Gigahertz repetitive pulses with individual colors and shapes unlock new potential in ultrafast imaging and laser processing.
The generation and shaping of highly repetitive pulses holds great promise for a variety of applications, including high-speed photography, laser processing and acoustic wave generation. Gigahertz (GHz) pulses with intervals of ~0.01 ~ ~10 nanoseconds are particularly valuable in visualizing ultrafast phenomena and improving the efficiency of laser processing.
While methods exist for generating GHz bursts of pulses, challenges remain, such as low throughput of pulse energy, poor tunability of pulse intervals, and complexity of existing systems. In addition, shaping the spatial profile of each GHz burst pulse is limited due to insufficient response of spatial light modulators.
To address these challenges, a team of researchers from the University of Tokyo and Saitama University has developed an innovative optical technology called "spectrum shuttle" that simultaneously generates and shapes the spatial contours of GHz burst pulses.
Japan creates optical technology that simultaneously generates and shapes gigahertz pulses.
(Image source: University of Tokyo)
The method involves horizontally dispersing ultrashort pulses through a diffraction grating, using parallel mirrors to spatially separate the pulses into different wavelengths. These vertically aligned pulses are able to be individually spatially modulated using a spatial light modulator. The resulting modulated pulses, with different time delays in the GHz range, produce spectrally separated GHz bursts of pulses, each with a unique shape in its spatial profile.
The method is reported to be successful in generating GHz burst pulses with discrete variations in wavelength and time interval. It demonstrates the formation of spatial profiles including position shifts and peak splitting. The application of the method to ultrafast spectral imaging demonstrates its ability to capture the dynamics of different wavelength bands simultaneously.
The method facilitates ultrafast imaging in sub-nanosecond to nanosecond time scales, enabling the analysis of fast, non-repetitive phenomena. Its potential applications include revealing unknown ultrafast phenomena and monitoring fast physical processes in industrial environments. The ability to individually shape GHz pulses is also promising in precision laser processing and laser therapy.
It is noteworthy that the above team has proposed innovative methods that lead to a compact design and enhance its portability, making it applicable to scientific research facilities and various industrial technology sectors.
Keitaro Shimada, a PhD candidate at the University of Tokyo's Department of Bioengineering, said, "Our unique optical structure allows for the manipulation of ultrashort pulses with a three-dimensional optical path, resulting in unprecedented spatial manipulation of GHz burst pulses."
He added, "Spectrum shuttling provides a wide range of GHz burst pulses with intervals ranging from 10 picoseconds to 10 nanoseconds. I believe that applications based on our technology for a variety of targets, including plasma, metals and cells, will accelerate scientific discovery and technological innovation in industry and medicine."
This innovative technology opens the way for advancing ultrafast imaging, with implications for both scientific research and industrial applications. Its ability to simultaneously generate and form bursts of GHz pulses introduces a versatile tool for studying fast phenomena and enhancing laser-based processes.
