Optical Pump Rectification Emission: Route to Terahertz Free-Standing Surface Potential Diagnostics

Peters, Luke; Tunesi, Jacob; Pasquazi, Alessia; Peccianti, Marco

doi:10.1038/s41598-017-08734-z

Cited by 21 publications

(6 citation statements)

References 41 publications

(34 reference statements)

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“…3(a)) are very similar for both emitters, despite the differences in the terahertz generation mechanisms. According to our experimentally measured azimuthal dependence of the terahertz radiation amplitude, terahertz emission from InAs can be mainly attributed to surface electric-field-induced optical rectification 18,19 , rather than photoejected electrons. The waveform we obtained from InAs (Fig.…”

Section: Experiments and Resultsmentioning

confidence: 86%

Terahertz emission from gold nanorods irradiated by ultrashort laser pulses of different wavelengths

Takano

Asai

Kato

et al. 2019

Sci Rep

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Electron photoemission and ponderomotive acceleration by surface enhanced optical fields is considered as a plausible mechanism of terahertz radiation from metallic nanostructures under ultrafast laser excitation. To verify this mechanism, we studied experimentally terahertz emission from an array of gold nanorods illuminated by intense (~10–100 GW/cm 2 ) femtosecond pulses of different central wavelengths (600, 720, 800, and 1500 nm). We found for the first time that the order of the dependence of the terahertz fluence on the laser intensity is, unexpectedly, almost the same (~4.5–4.8) for 720, 800, and 1500 nm and somewhat higher (~6.6) for 600 nm. The results are explained by tunneling currents driven by plasmonically enhanced laser field. In particular, the pump-intensity dependence of the terahertz fluence is more consistent with terahertz emission from the sub-cycle bursts of the tunneling current rather than with the ponderomotive mechanism.

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Section: Experiments and Resultsmentioning

confidence: 86%

Terahertz emission from gold nanorods irradiated by ultrashort laser pulses of different wavelengths

Takano

Asai

Kato

et al. 2019

Sci Rep

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“…We tackled this problem by considering a structured wave generated through a nonlinear optical process, as established, for example, in the state-of-the-art generation of THz radiation from ultrafast optical illumination. 36,37 As the THz beam is generated through a quadratic transformation (difference-frequency generation), there is a local linear dependence between the THz field and the incident optical intensity, namely, E THz (x, y, t) ∝ I opt (x, y, t). Such a relation allows precise control over the THz field profile both in time and space by shaping the incident optical pulse.…”

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confidence: 99%

Time-Resolved Nonlinear Ghost Imaging

et al. 2018

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Terahertz (THz) spectroscopy systems are widely employed to retrieve the chemical and material composition of a sample. This is single-handedly the most important driving motivation in the field and has largely contributed to shaping THz science as an independent subject. The limited availability of high-resolution imaging devices, however, still represents a major technological challenge in this promising field of research. In this theoretical work, we tackle this challenge by developing a novel nonlinear ghost imaging approach that conceptually outperforms established single-pixel imaging protocols at inaccessible wavelengths. Our methodology combines nonlinear THz generation with time-resolved field measurements, as enabled by state-of-theart time domain spectroscopy techniques. As an ideal application target, we consider hyperspectral THz imaging of semitransparent samples with nonnegligible delay contribution, and we demonstrate how time-resolved, full-wave acquisition enables accurate spatiotemporal reconstruction of complex inhomogeneous samples.

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“…where χ (3) is the third-order susceptibility of InAs, E sur f is the intrinsic surface potential field, E ω is the incident optical field and * stands for the complex conjugate. Quite interestingly, because the phenomenon is driven by a surface potential, it is also a measurable way to probe the dynamics of the carrier at the surface, and it has been proposed as the optical analogy of a Kelvin probe [48]. At very high pumping energies (above 10 μJ/cm 2 ), this phenomenon becomes critically saturated due to the electromagnetic screening role of dense carrier densities.…”

Section: A Route Towards Thinner Thz Emitters: Surface Emission From Quasi-2d Semiconductor Structuresmentioning

confidence: 99%

Route to Intelligent Imaging Reconstruction via Terahertz Nonlinear Ghost Imaging

et al. 2020

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Terahertz (THz) imaging is a rapidly emerging field, thanks to many potential applications in diagnostics, manufacturing, medicine and material characterisation. However, the relatively coarse resolution stemming from the large wavelength limits the deployment of THz imaging in micro- and nano-technologies, keeping its potential benefits out-of-reach in many practical scenarios and devices. In this context, single-pixel techniques are a promising alternative to imaging arrays, in particular when targeting subwavelength resolutions. In this work, we discuss the key advantages and practical challenges in the implementation of time-resolved nonlinear ghost imaging (TIMING), an imaging technique combining nonlinear THz generation with time-resolved time-domain spectroscopy detection. We numerically demonstrate the high-resolution reconstruction of semi-transparent samples, and we show how the Walsh–Hadamard reconstruction scheme can be optimised to significantly reduce the reconstruction time. We also discuss how, in sharp contrast with traditional intensity-based ghost imaging, the field detection at the heart of TIMING enables high-fidelity image reconstruction via low numerical-aperture detection. Even more striking—and to the best of our knowledge, an issue never tackled before—the general concept of “resolution” of the imaging system as the “smallest feature discernible” appears to be not well suited to describing the fidelity limits of nonlinear ghost-imaging systems. Our results suggest that the drop in reconstruction accuracy stemming from non-ideal detection conditions is complex and not driven by the attenuation of high-frequency spatial components (i.e., blurring) as in standard imaging. On the technological side, we further show how achieving efficient optical-to-terahertz conversion in extremely short propagation lengths is crucial regarding imaging performance, and we propose low-bandgap semiconductors as a practical framework to obtain THz emission from quasi-2D structures, i.e., structure in which the interaction occurs on a deeply subwavelength scale. Our results establish a comprehensive theoretical and experimental framework for the development of a new generation of terahertz hyperspectral imaging devices.

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Optical Pump Rectification Emission: Route to Terahertz Free-Standing Surface Potential Diagnostics

Cited by 21 publications

References 41 publications

Terahertz emission from gold nanorods irradiated by ultrashort laser pulses of different wavelengths

Terahertz emission from gold nanorods irradiated by ultrashort laser pulses of different wavelengths

Time-Resolved Nonlinear Ghost Imaging

Route to Intelligent Imaging Reconstruction via Terahertz Nonlinear Ghost Imaging

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