Apparatus and method for optical frequency conversion

A method of manufacturing an optical frequency converter configured to at least one of double and/or halve a carrier frequency of an input optical signal, the method comprising:

• forming a first insulator on a substrate;
• forming a patterned non-centrosymmetric non-linear crystalline material over a portion of a surface of the first insulator;
• forming a first centrosymmetric non-linear crystalline material and a second centrosymmetric non-linear crystalline material from portions of the patterned non-centrosymmetric non-linear crystalline material, wherein each of the first centrosymmetric non-linear crystalline material and the second centrosymmetric non-linear crystalline material is adjacent to a different side of a remaining portion of the patterned non-centrosymmetric non-linear crystalline material;
• and
• forming a second insulator over exposed surfaces of the first insulator, the first and the second centrosymmetric non-linear crystalline material, and the remaining portion of the patterned non-centrosymmetric non-linear crystalline material.

A method of operation of an optical frequency converter cladding, a core comprising non-centrosymmetric non-linear crystalline material, a first portion of centrosymmetric non-linear crystalline material, and a second portion of the centrosymmetric non-linear crystalline material, wherein the non-centrosymmetric non-linear crystalline material is between the first portion and the second portion, wherein the core is in the cladding, wherein the cladding has an index of refraction lower than the index of refraction of the core, the method comprising:

• receiving, at a first port of the optical frequency converter, an input optical signal in a transverse electric or magnetic mode and having a first carrier frequency;
• and
• generating, from the input optical signal and only in the non-centrosymmetric non-linear crystalline material, an output optical signal in respectively a transverse electric or magnetic mode and including at least one signal component having a second carrier frequency which is one half of or twice the first carrier frequency;
• wherein an order of the transverse electric or magnetic mode of the input optical signal is higher than an order of respectively the transverse electric or magnetic mode of the output optical signal, and wherein each of the first portion of the centrosymmetric non-linear crystalline material and the second portion comprises a non-linear crystalline material of the non-centrosymmetric non-linear crystalline material (a) in which ionic elements of the non-linear crystalline material have each been replaced by a proton and/or (b) with additional ions.