Abstract
An integrated total internal reflection prism is demonstrated that generates a transversely localized evanescent wave along the boundary between a photonic crystal and an etched out trench. The reflection can be described by either the odd symmetry of the Bloch wave or a tangential momentum matching condition. In addition, the Bloch wave propagates through the photonic crystal in a negative refraction regime, which manages diffraction within the prism. A device with three input channels has been fabricated and tested that illuminates different regions of the reflection interface. The reflected wave is then sampled by a photonic wire array, where the individual channels are resolved. Heterodyne near field scanning optical microscopy is used to characterize the spatial phase variation of the evanescent wave and its decay constant.
Highlights
The presence of an evanescent field is the signature of near-field optics
In microscopy [1, 2] and spectroscopy [3], this results in a method of depth sectioning, which adds increased resolution and specificity. Another benefit of evanescent illumination is that it is a dark field method in that the background illumination does not reach the collection optics, resulting in larger signal contrast. Evanescent waves in this context are most often created with a free space total internal reflection (TIR) prism illuminated above their critical angle
We demonstrate a photonic crystal (PC) TIR prism that can operate at small incident angles or even normal incidence
Summary
The presence of an evanescent field is the signature of near-field optics. There are two main characteristics of these waves that distinguish them from propagating waves. Another benefit of evanescent illumination is that it is a dark field method in that the background illumination does not reach the collection optics, resulting in larger signal contrast Evanescent waves in this context are most often created with a free space total internal reflection (TIR) prism illuminated above their critical angle. PCs have previously been used in the design of prisms that sort an incident wave based on its spectrum [9] or polarization state [10,11] These devices utilize the anomalous dispersive properties of Bloch waves in PCs. there is no transverse confinement in PC prisms, the diffraction of an optical beam can be controlled by using either the selfcollimation [12] or the negative refraction effect [13, 14]. Because the total internal reflection occurs in the second photonic band where slow or negative diffraction occurs, the PC TIR prism takes advantage of this parallelism
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