Preeti Rani

Complete photonic bandgap-based polarization splitter on silicon-on-insulator platform

Abstract. We propose a design for a polarization beam splitter based on the phenomenon of a photonic crystal directional coupler. The design consists of a honeycomb lattice arrangement of air holes of different radii in a silicon-on-insulator substrate exhibiting a complete photonic bandgap. The results obtained by the finite-difference time domain method show that the extinction ratio for transverse electric (TE) and transverse magnetic (TM) polarizations is 24.56 and 28.29 dB, respectively, at a wavelength of 1.55  μm. The degree of polarization for TE polarization is 99.29% and for TM polarization is 99.70%. Hence, the proposed design can be efficiently used as a polarization splitter for on-chip integrated devices.

Design and operation of photonic crystal based AND optical logic gate

We propose the design for AND optical logic gate. The design has been simulated using FDTD method and has a contrast ratio of 6.130dB. The design has a bit rate of 0.664Tbit/s.

Slow light effect in pinch waveguide in photonic crystal

In this paper, we have proposed a design for slow light effect in pinch photonic crystal waveguide. The design consists of two dimensional triangular arrangements of air holes in silicon on insulator substrate. From the calculations it has been found out that for the proposed structure the group index is high and group velocity dispersion is low. The confinement of light in the pinch waveguide with slow light effect can be a strong candidate for sensor applications.

Slow light enabled time and wavelength division demultiplexer in slotted photonic crystal waveguide

Abstract. We have proposed a design for slow light with ultraflat dispersion in a slotted photonic crystal waveguide consisting of a hexagonal arrangement of elliptical air holes on a silicon-on-insulator substrate. The proposed structure has low group velocity and low group velocity dispersion with a wide normalized bandwidth range of 0.0089. The proposed structure can be used as an optical buffer for the storage of a large amount of data due to the large value of the normalized delay bandwidth product equal to 0.634. An optimized structure for a slotted photonic crystal has been analyzed for its applications as both a time and wavelength division demultiplexer. Furthermore, the time delay between two adjacent wavelengths (1550 and 1555 nm) is more than that reported earlier.

Design of photonic crystal architecture for optical logic AND gates

Photonic crystals (PhCs) have emerged as one of the most significant topics in the field of optical communication since their first introduction by Yablonvitch 1 and John 2. Recently, interest has been grown in the design and development of optical logic gates based on different schemes 3-10. In this paper, we report the design of optical logic AND gate based on two structures, one of which is a hexagonal lattice with silicon (Si) rods in air (SRA) and another is the hexagonal lattice arrangement of air holes in silicon (AHS) with air waveguides. Both the gate structures are based on Y shaped PhC waveguides and analyzed by plane wave expansion (PWE) method. The simulation results show that the proposed structures operates as an AND gates and has a bit rate of 2.016Tbit/s for SRA and 1.785Tbit/s for AHS structure. By appropriately choosing the size and the interaction length of the central rod in SRA and size of central hole in AHS, the optimal performance of the proposed AND logic gates has been achieved.

Design of AND logic gate using NAND gate in photonic crystal waveguides

In this paper, we have proposed the design of all-optical AND logic gate using the combination of universal NAND gates. The structure consists of hexagonal arrangement of air holes in silicon. The proposed structure has been designed using the finite difference time domain (FDTD) method. The optimized NAND gates have been arranged in a combination such that the combined structure behaves as an all-optical AND logic gate. The proposed structure exhibits a response period of 6.48ps and bit rate of 0.154 Tb/sec.

Enhanced image resolution in photonic crystal structure by modification of the surface structure

In this paper, enhanced image resolution by modification in the two dimensional (2-D) photonic crystal structures has been proposed. The equal frequency contour (EFC) analysis have been done using plane wave expansion method which shows that the structure exhibits an effective isotropic refractive index, neff = -1 at a normalized frequency of ω = 0.2908(2πc/a) for TM polarization, located near the second band. At ω = 0.2908(2πc/a) for TM polarization, the considered PhC structure behaves as a superlens, as analyzed using the finite difference time domain (FDTD) method. The image resolution and stability of the photonic crystal slab lens has been enhanced by creating disorder in the top and bottom layer of the PhC structure. The intensity field distributions of the optimized structure exhibit the enhanced image quality with full width at half maximum (FWHM) of 0.311 λ. The proposed structure can also be used to sense the different type of blood constituents.

Photonic crystal based nano-displacement sensor

Photonic crystal based nano -displacement sensor for horizontal as well as vertical displacement has been proposed. The design is highly sensitive in the displacement region 40nm–120nm with sensitivity 0.00461nm-1 for horizontal displacement of the moving PhC waveguide. For vertical displacement of the moving PhC waveguide the design is highly sensitive in the region 150nm-200nm with sensitivity 0.00684nm-1 for zero horizontal displacement, 130nm- 200nm with sensitivity 0.00523 nm-1for 10nm horizontal displacement, 130nm-200nm with sensitivity 0.00418 nm-1 for 20nm horizontal displacement, 130nm-200nm with sensitivity 0.00461 nm-1for 30nm horizontal displacement,100nm-130nm with sensitivity 0.00466 nm-1for 40nm horizontal displacement. It has been concluded that the proposed design behaves as a Nano-displacement sensor for horizontal displacement of the moving PhC waveguide up to the region of displacement of magnitude of 400nm and for vertical displacement of the moving PhC waveguide up to the region of displacement of magnitude of 300nm.The proposed design can behave as a nano-Displacement sensor for both horizontal as well as vertical displacement.

Field enhanced plexitonic coupling between InAs quantum dot and silver film: Highly sensitive plasmonic composite

In this work we propose and study a highly sensitive quantum dot (QD)-metal film plasmonic composite. The system comprises of indium arsenide (InAs) QDs on silver film. The intensity is traced by scanning the absorption spectra for the system. We found that the behaviour of the plasmonic composite changes by varying the thickness of metal film. It is observed that the sensitivity of the composite varies with the thickness of metallic film and the quantum size effects dominate at sub-nanometer gap. The proposed system shows promising applications in lasing, sensing and spectroscopy.

Slow light enhanced slotted photonic crystal waveguide

Slotted waveguide with slow light effect in photonic crystal composed of hexagonal arrangement of square air holes on SOI substrate has been proposed. The proposed structure has high group index and low Group Velocity Dispersion.