S.P. Ojha

Wide Range Temperature Sensors Based on One-Dimensional Photonic Crystal with a Single Defect

Transmission characteristics of one-dimensional photonic crystal structure with a defect have been studied. Transfer matrix method has been employed to find the transmission spectra of the proposed structure. We consider a Si/air multilayer system and refractive index of Si layer has been taken as temperature dependent. As the refractive index of Si layer is a function of temperature of medium, so the central wavelength of the defect mode is a function of temperature. Variation in temperature causes the shifting of defect modes. It is found that the average change or shift in central wavelength of defect modes is 0.064 nm/K. This property can be exploited in the design of a temperature sensor.

Partial Guidance of Electromagnetic Waves by a Parabolic Cylindrical Boundary Separating Two Chiral Media

An investigation has been made of the electromagnetic wave propagation in a medium with two regions, having different chiral admittances, separated by a parabolic cylindrical surface. The resulting guide is analogous to a circular chirowaveguide when the circle is degenerated into a parabola. The eigenvalue equation and the cutoff conditions of such a chirowaveguide have been derived for different special cases.

Trapping of Light in Nonlinear 1-D Photonic Crystal

Theoretical studies on the group velocity of light wave in 1-D polystyrene/SiO2 nonlinear photonic crystal is investigated. The speed of light wave through these multilayered structures is calculated in the absence as well as in the presence of a high intensity controlling wave by using the transfer matrix method. This letter shows that we can trap a light wave inside the nonlinear 1-D photonic crystal by switching off the controlling wave.

Silicon Based One-Dimensional Photonic Crystal as a TM-Mode Filter

The effect of temperature and angle of incidence on the transmission spectra of a one dimensional photonic crystal for TE and TM polarizations has been studied. For a range of angle of incidence from 0° to 60°, the proposed structure works as an omni-directional reflector. For other angles of incidence more than 60°, the structure works as a selective TM-polarization filter i.e. a filter which completely blocks TE-polarized waves but allows certain frequencies of TM-polarized waves. At an angle of incidence of 89°, the structure works as a multi channel optical filter without introducing any defect in the geometry. Also, this multi-channel filter can work as a tunable filter by varying the temperature of the structure and the number of layers in the geometry. Only for two bi-layers the proposed structure works as a single channel filter. Therefore, such types of structure are easier to fabricate and may be cost effective as compared to defect one-dimensional photonic crystals.