Abstract:
Sensitive optical components such as semi-conductor laser diodes must be protected from back reflection. A conventional solution to this problem is Faraday optical diodes, which, however, require large magnetic fields, have a large footprint, and are not suited for integrated optical circuits. We offer a novel, performant optical diode exploiting spin-orbit coupling of light.
Background:
Reflections at optical interfaces are unavoidable and can cause a threat for sensitive optical components, for precise measurements, and for stable operation of an optical system. Conventionally, undesired reflected light is suppressed using Faraday optical diodes / isolators, which, however, are expensive, require large magnetic fields and are difficult to integrate into miniaturized optical circuits.
Technology:
When light is strongly confined, e.g. in a thin waveguide, it exhibits surprising properties. For example, in such structures, there is an inherent link between the local polarization of the light field and its propagation direction – an effect sometimes referred to as spin-orbit coupling of light. Implanting polarization-dependent absor-bers into such waveguide structures one can take advantage of this effect to realize a novel optical diode which is an interesting alternative to conventional Faraday-effect-based solutions.
• Can be miniaturized
• Compatible with integrated, on-chip optics
• Can work with low / without magnetic fields
• Transmission direction can be switched
• Direct integration into optical waveguides
• broad band and inexpensive
• strong polarization dependent absorber can possibly be required
• polarization-maintaining fibers may be required in some cases
• protection of sensitive devices such as semi-conductor laser diodes
• suppression of back-reflection to avoid built-up of standing wave between (integrated) optical elements
• construction of uni-directional optical elements
Angelika Valenta
