Direct UV-written broadband directional planar waveguide couplers

Abstract

We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation.

Fabrication of 2 /spl times/ 8 power splitters in silica-on-silicon by the direct UV writing technique

“…The experimental setup is similar to that used in earlier work [3], except for the fact that the scanning accuracy has recently been improved by means of interferometric position feedback [6]. The UV beam has a wavelength of 257 nm and may be blocked using a shutter as required in the scanning process.…”

“…1(a). Two input channels are combined through an asymmetrical broad-band directional coupler [6], which is written in two scans. An asymmetric structure in the central coupling region is achieved by decreasing the scan velocity in the first arm while increasing it in the second arm.…”

UV written integrated optical beam combiner for near infrared astronomical interferometry

“…The incident UV power is 45 mW while the scan velocity is in the range 100−900 µm/s depending on the desired waveguide index step and width. For most sections of the layout a scan velocity of 280 µm/s is used, which yields a waveguide width of 6.1 µm and a final index step of 0.0085 [3]. Optical components for astronomical interferometry must have low losses since stellar light levels are typically low (picoWatts).…”

“…1) was fabricated. Beam interference (outputs D and E) is achieved with an ultrabroadband asymmetrical 3 dB directional coupler [3], while photometric outputs (outputs C and F) are realized using 3 dB power splitters. The performance of these sub-components is controlled by changing the applied scan speed during UV writing.…”

Using the photoinduced reversible refractive-index change of an azobenzene co-polymer to reconfigure an optical Bragg grating

“…This technique is based on the localised refractive index increase of a photosensitive planar glass layer through exposure to a tightly focused UV beam. The translation of this beam relative to a suitable substrate 65 allows for the definition of two-dimensional waveguide structures, without photolithographic or subsequent processing 8,9 . Furthermore, Bragg gratings can be written directly into the substrate by direct grating writing.…”