Shape control of femtosecond-laser-induced birefringent structures by controlling spherical aberration

Birefringent optical elements can be fabricated by inscribing structures of nanogratings inside a silica glass by focusing femtosecond (fs) laser pulses. When birefringent optical elements are used as phase retarders, the retardance of the birefringence and transmittance are important properties to determine the quality as a phase retarder. Our target of application of fs-laser-induced birefringent structures inside a silica glass is a polarization imaging filter, which can capture the polarization distribution of detected light in a real-time. Larger retardance and higher transmittance of a filter are required to acquire polarization with higher accuracy and sensitivity. Therefore, it is necessary to elucidate the relationship between laser processing conditions and the induced birefringent structures. In this study, the authors have investigated fs-laser induced birefringent structures under various processing conditions. The authors have confirmed that the retardance and transmittance of the induced st...