Laser-induced formation of polymer Bragg grating filters for Dense Wavelength Division
Multiplexing (DWDM) applications is discussed. Acrylate monomers halogenated with both
fluorine and chlorine, which possess absorption losses less than 0.25 dB/cm and wide choice of
refractive indices (from 1.3 to 1.5) in the 1.5 &mgr;m telecom wavelength region were used. The
monomers are highly intermixable thus permitting to adjust the refractive index of the composition
within ±0.0001. Moreover they are photocurable under UV exposure and exhibit high contrast in
polymerization. These properties make halogenated acrylates very promising for fabricating
polymeric waveguides and photonic circuits.
Single-mode polymer waveguides were fabricated on silicon wafers using resistless contact
lithography. Submicron index gratings have been written in polymer waveguides using holographic
exposure with He-Cd laser beam (325 nm) through a phase mask. Both uniform and apodized
gratings have been fabricated. The gratings are stable and are not erased by uniform UV exposure.
The waveguide gratings possess narrowband reflection spectra in the 1.5 μm wavelength region of
0.4 nm width, nearly rectangular shape of the stopband and reflectivity R > 99%. The fabricated
Bragg grating filters can be used for multiplexing/demultiplexing optical signals in high-speed
DWDM optical fiber networks.
Design and analysis of a novel pressure sensor based on a silicon-on-insulator asymmetric integrated vertical coupler is presented. The coupler is composed of a single mode low index waveguide and a thin silicon slab. Wavelength selective optical modulation of asymmetric vertical coupler is examined in detail. Its potential for sensing applications is highlighted as an integrated optical pressure sensor which can be realized by standard silicon micro-fabrication. Sensitivity of transmission of such couplers on refractive index change of silicon slab ensures that they are good candidates for applications requiring high sensitivities.