Usha Malaviya

DESIGN OF A TUNABLE POLARIZER USING A ONE-DIMENSIONAL NANO SIZED PHOTONIC BANDGAP STRUCTURE

DESIGNOFATUNABLEPOLARIZERUSINGAONE-DIMENSIONALNANOSIZEDPHOTONICBANDGAPSTRUCTURES.K.AwasthiAmityInstituteofAppliedScienceAmityUniversityNoida-201301,IndiaU.MalaviyaDepartmentofPhysicsUniversityofLucknowLucknow-226007,IndiaS.P.OjhaChaudharyCharanSinghUniversityMeerut-25004,IndiaN.K.MishraandB.SinghU.P.AutonomousCollegeVaranasi-221007,IndiaAbstract—In this paper a transfer matrix treatment for thereflectivity and transmissivity spectra of electromagnetic wavespropagating in a nano sized multilayer periodic structure has beenpresented. Effect of varying the angle of incidence on the photonicbandgaps is shown. The design of a tunable polarizer by reflectionwhich is more efficient in comparison to that obtained by reflectionfromasingledielectricslab,hasbeensuggested.

Tunable and omnidirectional filters based on one-dimensional photonic crystals composed of single-negative materials

Tunable and omnidirectional filters have been demonstrated theoretically, using one-dimensional photonic crystals composed of single-negative materials. It is seen that a bilayer eight period structure can act as a tunable filter, which is sensitive to incident angle but insensitive to polarization. By increasing the number of periods to 16 and by tailoring the layer thicknesses, the same structure can act as an omnidirectional, polarization-independent filter for angles of incidence between 0° and 75°.

Design of a nano-layered tunable optical filter

A novel theory to design tunable band pass filters using one-dimensional nano-photonic structures is proposed. Periodic structures consisting of different dielectrics and semiconductor materials are considered. A detailed mathematical analysis is presented to predict allowed and forbidden bands of wavelengths with variation of angle of incidence and lattice parameters. It is possible to get desired ranges of the electromagnetic spectrum filtered with this structure by changing the incidence angle of light and/or changing the value of the lattice parameters.

Enhancement of omnidirectional high-reflection wavelength range in one-dimensional ternary periodic structures: a comparative study

A comparative study of enhancement of omnidirectional high-reflection wavelength range in one-dimensional ternary structured photonic crystals (PCs) was carried out. The PCs investigated are of the dielectric-birefringent type and the dielectric-metallic type. These were compared with a 1D all-dielectric ternary PC investigated earlier by us. The dielectric-birefringent PC gives a larger range enhancement as compared to the all-dielectric one, together with a reduction in the number of periods of the structure. Maximum range enhancement is obtained in the metallodielectric ternary PC, with a further reduction in size, as only six layers need to be deposited in this case. This implies easier fabrication methods and lower costs.

Design of a digitally tunable optical filter system for wavelength selective switching based optical networks

What is believed to be a novel design of a digitally tunable optical filter system for wavelength-selective-switching-based optical networks is demonstrated. It uses two-by-two wavelength-selection elements and semiconductor optical amplifiers. The system can be expanded to provide selection of more channels by simply inserting one additional semiconductor optical amplifier for every new set of four channels and one wavelength-selection element per channel.

Design of narrowband optical transmission filters using fractal Cantor multilayers

This paper presents a theory to design super narrow band pass optical filters using fractal Cantor multilayer structure without defect and fractal Cantor multilayer structure with embedded defect. It is shown that the width of transmission peaks can be narrowed by increasing the number of periods of the structure, while the number of peaks can be increased by either embedding defect layer in the structure or by successive repetition of the structure.

Filter performance of reduced sized defect photonic crystals based on single‐negative materials

Single‐ and multiple‐channeled filters based on single‐negative (SNG) photonic crystals with inversion defects have been demonstrated theoretically. Omnidirectional filters with wide angular apertures and multiple‐channeled filters at normal incidence have been reported. Sharp, high transmission peaks with frequencies lying within the SNG range are obtained. By variation of the structural parameters these structures can also be made to function as tunable or polarizing filters, though the frequencies of the transmission modes in these two cases will lie outside the SNG range. A significant feature of all the filter types discussed is the drastic reduction in size of the proposed structures in comparison to those reported earlier. This implies easier fabrication methods and lower cost. Improved performance of devices has been achieved by proper placement of defects.

Design of a tunable ultraviolet filter using metallodielectric photonic crystal

A theory to design a tunable ultraviolet filter using a 1-D metallodielectric photonic crystal composed of alternate layers of MgF2 and Co is proposed. It is possible to get different ranges of ultraviolet spectrum transmitted through the structure by varying the angle of incidence light. Due to high refractive index contrast in the present structure, regions of transmission separated by well-defined regions of high reflectivity (the photonic band gaps) are obtained with only 12 periods. The use of small number of periods in the present filter structure has advantages of small filter size, low weight and cost.