3-bit writing of information in nanoporous glass by a single sub-microsecond burst of femtosecond pulses.

We have found that a single sub-microsecond burst of femtosecond laser pulses produces a sub-micrometer cavity possessing the homogeneous birefringence with slow-axis orientation perpendicular to polarization of the laser beam in high-silicate nanoporous glass. Retardance and the root mean square of slow-axis orientation are investigated in dependence on the energy and the number of pulses in the burst. A burst of just three pulses with 98 ns inter-pulse intervals has been shown to induce homogeneous birefringence, and a burst of four pulses has provided birefringence with retardance of 35 nm, which is sufficient for reliable readout of the information recorded with multilevel encoding in slow-axis orientation.

Multilevel data writing in nanoporous glass by a few femtosecond laser pulses.

Multidimensional data recording inside nanoporous high-silica glass by a femtosecond laser beam has been investigated. It is shown that three femtosecond laser pulses at pulse repetition rates up to 1 MHz are sufficient for recording 3 bits of information inside nanoporous glass, which is an order of magnitude lower than the number of pulses required for data writing in silica glass and provides a corresponding gain in the data writing speed. Multilayer data recording and reading were demonstrated providing the storage density corresponding to the capacity of 25 GB in the optical compact disc form factor.