Search results for "Physics::Optics"
showing 10 items of 1958 documents
Chromatic compensation of broadband light diffraction: ABCD-matrix approach
2004
Compensation of chromatic dispersion for the optical implementation of mathematical transformations has proved to be an important tool in the design of new optical methods for full-color signal processing. A novel approach for designing dispersion-compensated, broadband optical transformers, both Fourier and Fresnel, based on the collimated Fresnel number is introduced. In a second stage, the above framework is fully exploited to achieve the optical implementation of the fractional Fourier transform (FRT) of any diffracting screen with broadband illumination. Moreover, we demonstrate that the amount of shift variance of the dispersion-compensated FRT can be tuned continuously from the spati…
Design of a narrow-band filter based on the Brewster phenomenon for microwave applications
2017
A high-efficiency narrow-band filter based on a Dielectric Frequency-Selective Surface (DFSS) has been predicted theoretically for oblique plane-wave incidence. A DFSS showing total reflection at a frequency of 10.5 GHz, based on the Brewster phenomenon for TM polarization, has been designed with a single dielectric grating, showing extremely low-reflectance sidebands adjacent to the resonance peak. The angular and spectral response of the designed filter has been studied. In addition, dielectric ohmic losses have been accounted for in this structure. This work was supported by the Agencia Estatal de Investigación (AEI) and by the Unión Europea through the Fondo Europeo de Desarrollo Region…
Phase-conjugate emission of a two-mirror solid state laser
2002
We show that phase conjugation strongly contributes to the emission of a solid state laser in a two-mirror (Fabry-Perot) resonator , enabling dynamic correction of thermal lensing . Full correction of thermal effects is reached by vector phase conjugation .
Towards Si-based photonic circuits: Integrating photonic crystals in silicon-on-insulator platforms
2007
In the context of Si-based photonics, we report on a strategy to integrate two optical components, a 3D photonic crystal light emitter and a waveguide, in a silicon-on-insulator patterned substrate. Self-assembled colloidal photonic crystals are produced with high crystalline quality and spatial selectivity. Plane wave expansion and finite-difference time-domain have been used to find suitable configurations for positioning emitters and waveguides. The first steps toward the realisation of these configurations are presented.
Relative line intensity measurement in absorption spectra using a tunable diode laser at 1.6 um: application to the determination of (13CO2)/(12CO2) …
2001
0946-2171; The measurement of relative intensities in CO2 combination bands spectrum is performed using wavelength modulation spectroscopy (WMS) and a DFB (distributed feedback) diode laser operating at 1.6 mum. The diode laser is stabilized with an external Fabry-Perot interferometer and absorption spectroscopy is performed in a multipass gas cell. A spectrum containing spectral lines of both 13CO2 and 12CO2 isotopic species is recorded. The variation of laser power during frequency scanning and the line shape are taken into account to accurately extract line intensities from experimental data. The isotopic concentration ratio is deduced from the intensity ratio. Both ratios are measured w…
Broadband stimulated Raman backscattering
2016
International audience; Broadband amplification employing stimulated Raman backscattering is demonstrated. Using seed pulses with a bandwidth of about 200 nm, we study the amplification in a wide spectral range in a single laser shot. With chirped pump pulses and a Ne gas jet, we observed under optimized conditions, amplification in a range of about 80 nm, which is sufficient to support the amplification of sub-20 fs pulses. This broad amplification range is also in excellent agreement with PIC simulations. The conversion efficiency is at certain wavelengths as high as 1.2% and was measured to be better than 6×10 −3 on average.
Localized surface plasmons on a torus in the nonretarded approximation
2005
International audience; The dispersion relations and field patterns of the localized surface plasmons of a torus are derived analytically in toroidal coordinates in the nonretarded approximation. Numerical calculations are provided in order to identify the conditions under which a toroidal nanostructure supports a significant magnetic dipole moment at optical frequencies.
Optimization of surface plasmons launching from subwavelength hole arrays: modelling and experiments
2009
International audience; The launching of surface plasmons by micro-gratings of subwavelength apertures milled in a thick metal film is important for the development of surface plasmon based circuits. By comparing the near-field optical images of such surface plasmon sources with the results of a Huygens-Fresnel principle based scattering model, we show that the properties of the locally launched SP beams such as divergence or uniformity can be tuned by adjusting the shape of the micro-gratings. This allows us to propose an optimized source array well adapted for providing a narrow, collimated and uniform beam. (c) 2007 Optical Society of America.
Differential method for modelling dielectric-loaded surface plasmon polariton waveguides
2008
International audience; This paper demonstrates the efficiency of the differential method, a conventional grating theory, to investigate dielectric loaded surface plasmon polariton waveguides (DLSPPWs), known to be a potential solution for optical interconnects. The method is used to obtain the mode effective indices (both real and imaginary parts) and the mode profiles. The results obtained with the differential method are found to be in good agreement with those provided by the effective index method or finite elements. The versatility of the differential method is demonstrated by considering complex configurations such as trapezoidal waveguides or DLSPPWs lying on a finite width metal st…
Imaging of surface plasmon propagation and edge interaction using a photon scanning tunneling microscope
1994
We report the direct imaging of surface plasmon propagation on thin silver films using the photon scanning tunneling microscope. It is found that the surface plasmon remains tightly confined in the original launch direction with insignificant scattering to other momentum states. A propagation length of 13.2 \ensuremath{\mu}m is measured at \ensuremath{\lambda}=632.8 nm. We also present images showing the interaction of a surface plasmon with the edge of the metal film supporting it. The most remarkable feature is the absence of specularly reflected beam.