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Complete characterization of ultrashort optical pulses with a phase-shifting wedged reversal shearing interferometer.

ABSTRACT: The ability of an interferometer to characterize the spatial information of a light beam is often limited by the temporal profile of the beam, with femtosecond pulse characterization being particularly challenging. In this study, we developed a simple, stable, controllable shearing and vectorial phase-shifting wedged reversal shearing interferometer that is able to characterize all types of coherent and partially coherent light beams. The proposed interferometer consists of only a single beam splitter cube with one wedged entrance face and is insensitive to environmental vibration due to its common path configuration. A near zero-path length difference of the proposed interferometer ensures its operation for ultrashort pulses, providing, for the first time, a simple and stable interferometric tool to fully characterize sub-100 fs laser pulses. All common beam characterization can be carried out with the interferometer, such as the amplitude, phase, polarization, wavelength, and pulse duration. Furthermore, this technique is sensitive to the wavefront tilt and can be used for precise beam alignment. Therefore, this interferometer can be an essential tool for beam characterization, optical imaging, and the testing required for a wide range of applications, including astronomy, biomedicine, ophthalmology, optical testing and imaging systems, and adaptive optics.

SUBMITTER: Lam B

PROVIDER: S-EPMC6106999 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Radiofrequency phase encoded half-pulses in simultaneous multislice ultrashort echo time imaging.

Project description:PurposeTo describe a simultaneous multislice (SMS) ultrashort echo time (UTE) imaging method using radiofrequency phase encoded half-pulses in combination with power independent of number of slices (PINS) inversion recovery (IR) pulses to generate multiple-slice images with short T2 * contrasts in less than 3 min with close to an eightfold acceleration compared with a standard 2D approach.Theory and methodsRadiofrequency phase encoding is applied in an SMS (NSMS = 4) excitation scheme using "sinc" half-pulses. With the use of coil sensitivity encoding (SENSE) and controlled aliasing in parallel imaging (CAIPI) in combination with a gradient echo 2D spiral readout trajectory and IR PINS pulses for contrast enhancement a fast UTE sequence is developed. Images are obtained using a model-based reconstruction method. Sequence details and performance tests on phantoms as well as the heads of healthy volunteers at 3T are presented.ResultsAn SMS UTE sequence with an undersampling factor of 4 is developed using radiofrequency phase encoded half-pulses and PINS IR pulses which enables the acquisition of 8 slices at 0.862 mm2 resolution in less than 3-min scan time. UTE images of the head are obtained showing highlighted signal of cortical bone. Image quality and T2 contrast are comparable to the one obtained by corresponding single slice acquisitions with only minor deviations.ConclusionsThe method combining radiofrequency phase encoded SMS half-pulses and PINS IR pulses presents a suitable approach to SMS UTE imaging. The usage of coil sensitivity information and increased sampling density by means of interleaved slice group acquisitions allows to reduce the total scan time by a factor close to 8.

| S-EPMC6435423 | biostudies-literature

All-optical phase modulation in a cavity-polariton Mach-Zehnder interferometer.

Project description:Quantum fluids based on light is a highly developing research field, since they provide a nonlinear platform for developing optical functionalities and quantum simulators. An important issue in this context is the ability to coherently control the properties of the fluid. Here we propose an all-optical approach for controlling the phase of a flow of cavity-polaritons, making use of their strong interactions with localized excitons. Here we illustrate the potential of this method by implementing a compact exciton-polariton interferometer, which output intensity and polarization can be optically controlled. This interferometer is cascadable with already reported polariton devices and is promising for future polaritonic quantum optic experiments. Complex phase patterns could be also engineered using this optical method, providing a key tool to build photonic artificial gauge fields.

| S-EPMC3926000 | biostudies-literature

Cardiac myocyte excitation by ultrashort high-field pulses.

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| S-EPMC2717245 | biostudies-literature

Optical control of filamentation-induced damage to DNA by intense, ultrashort, near-infrared laser pulses.

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| S-EPMC4899723 | biostudies-other

Controlled modification of biomolecules by ultrashort laser pulses in polar liquids.

Project description:Targeted chemical modification of peptides and proteins by laser pulses in a biologically relevant environment, i.e. aqueous solvent at room temperature, allows for accurate control of biological processes. However, the traditional laser methods of control of chemical reactions are applicable only to a small class of photosensitive biomolecules because of strong and ultrafast perturbations from biomolecule-solvent interactions. Here, we report excitation of harmonics of vibration modes of solvent molecules by femtosecond laser pulses to produce controlled chemical modifications of non-photosensitive peptides and proteins in polar liquids under room conditions. The principal modifications included lysine formylation and methionine sulfoxidation both of which occur with nearly 100% yield under atmospheric conditions. That modification occurred only if the laser irradiance exceeded certain threshold level. The threshold, type, and extent of the modifications were completely controlled by solvent composition, laser wavelength, and peak irradiance of ultrashort laser pulses. This approach is expected to assist in establishing rigorous control over a broad class of biological processes in cells and tissues at the molecular level.

| S-EPMC5514113 | biostudies-literature

Effects of ultrashort laser pulses on angular distributions of photoionization spectra.

Project description:We study the photoelectron spectra by intense laser pulses with arbitrary time dependence and phase within the Keldysh framework. An efficient semianalytical approach using analytical transition matrix elements for hydrogenic atoms in any initial state enables efficient and accurate computation of the photoionization probability at any observation point without saddle point approximation, providing comprehensive three dimensional photoelectron angular distribution for linear and elliptical polarizations, that reveal the intricate features and provide insights on the photoionization characteristics such as angular dispersions, shift and splitting of photoelectron peaks from the tunneling or above threshold ionization(ATI) regime to non-adiabatic(intermediate) and multiphoton ionization(MPI) regimes. This facilitates the study of the effects of various laser pulse parameters on the photoelectron spectra and their angular distributions. The photoelectron peaks occur at multiples of 2?? for linear polarization while odd-ordered peaks are suppressed in the direction perpendicular to the electric field. Short pulses create splitting and angular dispersion where the peaks are strongly correlated to the angles. For MPI and elliptical polarization with shorter pulse?s? the peaks split into doublets and the first peak vanishes. The carrier envelope phase(CEP) significantly affects the ATI spectra while the Stark effect shifts the spectra of intermediate regime to higher energies due to interference.

| S-EPMC5532372 | biostudies-literature

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Project description:In this work we firstly study the influence of different parameters in the temporal characterization of ultrashort laser pulses with the recently developed amplitude swing technique. In this technique, the relative amplitude of two delayed replicas is varied while measuring their second-harmonic spectra. Here we study the retrieval of noisy traces and the implications of having different delays or phase retardations (relative phases) between the two replicas. Then, we study the capability of the technique to characterize the pulses when the second-harmonic signal is spectrally uncalibrated or incomplete, presenting the analytical calculation of the marginal, which is used to calibrate the traces and to perform the pulse retrievals. We experimentally show the retrieval of different pulses using diverse delays and phase retardations to perform the amplitude swing trace and demonstrate that, from an uncalibrated trace, both the pulse information and the response of the nonlinear process can be simultaneously retrieved. In sum, the amplitude swing technique is shown to be very robust against experimental constraints and limitations, showing a high degree of soundness.

| S-EPMC7591537 | biostudies-literature

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Project description:The field of spintronics involves the study of both spin and charge transport in solid-state devices. Ultrafast magnetism involves the use of femtosecond laser pulses to manipulate magnetic order on subpicosecond time scales. We unite these phenomena by using picosecond charge current pulses to rapidly excite conduction electrons in magnetic metals. We observe deterministic, repeatable ultrafast reversal of the magnetization of a GdFeCo thin film with a single sub-10-ps electrical pulse. The magnetization reverses in ~10 ps, which is more than one order of magnitude faster than any other electrically controlled magnetic switching, and demonstrates a fundamentally new electrical switching mechanism that does not require spin-polarized currents or spin-transfer/orbit torques. The energy density required for switching is low, projecting to only 4 fJ needed to switch a (20 nm)3 cell. This discovery introduces a new field of research into ultrafast charge current-driven spintronic phenomena and devices.

| S-EPMC5669611 | biostudies-literature

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| S-EPMC6072769 | biostudies-literature

Cell and tissue manipulation with ultrashort infrared laser pulses in light-sheet microscopy.

Project description:Three-dimensional live imaging has become an indispensable technique in the fields of cell, developmental and neural biology. Precise spatio-temporal manipulation of biological entities is often required for a deeper functional understanding of the underlying biological process. Here we present a home-built integrated framework and optical design that combines three-dimensional light-sheet imaging over time with precise spatio-temporal optical manipulations induced by short infrared laser pulses. We demonstrate their potential for sub-cellular ablation of neurons and nuclei, tissue cauterization and optogenetics by using the Drosophila melanogaster and zebrafish model systems.

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