The proposed “spectral shuttle” method produces gigahertz (GHz) burst pulses from an ultrashort pulse, with each pulse having a different wavelength and customizable spatial profile. These GHz burst pulses pave the way for a multitude of optical applications, including ultrafast imaging in the GHz range and high-quality, high-throughput laser processing with ultrashort laser pulse bursts. Credit: K. Nakagawa (University of Tokyo).
The generation and manipulation of high-repetition pulses shows great promise in various applications, including high-speed photography, laser processing, and acoustic wave generation. Gigahertz (GHz) burst pulses, with intervals ranging from ~0.01 to ~10 nanoseconds, are particularly popular for visualizing ultrafast phenomena and improving laser processing efficiency.
Although methods for producing GHz burst pulses exist, challenges persist, such as low pulse energy throughput, poor tunability of pulse intervals, and complexity of existing systems. Furthermore, the formation of the spatial profile of each GHz burst pulse faces limitations due to the inadequate response of the spatial light modulators.
To address these challenges, a research team from the University of Tokyo and Saitama University developed an innovative optical technique called “spectral shuttle”, which simultaneously enables the production of GHz burst pulses and shaping individual of their spatial profiles.
The method involves horizontally dispersing an ultrashort pulse through diffraction gratings, spatially separating the pulse into different wavelengths using parallel mirrors. These vertically aligned pulses undergo individual spatial modulation using a spatial light modulator. The resulting modulated pulses, with varying time delays in the GHz range, produce spectrally separated GHz burst pulses, each having a unique shape in its spatial profile.
As shown in Advanced Photonics Nexus, the proposed method successfully produced GHz burst pulses with discretely varied wavelengths and time intervals. It demonstrated the formation of spatial profiles, including position changes and peak splitting.
Application of the method to ultrafast spectroscopic imaging demonstrated its ability to simultaneously capture dynamics in different wavelength bands.
The method facilitates ultrafast imaging in sub-nanosecond time frames, enabling the analysis of rapid, non-repetitive phenomena. Its potential applications include the discovery of unknown ultrafast phenomena and the monitoring of rapid physical processes in industrial settings. The ability to individually shape GHz burst pulses also holds promise in precision laser processing and laser therapy.
Notably, the compact design of the proposed method enhances its portability, making it applicable in scientific research facilities and various industrial technology sectors.
“Our unique optical configuration enables the manipulation of ultrashort pulses with a three-dimensional optical path, enabling unprecedented spatial manipulation of GHz burst pulses,” explains Keitaro Shimada, a Ph.D. candidate in the Department of Bioengineering at the University of Tokyo.
“The Spectral Shuttle offers a wide range of GHz burst pulses with intervals ranging from 10 picoseconds to 10 nanoseconds. I believe that applications based on our technique, aimed at various targets such as plasmas, metals and cells, will accelerate scientific discoveries and technological innovations in industry and medicine.
This innovative technique paves the way for the advancement of ultrafast imaging, with implications for both scientific research and industrial applications. Its ability to simultaneously produce and shape GHz burst pulses introduces a versatile tool for studying fast phenomena and improving laser processes.
More information:
Keitaro Shimada et al, Spectral shuttle to produce spatially shapeable GHz burst pulses, Advanced Photonics Nexus (2023). DOI: 10.1117/1.APN.3.1.016002
Quote: Research team develops optical technique to simultaneously produce and shape gigahertz burst pulses (December 19, 2023) retrieved December 19, 2023 from
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