All-optical controlled variable optical attenuator using photochromic sol gel material

In this letter, we report an all-optical controlled polarization-dependent variable optical attenuator using a photochromic sol gel material developed by us. Optical attenuation is achieved by means of photochromic phase modulation in a Mach-Zehnder interferometric waveguide device fabricated with the sol gel film. A 5-mW/mm² light illumination at 532 nm on a 3-mm-long sol gel arm was found to produce a complete 2π phase shift between the two arms of the device, resulting in a 15-dB attenuation dynamic range for transverse-electric-polarization light. The response time of the device is around 50 ms. The wavelength-dependent performance of the device has been characterized across the entire C-band.