Symmetrical waveguide devices fabricated by direct UV writing

Abstract

Abstract-Power splitters and directional couplers fabricated by direct UV writing in index matched silica-on-silicon samples can suffer from an asymmetrical device performance, even though the UV writing is carried out in a symmetrical fashion. This effect originates from a reduced photosensitivity in the vicinity of previous exposed areas. The imbalance can be counteracted by an appropriate reduction of the applied scan velocity in areas, where a previous scan has been carried out nearby.

Variable optical attenuator fabricated by direct uv writing

“…The optical layout of the experimental setup is shown in Fig. 1 and is similar to that used in previous work [10], [13]- [15], except for the fact that we now have extended the setup to automatically compensate for the slow drift of the UV beam direction and power. The UV beam has a wavelength of 257 nm and is generated with an intracavity-frequency-doubled argon-ion laser.…”

“…The length of each splitter is roughly 3 mm. The scan velocity used for the input waveguide and the first written output arm is 200 m s. However, a slight reduction of the photosensitivity in the immediate surroundings of exposed areas leads to an asymmetric splitting ratio if the same scan velocity is applied in the second output arm [13]. Optimization showed that equal splitting was achieved when the scan velocity in the second arm was reduced to 70 m s. Making the waveguides join in the middle of the interferometer is not a problem, since the stages have an accuracy of 0.1 m. The MZI arm length as measured between the splitter branching points is 14.8 mm.…”

“…Each splitter is written in three scans starting from the branching point and moving outwards, as described in [13]. The length of each splitter is roughly 3 mm.…”

UV written integrated optical beam combiner for near infrared astronomical interferometry

“…For the coupler a large bandwidth is achieved for applied scan velocities of 100,900 µm/s in the upper,lower arm of the central coupling region. The splitters are made symmetrical by decreasing the scan speed in one of the output arms to 200 µm/s to compensate for a proximity effect [4]. The total device length is 15 mm and the fabrication time for one component is ~270 seconds.…”

Direct UV-Written Integrated Optical Beam Combiner for Stellar Interferometry

“…The performance of these subcomponents is controlled by tailoring the applied scan velocity during UV writing. Achieving symmetrical Y-branch splitters requires compensation of a proximity effect associated with UV writing [14], which is done by reducing the scan velocity in one of the output arms to 200 µm/s. The coupler section follows an asymmetric design to achieve a large bandwidth.…”