A simple and efficient protocol is developed for the in situ generation of highly monodisperse small (2−3 nm) silver nanoparticles poly(vinyl alcohol) film fabrication their free-standing films. Efficient optical limiting with these nanoparticle-embedded polymer thin films demonstrated.

The vibrational modes of the explosive related solids 2,4- and 2,6-DNT have been measured with waveguide THz time-domain spectroscopy (THz-TDS) to unprecedented precision. Dramatic sharpening spectral features upon cooling beyond 80 K 12 is observed, illustrating high quality alignment polycrystalline thin films. Many observed linewidths below 15 GHz. These are approximately 8 times narrower than for corresponding measurements via conventional THz-TDS cooled pellets. For DNT, line narrowing...

Abstract The techniques and methods employed in the spectroscopic characterization of gases, liquids, solids terahertz frequency range are reviewed. Terahertz time‐domain spectroscopy is applied to address a broadband between 100 GHz 5 THz with sub‐10 resolution. unique spectral absorption features measured can be efficiently used material identification sensing. Possibilities limitations fundamental industrial applications discussed.

Waveguide terahertz time-domain spectroscopy is used to demonstrate the narrowing of vibrational lines for a thin polycrystalline film 1,2-dicyanobenzene in parallel plate metal waveguide. When compared corresponding linewidths pellet sample at room temperature, waveguide are found be significantly sharper. For measurements near 77K, dramatic line observed film, yielding as much five times sharper than pellet. These effects attributed smaller inhomogeneous broadening and result more...

One-dimensional (1D) Bragg waveguides are demonstrated at terahertz (THz) frequencies. Lithographically made 1D symmetric and asymmetric dielectric gratings on metallized high conductivity Si chips incorporated within metal parallel plate to form waveguides. These have throughput resonances with linewidths approaching 6 GHz Q as 430. high-Q resonant excellent structures for applications in THz sensing.

Low frequency vibrational modes of pharmaceutical molecules are dependent on the molecule as a whole and can be used for identification purposes. However, conventional Fourier transform far-infrared spectroscopy (FT-IR) terahertz time-domain (THz-TDS) often result in broad, overlapping features that difficult to distinguish. The technique waveguide THz-TDS has been recently developed, resulting sharper spectral features. Waveguide consists forming an ordered polycrystalline film metal plate...

We have characterized the terahertz (THz) vibrational spectroscopy of organic polycrystalline thin films using new experimental technique waveguide time domain (waveguide THz-TDS). The materials used in this study are tetracyanoquinodimethane (TCNQ) and 1,3-dicyanobenzene (13DCB). For each material, a film is cast onto one inner surfaces metal parallel plate (PPWG), followed by measurement low-frequency spectrum THz-TDS. spectra compared to corresponding standard pellet samples made...

One of the outstanding problems terahertz spectroscopy is measurement underlying vibrational spectrum a molecular solid, where individual transitions are often merged into broad absorption features by line-broadening processes. We address this problem using technique waveguide time-domain (THz-TDS), whereby thin polycrystalline film contained within single-mode metal parallel plate waveguide. Thin films solids cyclotrimethylene trinitramine (RDX explosive) and 4-iodo-4′-nitrobiphenyl serve...

Waveguide terahertz time-domain spectroscopy (THz-TDS) is used to characterize the temperature dependent vibrational properties of three threat-related materials: 4-amino-dinitrotoluene (4A-DNT), pentaerythritol tetranitrate (PETN), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). These materials are characterized as thin polycrystalline layers deposited in 50 micron gap a metal parallel plate waveguide. For each material waveguide THz-TDS at least partially resolves underlying...

Waveguide THz-TDS using metal parallel plate waveguides is employed to obtain a high-resolution terahertz vibrational spectrum of tris(hydroxymethyl)aminomethane, commonly known as Tris or THAM, an important biological buffer component, neuroinhibitor and organic thermal energy-storing molecule. Dropcast sublimated thin films are used characterize the sample. The development (with cooling) 3 broad resonances seen at room temperature into 12 highly resolved spectral features for dropcast...

We report on a new coupling scheme for high resolution terahertz spectroscopy of microcrystalline films using parallel-plate waveguides. Metal flares are used to couple the radiation into and out waveguide. Very good ratios as 35% at 1 THz from collimated free-space beam subwavelength gap obtained. This microwave approach is compared in terms ratio spectral characteristics established technique quasioptic waveguides silicon lenses. Various samples room cryogenic temperatures measured show...

We report the first ever femtosecond supercontinuum generation in a KDP crystal using ~100 fs pulses at 790 nm irradiation. Due to quadratic nonlinearities of an enhanced bandwidth 385 -960 is generated. The spatial and temporal coherence generated white light demonstrated Young's double slit interference configuration Michelson interferometer.

The interaction of two counterpropagating plasmas and shockwaves due to a 7 ns laser induced breakdown (LIB) ambient atmospheric air was studied using the 2D emission shadowgraphic imaging technique. effect separation distance (d) between plasma sources their energy ratio on shockwave evolution is presented. These low density temperature form stagnation layer in zone that showed an interesting dependence input sources. dynamics plumes shock waves are compared with respective single source...

We report the coupling and guiding of broadband terahertz radiation using a two-cylinder waveguide coupler. For transverse electromagnetic TEM (TM0) geometry, two opposing metal cylinders exhibit an amplitude transmission comparable to that cylindrical silicon lens coupled parallel-plate waveguide, but in transverse-electric orientation coupler shows much better transmission.

We report an enhanced supercontinuum generation (SCG) from a rare-earth ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mi mathvariant="normal">P</mml:mi> mathvariant="normal">r</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>+</mml:mo> </mml:msup> </mml:math> ) doped low bandgap zinc borate glass when excited with 60 fs pulses Ti-sapphire laser. The emission associated the absorption bands due to doping (around...

The influence of the metal substrate on measurement high resolution THz vibrational modes molecular solids with waveguide THz-TDS technique is investigated. sample film salicylic acid studied using three different substrates and two-surface passivated substrates. independence observed to demonstrated. Independently, surface passivation presented as a viable experimental addition aid characterization samples known reactivity surfaces.

The interaction and evolution dynamics of two counterpropagating shockwaves generated by collinear laser induced air plasmas equal unequal energies are presented. formation a stagnation layer during the from plasma sources, namely, S1 S2 separated distance 4 mm, were studied over duration 30 μs, using two-dimensional FLASH radiation hydrodynamic code. formed is observed to be “hard” in case energy = S2. While sources with &amp;gt; S1, allow propagation energy. For both cases maximum increase...

Abstract A clear visualization of the physical processes spatially confined ns laser induced atmospheric air plasma within a rectangular glass cavity using optical imaging is presented. The occurrence various starting from early and shock wave expansion dynamics to reflection at boundaries compression due reflected shockwaves studied defocused shadowgraphy self-emission techniques. Experimentally, we evidenced that counter propagating primary interact with expanding generating secondary...

We present the spatial and temporal characterization of copper (Cu) plasma produced by femtosecond laser filaments. The filaments various lengths intensities were generated with aid three different focusing lenses. Further, filamentation induced breakdown spectroscopy (FIBS) measurements carried out for each filament at positions along length filament. spatially characterized estimating temperature electron density. Our investigation has demonstrated that centre is best to obtain a maximum...

Femtosecond laser pulse induced filamentation in atmosphere is susceptible to a number of input laser, focusing optics and medium characteristics. Filamentation fs pulses an intense propagation regime where the geometry used focus play important role influencing filament intensity associated supercontinuum. We identified different optical elements for leading air classified them according aberrations. To clearly identify aberrations, all were taken have same focal length. The subsequent...