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Broadband coherent wave control through photonic collisions at time interfaces

Nature Physics volume 19, pages 1703–1708 (2023)Cite this article

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Abstract

Coherent wave control exploits the interference among multiple waves impinging on a system to suppress or enhance outgoing signals based on their relative phase and amplitude. This process inherently requires the combination of energy exchanges among the waves and spatial interfaces to tailor their scattering. Here we explore the temporal analogue of this phenomenon, based on time interfaces that support instantaneous non-conservative scattering events for photons. Based on this mechanism, we demonstrate ultrabroadband temporal coherent wave control and the photonic analogue of mechanical collisions with phase-tunable elastic features. We apply them to erase, enhance and reshape arbitrary pulses by suitably tailoring the amplitude and phase of counterpropagating signals. Our findings provide a pathway to effectively sculpt broadband light with light without requiring spatial boundaries, within an ultrafast and low-energy platform.

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Fig. 1: Temporal coherent wave control and photonic collisions enabled by time interfaces.
Fig. 2: Experimental implementation of broadband temporal CWC and photonic collisions in a TLM.
Fig. 3: Distributed instantaneous pulse shaping based on photonic collisions at a TI.

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Data availability

Authors can confirm that all relevant data are included in the paper and/or its Supplementary Information files. Source data are provided with this paper. Where very large datasets were produced, source data are available upon request from the corresponding author.

Code availability

The code used to produce these results is available upon request from the corresponding author.

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Acknowledgements

This work was supported by the Air Force Office of Scientific Research, the CHARM programme and the Simons Foundation. E.G. was supported by the Simons Foundation through a Junior Fellowship of the Simons Society of Fellows (no. 855344).

Author information

Author notes

  1. These authors contributed equally: Emanuele Galiffi, Gengyu Xu.

Authors and Affiliations

  1. Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, USA

    Emanuele Galiffi, Gengyu Xu, Shixiong Yin, Hady Moussa, Younes Ra’di & Andrea Alù

  2. Department of Electrical Engineering, City College, City University of New York, New York, NY, USA

    Shixiong Yin, Hady Moussa & Andrea Alù

  3. Department of Electrical Engineering and Computer Science, Syracuse University, Syracuse, NY, USA

    Younes Ra’di

  4. Physics Program, Graduate Center, City University of New York, New York, NY, USA

    Andrea Alù

Authors
  1. Emanuele Galiffi
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  3. Shixiong Yin
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  4. Hady Moussa
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Contributions

E.G. conceived the project, with contribution from A.A., and performed theoretical analysis. G.X. designed the experiments, performed measurements and interpreted the data. S.Y. performed numerical simulations. E.G. led the writing of the manuscript with contributions from all authors. A.A. supervised the project.

Corresponding author

Correspondence to Andrea Alù.

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The authors declare no competing interests.

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Nature Physics thanks Simon Horsley and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 Experimental setup for TI-enabled coherent wave control and photonic collisions.

(a) A photo of the fabricated TLM sample. (b) A simplified schematic for the measurement setup. A signal and an idler pulse are launched into the TLM from its two ports from an arbitrary waveform generator (AWG). The AWG is triggered by an external clock from a high voltage function generator. The clock is phase-locked to a control signal, sent by the same function generator to control the TLM switches. The phase between the clock and the control determines the spatial coherence between the signal and the idler at the instant of collision. The time evolution of voltages at both ports is monitored using a sampling oscilloscope.

Extended Data Fig. 2 Measured scattering parameters of the T-connectors.

Note that the frequency regime of interest is essentially dispersionless. The transmission coefficient between any two ports has a constant amplitude of −3.5 dB. As it is passive and reciprocal, the T-connector cannot be perfectly matched at all ports. This explains the −9.5 dB reflection seen from all ports despite the 50Ω termination. However, in a time domain measurement, any spuriously reflected signals due to impedance mismatch can be eliminated through time-gating.

Source data

Extended Data Fig. 3

Time-interface-enabled collision of modulated wave packets. Measurement of TI-enabled destructive (a,b) and constructive (c,d) collisions between Gaussian wave packets. (a) Complete annihilation (maximally destructive collision) of the signal using an idler with the same polarity and perfectly timed switching. The dashed green line corresponds to the case where no idler is present, and the signal experiences no collision. (b) If no switching occurs, the signal and the idler wave packets do not interact and simply pass through each other. As they reach the opposite port, some spatial reflection occurs due to the impedance mismatch introduced by the T-connector, which causes visible ‘echoes’ from the ends of the line at times t>150ns. Although these spatial reflections also occur in panel A, they are hardly visible due to the increased loss and dispersion in the ‘SWITCH ON’ configuration of our TLM, which causes increased pulse attenuation and broadening. (c) Constructive collision with the signal using an idler with opposite polarity. The resulting signal amplitude is approximately doubled compared to the output in the absence of idler. (d) Again, in the absence of switching, the signal and the idler do not collide and cannot exchange energy.

Source data

Supplementary information

Supplementary Note

Supplementary Sections 1–4.

Source data

Source Data Fig. 2

Unprocessed oscilloscope measurements.

Source Data Fig. 2

Unprocessed oscilloscope measurements.

Source Data Fig. 2

Unprocessed oscilloscope measurements.

Source Data Fig. 2

Unprocessed oscilloscope measurements.

Source Data Fig. 3

Finite-difference time-domain simulations.

Source Data Fig 3

Unprocessed oscilloscope measurements.

Source Data Extended Data Fig. 2

Vector network analyzer measurement for the T-connector.

Source Data Extended Data Fig. 3

Unprocessed oscilloscope measurements.

Source Data Extended Data Fig. 3

Unprocessed oscilloscope measurements.

Source Data Extended Data Fig. 3

Unprocessed oscilloscope measurements.

Source Data Extended Data Fig. 3

Unprocessed oscilloscope measurements.

Source Data Extended Data Fig. 3

Unprocessed oscilloscope measurements.

Source Data Extended Data Fig. 3

Unprocessed oscilloscope measurements.

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Galiffi, E., Xu, G., Yin, S. et al. Broadband coherent wave control through photonic collisions at time interfaces. Nat. Phys. 19, 1703–1708 (2023). https://doi.org/10.1038/s41567-023-02165-6

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