Optical deflection device and LIDAR apparatus

An optical deflection device that is a silicon photonics device comprising periodic structures of a refractive index, wherein the periodic structures comprise:

• a first periodic structure comprising a second refractive index medium at a period a in a first refractive index medium that is a silicon substrate, the second refractive index medium including a refractive index different from that of the first refractive index medium, the first periodic structure constituting an optical waveguide part, and the optical waveguide part including at least one end in a periodic direction as an incident end;
• and
• a second periodic structure comprising the second refractive index medium at a period Λ(a<Λ≤2a) that is longer than the period a of the first periodic structure in the first refractive index medium, the second refractive index medium including a refractive index different from that of the first refractive index medium, the second periodic structure constituting a diffraction grating, and the diffraction grating including a side end in the periodic direction as an emission end, wherein
• a position where the second periodic structure is disposed is a peripheral part of an intensity distribution of light propagating through the optical waveguide part composed of the first periodic structure,
• the period a is a=λ/2n (n is an equivalent refractive index of the light propagating through the optical waveguide part composed of the first periodic structure, and λ is a wavelength near a Bragg wavelength), and
• the diffraction grating is any one of
• an air-bridge diffraction grating comprising an air layer between air-bridge slow light waveguides or between claddings of an cladding embedded slow light waveguide,
• an embedded diffraction grating, in the cladding in which the cladding embedded slow light waveguide is embedded, embedded in an upper part of an upper cladding, in a lower cladding, or a lower cladding, and
• a diffraction grating formed on the silicon substrate.

An optical deflection device that is a silicon photonics device comprising periodic structures of a refractive index, wherein the periodic structures comprise:

• a first periodic structure comprising a second refractive index medium at a period a in a first refractive index medium that is a silicon substrate, the second refractive index medium including a refractive index different from that of the first refractive index medium, the first periodic structure constituting an optical waveguide part, and the optical waveguide part including at least one end in a periodic direction as an incident end;
• and
• a second periodic structure comprising the second refractive index medium at a period Λ(a<Λ≤2a) that is longer than the period a of the first periodic structure in the first refractive index medium, the second refractive index medium including a refractive index different from that of the first refractive index medium, the second periodic structure constituting a diffraction grating, and the diffraction grating including a side end in the periodic direction as an emission end, wherein
• a position where the second periodic structure is disposed is a peripheral part of an intensity distribution of light propagating through the optical waveguide part composed of the first periodic structure,
• the period a is a=λ/2n (n is an equivalent refractive index of the light propagating through the optical waveguide part composed of the first periodic structure, and λ is a wavelength near a Bragg wavelength),
• the periodic structure is a planar periodic structure of a photonic crystal comprising circular holes,
• the first periodic structure is a two-dimensional photonic crystal waveguide comprising a linear defect in the planar periodic structure, and
• the second periodic structure is a double periodic structure in which two types of circular holes with different diameters, which form the first periodic structure, are repeated along the two-dimensional photonic crystal waveguide in the same rows at a period longer than a period at which the circular holes of the first periodic structure are repeated.