Application of Terahertz Pulse Time-Domain Holography for Phase Imaging

Terahertz pulse time-domain holography (THz PTDH) is the powerful technique for high-resolution amplitude and phase THz imaging that allows mapping spectroscopic information across the imaged object. In this paper, we consider most sought after applications of phase imaging provided by this technique and experimentally demonstrate the ability of the method to reconstruct smooth and stepped relief features of an object that is transparent in THz region. Unlike the amplitude distribution, which does not contain any significant information in this case, phase distribution not only reveals the object qualitatively,but also allows the reconstruction of the object thicknessespattern, even in low signal-to-noise registration conditions. Mainlimitations of the proposed method, such as transverse resolutionand low signal-to-noise environment are carefully studied and mitigated

Photoluminescence quenching of dye molecules near a resonant silicon nanoparticle

Luminescent molecules attached to resonant colloidal particles are an important tool to study light-matter interaction. A traditional approach to enhance the photoluminescence intensity of the luminescent molecules in such conjugates is to incorporate spacer-coated plasmonic nanoantennas, where the spacer prevents intense non-radiative decay of the luminescent molecules. Here, we explore the capabilities of an alternative platform for photoluminescence enhancement, which is based on low-loss Mie-resonant colloidal silicon particles. We demonstrate that resonant silicon particles of spherical shape are more efficient for photoluminescence enhancement than their plasmonic counterparts in spacer-free configuration. Our theoretical calculations show that significant enhancement originates from larger quantum yields supported by silicon particles and their resonant features. Our results prove the potential of high-index dielectric particles for spacer-free enhancement of photoluminescence, which potentially could be a future platform for bioimaging and nanolasers

Survey on time-delay approach to networked control

This paper provides a survey on time-delay approach to networked control systems (NCSs). The survey begins from a brief summary on fundamental network-induced issues in NCSs and the main approaches to the modelling of NCSs. In particular, a comprehensive introduction to time-delay approach to sampled-data and networked control is provided. Then, recent results on time-delay approach to event-triggered control are recalled. The survey highlights time-delay approach developed to modelling, analysis and synthesis of NCSs, under communication constraints, with a particular focus on Round-Robin, Try-once-discard and stochastic protocols. The time-delay approach allows communication delays to be larger than the sampling intervals in the presence of scheduling protocols. Moreover, some results on networked control of distributed parameter systems are surveyed. Finally, conclusions and some future research directions are briefly addressed

Enhanced terahertz emission from imprinted halide perovskite nanostructures

Lead halide perovskites were known to be a prospective family of materials for terahertz (THz) generation. On the other hand, perovskite nanostructures, nanoantennas, and metasurfaces allow tailoring perovskites optical characteristics, resulting in more efficient interaction with incident or emitted light. Moreover, the perovskites are robust materials against formation of defects caused by mechanical deformations and can be efficiently nanostructured by various high throughput methods. In this work, we have enhanced THz emission from MAPbI3 perovskite upon femtosecond laser irradiation using nanoimprint lithography. The formed nanostructures not only improve absorption of the incident laser pulses, but also lead to a non-symmetric near-field distribution. As a result, we have enhanced the efficiency of THz emission from the nanostructured perovskite by 3.5 times as compared with a smooth perovskite film. Our results paved the way for a new application of large-scale perovskite nanostructuring, making halide perovskites competitive with more expensive conventional semiconductors for THz generation

Varying pre-plasma properties to boost terahertz wave generation in liquids

Terahertz frequency radiation provides a powerful tool for the investigation of matter from the life science to the solid state and plasmas. The authors experimentally and numerically present enhanced terahertz wave generation by single-color double-pulse excitation in flat liquid jets, providing a deeper understanding of the mechanism that underpins the terahertz generation in multi-pulse experiments

Transmission properties of van der Waals materials for terahertz time-domain spectroscopy applications

Abstract This work contains results from studying the electro-optical properties of bulk and few-layered Van der Waals materials including intercalated graphene, phosphorene, and tungsten disulfide thin films. Different production methods and substrates are considered. The objective of the research is to assess the relevance of application of these materials in terahertz (THz) time-domain spectroscopy (TDS). Therefore, the study is conducted in the visible, NIR (near-infrared) and THz frequency ranges as the most critically in need of research when searching for effective materials for TDS