The need for sensors in medical diagnostics has led to growing interest in the field of optical biosensors. These devices utilize optical techniques to detect and identify chemical or biological species. The interest in optical biosensors is motivated by several advantages, such as low cost, high sensitivity, high specificity, and the possibility of remote sensing and in vivo measurements. Optical biosensors can utilize a modification in the amplitude, phase, or frequency of an input beam in the detection mechanism. Thus there exist many different physical phenomena and detection schemes that can be exploited. In our research we aim at enhancing the light-matter interactions using various micro and nano structures, including photonic crystal, in which a periodic modulation of the dielectric function on a scale comparable to that of the light wavelength of interest allows the control of light propagation and its confinement close to the diffraction limit.