanocavity probes.

In this report, we demonstrate for the first time photonic nanocavities operating inside single biological cells. Here we develop a nanobeam photonic crystal (PC) cavity as an advanced cellular nanoprobe, active in nature, and configurable to provide a multitude of actions for both intracellular sensing and control. Our semiconductor nanocavity probes emit photoluminescence (PL) from embedded quantum dots (QD) and sustain high quality resonant photonic modes inside cells. The probes are shown to be minimally cytotoxic to cells from viability studies, and the beams can be loaded in cells and tracked for days at a time, with cells undergoing regular division with the beams. We present in vitro label-free protein sensing with our probes to detect streptavidin as a path towards real-time biomarker and biomolecule detection inside single cells. The results of this work will enable new areas of research merging the strengths of photonic nanocavities with fundamental cell biology.

Compact and low power consumption tunable photonic crystal nanobeam cavity

A proof-of-concept for a new and entirely CMOS compatible tunable nanobeam cavity is demonstrated in this paper. Preliminary results show that a compact nanobeam cavity (~20 μm(2)) with high Q-factor (~50,000) and integrated with a micro-heater atop, is able of tuning the resonant wavelength up to 15 nm with low power consumption (0.35nm/mW), and of attaining high modulation depth with only ~100 μW. Additionally, a tunable bi-stable behavior is reported.

Photonic Crystal Nanobeam Cavity With Stagger Holes for Ultrafast Directly Modulated Nano-Light-Emitting Diodes

A photonic crystal nanobeam cavity with stagger holes in InP/InGaAsP/InP heterostructure is proposed for ultrafast directly modulated nano-light-emitting diodes (nanoLEDs). With stagger holes, the quality factor Q can be engineered in the range of 102 ~ 104 while keeping a small mode volume (Veff). As a result, the modulation speed of nanoLEDs can be dramatically improved by a small Veff to enhanced spontaneous emission (SpE) rate and a moderate Q to counterbalance SpE lifetime and photon lifetime of the cavity. In our simulation, the direct modulation bandwidth could be higher than 60 GHz with optimal Q value of 2150 and Veff of 2.3( λ0/2n)3.

Cavity Quantum Electrodynamics in Semiconductors: Quantum Dot-Photonic Crystal Nanocavity Coupled Systems

Our recent advances in solid-state cavity quantum electrodynamics (CQED) and lasing oscillation in single quantum dot (QD)-photonic crystal (PhC) nanocavity coupled systems are discussed. These include the fabrication of high quality two-dimensional PhC nanocavities, which enable the generation of spontaneous two photon emission from a single QD, and the realization of lasing oscillation with single QD gain in the strong coupling regime. Moreover, CQED in a one-dimensional PhC nanobeam cavity is discussed.

High Q/V hybrid plasmonic photonic crystal nanobeam cavity: Towards low threshold nanolasers application

In this paper, we investigate a hybrid plasmonic photonic crystal nanobeam cavity with the low-index slot layer sandwiched between a metallic layer and a high-index layer. The cavity with ultrahigh Q/V can be achieved since the photon energy is well confined in the low index slot layer. By using quantum dots (QDs)-polymer as the active medium for the low-index slot layer, we demonstrate numerically that such hybrid laser structure has a gain threshold as low as gth=374cm−1, while maintaining an ultrasmall subwavelength mode volume of 0.0756 (λ/n)3.