Patent ID: 7266277

Claim:
An optical device that connects, by a signal beam, between an externally inputted input signal and an output signal to be outputted, the optical device comprising: a sheet-form optical transmission line having a refractive index distribution such that a highest refractive index part is provided in a direction of a thickness of the optical transmission line and a refractive index does not increase with distance from the highest refractive index part in the direction of the thickness of the optical transmission line, wherein a signal beam corresponding to the input signal is made incident on the optical transmission line as an incident beam, wherein inside the optical transmission line, the incident beam is transmitted, in a direction of a length of the optical transmission line that is orthogonal to the direction of the thickness of the optical transmission line, in multiple modes having a plurality of eigenmodes in a direction of a width of the optical transmission line that is orthogonal to both the direction of the length of the optical transmission line and the direction of the thickness of the optical transmission line, and an exiting beam is generated by the plurality of eigenmodes interfering with each other in the direction of the length of the optical transmission line, wherein the exiting beam is made to exit from the optical transmission line, and the output signal corresponding to the exiting beam is outputted, wherein the optical transmission line has a refractive index distribution such that a central position in the direction of the thickness of the optical transmission line has the highest refractive index and the refractive index does not increase with distance from the central position, and wherein the optical transmission line is made of polysilane, and the refractive index distribution is provided by an oxygen concentration distribution when the polysilane is cured.