Georgia Tech researchers develop first thermally tuned, integrated SiC optical switch

Researchers from the Georgia Institute of Technology (Georgia Tech; Atlanta, GA) have created a silicon carbide (SiC) photonic integrated chip that can be thermally tuned by applying an electric signal. The approach could one day be used to create a large range of reconfigurable devices such as phase-shifters and tunable optical couplers needed for networking applications and quantum information processing.

Although most optical and computer chips are made of silicon, there is increasing interest in SiC because it exhibits better thermal, electrical, and mechanical properties than silicon while also being biocompatible and operating at wavelengths from the visible to infrared (IR).

Researchers led by Ali Adibi from the School of Electrical and Computer Engineering at Georgia Tech detail, in a paper in Optics Letters, how they integrated a microheater and a microring resonator onto a SiC chip. The accomplishment represents the first fully integrated and thermally tunable SiC optical switch that operates at near-IR wavelengths.

“Devices such as the one we demonstrate in this work can be used as building-blocks for next generation quantum information processing devices and to create biocompatible sensors and probes,” said the paper’s first author Xi Wu.

SiC is particularly attractive for quantum computing and communication applications because it has defects that can be optically controlled and manipulated as quantum bits, or qubits.

“The SiC-on-insulator platform our group pioneered is similar to the silicon-on-insulator technology widely used in semiconductor industry for a variety of applications,” said Tianren Fan, member of the research team. “It enables wafer-level manufacturing of SiC devices, paving the way toward commercialization of integrated photonic quantum information processing solutions based on SiC,” said Ali A. Eftekhar, member of the research team.

Fully exploiting the new platform’s unique capabilities required developing the ability to tune its optical properties so that a single chip-based structure can be used to provide different functions. The researchers accomplished this by using the thermo-optic effect in which changing a material’s temperature modifies its optical properties, such as refractive index.

They began by fabricating tiny ring-shaped optical cavities, or microring resonators, using the crystalline SiC-on-insulator technology. When an electric current is applied to the integrated microheater, it locally increases the temperature of the SiC microring and thus changes its resonant wavelengths thanks to the thermo-optic effect.

The researchers tested the performance of the fabricated integrated microring resonators and microheaters by applying different levels of electrical power and then measuring the optical transmission of the waveguide coupled to the microring resonator. Their results showed that it is possible to achieve high-quality resonators with low-power thermal tunability through a robust device that can be manufactured using existing semiconductor foundry processes.

The researchers are now working to build elements with the crystalline SiC-on-insulator platform for quantum photonic integrated circuits (PICs), including on-chip pump lasers, single-photon sources, and single-photon detectors that could be used with the tunable microring resonator to create a fully functional chip for advanced optical quantum computing.

SOURCE: Georgia Institute of Technology; https://www.ece.gatech.edu/news/627047/tunable-optical-chip-paves-way-new-quantum-devices