1：Experimental Design and Method Selection

The design of the waveguide dimensions and AWG geometry was performed with commercial software WDM Phasar under consideration of the refractive indices of the applied materials. The waveguide dimensions were chosen to be as small as possible, while still being reliably producible with conventional contact lithography.

2：Sample Selection and Data Sources

SU-8 2002 photoresist was chosen as core material, polymethy-methacrylate (PMMA) as cladding, and silica as substrate.

3：List of Experimental Equipment and Materials

M-2000UI variable angle incidence spectroscopic ellipsometer, broad-spectrum laser (SC-5, Yangtze Soton Laser), optical spectrum analyzer (MS9740A, Anritsu), mercury discharge lamp (peak emission wavelength, 365 nm; irradiance, 23 mW/cm2, ABM-USA, Inc.).

4：Experimental Procedures and Operational Workflow

Negative photoresist SU-8 2002 was spin-coated as the core layer onto the silica substrate layer at a rotational speed of 1500 r/min and prebaked at 95 °C for 10 min. Then the coated chip was exposed to UV light for 3 s and post-baked at 95 °C for 10 min. After that, the unexposed SU-8 polymer was removed and then hard-baked at 125 °C. Finally, 5-μm-thick PMMA upper cladding was spin-coated on the waveguide cores and baked at 125 °C for 2.5 h.

5：Data Analysis Methods

The transmission spectrum of each channel of the AWG was monitored with the optical spectrum analyzer.