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4 March 2019 Selective light modulation in waveguide grating using phase change materials (Conference Presentation)
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This paper reports for the first time a high-contrast, low-power reflective color filter employing a phase change material in a waveguide grating with different periods. Refractive index modulation is produced by crystallographic phase transition of Germanium Telluride (GeTe) using an external stimulus, such as heat. Nanostrips of GeTe are used due to their reliable, fast, and reversible phase transitions. These thin nanostrips reduce the total light absorption and yield a vivid, bright reflected color. Moreover, a buried optical waveguide consisting of a silicon nitride (Si3N4) core, which was grown between two layers of silicon dioxide (SiO2) cladding, is placed under these gratings to enhance the color contrast. The waveguide resonance is enhanced using a bottom palladium reflector and GeTe gratings above with different periods. Selective absorption within visible-NIR region that depend on the period of the grating and the phase of the GeTe is introduced within these devices for the first time. A unique anti-reflective coating was also re-introduced to suppress the surface reflection, thus enhancing the color contrast. Vivid reflected red and green colors have been shown for a device with active area of 400 μm2. These colors were electrically transitioned to blue and yellow, respectively, for several cycles. We further report that GeTe nanostrips with different cross-sectional areas demonstrate different phase transition behaviors. Thus, several colors were achieved within the same area of the device employing GeTe nanostrips with different periods.
Conference Presentation
© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mohsen Jafari, L. Jay Guo, and Mina Rais-Zadeh "Selective light modulation in waveguide grating using phase change materials (Conference Presentation)", Proc. SPIE 10921, Integrated Optics: Devices, Materials, and Technologies XXIII, 109210L (4 March 2019);


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