Formation of ferroelectric single-crystal architectures in LaBGeO5 glass by femtosecond vs. continuous-wave lasers

We have succeeded in crystallizing LaBGeO5 glass with an 800 nm, 250 kHz repetition rate femtosecond laser and observed different crystallization behavior when varying focal depth. Despite glass and crystal having the same composition, an unidentified off-stoichiometric phase appeared before crystalline LaBGeO5 when focusing deep inside the glass. Crystal lines were written in three dimensions inside the glass, and the results were compared to 1064 nm continuous-wave laser crystallization of Sm-doped LaBGeO5 by samarium atom heat processing. Notable differences were found in the structure of the lines and crystal growth rates, with femtosecond laser crystallization requiring much higher writing speeds. Raman spectra were highly consistent, suggesting that the lines were highly oriented with a consistent alignment between the crystal lattice and the growth direction.