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Ultra-fast optical time-domain transformation techniques

Nature Reviews Methods Primers volume 5, Article number: 11 (2025) Cite this article

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Abstract

Owing to their inherent high-speed acquisition, ultra-short pulses are the major provider of big data in communications, metrology, spectroscopy, imaging and sensing. This has paved the way for various artificial intelligence and machine learning applications. The development of ultra-fast optical time-domain transformation (UO-TDT) techniques — specifically, time-stretched dispersive Fourier transform, temporal imaging and time-stretch imaging — has revolutionized photonic information acquisition. Dispersion-based frequency-to-time transformation of ultra-short pulses enables optical signal spectra to be converted into the time domain for ultra-fast spectral characterization. High-speed acquisition of information encoded on optical spectra means that new measurement techniques can effectively converge photonic and digital technologies. This Primer introduces the fundamental concepts and experimental set-up of various UO-TDT techniques with the associated transformation mechanisms. Recent advances in UO-TDT for various applications, from spectroscopy to velocimetry, and novel breakthroughs in ultra-fast imaging or quantum science are focused on. A range of experimental results are discussed, alongside an examination of reproducibility and limitations of the methods. Finally, a perspective on promising emerging techniques is provided.

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Fig. 1: Concept tree of the application-based UO-TDT techniques.
Fig. 2: Instrument set-up and components for UO-TDT techniques.
Fig. 3: Results of the TS-DFT techniques.
Fig. 4: Results of the temporal imaging system.
Fig. 5: Results of the time-stretch imaging system.
Fig. 6: Application examples of UO-TDT for all-optical manipulating, sensing and imaging.
Fig. 7: Example applications of UO-TDT for ultra-fast signal processing.

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Acknowledgements

This work was partially supported by the National Natural Science Foundation of China (grant nos. 62305299, 62205296 and W2433154), the Zhejiang Provincial Natural Science Foundation of China (grant nos. LQ23F050004 and LQ22F050007), the National Key R&D Program of China (grant no. 2023YFF0715802) and the ‘Pioneer’ and ‘Leading Goose’ R&D Program of Zhejiang (grant no. 2022C03084). S.K.T. acknowledges the support of the Engineering and Physical Sciences Research Council (project EP/W002868/1).

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Author notes

  1. These authors contributed equally: Yusheng Zhang, Chenning Tao.

Authors and Affiliations

  1. Hangzhou Institute of Advanced Studies, Zhejiang Normal University, Hangzhou, China

    Yusheng Zhang, Chenning Tao, Si Luo, Qiang Ling, Zuguang Guan & Daru Chen

  2. School of Optoelectronic Science and Engineering & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, China

    Kuen Yao Lau

  3. College of Information Engineering, Sanming University, Sanming, China

    Jiancheng Zheng

  4. Ceyear Technologies Co. Ltd, Qingdao, China

    Lin Huang, Aiguo Zhang & Liwen Sheng

  5. State Key Laboratory of Extreme Photonics and Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, China

    Yudong Cui & Jianrong Qiu

  6. ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou, China

    Yudong Cui

  7. Aston Institute of Photonic Technologies, Aston University, Birmingham, UK

    Sergei K. Turitsyn

  8. QTF Centre of Excellence, Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland

    Zhipei Sun

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  1. Yusheng Zhang
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Contributions

Introduction (S.K.T. and Z.S.); Experimentation (Y.Z., C.T., L.H. and Y.C.); Results (Y.Z., C.T., S.L., Q.L. and D.C.); Applications (S.L., K.Y.L., J.Z., A.Z., L.S., Z.G. and Y.C.); Reproducibility and data deposition (Z.G. and Y.C.); Limitations and optimizations (Y.Z., Z.S., D.C. and J.Q.); Outlook (S.K.T., Z.S. and J.Q.); overview of the Primer (all authors).

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Correspondence to Yudong Cui, Daru Chen, Sergei K. Turitsyn or Zhipei Sun.

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Glossary

Diffraction

A wave phenomenon that occurs when a wave encounters an obstacle or slit that is comparable in size with its wavelength. Diffraction causes the wave to bend, spread out or interfere with itself after passing through or around the object.

Fourier transform

A powerful tool to convert a signal from its time (or spatial) domain into its frequency domain and vice versa. This transform breaks down a complex signal into its constituent sinusoidal waves, revealing how much of each frequency is present in the original signal.

Group-velocity dispersion

(GVD). An optical phenomenon where different frequencies of a wave packet travel at different velocities, causing the packet to spread out over time. GVD occurs in optical fibres and other dispersive media, affecting the propagation of light pulses by broadening their temporal profile.

Mode-locked laser

A type of laser that produces extremely short pulses of light by locking the phases of different frequency modes. This synchronization creates constructive interference at regular intervals, resulting in a train of high-intensity, ultra-short pulses.

Optical non-linearity

A phenomenon where the optical response — such as the refractive index or polarization — of a material does not simply scale linearly with the intensity of the incident light during the interaction between light and matter. When the light intensity reaches a certain threshold, the optical properties of the material change, leading to non-linear effects.

Soliton

A self-reinforcing wave packet that maintains its shape while travelling at a constant velocity due to a balance between dispersion and non-linearity.

Soliton molecules

Bound states of multiple solitons that maintain a stable, fixed structure, behaving similarly to molecules with quantized bond distances between individual solitons.

Space–time analogy

A conceptual framework that draws parallels between spatial (space-related) and temporal (time-related) phenomena. This analogy is especially useful to understand and describe how light waves behave in different media, both in spatial and temporal dimensions.

Spatial dispersers

Spatial dispersers are optical devices or components that separate light based on spatial frequencies or wavelengths by spreading different spectral components across space. Unlike temporal dispersers, which separate wavelengths over time, spatial dispersers spread wavelengths in space, allowing each frequency component of light to propagate in different directions.

Temporal Fraunhofer regime

An analogy to the spatial Fraunhofer diffraction, but in the time domain. A temporal Fraunhofer regime occurs when a signal is observed far enough away in time from an event, allowing for a simplified analysis. In this regime, the temporal waveform behaves similar to a Fourier transform of the original signal, revealing its frequency components more clearly.

Temporal imaging

A technique that manipulates the temporal profile of optical signals, analogous to spatial imaging but in the time domain. Temporal imaging allows for the magnification, compression and reshaping of ultra-fast optical pulses, enabling detailed analysis and processing of temporal features.

Time lens

A concept that enables manipulation of light pulses in the time domain, analogous to how a spatial lens manipulates light in the spatial domain.

Time-stretched dispersive Fourier transform

(TS-DFT). A spectroscopy technique that uses optical dispersion to separate light wavelengths, transforming the spectrum of an ultra-short pulse into a time-stretched temporal waveform. This method is used to perform Fourier transforms on optical signals at high frame rates, enabling real-time analysis of fast dynamic processes.

Time-stretched imaging

A technique that builds on temporally stretching broadband pulses by using the dispersive properties of light in both spatial and temporal domains.

Ultra-short pulses

Electromagnetic pulses whose time duration lasts only a few trillionths of a second (femtoseconds) or less. They typically spread across a wide range of colours due to their broad optical spectrum.

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Zhang, Y., Tao, C., Luo, S. et al. Ultra-fast optical time-domain transformation techniques. Nat Rev Methods Primers 5, 11 (2025). https://doi.org/10.1038/s43586-025-00381-3

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