The pulsed laser repetition rate was 57.8 GHz with the introduction of a resonator graphene. The limitations of the manufacturing process were exceeded by graphene being synthesized directly into standard copper (Cu) wires.
Pulsed lasers emit light repeatedly as they flash for a short period of time. They have the advantage of focusing more energy than a continuous wave laser, as the intensity remains unchanged over time. If digital signals are loaded into a pulsed laser, each pulse can encode a bit of data. In this respect, the higher the repetition rate, the more data can be transmitted. However, conventional fiber optic pulsed lasers have typically been limited to increase the number of pulses per second above the MHz level.
Korean Institute of Science and Technology (BOX) announced that a research team led by Dr. Yong-Won Song could generate laser pulses at the Center for Optoelectronic Materials and Devices at least 10,000 times the state of the art. This achievement was achieved by inserting an additional graphene * resonator into a pulsed fiber optic laser oscillator operating in the femtosecond field (10-15 seconds). Data transmission and processing speeds are expected to be significantly increased by applying this method to data communications.
* Resonator: a device that generates waves or vibrations at a certain frequency using the resonance phenomenon.
The KIST research team stated that the wavelength and intensity characteristics of laser light that change over time are correlated (** Fourier transform). If a resonator enters the laser oscillator, the wavelength of the pulsed laser is filtered periodically, thereby changing the pattern of laser intensity change. Based on this study, Song Researcher Principal synthesized graphene, which has the characteristics to absorb and eliminate weak light and increase intensity, passing strong light to the resonator. This controls the precise change in laser intensity at a high rate, so that the pulse repetition level could rise to a higher level.
** Transformed Fourier: A mathematical technique that decomposes a signal into frequency components. In other words, if the time function (signal) is transformed by Fourier, that function becomes a function of frequency.
In addition, graphene is usually synthesized on the surface of the catalytic metal and then the product is separated from the catalyst and transferred to the surface of the desired substrate. In this process, it has usually been a problem of damaged graphene or the introduction of impurities. The aforementioned KIST research team solved the problem of reduced efficiency in the manufacturing process by forming the surface directly on a copper wire directly obtained from graphene and covering the wire with an optical fiber for use as a resonator.
As a result, it was possible to achieve a repetition rate of 57.8 GHz, thus exceeding the limits of pulsed lasers in terms of repetition speed, usually limited to MHz. In addition, the characteristic of graphene, as heat is generated locally when the laser is absorbed, was used to tune the characteristics of the graphene resonator by applying an additional laser to the device.
KIST researcher Seong-Jae Lee said, “In the current scenario, as demand for data traffic is growing exponentially, ultra-fast pulsed lasers that operate at ultra-high speeds and support tuning features are expected to provide a new approach to adaptation. to this rapidly changing data-processing scenario. ”Research Director Song Research added:“ We hope to achieve the development of ultrasonic pulse lasers based on resonators and graphene in the field of nanomaterials-based optical information devices in technology development and related market. ”
Reference: Sungjae Lee and Yong-Won Song, Sungjae Lee and Yong-Won Song, on November 2, 2020, Graphene Autophase Lockers inserted in Resonators formed around a Cu Wire Hub for Resonator Rings 578 Gigahertz Pulsed Fiber Lasers. ACS Nano.
DOI: 10.1021 / acsnano.0c07355
This research was carried out with a grant from the Ministry of Science and ICT (MSIT) as part of the KIST R&D Organization Program. The results of the study were published in the latest issue ACS Nano (IF: 14,588, 5.25% best in JCR), International Journal of Nanotechnology.