Bipin K. Singh

Photonic and Omnidirectional Band Gap Engineering in One-Dimensional Photonic Crystals Consisting of Linearly Graded Index Material

Engineering of photonic and omnidirectional band gaps has been demonstrated theoretically in one-dimensional photonic crystals (1-D-PCs) containing linearly graded and constant refractive index materials. The reflection spectra, photonic band gap spectra, reflection phase shift, and electric field distribution have been obtained by transfer matrix method in the 200-800 THz region. It has been found that the number of photonic bands increases with layers thickness. The omnidirectional band gap in a quarter-wave stacking arrangement of such PC has also been obtained. Results show that different constituted homogeneous layers can change the omnidirectional band gap remarkably. Moreover, we have demonstrated that photonic bandwidths can also be controlled by the contrast of initial and final refractive index of the graded layers.

Effect of temperature on terahertz photonic and omnidirectional band gaps in one-dimensional quasi-periodic photonic crystals composed of semiconductor InSb.

Engineering of thermally tunable terahertz photonic and omnidirectional bandgaps has been demonstrated theoretically in one-dimensional quasi-periodic photonic crystals (PCs) containing semiconductor and dielectric materials. The considered quasi-periodic structures are taken in the form of Fibonacci, Thue-Morse, and double periodic sequences. We have shown that the photonic and omnidirectional bandgaps in the quasi-periodic structures with semiconductor constituents are strongly depend on the temperature, thickness of the constituted semiconductor and dielectric material layers, and generations of the quasi-periodic sequences. It has been found that the number of photonic bandgaps increases with layer thickness and generation of the quasi-periodic sequences. Omnidirectional bandgaps in the structures have also been obtained. Results show that the bandwidths of photonic and omnidirectional bandgaps are tunable by changing the temperature and lattice parameters of the structures. The generation of quasi-periodic sequences can also change the properties of photonic and omnidirectional bandgaps remarkably. The frequency range of the photonic and omnidirectional bandgaps can be tuned by the change of temperature and layer thickness of the considered quasi-periodic structures. This work will be useful to design tunable terahertz PC devices.

A study of optical reflectance and localization modes of 1-D Fibonacci photonic quasicrystals using different graded dielectric materials

In this paper, we present an analytical study on the reflection properties of light through one-dimensional (1-D) quasi-periodic multilayer structures. The considered structures are as follows: F7, F8, F9, (F2)10, (F3)10 and some combinations such as: [(F2)10 (F7) (F2)10], [(F2)10 (F8) (F2)10], [(F3)10 (F7) (F3)10], [(F3)10 (F8) (F3)10], [(F2)10(F3)10], [(F2)10 (F7) (F3)10] and [(F2)10 (F8) (F3)10], where (Fj)n represents n period of the Fibonacci sequence of jth generation. These multilayer structures are considered of two types of layers. One type of layer is considered of graded material like normal, linear or exponential graded material, and the second type of layer is considered of constant refractive index material. Transfer matrix method is utilized to calculate the reflection spectra and localization modes of such structures in the frequency range 150–450 THz. This work would provide the basis of understanding of the effect of graded materials on the reflection and localization modes in Fibonacci photonic quasicrystal structures and obtained spectra can be used in the recognition of grading of materials. The considered heterostructures provide the broad reflection band and some localization modes in the calculated region.

Effect of Temperature on the Dispersion Properties of a Square Photonic Crystal Fiber

In this paper, effect of temperature on dispersion properties of a square photonic crystal fiber is studied. Cladding holes of PCF are filled with semi-conductor material, InSb which has a temperature dependence in terahertz frequency.

Tunability of temperature dependent THz photonic band gaps in 1-D photonic crystals composed of graded index materials and semiconductor InSb

Tunable temperature dependent terahertz photonic band gaps (PBGs) in one-dimensional (1-D) photonic crystal composed of alternating layers of graded index and semiconductor materials are demonstrated. Results show the influence of temperature, geometrical parameters, grading profile and material damping factor on the PBGs. Number of PBG increases with increasing the layer thickness and their bandwidth can be tuned with external temperature and grading parameters. Lower order band gap is more sensitive to the temperature which shows increasing trend with temperature, and higher order PBGs can also be tuned by controlling the external temperature. Band edges of PBGs are shifted toward higher frequency side with increasing the temperature. Results show that the operational frequencies of PBGs are unaffected when loss involved. This work enables to design tunable Temperature dependent terahertz photonic devices such as reflectors, sensors and filters etc.Tunable temperature dependent terahertz photonic band gaps (PBGs) in one-dimensional (1-D) photonic crystal composed of alternating layers of graded index and semiconductor materials are demonstrated. Results show the influence of temperature, geometrical parameters, grading profile and material damping factor on the PBGs. Number of PBG increases with increasing the layer thickness and their bandwidth can be tuned with external temperature and grading parameters. Lower order band gap is more sensitive to the temperature which shows increasing trend with temperature, and higher order PBGs can also be tuned by controlling the external temperature. Band edges of PBGs are shifted toward higher frequency side with increasing the temperature. Results show that the operational frequencies of PBGs are unaffected when loss involved. This work enables to design tunable Temperature dependent terahertz photonic devices such as reflectors, sensors and filters etc.

Enhanced light trapping in dye-sensitized solar cell by coupling to 1D photonic crystal and accounting for finite coherence length

Abstract Theoretical analysis of dye-sensitized solar cell integrated with photonic crystals based on coupled coherent and geometrical optics formalism has presented. The effect of structural parameters, such as thickness of layer, number of unit cells and light incident angle on the optical properties and photo-current magnification for the proposed photonic crystal based dye-sensitized solar cell have studied. The angular response of the cell in terms of light harvesting efficiency and cumulative photo-generation rate has also analysed. A strategy has presented to enhance the performance of the cell under oblique incidence. The effect of number of photonic crystal unit cells has also analysed in view of percentage enhancement in cumulative photo-generation rate. This work provides new insight into the design and tailoring of the photonic crystals to enhance the light harvesting efficiency in the solar cells.

Effect of Exponentially Graded Material on Photonic and Omni-Directional Band Gaps in 1-D Photonic Crystals

Photonic and Omni-directional band gaps have been obtained for one-dimensional (1-D) photonic crystal consists of exponential graded index material and constant refractive index material in range 150–750 THz of electromagnetic radiation. Transfer matrix method has been used for calculation of reflectance. The number of photonic band gaps and their bandwidths has been tuned by changing relative parameters, thickness of exponentially graded material and angle of incidence. This work will be useful in design of filters, optical sensors, reflectors etc., and provide more design freedom for alternative photonic devices.

Photonic and omnidirectional band gap engineering in stack of exponential graded index material and negative index material

We have investigated the photonic band gaps (PBG) and omnidirectional band gaps in one-dimensional photonic crystals made up of alternate layer of exponential graded index material and negative index material. We have considered the influence of material properties, geometrical parameters and material composition on the PBG and omnidirectional band gap. Results show that the parameters of exponential graded index material and negative index material can change the photonic and omnidirectional band structures remarkably. Number and bandwidth of PBG increases with increasing the negative index material layer thicknesses while thicknesses of graded index layer only have an effect on the bandwidth of PBGs. The bandwidth of PBG also depends on grading profile parameter of exponential graded index layers and bandwidth can be tuned with increase the value of grading profile parameter. This work can facilitate the design of filters and reflectors, and provide the basic understanding of the influence of graded index materials and metamaterials on the PBG properties.

Tunable mirror and multi-channel filter based on one-dimensional exponentially graded photonic crystals

A study on the tunability of photonic and Omni-directional band gaps has been demonstrated theoretically in one-dimensional (1-D) photonic crystals having one of the layers as exponential graded index materials and other layers of constant refractive index materials. Using numerical simulations, we have investigated the effect of relative parameters of exponential graded layers on the photonic and Omni-directional band gaps in 1-D graded photonic crystals (GPCs). We observe that the number of photonic band gaps increases with increase of the layer thicknesses and their bandwidths can be controlled by the contrast between initial and final refractive index of the graded layers. Moreover, we have studied the Omni-directional band gaps in quarter-wave and latent type layer stacking arrangements. Further, we obtained the range of refractive indices and thicknesses of constituted layers at which omnidirectional band gaps occurs. Accordingly, we find that the photonic as well as Omni-directional band gaps of desired bandwidths can be obtained by selecting appropriate parameters in GPCs. Our work will be useful in design of mirrors, channel filters, Optical sensors, Omni-directional reflectors etc. and provide more design freedom for alternative photonic devices.

Tunability of resonator based photonic crystal switch by elliptical rods

In this paper, we present a design of a photonic crystal optical switch which is based on an elliptical waveguide resonator to get response at optical wavelength (1.55μm). The objective of this work is to obtain desired operating wavelength by introducing the resonator cavity. The cavity is made up of photonic crystal by imparting two rods of elliptical shape. The radius of major and minor axes and refractive index of elliptical rods can be varied. Modifying the major and minor axes of the elliptical rods in resonator and also by decreasing the refractive index optimum results have been obtained. Finite Difference Time Domain software (OptiFDTD™) is implemented to analyze the characteristics of the switch. We perform switching on and off state by applying low pass filter (LPF) and high pass filter (HPF) respectively. Results show that transmitted power with respect to wavelength has been improved by implementing the proposed structure.