Home

Applied Physics B: Lasers and Optics

Image formation in scanning electron microscopy of ultracold atoms

Thu, 2010-02-18 19:53 — Guest
0
points

Abstract  
Imaging ultracold atoms by means of scanning electron microscopy involves several aspects that are different from standard optical imaging techniques. The quality of the images depends on the properties of the electron beam, and the signal depends on the details of the ionization process and subsequent detection strategy. We discuss the alignment and characterization procedure of the electron beam, the handling of different charge states that are produced upon electron impact, and correction algorithms to compensate for relative drifts between the field of view of the electron beam and the atomic target.
  • Content Type Journal Article
  • DOI 10.1007/s00340-009-3861-9
  • Authors
    • P. Würtz, Johannes Gutenberg-Universität Institut für Physik 55099 Mainz Germany
    • T. Gericke, Johannes Gutenberg-Universität Institut für Physik 55099 Mainz Germany
    • A.

A broadband reflector using a multilayered grating structure with multi-subpart profile

Thu, 2010-02-18 19:53 — Guest
0
points

Abstract  
In this paper, a broadband reflector exhibiting a flattened bandstop spectral response is proposed by using a multilayered grating structure possessing multi-subpart profile. It is shown that with the properly configured profile and a strongly modulated grating layer, in transverse electric (TE) polarized wave the presented reflector experimentally demonstrated a 240 nm-wide reflection spectrum from 1.56 to 1.8 μm, very high reflectivity (>97%), and a low sensitivity to incident angle at the range of −13.8°<θ<+14°. Effects of deviation from the design parameters on the performance of the reflector are also illustrated, and a reasonably good tolerance of fabrication error is exhibited in the proposed device.
  • Content Type Journal Article
  • DOI 10.1007/s00340-010-3917-x
  • Authors
    • H.

Influence of surface roughness on the elastic-light scattering patterns of micron-sized aerosol particles

Wed, 2010-02-10 08:47 — Guest
0
points

Abstract  The relation between the surface roughness of aerosol particles and the appearance of island-like features in their angle-resolved elastic-light scattering patterns is investigated both experimentally and with numerical simulation. Elastic scattering patterns of polystyrene spheres, Bacillus subtilis spores and cells, and NaCl crystals are measured and statistical properties of the island-like intensity features in their patterns are presented. The island-like features for each class of particle are found to be similar; however, principal-component analysis applied to extracted features is able to differentiate between some of the particle classes. Numerically calculated scattering patterns of Chebyshev particles and aggregates of spheres are analyzed and show qualitative agreement with experimental results.
  • Content Type Journal Article
  • DOI 10.1007/s00340-010-3914-0
  • Authors
    • J.-C.

Diagnostic and characterization of the VCSEL diodes based on GaSb

Tue, 2010-02-09 08:44 — Guest
0
points

Abstract  Vertical-Cavity Surface-Emitting Laser (VCSEL) diodes are among the youngest members of the semiconductor laser diode family. The main aim of our work focuses on the measurement of the basic properties (the spectral range of the laser emission, temperature and current tunability) of experimental VCSEL diode lasers based on GaSb operating in the infrared region around 4250 cm−1. A high-resolution FTIR Bruker IFS 120 HR spectrometer with a maximum resolution of 0.0035 cm−1 was used in the emission setup for the laser diagnostic research. The absorption spectra of atmospheric pollutants like methane, carbon monoxide and ammonia have been measured using these VCSELs for the first time.
  • Content Type Journal Article
  • DOI 10.1007/s00340-010-3907-z
  • Authors
    • I. Matulková, Academy of Sciences of the Czech Republic J.

Spectral shift of a twisted electromagnetic Gaussian Schell-model beam focused by a thin lens

Tue, 2010-02-09 08:44 — Guest
0
points

Abstract  Spectral changes of a twisted electromagnetic Gaussian Schell-model (EGSM) beam focused by a thin lens are investigated by using a tensor method. It is shown that the spectral shift is mainly determined by the degree of polarization, twist phase and correlation coefficients of the initial beam. Generically the blue shift occurs at on-axis points, while the red shift can occur at off-axis points.
  • Content Type Journal Article
  • DOI 10.1007/s00340-010-3906-0
  • Authors
    • S. Zhu, Soochow University School of Physical Science and Technology Suzhou 215006 China
    • Y.

Analysis of one-end-pumped Yb3+-doped gain guided and index antiguided fiber laser

Tue, 2010-02-09 08:44 — Guest
0
points

Abstract  The one-end-pumped Yb3+-doped gain guided and index antiguided (GG+IAG) fiber laser is analyzed with a rate equation model. By solving propagation rate equations, the pump and signal, the gain coefficients and other characteristics are obtained. Computation results show that a properly designed Yb3+-doped GG+IAG fiber laser can provide a large-mode laser with a short length. The most important issue addressed is the way of controlling the fiber laser length.
  • Content Type Journal Article
  • DOI 10.1007/s00340-010-3919-8
  • Authors
    • E. Zhou, Fudan University Department of Optical Science and Engineering Shanghai 200433 P.R. China
    • B. Zhao, The Chinese Academy of Sciences State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics Xi’an 710119 P.R. China
    • X.

Parametric characteristics for a broadband Gaussian beam in free space

Tue, 2010-02-09 08:44 — Guest
0
points

Abstract  Based on the theory of the second-order intensity moment and the method of Fourier transformation, some parameters for a broadband Gaussian beam in free space are studied analytically and numerically. It is shown that the beam width and the divergence angle for a broadband Gaussian beam in free space are both larger than those for a monochromatic Gaussian beam. The broader the bandwidth of a light beam, the larger the beam width and the divergence angle of the light beam. The beam propagation factor for a broadband Gaussian beam in free space is larger than that for a monochromatic Gaussian beam and increases slowly with bandwidth. The kurtosis parameter for a broadband Gaussian beam in free space increases with propagation distance and bandwidth. The kurtosis parameter for a broadband Gaussian beam with much broader bandwidth increases more remarkably with propagation distance.

Investigation of gold-coated bare fiber probe for in situ intra-vitreous coherence domain optical imaging and sensing

Tue, 2010-02-09 08:44 — Guest
0
points

Abstract  We have investigated the usage of gold-plated bare fiber probes for in situ imaging of retinal layers and surrounding ocular tissues using time-domain common-path optical coherence tomography. The fabricated intra-vitreous gold-plated micro-fiber probe can be fully integrated with surgical tools working in close proximity to the tissue to provide subsurface images having a self-contained reference plane independent to the Fresnel reflection between the distal end of the probe and the following medium for achieving reference in typical common-path optical coherence tomography. We have fully characterized the probe in an aqueous medium equivalent to the vitreous humor in the eye and were able to differentiate various functional retinal tissue layers whose thickness is larger than the system’s resolution.
  • Content Type Journal Article
  • DOI 10.1007/s00340-010-3910-4
  • Authors
    • J.-H.

Spectral and modulation properties of a largely tunable MEMS-VCSEL in view of gas phase spectroscopy applications

Mon, 2010-02-08 19:28 — Guest
0
points

Abstract  An extensive characterization of the spectral properties of a largely tunable laser in the 1.56-μm spectral range is reported. This device combines a vertical-cavity surface-emitting laser (VCSEL) with a micro-machined (MEMS) Bragg mirror in a very compact arrangement. The large tunability obtained by an electro-thermal actuation of the MEMS mirror makes this device very attractive for high-resolution spectroscopy. Relevant laser parameters for the implementation of wavelength modulation spectroscopy techniques in gas sensing, such as tuning and modulation properties, are presented. A preliminary gas spectroscopy experiment performed with this laser is also shown.
  • Content Type Journal Article
  • DOI 10.1007/s00340-010-3898-9
  • Authors
    • S. Schilt, IR Microsystems SA, PSE-C 1015 Lausanne Switzerland
    • K.

Supercontinuum generation in macromolecular media

Sat, 2010-02-06 10:18 — Guest
0
points

Abstract  The interaction of intense, ultrashort (femtosecond) pulses of infrared light with water leads to the generation of a white light supercontinuum due to nonlinear optical effects. This supercontinuum extends over the wavelength range 400–900 nm. The blue-sided components of this supercontinuum are due to laser-induced plasma effects and are found to sensitively depend on the presence in water of minute quantities of protein dopants (dilutions of 0.025%–0.1%). Salivary proteins like mucin and immunoglobulin-A lead to pronounced suppression of the blue-sided components, while proteins found in blood serum, such as transferrin, immunoglobulin G (IgG) and human serum albumin (HSA), do not show any such suppression. It is postulated that major salivary proteins have a propensity to efficiently scavenge plasma electrons and thereby extinguish the plasma that is formed upon laser irradiation.

123456789…next ›last »
Syndicate content