Crystal Sensor Array Research Articles

A photonic crystal sensor array side-coupled to a linear waveguide with enhanced bandwidth

We report a photonic crystal (PhC) sensor array consisting of six nanocavities which are side-coupled to a linear PhC waveguide. The design approach to cavities is based on rotating functional holes and changing their radius. Based on traditional linear waveguide, we also design a PhC waveguide with enhanced bandwidth by adjusting the holes on both sides of the central linear defect to weaken the Bragg reflector effect. With 3-D finite-difference time-domain (FDTD) method, the Q value and RI sensitivities for each sensor unit are adjusted from 3.67×105 to 5.41×106 and from 264 nm/RUI to 332 nm/RIU, respectively. Moreover, the free spectral range (FSR) values between every two adjacent sensing units are relatively larger enough compared with structures proposed previously. Accordingly, it provides the possibility to realize the integrated sensing and excellent sensing properties more effectively.

Highly Sensitive 1 × 8 Parallel Multiplexing of Ultra-Compact Integrated 1D Photonic Crystal Sensor Array Based on Silicon-on-Insulator Platform

We design a $1\times 8$ highly sensitive ultra-compact on-chip integrated sensor array consisting of a $1\times 8$ power splitter, eight one-dimensional photonic crystal slot nanobeam cavities (1DPC-SNCs) connected by additional 1D photonic crystal tapered nanobeam bandgap filters (1DPC-TNBF), and an $8\times 1$ power combiner. The performance of the device is numerically demonstrated by three-dimensional finite-difference-time-domain (3D-FDTD) method. The whole structure is lying on top of a $2~\mu \text{m}$ buried silicon oxide layer, while remaining high sensitivities (over 400 nm/RIU) of the eight sensors, simultaneously. The proposed 1DPC-SNCs can reach a high-quality factor of $3.6\times 10^{5}$ . On account of the additional band-stop filters and the $8\times 1$ power combiner, eight sensing segments interrogated simultaneously by one input and one output port is realized, with the ultra-compact footprint of $64\times 16\,\,\mu \text{m}^{2}$ ( $26\times 16\,\,\mu \text{m}^{2}$ in sensing region). Therefore, this design is a promising platform for realizing large-scale photonic integrated circuits with high integration density, especially for ultra-compact multiple on-chip sensing.

Molecularly imprinted polymer-based photonic crystal sensor array for the discrimination of sulfonamides

In this paper, molecular imprinting and photonic crystal techniques were combined to construct a four-channel sensor array for the simultaneous identification of various sulfonamides. The assay was composed of four units. Three of these units were prepared using sulfaguanidine, sulfamethazine, or sulfathiazole as template molecules. The fourth unit was prepared without a template molecule. The preparation was optimized to obtain maximum identification with a molar ratio of template, monomer, and cross-linker of 1:50:10. The response time was as short as 10 min. For demonstration, six sulfonamides were selected as analytes. The Bragg diffraction patterns of analytes at different concentrations were measured using the sensor array. Data obtained were analyzed using linear discrimination analysis (LDA) and principal component analysis (PCA). LDA can be applied for SAs discrimination. The message ratios of 87.6%, 94.4%, and 95.8% for six SAs at 10−4 mol L−1, 10−6 mol L−1, and 10−8 mol L−1 were achieved using LDA. The sensor array identified the mixture containing various SAs with an LDA coefficient of 86.1%, thereby indicating that the sensor array had a strong anti-interference ability. The sensor array was used to identify six SAs in fish samples. The measured data in spiked samples were consistent with the fingerprint collected from standard solutions. The accuracy rate reached 90.9%, indicating that the array can be used to identify SAs from food samples.

Design of side-coupled cascaded photonic crystal sensors array with ultra-high figure of merit

we propose a side-coupled cascaded photonic crystal sensors array (SCCPhCSA) with ultra-high figure of merit (FOM). The design consists of a photonic crystal waveguide (PCW) with changed lattice constants and three cascaded dumbbell-like resonant cavities (DLRCs) are side-coupled to the PCW. The result of finite-different time-domain (FDTD) simulation indicates that each sensing unit of the sensors array possesses a high quality factor (Q) of ~70,000 and high sensitivity up to 260nm/RIU, resulting in FOM of ~12,000. To our best knowledge, this value is optimized for photonic crystal sensors array by now and it means our design is a promising candidate for large degree of multiplexing sensing.

Performance investigation of side-coupled interlaced symmetric-shaft-shape photonic crystal sensor arrays

We design symmetric-shaft-shape photonic crystal sensor arrays (SSPhCSAs) which can be used in refractive index sensing, and the performance of the structure is investigated. The structure consists of four symmetric-shaft-shape photonic crystal (SSPhC) cavities side-coupled to a W1 photonic crystal (PhC) waveguide. Each cavity has slightly different cavity spacing with different resonant frequency. By using two dimensional finite-difference time-domain (2D-FDTD) method, the simulation result obtained indicates the performance of the sensor arrays. The sensitivities of the four sensor units are 178, 252, 328 and 398nm/RIU, respectively, with the detection limit of ~10−3. The crosstalk lower than ~20dB is obtained.

Design and Experimentation of Piezoelectric Crystal Sensor Array for Grain Cleaning Loss

In order to improve the accuracy and reliability for detection of grains cleaning loss, a piezoelectric crystal sensor array was proposed in full width of distribution to realize the online multipoints detection. The dynamic model for grain collision sensor array was evaluated by the method of experimental model analysis. The distribution of low-level vibration and deformation was tested for the sensitive elements of detection array using dynamic signal tester. The location and quantity of the piezoelectric crystal units were determined. The simulation was done based on the software ANSYS for the impacts of grains on the sensitive elements. A quantitative analysis was developed to correct the positions of the piezoelectric crystal units and the construction was adjusted according to the deformation contours. The exact positions were quantitatively analyzed and corrected based on the numerical results for the deformation placement, which was used for optimizing the array construction. Then, the grain impact experiment was established on the test bench. The results showed that the performance was stable for the piezoelectric sensor array, and output signal amplitude was about 2.5 V, with uniform sensitivity in the whole range. The present array sensor helps to provide a technical foundation for detection of grain cleaning loss.

Radius vertical graded nanoscale interlaced-coupled photonic crystal sensors array

A radius vertical graded photonic crystal sensors array based on a monolithic substrate is proposed, which is potentially to be used as label-free detection in aqueous environments. The sensors array device consists of five resonant cavities including three H1 cavities and two L2 cavities which are interlaced-coupled to a radius vertical graded single photonic crystal line defect waveguide (W1). Each resonator has a different resonant wavelength dip which can shift independently with crosstalk lower than −13dB in response to the refractive index change of air holes around every cavity. With three-dimensional finite-difference time-domain (3D-FDTD) method, simulation results demonstrate that the quality factors of microcavities are over 104. Besides, the refractive index sensitivity is 100nm/RIU with the detection limit approximately of 5.63×10−4. Meanwhile, the radius vertical graded photonic crystal with more interlaced cavities is more suited to ultracompact optical monolithic integration.

Nanoscale radius-graded photonic crystal sensor arrays using interlaced and symmetrical resonant cavities for biosensing

In this work, we propose radius-graded photonic crystal sensor arrays applied on nano-scale optical platform for label-free biosensing. Two L3 cavities and two H1 cavities are multiplexed and interlaced on both sides of a photonic crystal W1 waveguide on the radius-graded photonic crystal slab. The optical sensing characteristics of the nanocavity structure are predicted by three-dimensional finite difference time domain (3D-FDTD) simulation. In response to the refractive index change of air holes surrounding the cavities, four interlaced and symmetrical cavities are shown to independently shift their resonant wavelength without crosstalk. The simulation results demonstrate the refractive index sensitivity of sensor array varies from 66.67 to 136.67nm/RIU corresponding to the number of functionalized air holes ranged from 4 to 21. This design makes different cavities multiplexed on both sides of waveguide possible. Meanwhile, the radius-graded photonic crystal with more symmetrical and interlaced cavities is better for large integration in the sensor arrays.

Nanoscale photonic crystal sensor arrays on monolithic substrates using side-coupled resonant cavity arrays

We present nanoscale photonic crystal sensor arrays (NPhCSAs) on monolithic substrates. The NPhCSAs can be used as an opto-fluidic architecture for performing highly parallel, label-free detection of biochemical interactions in aqueous environments. The architecture consists of arrays of lattice-shifted resonant cavities side-coupled to a single PhC waveguide. Each resonant cavity has slightly different cavity spacing and is shown to independently shift its resonant peak (a single and narrow drop) in response to the changes in refractive index. The extinction ratio of well-defined single drop exceeds 20 dB. With three-dimensional finite-difference time-domain (3D-FDTD) technique, we demonstrate that the refractive index sensitivity of 115.60 nm/RIU (refractive index unit) is achieved and a refractive index detection limit is approximately of 8.65×10-5 for this device. In addition, the sensitivity can be adjusted from 84.39 nm/RIU to 161.25 nm/RIU by changing the number of functionalized holes.

Piezoelectric quartz crystal sensor array with optimized oscillator circuit for analysis of organic vapors mixtures

An array of piezoelectric quartz crystal sensors (PQCs) has been prepared for analyzing organic vapor mixtures. The circuit of oscillators has been modified and optimized to circumvent the problems associated with mutual interference among different oscillators connecting to sensors in the array. Organic coating materials were clustered into four groups according to their polarity and compounds representing different groups were selected including silicone OV-101, silicone OV-17, silicone OV-275, span 85, and polyethylene glycol 1000. The sensor array constructed gives characteristic response patterns for different organic vapors such as methanol, 1,2-dichloroethane, benzene and cyclohexane. The feasibility of using the sensor array for analysis of binary and tertiary mixtures has been tested by using PLS and MLR data treatment algorithms.

Discrimination of Vapours of Alcohols and Beverage Samples Using Piezoelectric Crystal Sensor Array

Abstract A piezoelectric crystal sensor array has been prepared as a vapour sensing system by coating with 12 adsorptive materials selected using cluster analysis. The frequency shift data obtained from the array as the response patterns for the vapour of aliphatic alcohol homologues and isomers are treated by principal component analysis. The two-dimensional display of the original and autoscaled data show well-defined clusters for different alcohol homologues and isomers. The method has been used for discrimination of commercial beverage samples.