A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Within the field of spectral imaging, the vast majority of instruments used are scanning devices. Recently, several snapshot spectral imaging systems have become commercially available, providing new functionality for users and opening up the field to a wide array of new applications. A comprehensive survey of the available snapshot technologies is provided, and an attempt has been made to show how the new capabilities of snapshot approaches can be fully utilized.

https://www.spiedigitallibrary.org/journals/optical-engineering/volume-52/issue-9/090901/Review-of-snapshot-spectral-imaging-technologies/10.1117/1.OE.52.9.090901.pdf

Review of snapshot spectral imaging technologies

Carnegie Airborne Observatory-2: Increasing science data dimensionality via high-fidelity multi-sensor fusion

We present optical designs with freeform optics in the context of hyperspectral imaging. Results show designs that are 5 × more compact in volume than similar designs using conventional spherical or aspherical surfaces. We will show how combining the concepts of spatial and spectral-band broadening, which will be introduced in this paper, led to the improvement in compactness that is uniquely enabled by freeform optics.

Freeform spectrometer enabling increased compactness.

Using a standing light wave potential, a stable quasi-one-dimensional attractive dilute-gas Bose-Einstein condensate can be realized. In a mean-field approximation, this phenomenon is modeled by the cubic nonlinear Schrodinger equation with attractive nonlinearity and an elliptic function potential of which a standing light wave is a special case. New families of stationary solutions are presented. Some of these solutions have neither an analog in the linear Schrodinger equation nor in the integrable nonlinear Schrodinger equation. Their stability is examined using analytic and numerical methods. Trivial-phase solutions are experimentally stable provided they have nodes and their density is localized in the troughs of the potential. Stable time-periodic solutions are also examined.

https://arxiv.org/pdf/cond-mat/0012096.pdf

Stability of attractive Bose-Einstein condensates in a periodic potential

We present the analytical design of an imaging spectrometer based on the three-concentric-mirror (Offner) configuration. The approach presented allows for the rapid design of this class of system. Likewise, high-optical-quality spectrometers are obtained without the use of aberration-corrected gratings, even for high speeds. Our approach is based on the calculation of both the meridional and the sagittal images of an off-axis object point. Thus, the meridional and sagittal curves are obtained in the whole spectral range. Making these curves tangent to each other for a given wavelength results in a significant decrease in astigmatism, which is the dominant residual aberration. RMS spot radii less than 5 µm are obtained for speeds as high as f/2.5 and a wavelength range of 0.4–1.0 µm. A design example is presented using a free interactive optical design tool.

/pdf/analytical-design-of-an-offner-imaging-spectrometer-mt13xocjwn.pdf

Analytical design of an Offner imaging spectrometer

Fourier analysis of non-paraxial self-focusing

The Z-scan technique is used to characterize the nonlinear refraction induced by a train of ultrashort laser pulses (80 fs, repetition rate 80.75 MHz) for a set of ionic liquids as a function of their structural parameters such as cation, anion type and alkyl chain length in the cation. The nonlinear refractive index change is originated by linear absorption processes which cause a nonlocal and inhomogeneous increase of temperature in the irradiated region of the sample that behaves as a thermal lens. The thermal refraction, according to the thermal lens model, is mainly related to three physical properties of the medium, which are the absorption at the excitation wavelength, the thermal conductivity and the thermo-optic coefficient. We explore the influence of anions and cations on these properties and on the thermal lens strength. The cationic influence was the object of study for the ILs based on the 1-butyl-3-methyl-imidazolium cation. The anionic influence was studied for the ILs based on the bis(trifluoromethylsulfonyl)imide anion. The obtained results show that both cation and anion affect significantly the thermal lens strength. The thermal refraction is 1.6 times higher in 1-butyl-3-methyl-imidazolium chloride than in 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide, and 3.3 times higher in trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide than in 1-butylpyridinium bis(trifluoromethylsulfonyl)imide. Optical absorption at 810 nm is influenced by both ionic parts, whereas the anion hardly determines the magnitude of the thermal conductivity. © 2014 Elsevier Ltd.

Thermal refraction in ionic liquids induced by a train of femtosecond laser pulses

We study the stabilization of a large negative scattering length Bose-Einstein condensate by using a multisoliton fringe system. Each fringe behaves like a quasiparticle and the whole cloud forms a stable system when the trapping in one or two directions is switched off. The resulting system can be used as a coherent source of atomic solitons. A discussion on how to generate the soliton fringe system experimentally is made. © 1999 The American Physical Society.

R. de la Fuente

Papers

Analytical design of an Offner imaging spectrometer

Fourier analysis of non-paraxial self-focusing

Thermal refraction in ionic liquids induced by a train of femtosecond laser pulses

Atomic soliton reservoir: How to increase the critical atom number in negative-scattering-length Bose-Einstein gases

Unusual modulation instability in fibers with normal and anomalous dispersions