Modulated scattering technique in the terahertz domain enabled by current actuated vanadium dioxide switches

The modulated scattering technique is based on the use of reconfigurable electromagnetic scatterers, structures able to scatter and modulate an impinging electromagnetic field in function of a control signal. The modulated scattering technique is used in a wide range of frequencies up to millimeter waves for various applications, such as field mapping of circuits or antennas, radio-frequency identification devices and imaging applications. However, its implementation in the terahertz domain remains challenging. Here, we describe the design and experimental demonstration of the modulated scattering technique at terahertz frequencies. We characterize a modulated scatterer consisting in a bowtie antenna loaded with a vanadium dioxide switch, actuated using a continuous current. The modulated scatterer behavior is demonstrated using a time domain terahertz spectroscopy setup and shows significant signal strength well above 0.5 THz, which makes this device a promising candidate for the development of fast and energy-efficient THz communication devices and imaging systems. Moreover, our experiments allowed us to verify the operation of a single micro-meter sized VO2 switch at terahertz frequencies, thanks to the coupling provided by the antenna

Ultrafast Laser-Based Spectroscopy and Sensing: Applications in LIBS, CARS, and THz Spectroscopy

Ultrafast pulsed lasers find application in a range of spectroscopy and sensing techniques including laser induced breakdown spectroscopy (LIBS), coherent Raman spectroscopy, and terahertz (THz) spectroscopy. Whether based on absorption or emission processes, the characteristics of these techniques are heavily influenced by the use of ultrafast pulses in the signal generation process. Depending on the energy of the pulses used, the essential laser interaction process can primarily involve lattice vibrations, molecular rotations, or a combination of excited states produced by laser heating. While some of these techniques are currently confined to sensing at close ranges, others can be implemented for remote spectroscopic sensing owing principally to the laser pulse duration. We present a review of ultrafast laser-based spectroscopy techniques and discuss the use of these techniques to current and potential chemical and environmental sensing applications

Fast three-dimensional nanostructure fabrication by laser-assisted nanotransfer printing

The authors present a laser-assisted nanotransfer printing technique for transferring metal nanopatterns onto prepatterned substrates. A fused quartz mold covered with an array of chromium nanodots is pressed against the surface of a photolithographically patterned substrate, while a single laser pulse from a quadrupled-frequency solid state Nd:YAG laser is used to melt the thin metal structures. By controlling the laser fluence, selective metal pattern transfer can be realized only on the protruded area of the substrate upon separation of the quartz support. The transferred chromium nanodots are then used as an etch mask to pattern three-dimensional structures.Peer reviewed: YesNRC publication: Ye

Alternative nano-structured thin-film materials used as durable thermal nanoimprint lithography templates

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Thermo-active elastomer composite for optical heating in microfluidic systems

Single-walled carbon nanotubes are used as doping agents to form thermo-active composites with an elastomeric block-copolymer. Thermal imaging reveals that the temperature response upon irradiation with NIR laser light is dependent (among other things) on the mass fraction of the nanotubes in the polymer matrix. Copyright \ua9 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Peer reviewed: YesNRC publication: Ye

Fabrication of high aspect ratio tungsten nanostructures on ultrathin c-Si membranes for extreme UV applications

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Magnetic nanocarriers : From material design to magnetic manipulation

Magnetic nanocarries play an increasing role in various biomedical applications such as the separation of magnetically "tagged" DNA, drug delivery or identification of bioligical species. Recent developments in nanotechnology allow the fabrication of both artificial nanocarriers and magnetic separation devices which may achieve great performances at an incredibly small-volume sample handling. However, as the sizes of magnetic carriers and separation devices diminish, important theoretical and experimental challenges may occur mainly due to the important variations of the surface-to-volume ratio. Under these circumstances, intrinsic properties of individual carriers and their influence on functionality and performances of the magnetic manipulation have to be investigated with a higher degree of accuracy. In this paper, we present the state-of-the-art techniques for extracting accurate information about individual magnetic entities from magnetic measurements performed on ordered arrays or clusters of magnetic nano-objects of various dimensionalities and geometries. As the mutual magnetic interactions may be responsible for collective effects, both analytical and numerial techniques for evaluating the mutual interactions between magnetic nanoparticles and nanowires are reviewed, special emphasis being put on the dimensionality of their assemblages. As the efficiency of the manicpulation and capture of individual magnetic carriers in magnetic confinement devices depend strongly on their size, the tehoretical description of the motion of magnetic particles under various conditions of flow and field configurations become very important especially with the transition to the nanoscale regime. The equations of motion of magnetic nanocarriers in continuous-flow microfluidic devices are reivewed and some solutions for superparamagnetic interacting clusters, non-interacting beads and ferromagnetic contiguous or codebar nanowires are presented. The influence of both carrier size and transition toward the nanoscale regime on the trappability of some magnetic nanocarriers is evaluated in terms of finite-length Navier boundary conditions and applied in order to compare the motion of superparamagnetic beads and ferromagnetic nanowires in conventional continuous-flow magnetic confinement devices.Peer reviewed: YesNRC publication: Ye