Patent ID: 8208770

Claim:
An optical deflection method comprising: emitting control light and signal light into a light absorption layer in a thermal lens forming optical element so that the control light and the signal light converge at different convergence points in the light absorption layer, wherein a wavelength of the control light is different from a wavelength of the signal light, the wavelength of the control light is selected from a wavelength band that the light absorption layer can absorb, and the wavelength of the signal light is selected from a wavelength band that the light absorption layer cannot absorb; and causing convergence and divergence of the control light and the signal light on an incidence plane of the light absorption layer or its vicinity in a light traveling direction, so that a thermal lens can be reversibly formed in the light absorption layer due to a temperature increase occurring in a region where the control light is absorbed and its peripheral region, and the refractive index of the thermal lens changes to change a traveling direction of the signal light, wherein beam-condensation or convergence of the control light and the signal light is caused in a range of 0 μm to +60 μm from the incidence plane of the light absorption layer in the light traveling direction, and wherein a distance between a convergence point of the control light and a convergence point of the signal light is in a range of 25 μm to 50 μm in a direction perpendicular to an optical axis.