Wavelength filter
View Patent ↗Provided is a wavelength filter including: an optical waveguide core that includes n (n is an integer greater than or equal to 2) number of mode conversion parts and n−1 number of cavity parts that are alternately connected to each other in series; and cladding that surrounds the optical waveguide core. The mode conversion parts convert light having a specific wavelength of a p-order mode (p is an integer satisfying p≥0) into light of a q-order mode (q is an integer satisfying q>p) and reflect the light. The cavity parts match phases of the light having the specific wavelength of the p-order mode propagating through the cavity part.
1. A wavelength filter comprising:
an optical waveguide core including n (n is an integer greater than or equal to 2) number of mode conversion parts and n−1 number of cavity parts, the mode conversion parts and the cavity parts being alternately connected to each other in series; and
cladding surrounding the optical waveguide core,
wherein
the mode conversion parts convert light having a specific wavelength of a p-order mode (p is an integer satisfying p≥0) into light of a q-order mode (q is an integer satisfying q>p) and reflect the light,
the cavity parts match phases of the light having the specific wavelength of the p-order mode propagating through the cavity parts,
the optical waveguide core further includes an input-side tapered part connected to a mode conversion part disposed at a farthest end in the series of the mode conversion parts and the cavity parts alternately connected to each other,
a width of the input-side tapered part continuously expands from one end of the input-side tapered part toward another end of the input-side tapered part, the other end of the input-side tapered part being connected to the mode conversion part disposed at the farthest end, and
the one end of the input-side tapered part has a width corresponding to the p-order mode.
2. The wavelength filter according to claim 1 ,
wherein gratings are formed in the mode conversion parts, and
the gratings satisfy 2π/Λ=2π(n p +n q )/λ with respect to a specific wavelength λ, where Λ represents a grating period, n p represents an equivalent refractive index to the light having the specific wavelength of the p-order mode, and n q represents an equivalent refractive index to the light of the q-order mode.
3. The wavelength filter according to claim 2 ,
wherein the mode conversion parts include a base formed to stretch in a length direction of the mode conversion parts and a plurality of protrusions periodically formed on side surfaces of the base,
each of the protrusions has a unique protrusion amount, and
the protrusion amount includes at least two or more different values.
4. The wavelength filter according to claim 1 , wherein some or all of lengths of the mode conversion parts are different from each other.
5. The wavelength filter according to claim 1 , further comprising:
an electrode for applying heat to the cavity parts, the electrode being formed at a position at which the cavity parts are covered via the cladding.