Design and Analysis of Ultralow Voltage Graphene on the Silicon Rich Nitride Tunable Ring Resonator-Based Add-Drop Filter for DWDM Systems

Table 1

Classic materials used in ring resonator-based tunable devices compared with innovative materials on the basis of optical properties to address thermal, polarization, and low tuning efficiency while keeping CMOS-compatibility [27, 37].

Materials	Refractive index	TOC (×10^−4/K)	CTE (×10^−6/K)
SiO2	1.445	0.1	0.38
Si	3.478	1.8	2.6
Si3N4	2.198	0.24	3.0
Polymer	1.3∼1.66	−4.5.0∼−1.0	200
TiO2 (Sputtered film)	2.42	−1∼2.15	11.8
TiO2 (Evaporated film)	2.13	−7.0∼−3.0	11.8
Sol-gel	1.07∼1.5	−3.0∼−0.8	—