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Ultra-precision Photonics Research Based on Ultrashort Femtosecond Lasers

Next-generation Femtosecond Oscillator Technology for Space Applications

“The ultrashort femtosecond laser oscillator (FSO), which was successfully tested for the first time in space over a year period in 2013 - 2014, is anticipated to promote diverse applications of ultra-precision photonics technologies to space environments. The fiber-based FSO together with its remote control system was qualified robust enough to endure harsh launching acceleration, severe thermal-vacuum cycles in orbits, and hazardous space radiation. Further improvements are being made in the FSO technology so that it can be deployed in the near future to carry out space missions such as satellite laser ranging, remote distance measurements and free-space optical communications between satellites and the ground station. In addition, the FSO technology is widely applicable to a broad range of industrial applications such as ultra-precision positioning for machine tools, nano-precision surface metrology and damage-free laser machining, which will play vital roles for the next-generation mass-production of semiconductors and flat-panel-displays.”

Space-compatible Femtosecond Laser Source

Femtosecond lasers of ultrashort pulse duration from hundreds to few fs (1 fs = 10-15 sec) are swiftly emerging as an important light source as it offers breakthroughs in various fields of science and technology in the 21st century. Since their establishment in 2008, the KIOST research team led by Professor Seung-Woo Kim has been dedicating their time and efforts on the ultra-precision photonics technology utilizing femtosecond lasers. With their excellence being highly recognized, the KIOST team was commissioned to develop a space-compatible femtosecond laser oscillator in January 2011 to be tested as a satellite payload for the STSAT-2C space mission. Through their hard work during a relatively short period of one and half year, the fiber-based femtosecond laser oscillator, named FSO in short, was made ready with a series of on-ground qualifications for its robustness against the launching acceleration, thermal-vacuum environment and space radiation. The FSO system was successfully launched into space in January 2013 and tested in actual space environments to validate its stable operation for a one-year mission period.

Through this accomplishment, Professor Kim’s team is recognized to have laid the foundation for diverse possibilities of the femtosecond laser for not only space missions but also industrial applications to be conducted in harsh environmental conditions. The ultrashort femtosecond laser technology is expected to be applicable in the following future basic science and engineering fields in space: high precision long-distance measurement between satellites flying in formation; altitude measurement from satellites to the ground of Earth or other planets; free-space optical communications between satellites and ground stations; high precision wavelength calibration of satellite spectrometers; next-generation optical clock development and utilization; Earth surveillance spectroscopic LIDAR technology for monitoring of global warming, fine dust, and yellow dust; and finally, numerous applications and advancements in future space applications such as remote time and frequency transfer between Earth and space.

In particular, the use of femtosecond laser for remote free-space optical communications is aimed to achieve unprecedented high-capacity data transmission by means of coherent phase modulation to an extent that the data amount of 1 hour of transfer time using the conventional microwave-based communications will be completed within 1 minute. The femtosecond-laser-based communications technology is expandable into multiple channels of different wavelengths using a single source without severe hardware burdens and complexities, thereby allowing for drastic enhancement of the transmission capacity so that the same transfer takes only few seconds. Moreover, compared to microwaves, the short-wavelength laser light used in communications provides strong directionality, making it useful in strengthening the security of space communications as demonstrated by NASA initiated single-channel optical communications between the moon and Earth in 2013 by light pulse intensity modulation.

It is also worthwhile to note that the large-size high-resolution space telescope technology using multiple satellites flying in formation requires precise measurement of the distance between satellites to form a large virtual telescope in space. For the purpose, precise position control of the small satellites in formation is critical, and the femtosecond laser is gaining interest as a viable light source in realizing this technology. In addition to space applications, the FSO technology is appropriate for a broad range of industrial applications requiring ultrashort light pulses at well-regulated repetition rates with high immunity to environmental disturbances. Examples include ultra-precision positioning for machine tools; nano-precision surface metrology; and damage-free laser machining for micro/nano structures fabrication, which will play vital roles for the next-generation mass-production of semiconductors and flat-panel-displays.

Prof. Kim, Seung-Woo
2014 Annual Report

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