Electrochromic Infrared Light Modulation in Optical Waveguides

Electrochromic materials and devices have attracted much attention with their ability to tune the transmissions of visible to infrared (IR) light, allowing the creation of smart windows. This study presents a novel electrochromic device (ECD)‐based photonic device that can modulate IR light intensity in a planar optical waveguide ECD. To configure it, a multilayer ECD made of WO3 is integrated on a polymer optical waveguide platform. By using the waveguide to change the optical properties of the ECD electrically, IR light propagating along the optical waveguide core undergoes electroabsorption loss due to the change in charge carrier density in WO3 layer and its intensity is modulated with an extinction depth of 0.6 dB mm−1. Experimental results show that the device is capable of discrete intensity attenuation by applying a distinct level gate voltage. Periodic application of gate voltage leads the device to serve as an optical modulator on the order of subseconds. The results also confirm that a new approach to consider ECD‐based optical modulators can pave the way for the development of planar photonic‐integrated circuits and systems. An electrochromic device (ECD) is integrated on an optical waveguide platform, completing the configuration of electrochromic infrared light modulator. By electrically changing the optical properties of ECD, the propagating IR light along the waveguide core undergoes electroabsorption loss and the output intensity of light is periodically modulated.