Volume plasma grating by noncollinear interaction of femtosecond filament arrays.

Stable propagation of multifilament arrays in transparent bulk media with adjustable separation distances between adjacent child filaments has always been desired for advanced manufacturing. Here, we report on the generation of an ionization-induced volume plasma grating (VPG) by the interaction of two batches of noncollinearly propagating arrays of multiple filaments (AMF). The VPG can externally arrange the propagation of the pulses along regular plasma waveguides via spatial reconstruction of electrical fields, which is compared with the self-formation of randomly distributed multiple filamentation originated from noises.

Hydrogenated Amorphous TiO and Its High Visible Light Photoactivity.

Hydrogenated crystalline TiO with oxygen vacancy (O) defect has been broadly investigated in recent years. Different from crystalline TiO, hydrogenated amorphous TiO for advanced photocatalytic applications is scarcely reported. In this work, we prepared hydrogenated amorphous TiO (HA-TiO) using a unique liquid plasma hydrogenation strategy, and demonstrated its highly visible-light photoactivity.

Tetraphenylethene-Embedded Pillar[5]arene and [15]Paracyclophane: Distorted Cavities and Host-Guest Binding Properties.

Two aggregation-induced emission (AIE) macrocycles ( and ) were prepared by embedding Tetraphenylethene (TPE) unit into the skeletons of Dimethoxypillar[5]arene (DMP[5]) and [15]Paracyclophane ([15]PCP) at meso position, respectively. In crystal, the showed a distorted cavity, and the incubation of hexane inside the cavity caused a distinct change in the molecular conformation compared to . There was no complexation between and 1,4-dicyanobutane (DCB).

Graphene-Coupled Terahertz Semiconductor Lasers for Enhanced Passive Frequency Comb Operation.

Optical frequency combs, consisting of well-controlled equidistant frequency lines, have been widely used in precision spectroscopy and metrology. Terahertz combs have been realized in quantum cascade lasers (QCLs) by employing either an active mode-locking or phase seeding technique, or a dispersion compensator mirror. However, it remains a challenge to achieve the passive comb formation in terahertz semiconductor lasers due to the insufficient nonlinearities of conventional saturable absorbers.

Terahertz and Photoelectron Emission from Nanoporous Gold Films on Semiconductors.

Efficient terahertz and photoelectron emission were observed from nano-porous gold (NPG) films deposited on an intrinsic gallium arsenide (GaAs) semiconductor substrate stimulated by femtosecond laser with pulse width of 60 fs. Time-domain THz emission and reflection spectroscopy confirmed that the free charges accelerated by irradiated femtosecond laser pulses transferred from the NPG films into the GaAs substrates. Accordingly, charges accumulation was reduced in the NPG films, resulting in a stronger emission of THz pulse than that from NPG films deposited on SiO₂ substrate.

Filamentary plasma grating induced by interference of two femtosecond laser pulses in water.

We present direct observation of filamentary plasma grating induced by interference between two noncollinear infrared femtosecond pulses in water by doping with gold nanoparticles. The gold nanoparticles act as scattering media in water and visualize the fine structure of local optical fields of plasma grating. By measuring the variation of local conductivity as laser undergoes filamentation in water, the generated electron density in water is qualitatively studied.

Terahertz modulation induced by filament interaction.

We experimentally demonstrated that nonlinear filament interaction could spectrally modulate terahertz (THz) radiation generated from asymmetric two-color filaments. It was the spatial plasma density modulation in plasma channels that induced the THz spectral modulation. As a result of optical manipulation of electron density in the filamentary plasma gratings, the proportion of high-frequency THz spectra increased, while that of low-frequency THz spectra decreased, indicating that the increase of free electron density in the filamentary plasma grating brought about THz frequency upshifts.