Nonlinearity characterization of array spectroradiometers for the solar UV measurements.

Array spectroradiometers are attractive alternatives to scanning spectroradiometers in solar ultraviolet measurements. However, the measurement of solar spectral irradiance imposes stringent requirements for the linearity of the instruments. In this article, two array spectroradiometers were characterized for nonlinearity.

On a propagation-invariant, orthogonal modal expansion on the unit disk: going beyond Nijboer-Zernike theory of aberrations.

Nijboer-Zernike's circle polynomials are broadly used for the evaluation of aberrations of optical systems or, more generally, wavefront analysis. This is because they are orthogonal over a unit circle and are directly related to the balanced classical aberrations for imaging systems with circular pupils. However, such expansion and successive extensions of the original theory suffer from a key limitation: it does not preserve its form under propagation.

Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry.

Optical scatterometry is the state of art optical inspection technique for quality control in lithographic process. As such, any boost in its performance carries very relevant potential in semiconductor industry. Recently we have shown that coherent Fourier scatterometry (CFS) can lead to a notably improved sensitivity in the reconstruction of the geometry of printed gratings.

On the nonparaxial corrections of Bessel-Gauss beams.

The nonparaxial corrections for Bessel-Gauss beams were derived recently using two different approaches [Borghi et al., J. Opt.

Dependence of the degree of paraxiality on field correlations.

A linearly polarized optical field can be obtained by filtering a stochastic field through an ideal linear polarizer. The produced field possesses a given degree of paraxiality that, as proved in the present Letter, can be affected by the correlations of the original stochastic field. An example with Gaussian beams is discussed in detail.

Comment on "Quality of paraxial electromagnetic beams".

We comment on a recent paper by Seshadri [Appl. Opt.45, 5335 (2006)]APOPAI0003-693510.

Degree of paraxiality for monochromatic light beams.

We introduce the degree of paraxiality as a paraxiality measure of a monochromatic light beam. Computation of this parameter is possible once the plane-wave spectrum of the field being analyzed is given for a starting source plane. On the basis of this definition, quantitative comparisons of the paraxiality of different types of fields are possible.