The measurement and control of light field oscillations enable the study of ultrafast phenomena on sub-cycle time scales. Electro-optic sampling (EOS) is a powerful field characterization approach, in terms of both sensitivity and dynamic range, but it has not reached beyond infrared frequencies. Here, we show the synthesis of a sub-cycle infrared-visible pulse and subsequent complete electric field characterization using EOS. The sampled bandwidth spans from 700 nm to 2700 nm (428 to 110 THz). Tailored electric-field waveforms are generated with a two-channel field synthesizer in the infrared-visible range, with a full-width at half-maximum duration as short as 3.8 fs at a central wavelength of 1.7 µm (176 THz). EOS detection of the complete bandwidth of these waveforms extends it into the visible spectral range. To demonstrate the power of our approach, we use the sub-cycle transients to inject carriers in a thin quartz sample for nonlinear photoconductive field sampling with sub-femtosecond resolution.

We study solutions to second-harmonic-generation equations in two-dimensional media with anomalous dispersion. The analytical solution is obtained in an approximate form of the planar spatiotemporal two-component soliton by means of the averaged Lagrangian method. It is shown that a decrease in the amplitudes of both soliton components and an increase in the value of the transverse coordinate are accompanied by an increase in their temporal duration. Within this variational approach, we have managed to find a stability criterion for the light bullet and a period of oscillations of soliton parameters. Then, we use the obtained form as an initial configuration to carry out the direct numerical simulation of soliton dynamics. We demonstrate stable propagation of spatiotemporal solitons undergoing small oscillations predicted analytically for a long distance. The formation of a two-component light bullet is shown when we launch a pulse only at the fundamental frequency. In addition, we investigate the phase and group-velocity mismatch effects on the propagation of pulses.

Simple and compact laser systems facilitate the stable and reproducible generation of high-power few-cycle laser pulses. We demonstrate the amplification of 15 fs pulses at 2.1 µm, employing a hybrid phase-matching scheme for optical parametric chirped pulse amplification. A combination of two BBO crystals with type-I and type-II phase-matching placed in close vicinity is utilized as a single amplification stage. This allows for a greatly simplified layout, achieving high conversion efficiency while avoiding the backconversion regime and the associated spatiotemporal distortions. The resulting system yields mJ-level pulses with integrated electro-optic sampling to directly measure the output waveform and study ultrafast light-matter interaction.

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Access to the complete spatiotemporal response of matter due to structured light requires field sampling techniques with sub-wavelength resolution in time and space. We demonstrate spatially resolved electro-optic sampling of near-infrared waveforms, providing a versatile platform for the direct measurement of electric field dynamics produced by photonic devices and sub-wavelength structures both in the far and near fields. This approach offers high-resolution, time- or frequency-resolved imaging by encoding a broadband signal into a narrowband blueshifted image, lifting the resolution limits imposed by both chromatic aberration and diffraction. Specifically, measuring the field of a near-infrared laser with a broadband sampling laser, we achieve 1.2 µm resolution in space and 2.2 fs resolution in time. This provides an essential diagnostic for complete spatiotemporal control of light with metasurface components, demonstrated via a metalens as well as a meta-axicon that forms broadband, ultrashort, truncated Bessel beams in the near infrared. Finally, we demonstrate the electric field dynamics of locally enhanced hot spots with sub-wavelength dimensions, recording the full temporal evolution of the electric field at each point in the image simultaneously. The imaging modality opens a path toward hyperspectral microscopy with simultaneous sub-wavelength resolution and wide-field imaging capability.

Figure 4. a) EOS (in red) and b) LPS (in blue) spectral response functions calculated with different GDD values applied to the VIS-UV pulse. c) EOS response calculated for a compressed VIS-UV pulse and different crystal thicknesses.

Access to subtle ultrafast effects of light-matter interaction often requires highly sensitive field detection schemes. Electro-optic sampling, being an exemplary technique in this regard, lacks high sensitivity in an imaging geometry. We demonstrate a straightforward method to significantly improve the contrast of electric field images in spatially resolved electro-optic sampling. A thin-film polarizer is shown to be an effective tool in enhancing the sensitivity of the electro-optic imaging system, enabling an adjustment of the spectral response. We show a further increase of the signal-to-noise ratio through the direct control of the carrier envelope phase of the imaged field.

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