Suneet Kumar Awasthi

DESIGN OF A TUNABLE OPTICAL FILTER BY USING A ONE-DIMENSIONAL TERNARY PHOTONIC BAND GAP MATERIAL

A band pass filter with a linearly periodic refractive index profile is discussed in analogy with Kroning Penney model in band theory of solids. The suggested filter is a one-dimensional ternary periodic structure and provides better control in dispersion relation as compared to a binary structure because it has two more controlling parameters relative to those of the binary one. Since three layers are involved in the formation of band gaps a much broader range of dispersion control is obtained. Both refractive index modulation and optical thickness modulation are considered. A mathematical analysis is presented to predict allowed and forbidden bands of wavelength with variation of angle of incidence. It is also possible to get desired ranges of the electromagnetic spectrum filtered with this structure by manipulating the value of the lattice parameters.

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.

Wide-Angle Broadband Plate Polarizer with 1D Photonic Crystal

Here a photonic crystal plate polarizer (with periodic air gaps), operating over a broad wavelength range extending from 1000 nm to 1770 nm and with a wide angular field of 16◦ measured in air, is suggested. The polarizer has an average degree of polarization equal to 0.9999, and a high extinction ratio (> 8.308 × 104) in transmitted light. Since the plate polarizer does not require optical cements, it is most suitable for use with high power laser systems. It is also smaller in size as compared with multilayered cube polarizers.

Entanglement sudden death and birth in qubit---qutrit systems under Dzyaloshinskii---Moriya interaction

We study entanglement dynamics of qubit–qutrit pair under Dzyaloshinskii–Moriya (DM) interaction. The qubit–qutrit pair acts as a closed system and one external qubit serve as the environment for the pair. The external qubit interact with qubit of closed system via DM interaction. This interaction frequently kills the entanglement between qubit–qutrit pair, which is also periodically recovered. On the other hand two parameter class of state of qubit–qutrit pair also affected by DM interaction and one parameter class of state remains unaffected. The frequency of occurrence of entanglement sudden death and entanglement sudden birth in two parameter class of state is half than qubit–qutrit pure state. We used our quantification of entanglement as negativity measure.

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.

Transmission properties of one-dimensional ternary plasma photonic crystals

Omnidirectional photonic band gaps (PBGs) are found in one-dimensional ternary plasma photonic crystals (PPC) composed of single negative metamaterials. The band characteristics and transmission properties are investigated through the transfer matrix method. We show that the proposed structure can trap light in three-dimensional space due to the elimination of Brewsters angle transmission resonance allowing the existence of complete PBG. The results are discussed in terms of incident angle, layer thickness, dielectric constant of the dielectric material, and number of unit cells (N) for TE and TM polarizations. It is seen that PBG characteristics is apparent even in an N ≥ 2 system, which is weakly sensitive to the incident angle and completely insensitive to the polarization. Finite PPC could be used for multichannel transmission filter without introducing any defect in the geometry. We show that the locations of the multichannel transmission peaks are in the allowed band of the infinite structure. The structure can work as a single or multichannel filter by varying the number of unit cells. Binary PPC can also work as a polarization sensitive tunable filter.

Infrared Omni-Directional Mirror Based on One-Dimensional Birefringent-Dielectric Photonic Crystal

In the present communication, we have theoretically in- vestigated and studied the re∞ection properties of one-dimensional birefringent-dielectric photonic crystal (1D BDPC) structure consist- ing alternate layers of BD material. From the analysis of the re∞ectance spectra it is found that 100% re∞ection region for both TE- and TM- mode can be enhanced signiflcantly in comparison with 1D dielectric- dielectric photonic crystal (DDPC). In order to obtain the re∞ection spectra of the proposed structure we have used the transfer matrix method (TMM). The structure proposed by us, has a wider omni- directional re∞ection (ODR) range in comparison to conventional all dielectric photonic crystals (PCs). The width of ODR can be enlarged by considering the suitable choice of lattice parameters.

Multichannel tunable filter properties of 1D magnetized ternary plasma photonic crystal in the presence of evanescent wave

The multichannel tunable filter properties of one-dimensional ternary plasma photonic crystal composed of magnetized plasma and lossless dielectric have been theoretically investigated using transfer matrix method in the microwave region. The proposed filters possess 2N − 2 comb-like sharp resonant peaks also called transmission channels for N > 1 in transmission spectra in the absence and presence of an external magnetic field. Due to the coupling between evanescent waves and propagating modes in plasma and dielectric layers, respectively, 2N − 2 transmission channels are found without the addition of any defect, enabling the structure to work as a multichannel filter. Next, the filter properties can be made tunable by the application of an external magnetic field, i.e., channel frequency can either be red or blue shifted depending upon the orientation of an external magnetic field. The number of channels and their positions can also be modulated by changing the number of periods (N) and the incident ang...