Silicon micro-ring resonator-based generation of all-optical (2×2) Walsh–Hadamard code is proposed. The energy-efficient, ultra-high-speed, and compact nature of micro-ring resonator-based devices is essential for optical computing. Both MATLAB and the Ansys Lumerical finite difference time domain (FDTD) approach are used to implement the generation of all-optical (2×2) Walsh–Hadamard code. The proposed design is simulated at about 260 Gbps. In the recommended circuit, the needed pump power for switching is merely 0.84 mW, which is extremely little in contrast. The “figure of merits” of the proposed design is evaluated through numerical simulation. The obtained contrast ratio and extinction ratio are considerably greater at 25.24 and 14.63 dB, respectively. On the other hand, the achieved amplitude modulation of 0.13 dB is extremely low. The on-off ratio for a single micro-ring resonator is 36.9 dB.
In this manuscript, a dielectric nanoparticle-assisted excitation of optical Tamm mode (OTM) is proposed using a 1DPhotonic Crystal configuration. The structure comprises a bilayer photonic crystal structure having silicon nanoparticles placed at the top interface of the structure. The structural parameters and nanoparticle sizes are optimized to break the translational symmetry. The reflectance spectrum and field distribution map are analytically studied by the finite element method. The analytical results exhibit the excitation and confinement of OTM. The excited OTM modes show a strong dependency on the angle of incidence and the nanoparticle size. The obtained results exhibit that dielectric nanoparticles can be utilized as compact surface mode exciters and scatterers. This further facilitates the development of OTM devices for integrated photonic applications.
In this paper, a hyperbolic-graded topological nanophotonic resonator is proposed to excite topologically protected edge states (TES). The index grading is introduced to modify the dispersion characteristics and enhance the mode field confinement of TES. The optimized structure leads to the excitation of a TES at a 1521nm operating wavelength. Further, the structural capability of the refractive index sensor is demonstrated. The analytical results demonstrate a sensitivity of 1806 nm/RIU (with a refractive index range from 1.35 to 1.40). Thus, showing its potential to detect and sense various biochemical analytes accurately.
We have fabricated a phototransistor based on multilayer MoTe2 and investigated its optical response. Under dark, the transistor exhibits ambipolar behavior with an on-off ratio of around 1000 for hole transport. The photocurrent of the transistor is modulated by illuminating the transistor with laser light and varying its power and the electrostatic gate voltage. We investigated the correlation between the laser power and the on/off ratio, photocurrent, and maximum current of the device. Finally, we analyzed the regions in the transfer curve that are least sensitive and most sensitive to incident laser light.
In this study, HTL optimisation techniques have been used to analyse a double halide perovskite (which is lead-free) Cs2NaGaBr6 n-i-p solar cell in order to improve photovoltaic performance. A robust solar cell modeling tool called SCAPS- 1D was used for all of the simulations. The suggested photovoltaic design uses a double perovskite material. With a bandgap of 1.762 eV, Cs2NaGaBr6 is a direct band gap halide double perovskite material that is extremely close to organicinorganic perovskite material. With an improved hole transport layer (HTL) doping (1×1018 cm-3–1×1022 cm-3), the proposed solar cell had a better efficiency of 26.19%. Additionally, Jsc, Voc, FF, and PCE (η) have all been examined as photovoltaic performance parameters. In order to create effective Pb-free perovskite for solar applications, the proposed device may be used.
In this paper, we demonstrate the operation of flexible and highly sensitive MXENE-based capacitive strain sensor fabricated on a paper substrate. The use of common printing paper as a substrate not only makes the fabrication facile and inexpensive but also makes the sensor eco-friendly and biodegradable. The presented sensor has been mounted on the human body to monitor the movements of various joints like the wrist and the elbow. Upon application of strain, a noticeable change of more than 30% in the total capacitance of the sensor is observed. By measuring the change in the capacitance of the sensor, the movements of human joints can be monitored and used for applications like exercise and therapy.
This paper investigates the performance of 2D-materials (such as Graphene and Maxine) assisted paper substrate-based electrodes for electrocardiogram (ECG) monitoring in personalized and ubiquitous healthcare. As a cost-effective rapid prototyping, the paper substrate-based technique allows the personalization of electrode sizes and shapes. It can be used with a range of different inks to provide better skin contact, which provides a very efficient and accurate measurement of the ECG signal. We compare the performance of graphene and MXene ink-based electrodes, which are printed directly on a paper substrate using graphite pencil and drop cast methods. The time-frequency decomposition of the collected signals is explored and reported. The results demonstrate that both electrodes can record ECG information with comparable performance to conventional Ag/AgCl electrodes.
In this manuscript, a 4-N, N-dimethylamino-4′ -N′ -methyl-stilbazolium tosylate (DAST) material assisted electro-optically tuned Bloch Surface Wave Sensor is proposed. The structure is designed using a one-dimensional photonic crystal (1D-PhC) structure. A top defective layer of DAST as an electro-optic material is used. The analysis shows that by illuminating the device with poly-chromatic light at an incident angle of 45.11◦ results in Bloch mode excitation at a 632.8nm operating wavelength. The analytical results also demonstrate the post fabrication 47 nm BSW wavelength tuning by applying only ±5 V potential. The structure also exhibits both wavelength stability (at varying angle) and angular stability (at varying wavelength). Moreover, the structure exhibits 105.71nm/RIU sensitivity at 0V applied bias voltage having very low FWHM of <1nm. Thus, the proposed design possesses the advantage in terms of low voltage wavelength tuning, stable response, easy fabrication, and integration capability in integrated circuits.
A disordered photonic crystal (D-PhC) structure is analyzed to study the interface mode localization characteristics. The design comprises a bilayer-disordered PhC structure, where layers are arranged in Thue–Morse sequence (TMS). The impact of local symmetric substructures on eigenstates coupling is also considered over a wider wavelength range. The mode hybridization study is carried out for varying refractive index contrast values of TMS structures at an operating wavelength of 550, 632.8, and 750 nm, respectively. The dispersion analysis confirms the localization of bulk guided, and edge-guided modes for different incidence angles at the structural local resonators. Further, increasing the RI contrast value leads to generation of hybrid interface modes of very high electric field intensity. Thus, showing its potential applications in both sensing and light guiding applications. Moreover, because of the higher surface electric field intensity this structure can also be used for fluorescence-based detection and surface-enhanced Raman spectroscopy as well.
This review covers the recent progress made in the nanophotonic devices-based daytime passive radiative coolers. The radiative cooling capabilities along with the structural description of various natural species are discussed. The design principle along with key characteristics of the omnidirectional solar reflectors as well as thermal adiators is discussed in detail. Several analogues planner one-dimensional and two-dimensional photonic nanostructures and their current state-of-the-art techniques have been discussed. For each kind of the photonic structure, the novelty, measurement principle, and their respective daytime radiative cooling capability are presented. The reported works and the corresponding results predict the possibility to realize an efficient and commercially viable radiator for passive radiative cooling applications.
A one-dimensional photon crystal structure is proposed to design an omnidirectional broadband reflector. The structural parameters are optimized to reflect complete solar spectrum (0.3 to 2.3 μm) for both TE and TM polarized light. The design analysis is carried out using transfer matrix method. The structure is designed using alternate dielectric–dielectric layers of appropriate refractive indices and layer thicknesses. The proposed structure demonstrates more than 98% reflectivity for the complete wavelength range from 0.3 to 2.3 μm along with 73% emission in 8 to 13 μm, thus showing its potential as a dielectric-based reflector in applications such as daytime passive radiative coolers, and as a heliostat in concentrated solar power.
A multilayer photonic band gap structure is proposed for sensing applications in visible wavelength range. The structure is designed by introducing alternate layers of dielectric material on a glass substrate. To ease the analyte infiltration and to improve the sensitivity, porosity is introduced deliberately within each layer. Extensive analysis is carried out to optimize the number of dielectric layers, their thickness, and percentage of porosity. The transmission/reflection spectral characteristic and sensitivity of the proposed structure are analyzed by a three-dimensional finite difference time domain method. The porosity value and structural parameters are optimized to obtain highest possible sensitivity. The proposed structure exhibits a 0.05-nm shift in reflection/transmission wavelength with corresponding refractive index change of 10 − 3. Analyte can also be distinguished by seeing the sample color change with naked eyes. Thus, multiparametric characterization of the proposed structure demonstrates its potential for sensing applications.
This paper demonstrates an approach for fabricating large-scale photonic crystal (PhC)-based devices using a combination of optical and focused ion beam (FIB) lithography techniques. Optical lithography along with reactive ion etching parameters is optimized to realize the layout of device structure and thereafter FIB milling is optimized to realize the designed PhC structure at those identified locations. At first, with the help of a specially designed mask and using optical lithography along with reactive ion etching, a number of rectangular areas of dimension of 10 μm×20 μm along with input and output waveguides of width ∼700 nm and thickness of ∼250 nm have been fabricated. Subsequently, use of FIB milling, a periodic PhC structure of lattice constant of 600 nm, having a hole diameter of ∼480 nm along with a defect hole diameter of ∼250 nm have been realized successfully on the selected areas. This method shows a promising application in fabricating PhC structure with device size >1 cm2 at large scale, eliminating the problems of standard nanolithography techniques.
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