Fabricating fiber Bragg gratings using phase modulated direct UV writing

The authors present a direct UV writing approach to fabricate fiber Bragg gratings (FBGs) and gratings in photolithographic waveguides. The technique uses two coherent UV beams, which are focused to a small spot (~7µm diameter) at the point at which they overlap. The resulting interference pattern at the foci consists of fringes which are used to define several grating planes per exposure, giving greater design flexibility and a significantly larger accessible spectral range compared to traditional approaches. The typical index contrast during grating fabrication is observed to be 4.7x10-3, at writing speeds of 8 mm/min

Propagation loss measurement using ultra-broadband chirped Bragg gratings in integrated UV written waveguides

Waveguide propagation loss is a key parameter for integrated devices, yet characterisation of this parameter can be challenging. This is especially true for more complex integrated devices where it can be difficult to extract the propagation loss using cut-back measurement or Fabry-Pérot methods. An ideal technique would perform the measurement in situ, and be able to determine variations in the loss along the waveguide. We shall present our latest work on measuring propagation losses of integrate waveguides using chirped gratings. In addition to the above preliminary work we aim to make use of the cavity to provide another estimate of loss and use the chirped grating to measure variation in loss along our waveguides

Flexible photonics in low stiffness doped silica for use in fibre reinforced polymer composite materials

The production of a flexible photonic device in doped silica with a Young’s modulus that is significantly less than that of traditional silica glass is described. Here the purpose of reducing the modulus is to make planar sensors more applicable for integration into fibre reinforced polymer composite structures. The flexible planar substrate (58 µm thick) consists of three doped silica layers, fabricated using sacrificial silicon wafer processing. It is demonstrated that a Young’s modulus of around 40 GPa can be achieved in comparison to a value above 70 GPa for typical silica glass. The optical response of a few mode waveguide that is direct UV written within the central core layer of the flexible glass platform is described. The mechanical stiffness of the platform is determined using nano-indentation tests and confirmed in mechanical tests that demonstrate clearly the flexible nature of the platform. To assess usability for applications integrated into structures undergoing mechanical loading the fatigue lifetime for one million bending cycles is investigated. No degradation to the optical response was observed under the performed testing

High-birefringence direct-UV-written silica waveguides for heralded single-photon sources at telecom wavelengths

We present design, fabrication and characterization of direct-UV-written silica-on-silicon waveguides using novel silicate glasses made by flame hydrolysis deposition. We report waveguide birefringence from 5.24 ± 0.18×10-4 to 5.79 ± 0.10×10-4 suitable for heralded single-photon sources at telecom wavelengths

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

Terahertz bandwidth photonic Hilbert transformers are proposed and experimentally demonstrated. The integrated device is fabricated via a direct UV grating writing technique in a silica-on-silicon platform. The photonic Hilbert transformer operates at bandwidths of up to 2 THz (~16nm), which is at least ten fold greater bandwidth than any previously reported experimental approaches. Achieving this performance requires detailed knowledge of the system transfer function of the direct UV grating writing technique, this allows improved linearity, and yields THz bandwidth Bragg gratings with improved spectral quality. By incorporating a flat-top reflector and Hilbert grating with a waveguide coupler an ultra wideband all-optical single-sideband filter is demonstrated

Small-spot UV-written apodised fibre Bragg gratings at 780 nm

Fibre Bragg gratings (FBG) are versatile devices in photonics, with applications ranging from laser cavities to various sensor geometries. Most operate at telecoms wavelengths, but for applications found in quantum information processing the wavelength of 780 nm is widely used due to the atomic transition of rubidium and the availability of high efficiency silicon single-photon detectors at this wavelength

Fiber Bragg gratings fabricated using highly detunable small-spot uvwriting around 1550 nm

We shall present a flexible technique for fabricating fiber Bragg gratings for use around 1550nm. The approach uses small-spot UV-writing on a suspended fiber to achieve highly apodised, chirped gratings with a wide tuning range

45° tilted gratings for silica-based integrated polarizers

We report a novel study and demonstration of a broadband tilted grating-based integrated polarizer on a silica platform and demonstrate a polarisation extinction ratio of 4.9±0.4dB and operation in the C-band

At the cross-roads of effective quantum information processing with integrated optical gates

The use of a silica integrated optical platform developed for the telecoms industry is allowing demonstrations of quantum operations with single photons and Bragg gratings that are challenging notions of classical computing. Operations such as Boson Sampling, number resolving photon detection at 1550nm, quantum teleportation and non-classical interferometry will be reported