Diode lasers develop very fast and are widely used in various optical equipment. Diode laser sources produce fields that
show fundamental variations with respect to the canonical Gaussian beam. A partially coherent Lorentz model is
employed to describe the far field of a single mode diode laser beam. This paper is concerned with laser junctions
significantly narrower than the wavelength. Two lenses system are placed in front of the laser diode, so that the
diverging beam is transformed into a converging beam. The across spectral density function in the plane perpendicular to
the diode junction is considered in detail, and subsequently employed to predict the light intensity at various beam cross
sections near the focus by using the generalized Huygens diffraction integral. The intensity profile at a focused spot
produced by a partially coherent Lorentz beam is investigated and compared with that of Gaussian Schell-model beam. It
is shown that it has a simple form but fairly describes the optical field in the focal region. The theoretical results are well
fit to the practical results in this model and the variations between theory and the experiments are quite less than that of
in Gaussian beams. Since Gaussian beams have a minimum uncertainty field, i.e. it possesses the minimum achievable
angular spreading once the spatial extension is fixed. Since diode lasers produce highly diverging fields, a Gaussian
description for the transverse fields fails. In this case, our results show that partially coherent Lorentz model is a better
approximation, and the numerical simulation and discussions are given in detail.
Using the technique of Lie operator algebra, we present a recursive formulation for calculating the third and fifth order aberrations of a general optical system and express the third and fifth order aberration coefficients in the 7×7 and 12×12 matrix forms, respectively. One advantage of our formulae is their explicit algebraic expressions suitable for practical application and numerical calculations, another is that the formulae provide a formulation of the matrix method for general nonlinear transformation and the generalized matrix method employing Lie algebraic tools proposes a new view for aberration optics computation. With the method it should be possible to evaluate all the aberration terms for any optical system. Applications of the matrix method are illustrated with thick lens and some well known imaging systems.
The criterions for determining the minimum number of arrayed waveguides are presented using the design theory of arrayed waveguide gratings (AWGs) and Fraunhofer diffraction principle for the optimal design of AWGs. In addition, some parameters such as the cross section of waveguides and the waveguide separation between adjacent waveguides are chosen to optimize the AWG structure to satisfy the performance specifications and to match the fabrication conditions in our laboratory. As an example to demonstrate the effectiveness of the proposed method, the simulated results of the designed 16 16 AWGs with silica-based sol-gel material were provided using the beam propagation method (BPM). And the effectiveness of optimal parameters, especially to the selection of the minimum number of arrayed waveguides on the performance of the AWG, has been perfectly verified by comparing the transmission spectra of the designed AWGs. The design methodology can serve as a simple and useful tool for the optimal design of AWG multiplexers/demultiplexers.
An orthogonal projection sampling method is proposed in this paper and is applied in the reconstruction of incomplete data field by using the prior knowledge algorithm based on the modified ART, by which the satisfying reconstruction results can be obtained even with less sampling directions and limited sampling angular range. The Mean Square Error (MSE) and peak value between the origin field, the reconstructed field using orthogonal projection sampling method and traditional projection sampling method are analyzed with the numerical simulation of computer. The results indicate that the orthogonal projection sampling can reduce the MSE greatly in the reconstruction of incomplete data. Thus our researches provide a new means for the reconstruction of incomplete data field.
Proc. SPIE. 6028, ICO20: Lasers and Laser Technologies
KEYWORDS: Diffraction, Gaussian beams, Coherence (optics), Matrices, Laser applications, Free space, Laser beam propagation, Beam propagation method, Systems modeling, Global system for mobile communications
We investigate the twist properties of the ten-parameter family of partially coherent general anisotropic Gaussian Schell model (AGSM) beams passing through first-order optical systems. By utilizing the generalized Huygens-Fresnel diffraction integral for asymmetric first-order optical systems, the explicit twist expressions for the principal axes of intensity distribution, transverse coherence distribution and the principal curvatures of phase front in the cross-spectral density function of AGSM beams are obtained. In some special cases when the beams are the twist Gaussian Schell-Model, Gaussian Schell-Model, Li-Wolf and Gori-Guattari beams, our results reduce to well known expressions. It is shown that, under some conditions, although the ten parameters are all not zero and any one of the intensity distributions, transverse coherence distribution and the phase front has its independent principal axis, the beam spot does not twist when the beam passing through free-space. As a result, special partially coherent beams called the twisted-free ten-parameter family of partially coherent general anisotropic Gaussian Schell model (TF-AGSM) beams are introduced and their properties are discussed.