What is the maximum differential group delay achievable by a space-time wave packet in free space?

Abstract

The group velocity of 'space-time' wave packets $-$ propagation-invariant pulsed beams endowed with tight spatio-temporal spectral correlations $-$ can take on arbitrary values in free space. Here we investigate theoretically and experimentally the maximum achievable group delay that realistic finite-energy space-time wave packets can achieve with respect to a reference pulse traveling at the speed of light. We find that this delay is determined solely by the spectral uncertainty in the association between the spatial frequencies and wavelengths underlying the wave packet spatio-temporal spectrum $-$ and not by the beam size, bandwidth, or pulse width. We show experimentally that the propagation of space-time wave packets is delimited by a spectral-uncertainty-induced `pilot envelope' that travels at a group velocity equal to the speed of light in vacuum. Temporal walk-off between the space-time wave packet and the pilot envelope limits the maximum achievable differential group delay to the width of the pilot envelope. Within this pilot envelope, the space-time wave packet can locally travel at an arbitrary group velocity and yet not violate relativistic causality because the leading or trailing edge of superluminal and subluminal space-time wave packets, respectively, are suppressed once they reach the envelope edge. Using pulses of width $\sim$4ps and a spectral uncertainty of $\sim$ 20 pm, we measure maximum differential group delays of approximately $\pm$ 150 ps, which exceed previously reported measurements by at least three orders of magnitude.

References in corpus (22)

• Diffraction-free space-time beams
• Spontaneously generated X-shaped light bullets
• Conical emission, pulse splitting and X-wave parametric amplification in nonlinear dynamics of ultrashort light pulses
• Photons that travel in free space slower than the speed of light
• Classification of propagation-invariant space-time wave packets in free space: Theory and experiments
• Airy wave packets accelerating in space-time
• Directly measuring the spatiotemporal electric field of ultrashort Bessel-X pulses
• On the Localized superluminal Solutions to the Maxwell Equations
• Ultrashort Tilted-Pulse-Front Pulses and Nonparaxial Tilted-Phase-Front Beams
• Self-healing of space-time light sheets
• Gaussian beams diffracting in time
• Spatiotemporal Amplitude and Phase Retrieval of Bessel-X pulses using a Hartmann-Shack Sensor
• Sub-luminal wave bullets: Exact Localized subluminal Solutions to the Wave Equations
• Spatiotemporal diffraction-free pulsed beams in free-space of the Airy and Bessel type
• Spatial and temporal characterization of a Bessel beam produced using a conical mirror
• Abruptly Focusing and Defocusing Needles of Light and Closed-Form Electromagnetic Wavepackets
• Time-diffracting beams: On their nature, diffraction-free propagation as needles of light, and nonlinear generation
• Reexamination of group velocities of structured light pulses
• Analytical expressions for the longitudinal evolution of nondiffracting pulses truncated by finite apertures
• Pulsed light beams in vacuum with superluminal and negative group velocities
• Classical entanglement underpins the propagation invariance of space-time wave packets
• Optical space-time wave packets having arbitrary group velocities in free space

Cited by in corpus (33)

• Anomalous refraction of optical space-time wave packets
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• Accelerating and decelerating space-time optical wave packets in free space
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• Hybrid guided space-time optical modes in unpatterned films
• The space-time Talbot effect
• Free-space optical delay line using space-time wave packets
• Veiled Talbot effect
• Changing the speed of optical coherence in free space
• Arbitrarily accelerating space-time wave packets
• Omni-resonant space-time wave packets
• V-Waves: Spatio-temporally induced group-velocity dispersion in free space
• Reactive energy in non-diffracting localized waves
• Temporal Talbot effect in free space
• Axial spectral encoding of space-time wave packets
• Observation of optical de Broglie-Mackinnon wave packets
• Observation of ultrabroadband striped space-time surface plasmon polaritons
• Refraction of space-time wave packets: I. Theoretical principles
• Non-Dispersive Space-Time Wave Packets Propagating in Dispersive Media
• The consequences of non-differentiable angular dispersion in optics: Tilted pulse fronts versus space-time wave packets
• Isochronous space-time wave packets
• Non-differentiable angular dispersion as an optical resource
• Relativistic transformations of quasi-monochromatic optical beams
• Refraction of space-time wave packets in a dispersive medium
• Transverse spin angular momentum of space-time surface plasmon polariton wave packet
• Spectrally recycling space-time wave packets
• Theory of space-time supermodes in planar multimode waveguides
• Exciting space-time surface plasmon polaritons by irradiating a nanoslit structure
• Realizing normal group-velocity dispersion in free space via angular dispersion
• Refraction of space-time wave packets: III. Experiments at oblique incidence
• Excitation of Surface Plasmon Polaritons by Diffraction-Free and Vector Beams
• Space-time wave packets violate the universal relationship between angular dispersion and pulse-front tilt
• Refraction of space-time wave packets: II. Experiments at normal incidence