Silicon Thermo-Optic Switches with Graphene Heaters Operating at Mid-Infrared Waveband

• Published in: Nanomaterials (Basel, Switzerland) Vol. 12; no. 7; p. 1083
• Main Authors: Zhong, Chuyu, Zhang, Zhibin, Ma, Hui, Wei, Maoliang, Ye, Yuting, Wu, Jianghong, Tang, Bo, Zhang, Peng, Liu, Ruonan, Li, Junying, Li, Lan, Hu, Xiaoyong, Liu, Kaihui, Lin, Hongtao
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 25.03.2022; MDPI
• Subjects: 2 μm waveband; Chemical perception; Chemical vapor deposition; Chemoreception; Cladding; Electric potential; Energy efficiency; Extinction; Figure of merit; Graphene; graphene heater; Heat conductivity; Heaters; Lasers; Light; Mach-Zehnder interferometers; Micrometers; mid-infrared; Modulation; Nanomaterials; Optical communication; Optical interconnects; Optical properties; Optics; Performance evaluation; Phase shifters; Photonics; Polymers; Power consumption; Power management; Response time; Silicon; Switches; thermo-optic switch; Voltage; Wavelengths; graphene heater; 2 μm waveband; thermo-optic switch; mid-infrared
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano12071083

The mid-infrared (MIR, 2-20 μm) waveband is of great interest for integrated photonics in many applications such as on-chip spectroscopic chemical sensing, and optical communication. Thermo-optic switches are essential to large-scale integrated photonic circuits at MIR wavebands. However, current technologies require a thick cladding layer, high driving voltages or may introduce high losses in MIR wavelengths, limiting the performance. This paper has demonstrated thermo-optic (TO) switches operating at 2 μm by integrating graphene onto silicon-on-insulator (SOI) structures. The remarkable thermal and optical properties of graphene make it an excellent heater material platform. The lower loss of graphene at MIR wavelength can reduce the required cladding thickness for the thermo-optics phase shifter from micrometers to tens of nanometers, resulting in a lower driving voltage and power consumption. The modulation efficiency of the microring resonator (MRR) switch was 0.11 nm/mW. The power consumption for 8-dB extinction ratio was 5.18 mW (0.8 V modulation voltage), and the rise/fall time was 3.72/3.96 μs. Furthermore, we demonstrated a 2 × 2 Mach-Zehnder interferometer (MZI) TO switch with a high extinction ratio of more than 27 dB and a switching rise/fall time of 4.92/4.97 μs. A comprehensive analysis of the device performance affected by the device structure and the graphene Fermi level was also performed. The theoretical figure of merit (2.644 mW μs ) of graphene heaters is three orders of magnitude higher than that of metal heaters. Such results indicate graphene is an exceptional nanomaterial for future MIR optical interconnects.