FORMATION OF BIREFRINGENT MICROSTRUCTURES IN FUSED SILICA BY A SUB-NANOSECOND BURST OF ULTRASHORT LASER PULSES
V. S. Tsarev, G. K. Alagashev, A. G. Okhrimchuk
Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia
Keywords: direct laser writing, birefringence, optical memory
Abstract
We investigate a method for forming birefringent microstructures in fused silica using a burst of ultrashort linearly polarized laser pulses separated by sub-nanosecond equidistant intervals. The method utilizes a tensile deformation wave induced by a pressure jump in the region of electron-hole plasma formation. This tensile deformation reduces the laser pulse energy required to reach the modification threshold of glass and to inscribe a birefringent structure. It is established that a sub-nanosecond burst of ultrashort laser pulses, comprising a first pulse with an energy no more than twice the glass modification threshold energy and followed by several subsequent pulses with energies an order of magnitude lower than the first, enables the creation of a submicron-sized birefringent structure. It is suggested that the mechanism of birefringence formation is based on the anisotropy of the deformation wave excited by the first pulse. This new approach to generating a sub-nanosecond burst is promising for increasing the writing speed of birefringent structures in fused silica, which can be used for fabricating various elements in photonics.
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