Imaging of single-step UV-laser-written channel waveguides by confocal micro-luminescence

We report on the observation of confocal micro-luminescence originated by defects created in direct UV written silica-on-silicon waveguides. Spatial and spectral analysis of the visible luminescence bands was performed with 488nm excitation. This has revealed the UV formation of different defects which are related to the different compositions of core and cladding layers

Quantitative determination of photosensitivity proximity effects in multi-exposure direct UV writing for high density integrated optics

UV direct writing is used to write planar channel waveguide gratings and simultaneously investigate photosensitivity proximity effects. Increases are seen up to 9µm away from the initial exposure with maximum effective index increase of 8.3 x 10-4

Towards high-speed liquid crystal electrically tunable planar Bragg gratings for integrated optical networks

Liquid crystal-based integrated optical devices offer the potential for high speed and dynamically tunable optical switches in modern telecommunications networks. Here, electrically tunable devices have major advantages over their thermal counterparts, with superior response times and low operating voltages (~100V). Our approach to achieving such devices is to fabricate planar optical waveguides with integrated Bragg gratings via direct UV writing1 into silica-on-silicon samples with evanescent field coupling into a liquid crystal overlay through an etched window (Fig. 1(a)). Such electrically tunable devices work on the principle of shifting the Bragg wavelength by modifying the effective index of a waveguide in a multilayer substrate. Electrically controlled liquid crystal birefringence modifies the waveguide effective index, producing a Bragg wavelength shift. In our early samples, Merck 18523 nematic liquid crystal is used as it has a compatible refractive index to silica (n=1.49 at lambda=1550nm). Homeotropic alignment of the liquid crystal is provided by application of a surfactant layer

100 GHz electrically tunable planar Bragg gratings via liquid crystal overlay

We demonstrate 114GHz electrically tunable liquid crystal Bragg gratings using 170Vpp voltage. The devices were made using direct UV grating writing and use evanescent coupling into an electrically tuned nematic liquid crystal. Reconfigurable integrated optical devices are essential in today's dense and complex telecommunication meshes. A commonly employed component on the silica platform fulfilling the above role is a planar Bragg grating. The ability to tune the reflection peak of these gratings is one of the key enablers in realizing an all optical dynamic network. To date, little has been reported on electrically tunable planar Bragg gratings given their potentially superior response times over temperature tuned devices. Such electrically tunable devices work on the principle of shifting the Bragg wavelength by modifying the effective index of a waveguide in a multilayer substrate. One route to achieve this is by overlaying the grating with a liquid crystal as many liquid crystals display refractive index anisotropy that can be electrically manipulated. Modifying the liquid crystal refractive index subsequently alters the effective index of the waveguide, leading to Bragg wavelength shift. Using this approach, Sparrow et al [1] have previously demonstrated 35GHz tunability at 1560nm using 80Vpp (peak-to-peak) square-wave with 250mm-spaced aluminium electrodes. Here, we report a maximum tunability of 114GHz at 1561.8nm using patterned ITO glass electrodes with 170Vpp voltage at 1kHz. Two distinct threshold behaviors which manifest only during the increase of supply voltage were also observed

Direct UV written optical waveguides in flexible glass flat fiber chips

A glass based substrate technology that fills the gap between a truly flexible extended length distributed sensor medium and the multi-functionality of optical chips is demonstrated. Flat Fiber chips will open further degrees of freedom to control the behavior of light via mechanical manipulation. A flexible flat format will also allow straightforward incorporation into smart structures. Coupled with low manufacturing costs, these flexi-chips can also be a key enabler to disposable high-end sensing devices or fully distributed point sensors. In this work, Bragg gratings were used to demonstrate the optical flatness of the Flat Fiber core layer. Furthermore, the effective index values obtained from the grating experiment were input into a dynamic model, subsequently proving the influence of the dumbbell shaped Flat Fiber cross section on the resultant UV written waveguides. Evanescent field sensing was also demonstrated by adopting a stepped Bragg approach