High refractive index contrast in fused silica waveguides by tightly focused, high-repetition rate femtosecond laser

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

“…No dependence of the core shape on laser polarization is found by changing the femtosecond beam polarization from vertical to horizontal and circular states. A domain of optical waveguide writing with high refractive index contrast (0.022) is reported in fused silica by strong focusing of a 522 nm wavelength, 500 kHz repetition rate femtosecond laser with oil-immersion optics [309]. It is suggested that the effective 2-fold higher fluence provided by green femtosecond laser pulses enables a stronger interaction with fused silica compared to the fundamental wavelength.…”

Control of waveguide properties by tuning femtosecond laser induced compositional changes

“…19 Also, the small mode field diameter observed, well below 10 lm is a clear indication of the strong confinement achieved and large refractive index change induced. 11,18,19 The insets of Fig. 4 show the refractive index and La-K compositional maps of the same structure.…”

[INVITED] Ultrafast laser micro-processing of transparent material

“…Therefore, it is possible to control the amount of index change by changing the stress by some means. Eaton et al reported a successful fabrication of asymmetric waveguide structures with high refractive index (2.2 Â 10 À 2 ) using high-repetition-rate laser pulses (500 KHz) [75]. Hashimoto et al demonstrated just recently that even low-repetition-rate (1 KHz) laser pulses can induce high refractive index changes (2.9 Â 10 À 2 ) [76] They observed a movement of void during the fabrication process and attributed it to the index enhancement and the asymmetric cross-section of the waveguide.…”