Patent ID: 8004748
Filing Date: 2011-08-23
Classification: G02F

Abstract:
1. A thermal lens forming element including an optical cell filled with a solution containing a dyestuff dissolved in a solvent, wherein the dyestuff does not absorb light having a wavelength identical to that of signal light and absorbs control light, wherein the optical cell includes a control light absorbing region where at least the control light can focus, wherein the solvent has a viscosity of 0 to 3 mPa·s at 160° C. or above, and a ratio of the viscosity of the solvent at 160° C. to a viscosity of the solvent at 40° C. is not less than 1 and not greater than 6, wherein the control light absorbing region is convergently irradiated with the control light having a wavelength selected from a wavelength band absorbed by the control light absorbing region and the signal light having a wavelength selected from a wavelength band not absorbed by the control light absorbing region, wherein the control light and the signal light have convergence points identical or different in their positions, wherein a thermal lens is formed based on a distribution of the refractive index reversibly formed due to an increase in temperature at a portion where the control light is absorbed or its peripheral region in the control light absorbing region, wherein the thermal lens forming element realizes the following states according to on/off of the control light: a state where the converged signal light is output from the thermal lens forming element with an ordinary divergence angle in a progressive direction if the control light is not emitted and the thermal lens is not formed; a state where the converged signal light is output from the thermal lens forming element with a divergence angle larger than the ordinary divergence angle if the convergence point of the control light agrees in position with the convergence point of the signal light when the thermal lens is formed under irradiation of the control light; and a state where the converged signal light is output from the thermal lens forming element with a divergence angle different from the ordinary divergence angle in a direction different from the progressive direction if the convergence point of the control light disagrees in position with the convergence point of the signal light when the thermal lens is formed under irradiation of the control light.