Slotted Photonic Crystal Nanobeam Cavity Research Articles

High-Sensitivity and Wide Detection-Range Refractive-Index Sensor Based on Amplitude Change in Slotted Photonic Crystal Nanobeam Cavity

High Q-factor is essential for the realization of high sensitivity photonic crystal-based sensors. The Q-factor is usually optimized for a specific refractive-index (RI) value of the ambient background. However, a small change in the RI reduces the Q value, and therefore limits the performance of the sensor to a narrow RI range. Here, we report a high-sensitivity RI sensor with a wide detection-range based on amplitude change of the fundamental mode in slotted photonic crystal nanobeam cavity. Both wavelength and amplitude sensitivity of 333 nm/RIU and 188/RIU are realized in the RI range from 1.3 to 1.6, respectively. To the best of our knowledge, this represents the widest sensing range ever reported in photonic crystal cavities. Owing to the wide sensing range and the insignificance of the Q value, this approach would find applications in various research areas in integrated lab-on-chip systems for optofluidic- and bio-sensing applications.

Ultrafast all-optical switching in a silicon-polymer compound slotted photonic crystal nanobeam cavity

Ultrafast all-optical switching in a silicon-polymer compound slotted photonic crystal nanobeam cavity

On-chip trapping and sorting of nanoparticles using a single slotted photonic crystal nanobeam cavity

In this work, we propose a slotted photonic crystal nanobeam cavity (PCNC) to trap and sort the 120 nm and 30 nm nanoparticles. The simulation shows that the maximum optical trapping force of the 120 nm particle is 38.7 pN/mW, and that of the 30 nm particle is 10.8pN/mW. It is calculated that the trapping threshold power of the 120 nm particle is 35.3µW, and that of the 30 nm particle is 41.6 µW. Because the width of the slot is 100 nm, when the input power is between 35.3 µW and 41.6 µW, only the 120 nm particle can be trapped in the upper cladding of the slotted-PCNC. When the input power is greater than 41.6 µW, the 120nm particle is still trapped in the upper cladding of the slotted-PCNC, while the 30 nm particle is trapped inside the slot of the slotted-PCNC. By properly controlling the input power and the direction of flow in the microfluidic channel, the sorting of particles can be achieved. In addition, trapping of the particles causes different redshifts of peak wavelengths. Thus, the proposed slotted-PCNC can detect particle trapping and sorting by monitoring the resonant wavelength shifts. What is the most important, compared with previous reported single particle trapping work, is that the proposed work can realize both trapping and sorting. Therefore, provided with the ultra-compact footprint and excellent performance, the proposed slotted-PCNC shows great potential for a multifunctional lab-on-a-chip system.

High sensitivity and anti-external interference dual-parameter sensor based on a multimode slotted photonic crystal nanobeam cavity

We put forward a multimode slotted nanobeam cavity (MM-SPCNC) supporting both air and dielectric modes through a specific design of band properties. Dual-parameter detection is realized by jointly measuring the resonance wavelength shifts of both air and dielectric modes. The proposed sensor is robust against external interference and shows higher sensitivity compared with other dual-parameter sensors. The maximum external interference ranges of the proposed sensor are 4.82×10−6 and 0.05 for refractive index (RI) and temperature (T), respectively, which indicates that the sensor can effectively resist against external interference. The RI and T sensitivities of the fundamental air mode are 421 nm/RIU and 58 pm/K respectively, whereas those of the fundamental dielectric mode are 706 nm/RIU and 46 pm/K respectively. The proposed sensor thus represents a promising candidate for future multifunctional and lab-on-chip sensing applications.

Design and analysis of refractive index sensors based on slotted photonic crystal nanobeam cavities with sidewall gratings.

We propose and numerically investigate a refractive index sensor based on a one-dimensional slotted photonic crystal nanobeam cavity with sidewall gratings for refractive index sensing in a gaseous environment. By using the three-dimensional finite-difference time-domain method, we demonstrate that our proposed sensor simultaneously possesses a high quality factor of $ 3.71 \times {10^6} $3.71×106 and a high sensitivity of 508 nm/RIU (refractive index unit) at the resonant wavelength near 1583 nm, yielding a detection limit as low as $ 1.97 \times {10^{ - 6}} $1.97×10-6 RIU. Moreover, the mode volume of the cavity's fundamental resonant mode is found to be as small as $ 0.022(\lambda /n)^3 $0.022(λ/n)3, resulting in a very compact effective sensing area. We finally study and assess the effect of fabrication disorder on the performances of our proposed sensor. We believe our proposed sensor will be a promising candidate for applications not only in multiplexed biochemical sensing and multielement mixture detection, but also in optical trapping of single biomolecules or nanoparticles.

A Slotted Photonic Crystal Nanobeam Cavity for Simultaneous Attainment of Ultra-High Q-Factor and Sensitivity

An optical refractive index (RI) sensor is proposed based on a slotted photonic crystal nanobeam cavity. Three rows of parabolic-tapered air-holes are used to design the cavity and an embedded narrow slot is used to obtain a highly localized optical field in a low refractive index region in order to produce a strong light matter interaction. The number and the radii of the air holes, the width of the slot, and the number of rows are optimized to address the most challenging issue of RI sensor design, i.e. to obtain a high Q-factor and sensitivity, simultaneously. The plane wave expansion method has been used to facilitate the design procedure and a 3-D finite difference time domain method has been used to obtain the simulation outcome. The outcomes for the optimized cavity show an ultra-high Q-factor $\sim 4.3\times 10^{7}$ along with a sensitivity ~975 nm/RIU at a wavelength 1534 nm, for which the figure-of-merit is calculated as $2.73\times 10^{7}$ . However, the slot-width can be varied to obtain a Q-factor of $8\times 10^{7}$ and sensitivity of 1100 nm/RIU individually. The device also has an ultra-small mode volume of the order of 0.0253 $(\lambda /n)^{3}$ . Hence, all together, the sensor is expected to be a promising candidate for the lab-on-chip sensor application.

Strong optomechanical coupling in a slotted photonic crystal nanobeam cavity with an ultrahigh quality factor-to-mode volume ratio.

We describe the design, fabrication, and characterization of a one-dimensional silicon photonic crystal cavity in which a central slot is used to enhance the overlap between highly localized optical and mechanical modes. The optical mode has an extremely small mode volume of 0.017(λvac / n)3, and an optomechanical vacuum coupling rate of 310 kHz is measured for a mechanical mode at 2.69 GHz. With optical quality factors up to 1.2 × 105, fabricated devices are in the resolved-sideband regime. The electric field has its maximum at the slot wall and couples to the in-plane breathing motion of the slot. The optomechanical coupling is thus dominated by the moving-boundary effect, which we simulate to be six times greater than the photoelastic effect, in contrast to most structures, where the photoelastic effect is often the primary coupling mechanism.

Design of an ultra-compact slotted photonic crystal nanobeam cavity for biosensing

Here, we elucidate a novel biosensor in aqueous environments based on a slotted photonic crystal nanobeam cavity. A slot is introduced in the center of the photonic crystal nanobeam cavity, which reduces the mode volume by an order of 10 without sacrificing the quality factor and sensitivity. This sensor is characteristic of an ultra-small mode volume of 0.076(λ/n)3 and shows a prominent advantage in regards to single nanoparticle detection, where the minimum detectable nanoparticle radius is around 1 nm. Additionally, its quality factor is as high as 6.08×106 and its sensitivity is around 460 nm/RIU, which is promising for refractive index sensing. This sensor can also be integrated into a high-density array of sensor networks because of the unparalleled fabrication advantages.

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.

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.