2020/08/13
Keio University
Associate Professor Hideyuki Maki and his research group at the Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, have developed a narrow-linewidth light source driven solely by light in the telecommunication wavelength band. This was achieved by integrating single-walled carbon nanotubes—a fine one-dimensional material approximately 1 nm in diameter—with optical devices (silicon photonics) fabricated on a silicon chip. This technology is expected to have applications in new on-chip optical devices on silicon, such as photonic integrated circuits and quantum cryptography communication chips integrated on silicon chips.
In addition to emitting light in the telecommunication wavelength band required for optical communications and silicon photonics, carbon nanotubes are also anticipated for quantum information applications such as quantum cryptography, due to their recently demonstrated ability to act as single-photon sources at room temperature and in the telecommunication wavelength band. However, many conventional carbon nanotube optical devices on silicon have not achieved direct coupling with silicon optical circuits. Even for devices coupled with silicon photonics, realization as on-chip optical devices has been challenging due to factors such as external optical excitation from above the chip and excitation drive at wavelengths other than the telecommunication band.
In this work, we have successfully developed an on-chip carbon nanotube light source where all excitation and emission can be operated in the telecommunication wavelength band. This was achieved by directly forming carbon nanotubes on the resonators of silicon photonics devices, which have optical waveguides as well as ring and disk resonators fabricated on a silicon chip. This configuration allows both the excitation light and photoluminescence (PL) emission to be input and output in-line entirely through the silicon waveguide. This technology makes it possible to use carbon nanotubes as a light source for silicon photonics. Therefore, it is expected to be applied to various on-chip integrated optical device technologies, such as photonic integrated circuits and optical interconnects based on silicon photonics—a promising next-generation technology for high-speed, high-integration, and low-power consumption integrated chips—as well as quantum cryptography chips that can operate at room temperature and in the telecommunication wavelength band for quantum cryptography technology, which is currently being put into practical use.
The results of this research were published in the online edition of the American Chemical Society's (ACS) *ACS Applied Nano Materials* on August 5, 2020.
For the full press release, please see below.