Anti-Resonant Reflecting Optical Waveguides (Arrows) As Optimal Optical Detectors For Mu Tas Applications

Anti-Resonant Reflecting Optical Waveguides (ARROW) have been developed for integrated optical devices, as they permit waveguiding in low-index layers fabricated from materials such as silicon dioxide. They have been developed mainly for integrated optics applications, as they are compatible with Standard silicon processing techniques [1,2]. The main feature of ARROW waveguides is that light confinement is by Fabry-Perot anti-resonant reflectors, rather than total internal reflection (TIR). As a result of the light confinement mechanism, ARROWs can be constructed such that the light is confined in a low refractive index medium surrounded by high refractive index reflecting boundaries. ARROWs have been proposed as optical sensors [3], but the configuration suggested used the evanescent field outside the ARROW waveguide to perform sensing, leading to very low sensitivity.ARROWs are extremely well suited to mu TAS applications, since they permit waveguiding in a low index medium such as an aqueous solution. A simple refinement of the basic ARROW structure permits simple in- and out-coupling of light by frustrated total internal reflection (FTR), eliminating the need for complex coupling arrangements such as end-fire or grating couplers. ARROWs can be used to monitor optical absorption and refractive index, as well as to excite fluorescence.