Single pass fs writing of photonics components in low-iron soda lime glass through selective pulse number control

This article presents single-pass, ultra-fast laser writing of different photonic components, based on modulating the laser pulse picker by an arbitrary waveform. The effect of various writing parameters on the induced refractive index change for obtaining positive index single-mode waveguides inside a low-iron soda lime glass sample is studied. An index contrast of 5.8 ×10 ^{- 3} is achieved. The technique can also inscribe a strong uniform Bragg grating waveguide (BGW) in the same writing passage with a transmission dip of 35 dB in the C-band, a mode taper to match a standard single-mode fiber, and a no-bend coupler. The inscription of BGW shows a strong dependence on the laser polarization state relative to the scan direction. Polarization parallel to the scan direction increases the attenuation level by around 10 dB compared to the orthogonal state writing. Furthermore, we show that the capability of this method for inscribing tapered waveguides improves coupling efficiency to the smf-28 fiber by an amount of 3.26 dB compared to the un-tapered waveguide. The effect of pulse numbers on mode-field diameter (MFD) allows the inscription of straight couplers with coupling constants ranging from 16.6 m^{- 1} to 42.4 m^{- 1} which has the benefit of no bending loss.