Photoinscription domains for ultrafast laser writing of refractive index changes in BK7 borosilicate crown optical glass

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].…”

“…Low intensity in a narrow processing window induces soft positive isotropic refractive index changes involving changes of electronic configuration and polarizabillity (type I) [86][87][88]; intermediate intensity results in birefringent anisotropic zones (type II) [89][90][91]; and high intensity generates voids in glass (type III) [92][93][94]. Isotropic and anisotropic changes determine specific optical signatures ranging from optical guiding to polarization sensitivity.…”

“…The possibility of modifying the refractive index of the local region in transparent materials by the use of focused intense femtosecond near-infrared laser pulses from a Ti:sapphire laser at 800 nm has attracted a lot of attention during the past several years mainly due to the localized refractive index change allowing for creating the building blocks of more complex photonic systems embedded in optical materials [70,82,[85][86][87]96,98,262]. The first pioneering work was conducted by H. Misawa in Matsuhara Microphotoconversion Project, Japan Science and Technology Agency.…”

Direct writing of birefringent elements by ultrafast laser nanostructuring in multicomponent glass

“…16 Recently, evidence for femtosecond laser-induced nanogratings has been observed in glasses other than SiO 2 , including several studies reported nanogratings in GeO 2 glass, [17][18][19] binary titanium silicate glass (ULE, Corning), 20,21 and two multicomponent borosilicate glasses (BK7 and Borofloat 33, Schott). 20,22 Germanium dioxide is formed by a three-dimensional network of [GeO 4 ] tetrahedra with all bridging oxygen atoms, whereas ULE glass also possesses structure similar to pure SiO 2 24 were not revealed using scanning electron microscopy despite the induced retardance was of the same level as in Borofloat 33. 20 The birefringence in both multicomponent glasses could only be observed in a very limited range of pulse durations (150-200 fs) and the induced retardance was more than one order of magnitude weaker than in fused silica glass.…”

Acquisition of Multi-Modal Images of Structural Modifications in Glass with Programmable LED-Array-Based Illumination

“…In phase-contrast microscopy, a ring aperture is placed at the condenser diaphragm to match the ring-shaped phase plate of the objective lens. Phase-contrast microscopy is useful for the observation of refractive index change in the glass to enhance the 2 of 9 contrast of modifications [12,13] because the refractive index change is small (typically on the order of 10 −2 -10 −3 [1]). These observation methods require replacement of optical elements: a special objective lens for phase-contrast imaging and an iris diagraph.…”