ARROW waveguide

In optics, an ARROW (anti-resonant reflecting optical waveguide) is a type of waveguide that uses the principle of thin-film interference to guide light with low loss. It is formed from an anti-resonant Fabry–Pérot reflector. The optical mode is leaky, but relatively low-loss propagation can be achieved by making the Fabry–Pérot reflector of sufficiently high quality or small size.

In optics, an ARROW (anti-resonant reflecting optical waveguide) is a type of waveguide that uses the principle of thin-film interference to guide light with low loss. It is formed from an anti-resonant Fabry–Pérot reflector. The optical mode is leaky, but relatively low-loss propagation can be achieved by making the Fabry–Pérot reflector of sufficiently high quality or small size. t_j={\lambda \over 4n_j}(2N-1)[1-{n_c^2 \over n_j^2}+{\lambda^2 \over 4n_j^2t_c^2}]^{-1/2}, N = 1, 2, 3,... t_j = thickness of the antiresonant cladding layer t_c = thickness of the guiding core layer \lambda = wavelength n_j = refractive index of antiresonant cladding layer n_c = refractive index of guiding core layer while n_j > n_c > n_{air} ARROW are often used for guiding light in liquids, particularly in photonic lab-on-a-chip analytical systems (PhLoCs). Conventional waveguides rely on the principle of total internal reflection, which can only occur if the refractive index of the guiding core material is greater than the refractive indexes of its surroundings. However, the materials used to make the guiding core are typically polymer and silicon-based materials, which have higher refractive indexes (n=1.4-3.5) than that of water (n = 1.33). As a result, a conventional hollow-core waveguide no longer works once it's filled with water solution, making the PhLoCs useless. An ARROW, on the other hand, can be liquid-filled since it confines light completely by interference, which requires that the refractive index of the guiding core to be lower than the refractive index of the surrounding materials. Thus, ARROWs become the ideal building blocks for PhLoCs. Though ARROWs carry big advantage over conventional waveguide for building PhLoCs, they are not perfect. The main problem of ARROW is its undesirable light loss. Light loss of ARROWs decreases the signal to noise ratio of the PhLoCs. Different versions of ARROWs have been designed and tested in order to overcome this problem.

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