JEOS:RP - Journal of the European Optical Society Rapid publications
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Applications of Digital Holography: From Microscopy to 3D-Television
Get PDFThe paper gives an overview of the applications of digital holography based on the one hand on CCD-recording, computer storage, and numerical reconstruction of the wave
fields, and on the other hand on numerical calculation of computer generated holograms (CGH) and the transfer of these CGHs to spatial light modulators (SLM) for optical
reconstruction of the wave fields. The first mentioned type of digital holography finds applications in digital holographic microscopy, particle analysis, and interferometric form and deformation measurement, while the second type constitutes the basis for holographic 3D TV. The space-bandwidth-problem occuring in this context is addressed and first partial solutions are presented
An all fiber based Talbot self-imaging mirror device for phase-locking of a multi-fiber laser
Get PDFBy propagating beamlets from a periodically placed array of single-mode fiber amplifiers in a large mode-are (LMA) fiber, we find that a self-image of the initial beamlets is formed at certain distances in the LMA fiber. A Talbot mirror fiber device (TMFD) based on this property is proposed for phase-locking of a multi-fiber laser. For this laser system, we investigate how the LMA fiber length variation; the fiber amplifier phase variation, amplitude variation, and displacement affect the self-image qualities and the coupling efficiency
Analysis of the optical transmission through a nonlinear thin layer near the critical angle of incidence
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In this communication, we present a numerical study of the linear and nonlinear optical transmission through a thin layer near the critical angle of incidence. The optical linear transmission presents very important variations according to the optical Kerr effect. The study of the linear optical transmission allows defining the operation point of the thin layer in nonlinear regime. This study effects are important for optical applications such the all optical switching and the sensitive determination of the nonlinear refractive index (n2) of materials
Raman amplification of optical pulses in silicon nanowaveguides: Impact of spectral broadening of pump pulses
Get PDFWe consider the Raman amplification problem for silicon waveguides in the regime in which both the pump and signal pulses are relatively short but wide enough that their duration exceeds the phonon lifetime (about 3 ps in silicon). We use the coupled pump-signal equations for numerical simulations that include all competing nonlinear effects such as self- and cross-phase modulations, two-photon and free-carrier absorptions, and changes in the refractive index induced by the free carriers. However, numerical simulations do not provide much physical insight. For this reason, we also develop an approximate analytic approach for solving the Raman amplification problem. We introduce the concept of an effective Raman gain and show analytically how it depends on the pump bandwidth. As the pump spectrum broadens inside the silicon waveguide, the effective Raman gain is reduced considerably. We obtain an analytical form of the nonlinear phase accumulated during propagation inside a silicon waveguide and use it to calculate the total spectral broadening experienced by a pump pulse. Using this result, we can predict changes in the effective Raman gain as a function of pump pulse energy. A comparison of our predictions with the recent experimental data shows that our model is reasonable and captures the essential physics
Scattering and absorption properties of carbon nanohorn-based nanofluids for solar energy applications
Get PDFIn this work we investigated the scattering and absorption properties of nanofluids consisting in aqueous suspensions of single wall carbon nanohorns of different morphologies and prepared with different amounts of surfactant. The characteristics of these nanofluids were evaluated in order to
use them as direct sunlight absorber fluids in solar devices. The differences in optical properties induced by carbon nanoparticles compared to those of pure water lead to a considerably higher
sunlight absorption with respect to the pure base fluid. Scattered light over the total attenuation of light was found to be nearly negligible at NIR wavelengths. Both these effects, together with
the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device
Three-dimensional imaging and force characterization of multiple trapped particles in low NA counterpropagating optical traps
Get PDFAn experimental characterization of the three-dimensional (3D) position and force constants, acting on one or multiple trapped polystyrene beads in a weak counterpropagating beams geometry is reported. The 3D position of the trapped particles is tracked by imaging with two synchronized CMOS cameras from two orthogonal views and used to determine the stiffness along all three spatial directions through power spectrum analysis and the equipartition method. For the case of three trapped beads we measure the dependence of the force constants on the counterpropagating beams waist separation. The maximal transverse stiffnesses, is about 0.1 pN/µm per mW at a beam waist separation of 67 µm whereas the longitudinal stiffness is approximately 20 times lower. The experimental findings are in reasonable agreement with a recent physical-geometric optics calculation
Analytical expressions for diffraction-free beams through an opaque disk
Get PDFWe establish analytical expressions that demonstrate that the beam produced after diffraction of a gaussian beam by an opaque disk and collimation by a lens can be approached by a diffraction-free J0 Bessel function. We further demonstrate that a similar analytical expression can be established in the
case of femtosecond incident pulse
Spectroscopy and terahertz imaging for sigillography applications
Get PDFSigillography is the science that studies the manifold aspects of the seals. A seal can be defined as an imprint obtained on a malleable medium by imprinting an incised matrix, which transfers on it the characteristic signs of a person or an institution. We use THz spectroscopy and imaging for non-destructive evaluation of natural seals. Using a time domain THz spectroscopy and imaging system, THz transmission images are generated in the 0.1–3 THz range
Three-grating monolithic phase-mask for the single-order writing of large-period gratings
Get PDFA new type of achromatic high-efficiency monolithic phase mask is presented. The mask comprises three submicron period diffraction gratings at a single substrate side that create a purely single spatial frequency interferogram of large period. The optical scheme is that of an integrated Mach-Zehnder interferometer where all light circulation functions are performed by diffraction gratings. The paper describes the operation principle of the phase mask, the fabrication process, and its utilization in a write-on-the-fly scheme for the writing of a long, 2 µm-period grating
High efficiency, diode pumped 170 W Nd:YAG ceramic slab laser
Get PDFA new thin-slab ceramic Nd:YAG laser is presented based on a novel zig-zag configuration. The slab is shaped in such a way that the beam propagates internally bouncing on the thin lateral faces (Edge zig-zag). Preliminary experiments have demonstrated a power extraction of 170 W (CW) at an optical conversion efficiency of 36%. Measurements have also been performed to assess the propagation properties, at least in the thinner transverse direction, of the beam extracted with a simple stable resonator. This laser format appears as a good competitor of the more traditional face-pumped or edge-pumped zig-zag slab laser schemes