BACKGROUND

1. Technical Field

The present disclosure relates to an optical device and to a photodetection system.

2. Description of the Related Art

Various devices capable of scanning a space with light have been proposed.

International Publication No. 2013/168266 discloses a structure that can perform optical scanning using a driving unit for rotating a mirror.

Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2016-508235 discloses an optical phased array including a plurality of nanophotonic antenna elements arranged in two dimensions. Each antenna element is optically coupled to a corresponding variable optical delay line (i.e., a phase shifter). In this optical phased array, a coherent light beam is guided to each antenna element through a corresponding waveguide, and the phase of the light beam is shifted by a corresponding phase shifter. In this manner, an amplitude distribution of a far-field radiation pattern can be changed.

Japanese Unexamined Patent Application Publication No. 2013-16591 discloses a light deflection element including: a waveguide including an optical waveguide layer through which light is guided and first distributed Bragg reflectors formed on the upper and lower surfaces of the optical waveguide layer; a light inlet for allowing light to enter the waveguide; and a light outlet formed on a surface of the waveguide to allow the light entering from the light inlet and guided through the waveguide to be emitted.

SUMMARY

One non-limiting and exemplary embodiment provides a novel optical device having a relatively simple structure.

Solution to Problem

In one general aspect, the techniques disclosed here feature an optical device including: a first waveguide that propagates light in a first direction; and a second waveguide including a first mirror, a second mirror, and an optical waveguide layer, the first mirror extending in the first direction and having a first reflecting surface, the second mirror extending in the first direction and having a second reflecting surface facing the first reflecting surface, the optical waveguide layer being located between the first mirror and the second mirror and propagating the light in the first direction. A forward end portion of the first waveguide is disposed inside the optical waveguide layer. In a region in which the first waveguide and the second waveguide overlap each other when viewed in a direction perpendicular to the first reflecting surface, at least part of the first waveguide and/or at least part of the second waveguide includes at least one grating whose refractive index varies periodically in the first direction.

According to the above aspect of the present disclosure, a relatively simple structure can be achieved.

It should be noted that general or specific embodiments of the present disclosure may be implemented as a device, a system, a method, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments will become apparent from the present specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the present specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages.

