Mirta A. Gil

Spherical aberration in spatial and temporal transforming lenses of femtosecond laser pulses

We study the influence of third-order spherical aberration on the group velocity dispersion and on the propagation time delay of a plane pulse that is focused by a thin lens. Applications in refractive-diffractive propagation time delay compensation systems and in Gaussian temporal-shaped pulses are analyzed.

Czerny-Turner monochromator: astigmatism in the classical and in the crossed beam dispositions

The images obtained with a classical Czerny-Turner design and a crossed beam Czerny-Turner design are compared, imposing in both cases the Fastie and the Pribram and Penchina conditions. The results show that the astigmatic line may be made parallel to the spectral line only with the classical design, which makes it superior to the crossed beam design. Also, the importance of an adequate choice of the construction parameters is shown. The analytical calculations are checked by ray tracing.

Czerny-Turner spectrograph with a wide spectral range

In this work we present the design of a Czerny-Turner spectrograph with practically constant images over a wide spectral range (3500-7500 A). The plate diagram method is used to determine the parameters and the resulting design is evaluated by ray tracing.

Coma compensation in a parabolized Ebert monochromator

Coma compensation in a parabolized Ebert monochromator is studied using the plate diagram. It is shown that two different criteria may be used: narrowest images or symmetrical ones; however, both may not be satisfied simultaneously. Symmetrical or narrowest images may be obtained for an extended range of wavelengths with displacement of at least one of the slits. With fixed slits only incomplete compensation may be obtained.

Diffraction grating and optical aberrations: a new and exact formulation

The effects introduced by a plane diffraction grating on the diffracted wave front when a quasi-plane beam incides on it are calculated. These effects are evaluated by ray tracing and by analytical expressions.

Aberrations in Off-plane Spectrometers

The aberrations of two off-plane spectrometers that used parabolic mirrors, the Ebert and the Littrow, are calculated. This completes a comparative study undertaken by the authors of all the plane grating spectrometers with one mirror in the camera and another in the collimator, which makes it possible to establish clearly the optimal field of application for each design.

Aberrations in Plane Grating Spectrometers

The aberrations of off-axis plane grating spectrometers with one mirror in the camera and another in the collimator are calculated by means of the plate diagram method. Spectrometers in the Z and U configurations with spherical, centred parabolic and off-axis parabolic mirrors are studied. Making use of the opportunity provided by the method, the aberrations in each system are rapidly analysed in order to make a first selection among the designs under consideration. The analytical results are compared with those obtained by ray tracing. The study shows clearly the optimal field of application of each design.

Distortion and Split-image Curvature Calculated by the Plate Diagram Analysis in Monochromators with Off-axis Mirrors

Calculation of distortion is developed by means of the plate diagram. This method is valid for all systems with one or two mirrors in the collimator and in the camera, and also for those with three or more mirrors, provided that their curvature centres, in each branch, are aligned. The problem of the slitimage curvature may also be solved by this method for spectrographs and monochromators which fulfil the condition established above. The results are checked with those obtained by K. P. Miyake with the light-path function for monochromators with off-axis parabolical mirrors.

New plane grating monochromator with off-axis parabolical mirrors

The design of a new plane grating monochromator is described. The system employs off-axis parabolical mirrors both in the collimator and the camera. The entrance and exit slits lie on the same side of the grating and are curved to obtain the invariance of the curvature of the spectral lines with respect to wavelength variations. The grating is oriented to avoid multiple dispersions. The system is free from aberrations in the center of the field, and since the dependence of the aberrations on any other point of the field is very weak, it is possible to use long slits. The images obtained with this design are of excellent quality and may be improved even further using mirrors with slightly different off-axis angles and focal lengths for the collimator and the camera. Analytical expressions of the aberrations are obtained by the plate diagram method; the results are checked by finite ray tracing for a particular case.

Diffraction gratings and optical aberrations

The effects introduced by a plane diffraction grating on the diffracted wave front when a quasi-plane beam incides on it are calculated. Effects not previously discussed appear.