Optical Tunneling Effect Research Articles

A Silicon-Based ROTE Sensor for High-Q and Label-Free Carcinoembryonic Antigen Detection.

This paper presents a biosensor based on the resonant optical tunneling effect (ROTE) for detecting a carcinoembryonic antigen (CEA). In this design, sensing is accomplished through the interaction of the evanescent wave with the CEA immobilized on the sensor's surface. When CEA binds to the anti-CEA, it alters the effective refractive index (RI) on the sensor's surface, leading to shifts in wavelength. This shift can be identified through the cascade coupling of the FP cavity and ROTE cavity in the same mode. Experimental results further show that the shift in resonance wavelength increases with the concentration of CEA. The biosensor responded linearly to CEA concentrations ranging from 1 to 5 ng/mL with a limit of detection (LOD) of 0.5 ng/mL and a total Q factor of 9500. This research introduces a new avenue for identifying biomolecules and cancer biomarkers, which are crucial for early cancer detection.

Photonic Spin Hall Effect as a Highly Sensitive Refractive Index Sensing Platform for Glucose

AbstractThis study presents an innovative refractive index (RI) sensor that measures glucose concentration by utilizing the photonic spin Hall effect (SHE) in a resonant optical tunneling effect (ROTE) structure. The ROTE structure consists of three InP layers with the high RI and two analyte layers (with a high‐low‐high‐low‐high RI distribution), in which glucose solution samples with the low RI are injected. By subjecting the InP layers to external bias‐assisted light, the photonic SHE can be flexibly manipulated, enabling the modulation of the sensing performance accordingly. It is found that the transverse shift of photonic SHE presents a large variation in response to the tiny change in glucose concentrations. By optimizing the parameters (i.e., intensity or wavelength) of bias light, the sensitivity of this sensor can reach as high as 735.7 µm RIU−1. Compared to traditional glucose sensors, this original work implements the novel photonic SHE with the superior sensing performance. Therefore, the proposed design shows promising potential for biomedical applications, such as medical diagnoses and drug discovery.

An Optical Measuring Transducer for a Micro-Opto-Electro-Mechanical Micro-g Accelerometer Based on the Optical Tunneling Effect

Micro-opto-electro-mechanical (MOEM) accelerometers that can measure small accelerations are attracting growing attention thanks to their considerable advantages—such as high sensitivity and immunity to electromagnetic noise—over their rivals. In this treatise, we analyze 12 schemes of MOEM-accelerometers, which include a spring mass and a tunneling-effect-based optical sensing system containing an optical directional coupler consisting of a fixed and a movable waveguide separated by an air gap. The movable waveguide can perform linear and angular movement. In addition, the waveguides can lie in single or different planes. Under acceleration, the schemes feature the following changes to the optical system: gap, coupling length, overlapping area between the movable and fixed waveguides. The schemes with altering coupling lengths feature the lowest sensitivity, yet possess a virtually unlimited dynamic range, which makes them comparable to capacitive transducers. The sensitivity of the scheme depends on the coupling length and amounts to 11.25 × 103 m−1 for a coupling length of 44 μm and 30 × 103 m−1 for a coupling length of 15 μm. The schemes with changing overlapping areas possess moderate sensitivity (1.25 × 106 m−1). The highest sensitivity (above 6.25 × 106 m−1) belongs to the schemes with an altering gap between the waveguides.

Strong enhancement of Goos-Hänchen shift through the resonant optical tunneling effect.

The resonant optical tunneling effect (ROTE) originates from the frustrated total reflection effect because unique transmission characteristics are used to study high-sensitivity sensors. In this study, we theoretically demonstrated that choosing a suitable transmission gap made it possible for the ROTE structure based on hexagonal boron nitride and graphene to obtain a large Goos-Hänchen shift as high as tens of thousands of times the incident wavelength at a specific incident angle. The amplitude of the Goos-Hänchen shift was found to be sensitive to the central layer thickness but was also modulated by the tunneling gap on both sides. In addition, adjusting the chemical potential and relaxation time of the graphene sheets could alter the Goos-Hänchen shift. Our work provides a new way to explore the Goos-Hänchen effect and opens the possibility for the application of high-precision measurement technology based on the ROTE.

Goos–Hänchen shift of a light beam tunable by graphene in the resonant optical tunneling structure

The structure for implementing resonant optical tunneling effect is a simple layered system of dielectrics that provides full light transmission for resonance condition, despite the presence of barrier layers partially locking light. The presence of a sharp resonant peak both for the intensity and for the spatial shift of the transmitted light beam makes such a structure promising for the creation of sensors and light control devices. This paper focuses on the spatial shift called the Goos–Hänchen shift of such a structure with interfaces of the waveguide layer coated by graphene. The effect of Goos–Hänchen shift near the resonance in this case may be controlled by small changes in the chemical potential or the Fermi energy of graphene, which can be controlled both chemically and by electrical bias. The characteristics of transmitted light beam strongly depend on the beam width for the selected optimal focusing condition.

Highly Sensitive Refractive Index Sensing Based on Photonic Spin Hall Effect and Its Application on Cancer Detection

The photonic spin Hall effect (SHE), manifesting itself as a spin-dependent splitting of left- and right-handed circularly polarized light, exhibits unique potential for nanophotonic devices, precise metrology and optical sensors. This work presents an original design of refractive index sensor for the cancer detection based on novel photonic SHE. The device consists of BK7 prism, monolayer graphene, glass substrate, and the analyte layer, in which the cell solution is introduced. Three groups of human normal (gastric, liver, epidermal) cells and corresponding cancer cells were chosen for the discrimination. The external optical pumping is applied on monolayer graphene in order to flexibly modulate the photonic SHE, and then the sensing performance can be accordingly tuned. It is found that the proposed sensor can not only discriminate the normal cells and cancer cells, but also distinguish the cancer cells for different concentrations. The superior intensity sensitivity of <inline-formula> <tex-math notation="LaTeX">${6.1} \times {10}^{{5}} \,\,\mu \text{m}$ </tex-math></inline-formula>/RIU for discriminating the gastric normal and cancer cells can be generated under the optimal pumping power, which is four orders of magnitude greater than previous reported sensors based on the resonant optical tunneling effect. These findings may provide practical applications in medical diagnose, drug discovery and cellular pathological analyse.

High-Sensitivity Biosensor With Optical Tunneling Effect Excited by Long-Range Surface Plasmon Resonance

Optical tunneling is an effect extremely sensitive to wavelength changes. In this article, we use this effect to design a new type of biosensor. The tunneling effect is excited by long range surface plasmon resonance, the energy is concentrated in the sensing medium in the form of standing waves, which lead a very high wavelength sensitivity and quality factor. By using COMSOL for finite element analysis, for the sensor structure of (BK7/Cytop /Al2O3/Ag/Al2O3/sensing media/air), a quality factor of 10296 RIU-1 is achieved under angle modulation,a sensitivity of 170,000 nm/ RIUand a quality factor of 11333 RIU-1 are obtainedunder wavelength modulation. At the same time, the advantage of this structure is that there is no excessive requirement on the refractive index of the material, and a good sensing effect can be achieved even if the material is cheap and easy to prepare. After optimization, this structure is suitable for sensing media with a refractive index of 1.335-1.375, which can be applied to most liquid solutions.

Frame micro-optoelectromechanical angular velocity transducer with optical readout units based on the optical tunneling effect

Frame micro-optoelectromechanical angular velocity transducer with optical readout units based on the optical tunneling effect

Biosensing Near the Exceptional Point Based on Resonant Optical Tunneling Effect.

Inspired by exceptional point (EP) sensing in non-Hermitian systems, in this work, a label-free biosensor for detecting low-concentration analytes is proposed, via a special multilayer structure: a resonant optical tunneling resonator. Due to the square root topology near the exceptional point, a recognized target analyte perturbs the system deviated from the exceptional point, leading to resolvable modes splitting in the transmission spectrum. The performance of the designed sensor is analyzed by the coupled-mode theory and transfer matrix method, separately. Here, the simulation results demonstrate that the obtained sensitivity is 17,120 nm/imaginary part unit of refractive index (IP) and the theoretical detection limit is 4.2 × 10−8 IP (regarding carcinoembryonic antigen (CEA), the minimum detection value is 1.78 ng). Instead of the typical diffusion manner, the liquid sample is loaded by convection, which can considerably improve the efficiency of sample capture and shorten the response time of the sensor. The sketched sensor may find potential application in the fields of biomedical detection, environment protection, and drinking water safety.

Edge effects for the light beam transmission through the resonant optical tunneling structure: Analytical theory

The resonant optical tunneling effect (ROTE) is a special phenomenon of complete light transmission through a layered structure with overcoming optical barriers, partially locking the light. The presence of a sharp resonant peak makes ROTE structures promising for creating optical sensors and switching optical devices. In many studies, the theoretical analysis of the light transmission through ROTE structures is limited to the approximation of plane waves, which narrows the understanding of the effect. The presented analytical theory allows explicitly establishing the outgoing electromagnetic field distribution for an arbitrary light beam, incident on the ROTE structure, within acceptable approximations. The theory application for a simple Gaussian beam is demonstrated. Changes in the resonant effect characteristics depending on the beam parameters may be significant.

Enhancement of the volume refractive index sensing by ROTE and its application on cancer and normal cells discrimination

A volume refractive index (RI) sensor based on the resonant optical tunneling effect (ROTE) is presented in this study. Compared with the classic volume RI sensing structure, the Fabry-Pérot (FP) etalon, the ROTE structure has a higher figure of merit (FOM) than that of the FP cavity with the same cavity length. The sensitivity of the ROTE structure is almost 20 times as high as that of the FP structure, although the Q value of the ROTE structure is lower than that of the FP etalon. Given the excellent volume RI sensing performance of the ROTE structure, three groups of normal human cells and corresponding cancer cells were tested for discrimination in this paper. According to experimental results, the reflection resonant dips of each type of human cancer cell showed a red shift with respect to corresponding normal cells at the same density. The RI sensor based on the ROTE has broad application prospects in biomedical, drug screening, and early cancer diagnoses.

Parity-time symmetry based on resonant optical tunneling effect for biosensing

This paper proposes and analyzes a parity-time (PT) symmetry structure based on resonant optical tunneling effect (ROTE) by using two directly coupled ROTE resonators to achieve a balanced gain-loss distribution. The unbroken/broken states of the PT symmetric system are theoretically verified by coupled-mode theory (CMT), transmission matrix method (TMM) and finite-difference time-domain (FDTD). To demonstrate the application potential, we further propose a label-free biosensing scheme that takes advantages of the square-root dependence in frequency splitting near exceptional point (EP). The theoretical results show that the sensor has a maximum sensitivity of 1 × 105 nm/IP unit (imaginary part unit of refractive index) and a theoretical detection limit of 5 × 10−10 IP unit (corresponds to 0.4 ng carcinoembryonic antigen (CEA)). Compared with the PT systems based on coupled waveguides or resonators, our design has some distinctive features. It is a multi-layer structure and does not need complicated nanoscale fabrication; the liquid samples “flow-through” the sensing region in the mid of PT structure and would greatly enhance the analyte binding efficiency as compared with the common “flow-over” manner. This simple yet highly sensitive platform would find applications in biomedical sensors, drinking water safety, and drug screening.

Performance test of an internally modulated He-Ne laser based on optical tunneling effect

To figure out some characteristics of a novel internally modulated He-Ne laser based on optical tunneling effect, especially its modulation characteristics, some experiments are carried out and the measurement results are discussed. By measuring the amplitude-frequency response curve of the laser power, the modulation bandwidth is determined as hundreds of Hz, and an obvious trap band at ~100 Hz was observed. By comparing with the test results of the laser vibrometer, it is found that the modulation characteristics of this kind of laser are mainly determined by the characteristics of the tunneling displacement device and the intra-cavity loss characteristics of the laser.

Microoptoelectromechanical ring angular velocity transducer based on the optical tunnel effect for control system of mobile objects

In this article, the influence of the ring resonator parameters on the characteristics of the angular velocity transducer based on the optical tunneling effect (OTE) is investigated and model is introduced. The sensitivity of the module based on the optical tunneling effect is calculated to provide a quasi-linear range. The analysis of influence of linear acceleration on the ring angular velocity transducer based on the OTE is described. The compensation of the linear acceleration effect by using the differential processing method and switching, which provide the measurement of angular velocities with high accuracy for the entire measurement range, is described.

Highly Sensitive Cell Concentration Detection by Resonant Optical Tunneling Effect

This paper presents an original design for a volume refractive index (RI) sensor for cell concentration detection based on the unique resonant optical tunneling effect (ROTE). In this design, the solution sample is introduced into the ROTE resonant cavity, whose reflection spectrum presents a large shift of its resonant dip in response to the tiny change of the solution RI. Performance calibration using the polystyrene particle solution indicates that the sensitivity is 19,000 nm/RIU and the total Q factor is 620. Experiments with hepatoma cells have obtained sensitivity values as high as 2.53 nm/(amol/ml) and a detection limit of 1.2 × 105 cells/ml. Compared with previously reported optical cell sensors, this original work implements the ROTE mechanism for the first time and presents superior device performance. Thus, the proposed design has a high potential for use in biomedical applications, such as drug discovery, cell research, and medical diagnoses.

Optical and quantum models of resonant optical tunneling effect

Abstract Resonant optical tunneling effect (ROTE) is a special phenomenon that light can fully go through the seemingly impenetrable optical structure. It is a prominent example to study the analogy of wave optics and quantum physics. Previous theoretical work mostly focused on the optical modeling of transmission spectrum using the transfer matrix method (TMM), but put little effort in the quantum model. This paper advances the optical modeling by using the finite-difference time-domain method (FDTD) to simulate the electric field distribution and by using the plane wave expansion (PWE) to predict the optical bandgap. Moreover, we present the first analytical quantum model of the ROTE and further derive a direct expression of the transmission peak positions. This expression cannot be derived by the optical models, but its predicted peak positions match the optical modeling results using the FDTD, the PWE and the TMM. This well demonstrates the merit of the quantum analogy for analyzing the optical systems. This work may inspire the transplantation of the established ideas and designs in the quantum field into the optical field to create new optical and photonic devices.

Investigation of the Characteristics of the Three-axis Ring Typed Angular Velocity Transducer Based on Optical Tunneling Effect

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Resonant optical tunneling-induced enhancement of the photonic spin Hall effect

Due to the quantum analogy with optics, the resonant optical tunneling effect (ROTE) has been proposed to investigate both the fundamental physics and the practical applications of optical switches and liquid refractive index sensors. In this paper, the ROTE is used to enhance the spin Hall effect (SHE) of transmitted light. It is demonstrated that sandwiching a layer of a high-refractive-index medium (boron nitride crystal) between two low-refractive-index layers (silica) can effectively enhance the photonic SHE due to the increased refractive index gradient and an enhanced evanescent field near the interface between silica and boron nitride. A maximum transverse shift of the horizontal polarization state in the ROTE structure of about 22.25 µm has been obtained, which is at least three orders of magnitude greater than the transverse shift in the frustrated total internal reflection structure. Moreover, the SHE can be manipulated by controlling the component materials and the thickness of the ROTE structure. These findings open the possibility for future applications of photonic SHE in precision metrology and spin-based photonics.

Методика расчета одноосевого микро-опто-электро-механического преобразователя угловых скоростей

The method for calculating of single-axis micro-opto-elctro-mechanical (MOEM) angular velocity transducer based on the optical tunneling effect (OTE) is conceived. This paper is created the algorithm and the software development that allows calculating transducer’s basic parameters in providing of defined technical requirements.

Three-Axis Micro-Opto-Electro-Mechanical Angular Velocity Transducer Based on the Optical Tunneling Effect

A three-axis micro-opto-electro-mechanical (MOEM) angular velocity transducer model based on the optical tunneling effect was developed. The transfer function was determined, and the effect of destabilizing factors on the characteristics of the three-axis MOEM angular velocity transducer was evaluated. The dynamic range of the MOEM transducer based on the optical tunneling effect was calculated.