In high-power laser system such as Petawatt lasers, the laser beam can be intense enough to result in saturation of nonlinear refraction index of medium. Based on the standard linearization method of small-scale self-focusing and the split-step Fourier numerical calculation method, we present analytical and simulative investigations on the hot-image formation in cascaded saturable nonlinear medium slabs, to disclose the effect of nonlinearity saturation on the distribution and intensity of hot images. The analytical and simulative results are found in good agreement. It is shown that, saturable nonlinearity does not change the distribution of hot images, while may greatly affect the intensity of hot images, i.e., for a given saturation light intensity, with the intensity of the incident laser beam, the intensity of hot images firstly increases monotonously and eventually reaches a saturation; for the incident laser beam of a given intensity, with the saturation light intensity lowering, the intensity of hot images decreases rapidly, even resulting in a few hot images too weak to be visible.
In high-power laser system such as Petawatt lasers, the laser beam can be intense enough to result in saturation of nonlinear refraction index of medium. We present an analytical and simulative investigation of hot image formation in an intense laser beam through a saturable nonlinear medium slab based on Fresnel-Kirchhoff diffraction integral and the standard split-step Fourier method. The analytical results are found in agreement with the simulative ones. It is shown that, hot images can still form in an intense laser beam through a saturable nonlinear medium slab, additionally, the saturable nonlinearity does not change the location of hot images, while may decrease the intensity of hot images, i.e., the intensity of hot images decreases with the saturation light intensity lowering, and can stop to increase with the intensity of the incident laser beam heightening due to saturation of nonlinearity. Moreover, variations of intensity of hot images with the obscuration type and the slab thickness are discussed.
In this work, we present a method for generating vector vortex beams with metasurfaces. A Jones calculation is employed to theoretically analyze the phase and polarization transformation from metasurfaces. The experimental results are shown to agree well with our theoretical calculation. Lastly, as a geometrical representation, the hybrid-order Poincaré sphere is proposed to describe the evolution of polarization state and phase of light wave propagating in metasurfaces. The hybrid-order Poincaré sphere can intuitively demonstrate the change of polarization state and. So it can also become an effective tool to provide help in designing metasurfaces.
We present a hybrid Poincaré sphere, whose eigenstates are defined as a pair of circularly polarized fundamental-mode Gaussian beam and a Laguerre-Gaussian beam, to describe the so-called full Poincaré beam. We also show that any desired full Poincaré beam over the hybrid Poincaré sphere via modulating the incident polarization state of light and two cascaded half-wave plates. This research provides an alternative way for charactering and manipulating the full Poincaré beam and an effective method to control the polarization state of light.
The spin Hall effect (SHE) of light originates from the spin-orbit interaction, which can be explained in terms of two geometric phases: the Rytov-Vladimirskii-Berry phase and the Pancharatnam-Berry phase. Here we present a unified theoretical description of the SHE based on the two types of geometric phase gradients, and observe experimentally the SHE in structured dielectric metasurfaces induced by the PB phase. Unlike the weak real-space spin-Hall shift induced by the SRB phase occurring at interfacial reflection/refraction, the observed SHE occurs in momentum space is large enough to be measured directly.
We report the demonstration of intrinsic spin Hall effect (SHE) of cylindrical vector beam. Employing a fan-shaped aperture to block part of the vector beam, the intrinsic vortex phases are no longer continuous in the azimuthal direction, and results in the spin accumulation at the opposite edges of the light beam. Due to the inherent nature of the phase and independency of light-matter interaction, the observed SHE is intrinsic. Modulating the topological charge of the vector beam, the spin-dependent splitting can be enhanced and the direction of spin accumulation is switchable.
Nanosecond-level pulses of specific shape is usually generated by stacking chirped pulses for high-power inertial
confinement fusion driver, in which nonlinear imaging of scatterers may damage precious optical elements. We present a
numerical study of the characteristics of nonlinear imaging of scatterers in broadband laser stacked by chirped pulses to
disclose the dependence of location and intensity of images on the parameters of the stacked pulse. It is shown that, for
sub-nanosecond long sub-pulses with chirp or transform-limited sub-pulses, the time-mean intensity and location of
images through normally dispersive and anomalously dispersive self-focusing medium slab are almost identical; While
for picosecond-level short sub-pulses with chirp, the time-mean intensity of images for weak normal dispersion is
slightly higher than that for weak anomalous dispersion through a thin nonlinear slab; the result is opposite to that for
strong dispersion in a thick nonlinear slab; Furthermore, for given time delay between neighboring sub-pulses, the
time-mean intensity of images varies periodically with chirp of the sub-pulse increasing; for a given pulse width of
sub-pulse, the time-mean intensity of images decreases with the time delay between neighboring sub-pulses increasing;
additionally, there is a little difference in the time-mean intensity of images of the laser stacked by different numbers of
sub-pulses. Finally, the obtained results are also given physical explanations.
Observation of photonic spin Hall effect (SHE) manifested by spin-dependent splitting of light in a dielectric-based birefringent metasurface is reported experimentally. By designing the metasurface with homogeneous phase retardation but space-variant optical axis directions, we govern the photonic SHE via space-variant Pancharatnam-Berry phase originated from the local polarization manipulation of the metasurface, essentially, the spin-orbit interaction between the light and the metasurface. Modulating the polarization distribution of the incident light and/or the structure geometry of the metasurface, the photonic SHE could be tunable. This type of metasurface offers an effective way to manipulate the spin-polarized photons and a route for spin-controlled nanophotonic applications.