INTEGRATED OPTICAL-DETECTION CELL-BASED ON BRAGG REFLECTING WAVE-GUIDES

In modern capillary electrophoresis systems with optical detection, the light beam is usually transmitted through the capillary crosswise. The disadvantages of this system are the small absorbent path length and the large amount of stray light. A new concept for a planar integrated optical detection cell with light guided in the liquid a defined length between 1 mm and 1 cm along the capillary is proposed, Using ARROWs (anti-resonant reflecting optical waveguides) or high-reflecting TiO2-SiO2 layers (Bragg layers), low-loss waveguiding can be established with confinement of the wave energy within the liquid exceeding 95%. Advantages of this system are an increased path length and a high signal-to-noise ratio while maintaining small inner dimensions below 20 mu m x 20 mu m. The stray light may be easily suppressed by masks on either side of the light path, which can be used as input slits for a spectrometer.