Fluorophore-doped xerogel antiresonant reflecting optical waveguides

• Published in: Optics express 2011-03, Vol.19 (6), p.5026-5039
• Main Authors: Llobera, A, Cadarso, V J, Carregal-Romero, E, Brugger, J, Domínguez, C, Fernández-Sánchez, C
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.19.005026

Rhodamine B and Alexa Fluor 430 fluorophores have been used as doping agents for xerogel waveguides defined over an antiresonant (ARROW) filter. This configuration has a significant level of integration, since it merges the waveguide, the light emitter and the filter in a single photonic element. Different technologies have been combined for their implementation, namely soft lithography, standard silicon-based technology and silicon bulk micromachining. The spectral response of 15-mm long waveguides without fluorophore is first analyzed as a function of the waveguide width. Here, it has been observed how the xerogel used has a high transparency in the visible spectra, having only significant absorption at the wavelength where the ARROW filter is in resonance. In a second step, identical waveguides but doped with two different concentrations of Rhodamine B and Alexa Fluor 430 are studied. In addition to the effect of the filter, fluorophore-doped xerogel waveguides show losses close to -2 dB (equivalent to 2 dB of light emission). In addition, it has been observed how an increase of the fluorophore concentration within the xerogel matrix does not provide with a emission increase, but saturation or even a decrease of this magnitude due to self-absorption. Finally, the total losses of the proposed waveguides are analyzed as a function of their width, obtaining losses close to 5 dB for waveguide widths higher than 50 µm.