Table 2.

Performance list of TOPS with silicon substrate undercut designed and fabricated by different organizations

Heater type	Waveguide type	Test structure	Tuning efficiency/(mW·π–1)	Heating time/μs	Cooling time/μs	Organization	References
Tungsten	Single strip WG	MZI	1.42	198	227	IMEC	[50]
Silicide	Single strip WG	MZI	1.49	188	218	IMEC	[50]
Doped silicon	Single strip WG	MZI	1.42	151	217	IMEC	[50]
TiN	Single strip WG	MZI	0.49	144	122	IME	[52]
TiN	Single strip WG	MI	0.05	780	500	IME	[53]
Pt	Single strip WG	MZI	0.54	141	NR	OSU	[54]
TiN	Threefolded strip WG	MZI	0.5	640	700	Huawei	[57]
TiN	9-folded strip WG	MZI	0.095	750	1200	UBC	[58]

TiN: titanium nitride, WG: waveguide, NR: not reported, MZI: Mach–Zehnder interferometer, MI: Michelson interferometer