Retro-reflective structures

An optical sensor probe, the optical sensor probe comprising a photonic integrated circuit, comprising at least one signal processing circuit, the at least one signal processing circuit comprising at least one input coupling element for coupling incident light from an incoupling direction into the photonic integrated circuit, and at least one output coupling element for coupling light out of the photonic integrated circuit into an outcoupling direction, the photonic integrated circuit being adapted such that light coupled into the photonic integrated circuit through the input coupling element is propagated through the signal processing circuit and coupled out of the output coupling element, the signal processing circuit further comprising at least one optical component adapted for generating an optical response to an external parameter,

• wherein the relation between the incoupling direction and the outcoupling direction is different from a relation for reflection at a surface according to the law of reflection, the incoupling direction and the outcoupling direction being substantially opposite so that retro-reflective operation is obtained and the light is sent back into the direction it originated from.

A photonic integrated circuit comprising at least one signal processing circuit, the at least one signal processing circuit comprising at least one input coupling element for coupling incident light from a predetermined incoupling direction into the photonic integrated circuit, and at least one output coupling element for coupling light out of the photonic integrated circuit into an outcoupling direction,

• wherein the relation between the incoupling direction and the outcoupling direction is different from a relation for reflection at a surface according to the law of reflection, the incoupling direction and the outcoupling direction being substantially opposite so that retro-reflective operation is obtained and the light is sent back into the direction it originated from, and
• wherein the at least one signal processing circuit comprises a plurality of input coupling elements, each of the input coupling elements being optimized to cover a specific range of angles of incidence, such that the response or the properties of the light coupled out of the photonic integrated circuit are insensitive to the direction of light incidence on the photonic integrated circuit.