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Article: An Integrative Biosensor Based on Contra-Directional Coupling Two-dimensional Photonic Crystal Waveguides[show abstract] [hide abstract]
ABSTRACT: We propose an integrative biochemical sensor utilizing the dip in the transmission spectrum of a normal single-line defect photonic crystal (PC) waveguide, which has a contra-directional coupling with another PC waveguide. When the air holes in the PC slab are filled with a liquid analyte with different refractive indices, the dip has a wavelength shift. By detecting the output power variation at a certain fixed wavelength, a sensitivity of 1.2×10 −4 is feasible. This structure is easy for integration due to its plane waveguide structure and omissible pump source. In addition, high signal to noise ratio can be expected because signal transmits via a normal single-line defect PC waveguide instead of the PC hole area or analyte. PACS: 42. 70. Qs, 78. 20. Bh Biological and chemical sensors are used in exten-sive areas including health care, environmental con-trol, food safety and antiterrorism. Biochemical sen-sors in a number of different ways have been proposed up to date. [1−4] , In recent years, researchers have paid much attention to the applications of photonic crys-tals (PC) for biochemical sensors. [5−8] By introducing defects into the PC structures, the optical field can be confined in the vicinity of the device internal surface where the refractive index change occurs. Thus, PC biosensors are considered to be more sensitive com-pared to the sensing platforms that utilize the inter-action between a small evanescent tail of the field and the analyte, especially for ultrasmall volume of ana-lyte. In 2006, Lee et al. experimentally demonstrated a biosensor based on a two-dimensional (2-D) PC mi-crocavity slab,  however the signal-to-noise ratio is not very high because of the cavity emission in the direction perpendicular to the PC slab and the loss at the junction of microcavity and waveguides. Loncar et al demonstrated another kind of biochemical sen-sors based on a PC nanocavity laser,  whereas this structure is difficult for integration because of the use of light pump source and the output light emission in all the directions. In this Letter, we propose a novel biochemical sensor utilizing the dip in the transmis-sion spectrum of a normal single-line defect PC waveg-uide, which has a contra-directional coupling with an-other PC waveguide that is formed by enlarging a line of air holes. When the air holes in the PC slab are filled with a liquid analyte with different refractive indices, the dip in the transmission spectrum has a wavelength shift. According to our calculation, sensi-tivity of about 0.01 with a large detective range from 1.00 to 1.38 can be obtained by detecting wavelength shifts, and a sensitivity of 1.2 × 10 −4 can be reached by detecting the power intensity variation at a specific wavelength. This structure is easy for integration due to its plane waveguide structure and omissible pump source. In addition, this sensor not only is quite sen-sitive to the analyte because of its enlarging air hole waveguide, but also has a high signal to noise ratio because the signal transmits via a normal single-line defect PC waveguide instead of the PC hole area or analyte.01/2008; 25.
Beijing, Beijing Shi, China
- Department of Electrical Engineering