ARROW waveguide
Encyclopedia
In optics
, an anti-resonant reflecting optical waveguide
(ARROW) 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.
ARROWs can be realized as cylindrical waveguides (2D confinement) or slab waveguides (1D confinement).
The latter ARROWs are practically formed by a low index layer, embedded between higher index layers. Note that the refractive indices of are reversed, when comparing to usual waveguides. Light is confined by total internal reflection
(TIR) on the inside of the higher index layers, but achieves a lot of modal overlap with the lower index central volume.
This strong overlap can be made plausible in a simplified picture imagining "rays", as in geometrical optics
. Such rays are refracted into a very shallow angle, when entering the low index inner layer. Thus, one can use the metaphor that these rays "stay very long inside" the low index inner layer. Note this is just a metaphor and the explanatory power of ray optics is very limited for the micrometer scales, at which these ARROWs are typically made.
ARROW structures are often used for guiding light in liquids, particularly in microfluidic systems. This is due to the difficulty of finding suitable optical cladding materials, with a lower refractive index than the liquid, which would be required to form a conventional waveguide structure.
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
, an anti-resonant reflecting optical waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
(ARROW) 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.
ARROWs can be realized as cylindrical waveguides (2D confinement) or slab waveguides (1D confinement).
The latter ARROWs are practically formed by a low index layer, embedded between higher index layers. Note that the refractive indices of are reversed, when comparing to usual waveguides. Light is confined by total internal reflection
Total internal reflection
Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is...
(TIR) on the inside of the higher index layers, but achieves a lot of modal overlap with the lower index central volume.
This strong overlap can be made plausible in a simplified picture imagining "rays", as in geometrical optics
Geometrical optics
Geometrical optics, or ray optics, describes light propagation in terms of "rays". The "ray" in geometric optics is an abstraction, or "instrument", which can be used to approximately model how light will propagate. Light rays are defined to propagate in a rectilinear path as far as they travel in...
. Such rays are refracted into a very shallow angle, when entering the low index inner layer. Thus, one can use the metaphor that these rays "stay very long inside" the low index inner layer. Note this is just a metaphor and the explanatory power of ray optics is very limited for the micrometer scales, at which these ARROWs are typically made.
ARROW structures are often used for guiding light in liquids, particularly in microfluidic systems. This is due to the difficulty of finding suitable optical cladding materials, with a lower refractive index than the liquid, which would be required to form a conventional waveguide structure.
See also
- Integrated Hollow ARROWs
- Waveguide (optics)Waveguide (optics)An optical waveguide is a physical structure that guides electromagnetic waves in the optical spectrum. Common types of optical waveguides include optical fiber and rectangular waveguides....