Different refractive index change behavior in borosilicate glasses induced by 1 kHz and 250 kHz femtosecond lasers

Abstract

Abstract:We report on different refractive index change (RIC) behavior in borosilicate glasses induced by focused 1 kHz and 250 kHz femtosecond (fs) laser irradiation. The influence of fs laser irradiation condition and annealing temperature on RIC was examined. Absorption, electron spin resonance and Raman spectra, and transmission electron microscope were used to clarify the mechanisms of the RIC. Smaller RIC (up to 10 −4 ) was observed after 1 kHz fs laser irradiation, while larger RIC (up to 10 −1 ) was detected after 250 kHz fs laser irradiation, which were ascribed to the formation of color centers and precipitation of nanocrystals, respectively. The result highlights that the mechanisms of RIC induced by fs laser can be very different depending on the irradiation conditions.

Femtosecond laser induced phenomena in transparent solid materials: Fundamentals and applications

“…Shifts of Raman peaks related to the (POP) sym and (PO 2 ) sym network vibration modes to lower wavenumbers in Er-Yb doped phosphate glass are observed in the regions of decreased refractive index induced by cumulative-heating thermal effects after irradiation by a high repetition rate femtosecond laser, consistent with the results in Ge-based glass [306,307]. With low repetition rates (1 kHz), positive refractive index is generated resulting from the formation of color centers in Yb doped phosphate glass, silica, etc, confirmed by Raman spectroscopy, refractive near-field profilometry, ESR spectroscopy, phase contrast microscopy, photoluminescence of defects and incoherent secondary light emission [87,95,300,301,308]. For the mechanical contributions, pressure wave is dertemined by a transient lens (TrL) method, developed by Sakakura et al [53,54,303,304].…”

“…Except some aluminum-silicate glasses, all other glasses so far studied exhibite a negative/nonuniform index change. For some glasses with more complex compositions, ions migration and exchange and crystal precipitation can also induce rearrangements of the glass structure accompanied with refractive index change [20,300,311,312]. As discussed above, the change in the refractive index of phosphate glasses induced in the high repitation rate regime is different from that in the low repitation rate regime.…”

“…Depending on the regime of laser interaction, particularly on the incident fluence, pulse duration, wavelength, laser polarization, focusing conditions and scanning speed, femtosecond laser pulses can induce either positive isotropic refractive index changes (Δn ~ 10 -4 -10 -3 ) or void-like rarefaction regions of lower density with compression shells, or self-organized nanoscale layered structures resulting in formation of birefringence with overall negative index changes [86,95,96,290,[296][297][298]. Several mechanisms are considered to be responsible for index changes: (i) thermal mechanisms (fictive temperature model), when higher density local structures are created after fast quenching from a high temperature melt [297,299], (ii) non-thermal mechanisms, when index changes originate from the generation of color centers [66,86,98,157,300,301], (iii) density changes originating from defects induced structural network reorganization (defects induced densification) [86,297,302], and (iv) mechanical contributions, when compaction and rarefaction of material result from the pressure wave release [53,54,303,304].…”

Nonlinear increase, invisibility, and sign inversion of a localized fs-laser-induced refractive index change in crystals and glasses

“…The shift in the absorption edge in BaAlBO 3 F 2 and borosilicate glasses has been observed by two other groups, but has not been investigated 34,35 . It is very difficult to obtain a quantitative measurement of the electronic resonance shift dλ 1 from the transmission spectrum (inset of Fig.…”

Time resolved measurements of gratings photo-induced by femtosecond pulses in a lead doped glass

“…The interaction of ultrafast laser pulses with soda-lime glasses and borosilicate glasses is also known for producing nonlinear effects including coloration. The latter also induces a change of the refractive index that is due to laser-induced color centers [5,6]. Hereafter, we have studied the impact of femtosecond laser-induced defects in a SF59 lead glass sample during the formation of photo-induced gratings.…”