Ultra-wide detuning planar Bragg grating fabrication technique based on direct UV grating writing with electro-optic phase modulation

Abstract

A direct UV grating writing technique based on phase-controlled interferometry is proposed and demonstrated in a silica-on-silicon platform, with a wider wavelength detuning range than any previously reported UV writing technology. Electro-optic phase modulation of one beam in the interferometer is used to manipulate the fringe pattern and thus control the parameters of the Bragg gratings and waveguides. Various grating structures with refractive index apodization, phase shifts and index contrasts of up to 0.8 × 10 −3 have been demonstrated. The method offers significant time/energy efficiency as well as simplified optical layout and fabrication process. We have shown Bragg gratings can be made from 1200nm to 1900nm exclusively under software control and the maximum peak grating reflectivity only decreases by 3dBover a 250 nm (~32THz) bandwidth.

Bragg grating based integrated photonic Hilbert transformers

“…We use the phase-modulated direct UV grating writing technique in a silica-on-silicon planar format [14], which provides a route to realize compact optical modules for integrated optical applications. These devices have the benefits of compact structures with fiber compatibility, long term thermal stability and could be used alongside etched silica-on-silicon devices..…”

“…The proposed planar structures were fabricated using the direct UV grating writing technique [14,15], shown in Fig. 5.…”

“…We can use the active phase control, e.g. thermal tuning [14], to compensate any PHT phase error. This initial proof-of-concept device demonstrates 12nm (~1.5THz) operation bandwidth PHT.…”

Terahertz bandwidth photonic Hilbert transformers based on synthesized planar Bragg grating fabrication

“…We use phase-modulated direct UV grating writing in a silica-on-silicon planar format [11], which provides an approach realizing compact optical modules for integrated optical applications. Furthermore, the linearity of this fabrication process is improved by considering the photosensitivity response and improving the spectral quality.…”

“…The proposed planar structures were fabricated using the direct UV grating writing (DGW) technique with phase modulation [11]. This method involves focusing two crossed laser beams (λ = 244 nm) into the photosensitive core layer of a planar sample.…”