INVESTIGATION OF ULTRA-WIDE REFLECTION BANDS IN UV REGION BY USING ONE-DIMENSIONAL MULTI QUANTUM WELL PHOTONIC CRYSTAL

Abstract

Enhancement of the reflection bands in ultraviolet region by using one-dimensional multi quantum well (MQW) photonic crystal (PC) structure has been investigated theoretically. The proposed structure is composed of three MgF2/SrTiO3 MQWs. The range of reflection band is investigated from the reflectance spectra of the one-dimensional MQW photonic crystal structure obtained by Transfer Matrix Method (TMM). From the numerical analysis it is observed that a range of reflection band for a single MQW PC is very narrow though it increases as the thickness of layers increases. But when three MQWs of MgF2/SrTiO3 are used we get much enlarged reflection band covering the range 119.8 nm- 311.3 nm (reflectivity > 99%) with bandwidth 191.5 nm, for normal incidence. Further, we see that when the angle of incidence is increased, the width of reflection band increases in case of TE wave with a decrease for TM wave, because this omnidirectional reflection (ODR) band is very much narrow in UV region. We have computed ODR band upto incidence angle 50 ◦ for single as well as combined MQW PC. Analyzing the reflectance curve for incidence angle up to 50 ◦ for both TE and TM polarizations we find that by applying the combined MQW PC, omnidirectional reflection band increases significantly in comparison to single MQW structure. The proposed MQW photonic crystal structure is very useful in designing ultraviolet shielding for drugs, ultraviolet reflector for protecting damage of DNA and in skin diseases especially for skin cancer.