The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

In order to enable optical systems to operate with a high degree of compactness and reliability it is necessary to combine large number of optical functions in small monolithic structures. A development, somewhat reminiscent of that that took place in Integrated Electronics, is now beginning to take place in optics. The initial challenge in this emerging field, known appropriately as "Integrated Optics", is to demonstrate the possibility of performing basic optical functions such as light generation, coupling, modulation, and guiding in Integrated Optical configurations. The talk will review the main theoretical and experimental developments to date in Integrated Optics. Specific topics to be discussed include: Material considerations, guiding mechanisms, modulation, coupling and mode losses. The fabrication and applications of periodic thin film structures will be discussed.

Integrated optics

This review covers photonic crystal cavities (PCCs) and their applications in optical sensors, with a particular focus on the structures of different PCCs. For each kind of optical sensor, the specific measurement principle, structure of PCC, and the corresponding sensing properties are all presented in detail. The summary of the reported works and the corresponding results demonstrate that it is possible to realize miniature and high-sensitive optical sensors due to the ultra-compact size, excellent resonant properties, and flexibility in structural design of PCCs. Finally, the key problems and new directions of PCCs for sensing applications are discussed.

/pdf/a-review-for-optical-sensors-based-on-photonic-crystal-wcqhfbx0s5.pdf

A review for optical sensors based on photonic crystal cavities

This paper discusses the use of artificial neural network (ANN) models for predicting daily flows from Khosrow Shirin watershed located in the northwest part of Fars province in Iran. A Multi-Layer Perceptron (MLP) neural network was developed using five input vectors leading to five ANN models: MLP1, MLP2, MLP3, MLP4, and MLP5. Two activation functions were used and they were logistic sigmoid and tangent sigmoid. The MLP_Levenberg–Marquardt (LM) algorithm was used for the training of ANN models. A 5-year data record, selected randomly, was used for ANN training and testing. The predicted outflow showed that the tangent sigmoid activation function performed better than did the logistic sigmoid activation function. The values of R2 and RMSE for MLP4 with the tangent sigmoid activation function for the validation period were equal to 0.89 and 1.7 m3/s, respectively. Appropriate input vectors for MLPs were determined by correlation analysis. It was found that antecedent precipitation and discharge with 1 day time lag as an input vector best predicted daily flows. Also, comparison of MLPs showed that an increase in input data was not always useful.

Daily Outflow Prediction by Multi Layer Perceptron with Logistic Sigmoid and Tangent Sigmoid Activation Functions

Ship detection in synthetic aperture radar (SAR) images is becoming a research hotspot. In recent years, as the rise of artificial intelligence, deep learning has almost dominated SAR ship detection community for its higher accuracy, faster speed, less human intervention, etc. However, today, there is still a lack of a reliable deep learning SAR ship detection dataset that can meet the practical migration application of ship detection in large-scene space-borne SAR images. Thus, to solve this problem, this paper releases a Large-Scale SAR Ship Detection Dataset-v1.0 (LS-SSDD-v1.0) from Sentinel-1, for small ship detection under large-scale backgrounds. LS-SSDD-v1.0 contains 15 large-scale SAR images whose ground truths are correctly labeled by SAR experts by drawing support from the Automatic Identification System (AIS) and Google Earth. To facilitate network training, the large-scale images are directly cut into 9000 sub-images without bells and whistles, providing convenience for subsequent detection result presentation in large-scale SAR images. Notably, LS-SSDD-v1.0 has five advantages: (1) large-scale backgrounds, (2) small ship detection, (3) abundant pure backgrounds, (4) fully automatic detection flow, and (5) numerous and standardized research baselines. Last but not least, combined with the advantage of abundant pure backgrounds, we also propose a Pure Background Hybrid Training mechanism (PBHT-mechanism) to suppress false alarms of land in large-scale SAR images. Experimental results of ablation study can verify the effectiveness of the PBHT-mechanism. LS-SSDD-v1.0 can inspire related scholars to make extensive research into SAR ship detection methods with engineering application value, which is conducive to the progress of SAR intelligent interpretation technology.

LS-SSDD-v1.0: A Deep Learning Dataset Dedicated to Small Ship Detection from Large-Scale Sentinel-1 SAR Images

In this paper, we proposed a novel all optical analog-to-digital (ADC) converter based on photonic crystals. First of all, we designed a three port nonlinear demultiplexer, for producing discrete levels of input optical intensity. Then, an optical coder was used to generate a 2-bit standard binary code out of the discrete levels coming from the nonlinear demultiplexer. The final structure was realized by combining the nonlinear demultiplexer with the optical coder. The maximum sampling rate of the proposed structure obtained to be about 200 GS/s, and the total footprint is about 806 μm2.

A Novel Proposal for All Optical Analog-to-Digital Converter Based on Photonic Crystal Structures

A novel design for realizing all optical analog to digital converter will be proposed in this paper. The proposed structure consists of two main parts; a nonlinear 3-channel demultiplexer, followed by an optical coder. The nonlinear demultiplexer will be used to quantize the input analog signal according to its optical intensity and the coder will convert the quantized levels into 2-bit binary codes. The nonlinear demultiplexer will be realized using three nonlinear resonant cavities. At appropriate values of input signal optical intensity one of the cavities can drop the optical beam to its corresponding output port. The proposed structure is capable of supporting maximum sampling rate up to 52 GS/s and total footprint of the structure is about 924 µm2.

All optical 2-bit analog to digital converter using photonic crystal based cavities

In this study, an all optical 4-to-2 encoder have been proposed which has four input and three output ports. The proposed structure can generate a 2-bit binary code considering which input port is active. For realising the proposed structure first the authors proposed and designed a BUFFER and an OR gate. Then combined these basic gates to realise the proposed encoder. The maximum switching delay and footprint for the proposed structure are about 200 fs and 880 μm2, respectively.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-opt.2016.0022

Proposal for 4-to-2 optical encoder based on photonic crystals

In this paper, we used the novel defective resonant cavities to design an eight-channel photonic crystal demultiplexer. We showed that by choosing appropriate values for the width of the resonant cavity, the desired wavelengths can be separated. The proposed platform has a square lattice of dielectric rods immersed in air. The value of transmission efficiency for channels was obtained in 94$$-$$-99 % range. In addition, the maximum value of crosstalk and average quality factor for channels were calculated ---11.2 dB and 2200, respectively.

A new proposal for eight-channel optical demultiplexer based on photonic crystal resonant cavities

In this paper, we propose what we believe is a novel all-optical analog-to-digital converter (ADC) based on photonic crystals. The proposed structure is composed of a nonlinear triplexer and an optical coder. The nonlinear triplexer is for creating discrete levels in the continuous optical input signal, and the optical coder is for generating a 2-bit standard binary code out of the discrete levels coming from the nonlinear triplexer. Controlling the resonant mode of the resonant rings through optical intensity is the main objective and working mechanism of the proposed structure. The maximum delay time obtained for the proposed structure was about 5 ps and the total footprint is about 1520  μm2.

Mohammad Soroosh

Papers

A Novel Proposal for All Optical Analog-to-Digital Converter Based on Photonic Crystal Structures

All optical 2-bit analog to digital converter using photonic crystal based cavities

Proposal for 4-to-2 optical encoder based on photonic crystals

A new proposal for eight-channel optical demultiplexer based on photonic crystal resonant cavities

Ultra-fast analog-to-digital converter based on a nonlinear triplexer and an optical coder with a photonic crystal structure.