1：Experimental Design and Method Selection

The research demonstrates an efficient electro-optic (EO) modulator that is mechanically tunable on a multiple optical waveguide system functioned with a soft capacitor structure incorporating graphene and poly(methyl methacrylate) (PMMA). The flexible capacitor can be mechanically detached and re-attached from and onto a rigid surface of the waveguide.

2：Sample Selection and Data Sources

Graphene was synthesized on a Cu foil via chemical vapor deposition (CVD). The graphene with the PMMA layer was transferred to the substrate after washing the etchant three times in distilled water.

3：List of Experimental Equipment and Materials

Cu foil (Alfa Aesar, 25 um, 99.8%), PMMA (Sigma Aldrich, MW = 996 k), chlorobenzene (Sigma aldrich, anhydrous, 99.8%), ammonium peroxydisulfate (CAS No. 7727-54-0), single mode fiber (Corning, SMF-28e), epoxy resin (EPO-TEK, 353ND), sandpapers (Thorlabs, LF03P), translation stage (SIGMAKOKI, TSD-605C), rotation stage (SIGMAKOKI, KSP-606M), goniometer stage (SIGMAKOKI, GOH-60A50), continuous wave laser (Anritsu, MT9810A), fiber type polarization controller, DC power supply (KEYSIGHT, E36106A), optical spectrum analyzer (YOKOGAWA, AQ6370C), pattern generator (KEYSIGHT, 33120A), electrical amplifier (Mini-circuit, ZHL-6A+), bias tee (Mini-circuit, ZFBT-6GW-FT+), photodetector (EOT, ET-3500F), RF spectrum analyzer (Keysight, N9000B.26G).

4：Experimental Procedures and Operational Workflow

Graphene was synthesized via CVD and transferred using a wet-transfer method. The graphene capacitor structure was fabricated by transferring the PMMA/graphene layers onto the electrode-patterned SiO2/Si substrate twice. The fabricated graphene capacitor structure was physically contacted with the D-shaped fiber using a set of precise translation stages. The modulation effects were analyzed by propagating a continuous wave laser into the D-shaped fiber in physical contact with the graphene capacitor.

5：Data Analysis Methods

The modulated optical signals were converted to electrical signals by a photodetector and analyzed by an optical power meter and an RF spectrum analyzer.