Journal of Optoelectronical Nanostructures
Volume:8 Issue: 4, Autumn 2023

 New design in photonic crystal structures has provided a great opportunity to employ optical decoders with high contrast ratio and low response time. Based on the last published articles, photonic crystal-based decoders result in a contrast ratio higher than 20 dB and a response time of 200 fs which is proper to use in optical circuits. Changing the path of a signal may occur with the help of a resonator in the form of a cavity or ring. Dropping a signal at a wavelength makes a possible to direct it toward the desired path. We present an introduction to the decoding operation and its advantages in different applications, followed by an explanation of the excellent features of photonic crystals including forbidden bandgap and the optical Kerr effect. Furthermore, we discuss the key role of the resonance phenomenon in photonic crystal structures. Then, we investigate the valuable designs in approaching the decoding. It has been tried to present an algorithm to design photonic crystal-based decoders which is so needed for research.

In this research, the photocarrier transmission mechanism and the effect of the deposition conditions on the IBC-SHJ cell efficiency have been studied. In this regard, short-circuit current density, open-circuit voltage, fill factor and cell efficiency values have been extracted using J–V curves for various deposition parameters. The optimization of the front SRV, the thickness and doping concentration of the c-Si substrate, the thickness and doping concentration of i-a-Si layers, the doping concentration of the emitter region, the width and the doping concentration of the n- and p-strip, the gap width between electrodes and the doping concentration of the BSF region have been carried out to achieve optimum efficiency in the IBC-SHJ solar cell. In addition, the investigation of the electric field distribution in photocarrier transmission to the interdigitated back contacts has also been comprehensively studied. The results show that the n- and p-stripe width and their doping concentration were the most influential parameters for efficiency improvement. Finally, the cell efficiency of improved IBC-SHJ structure achieved 23.52%.

A detailed study of a novel configuration for junctionless tunneling FET (J-TFET) with extremely low off- (Ioff) and ambipolar current (Iamb) is reported in this paper. In order to achieve desirable on/off current ratio (Ion/Ioff), we have employed voltage difference technique on the gate electrode based on the potential distribution benefits. Main and side gates with an optimum voltage difference creates a stepped potential profile along the channel. This raises the drain side’s bands, reduces the electric field, puts restriction on the flow of charge carriers, and finally remarkable reduction of Iamb from 6.52×10-10 A/µm to 1.14×10-17 A/µm. Also an extremely low subthreshold swing (SS) (22 mV/dec) is achieved thanks to the sharp transition from off- to the on-state. Finally we have investigated the electrical performance of the proposed device for sub-30 nm channel length to examine its immunity against short channel effects. Therefore, our approach renders the novel structure more desirable for the future low power applications.

Apochromat is usually designed for color correction in the range of the visible spectrum. But to correct the chromatic aberration of optical systems outside the visible spectrum, apochromatic lens in the same spectral band should be used. In this work, firstly, a three-element apochromatic lens in the UVA spectral region is pre-designed and optimized by spherical lenses with suitable glasses. The primary spherical aberration of this apochromat is almost zero and its tertiary spectrum has a small value of 2.558 microns.  Nevertheless, the spherical aberration of higher orders causes the RMS radius in the spot diagram to be several times larger than the Airy radius.  Then, by selecting aspheric surfaces and re-optimizing the system,  a spherical aberration-free apochromatic with a small tertiary spectrum is designed. In this last design, the RMS radius is smaller than the Airy radius, so almost all points are located inside the Airy disk. This lens can be used to correct chromatic aberration in UVA imaging spectrometers and cameras.

Discrete energy levels of quantum dots (QD) have electronic and optoelectronic applications. In this paper, a novel graphene nanoribbon (GNR) field effect transistor (FET) is modeled numerically using the NEGF formalism. In the new device model of this paper, the channel region is composed of one or two QDs, made by only one metallic gate electrode. This model utilizes a semiconductor armchair graphene nanoribbon through which the current may pass. The two highly doped ends of GNR act as source and drain contacts. At this unique model, one or two quantum dots form on GNR channel.  The discreteness of energy levels of the two coupled quantum dots, revealed by applying gate voltage, gives rise to resonant tunneling.  Resonant tunneling through these levels results in negative differential conductance. The coupling between QDs determines the current characteristics of device. Step-wise increment of current by increasing drain voltage manifests QDs discrete energy levels.

Here, several ring resonator nanostructure for biosensors are proposed. To evaluate the results, finite difference time domain (FDTD) method is applied. Also, several main parameters including transmission spectrum is analyzed to obtain of sensitivity and figure of merit. As the technology goes on, using sensors and biosensors are more attracted by many researchers in various fields such as medicine. Biosensors are devices, in them biological elements and analytes have interacted and the reaction between them is measured then would be expressed as understandably in output. Biosensors have various components such as analyte, bioreceptor, transformer, electronics and display and are in different groups based on their mechanisms. Biosensors could be used to detect and diagnose bacteria, viruses, and early detect of breast cancer. Various methods such as X-ray mammography, ultrasound scan, DBT, ultrasonography of breast, and so on have been provided, but they have some disadvantages. In the biosensors field, various methods are introduced for early detection of breast cancer. In this study some researches and experienced have been investigated.