Patent ID: 8619351

Claim:
A optical phase shifter comprising: a thermo-optical element where a refractive index of the thermo-optical element with respect to an input optical signal is temperature dependent; a temperature change section contacting one end of the thermo-optical element, and a temperature of the temperature change section changes a temperature of the thermo-optical element to a desired temperature; a heat dissipation section disposed on an opposite side of the thermo-optical element than the temperature change section and which enters a state of thermal equilibrium at a different temperature than the temperature of the temperature change section; and a temperature buffer section disposed between and contacting the temperature change section and the heat dissipation section where the temperature buffer section has a heat resistance greater than the heat dissipation section, wherein the thermo-optical element is surrounded by an ambient gas, and wherein a product R 1 Ã—SÃ—h of a heat resistance R 1 of the thermo-optical element, an area S of a surface of the thermo-optical element surrounded by the ambient gas, and a heat transfer ratio h of the ambient gas is less than a desired refractive index distribution ratio Î´ of the thermo-optical element.