Mikael Svalgaard

Symmetrical waveguide devices fabricated by direct UV writing

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

It is demonstrated that direct ultraviolet writing of waveguides is a method suitable for mass production of compact variable optical attenuators with low insertion loss, low polarization-dependent loss, and high dynamic range. The fabrication setup is shown to be robust, providing good device performance over a period of many months without maintenance.

Direct UV written Michelson interferometer for RZ signal generation using phase-to-intensity modulation conversion

An integrated Michelson delay interferometer structure making use of waveguide gratings as reflective elements is proposed and fabricated by direct ultraviolet writing. Successful return-to-zero alternate-mark-inversion signal generation using phase-to-intensity modulation conversion is demonstrated up to 40 Gb/s using the device. Compared to other implementations, the device is compact, inherently stable, and allows for easy customization of the pulsewidth by proper positioning of the gratings on a single coupler structure.

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

In this letter, we present the first demonstration of 2 /spl times/ 8 power splitters made in silica-on-silicon by direct ultraviolet (UV) writing. The fabricated components are compact and exhibit good performance in terms of loss, uniformity, and bandwidth, showing that direct UV writing can become a competitive technology for fabrication of low-cost integrated optical devices.

Direct characterization of ultraviolet-light-induced refractive index structures by scanning near-field optical microscopy

We have applied a reflection scanning near-field optical microscope to directly probe ultraviolet (UV)-light-induced refractive index structures in planar glass samples. This technique permits direct comparison between topography and refractive index changes (10/sup -5/-10/sup -3/) with submicrometer lateral resolution. The proposed method yields detailed information about the topography and index profiles of UV-written waveguides.

Characterizing Fiber Bragg Grating Index Profiles to Improve the Writing Process

We demonstrate an accurate method for identifying both systematic and random errors in a fiber Bragg grating (FBG) writing system and show its application to calibration of the writing process. We first measure the FBG impulse response using low-coherence interferometry, and then we calculate the refractive index profile using layer peeling. This yields the complex longitudinal refractive index profile, which includes both the index modulation amplitude and the effective index as a function of position along the FBG. We demonstrate how this measurement can be applied to the calibration of a scanning-beam dithered phase mask FBG writing system. We demonstrate the ability to identify errors in the writing process that would not likely be found from a measurement of the FBG reflection spectrum alone

Direct UV-Written Integrated Optical Beam Combiner for Stellar Interferometry

In this paper, we report the fabrication of an optical-beam combiner for stellar interferometry by means of direct ultraviolet (UV) writing. The component is shown to have good performance (fringe contrast > 95%, total loss ~0.7, -40-dB crosstalk, broadband operation covering at least the range 1.49-1.65 mum, and low differential chromatic dispersion). The overall performance exceeds that of similar components currently used for astronomical research. This result, combined with the fast-prototyping ability of UV writing, opens up new possibilities for the realization of highly optimized integrated-optical components for astronomical research

Sensitivity of a long-period optical fiber grating bend sensor

Summary form only given. We have investigated the sensitivity of long-period fiber gratings used in curvature measuring fibre optic sensors and found a bend coefficient of 0.77 dB cm/mrad. In the current setup this corresponds to the ability of detecting curvatures with a radius up to approximately 200 m.

Sidewall Roughness Measurement of Photonic Wires and Photonic Crystals

The performance of nanophotonic building blocks such as photonic wires and photonic crystals are rapidly improving, with very low propagation loss and very high cavity Q-factors being reported. In order to facilitate further improvements in performance the ability to quantitatively measure topological imperfections such as sidewall roughness on a sub-nm scale becomes essential. In this paper we use atomic force microscopy (AFM) on tilted samples to obtain the most detailed sidewall roughness measurements yet on nanophotonic structures.

UV written integrated optical beam combiner for near infrared astronomical interferometry

A near infrared integrated optical beam combiner for astronomical interferometry is demonstrated for the first time by direct UV writing. High fringe contrast >95%, low total loss (0.7 dB), low crosstalk and broadband performance is demonstrated.