ABSTRACT
A new method that reshapes a Gaussian laser beam into a polygon of diffraction-limited size with a flat or a pyramidal top is presented. The technique is based on the use of computer-generated holograms with phase dislocations (singularities).
ABSTRACT
A precision laser pattern generator for writing arbitrary diffractive elements was developed as an alternative to Cartesian coordinate laser/electron-beam writers. This system allows for the fabrication of concentric continuous-relief and arbitrary binary patterns with minimum feature sizes of less than 0.6 microm and position accuracy of 0.1 microm over 300-mm substrates. Two resistless technologies of writing on chromium and on amorphous silicon films were developed and implemented. We investigated limit characteristics by writing special test structures. A 58-mm f/1.1 zone plate written directly is demonstrated at a lambda/50 rms wave-front error corresponding to a 0.06-microm pattern accuracy. Several examples of fabricated diffractive elements are presented.
ABSTRACT
Two subfamilies of concave grating superstationary anastigmatic mounts that provide minimum chromatic aberrations are described. The obtained approximate formulas can be used to design flat-field spectrographs and multi/demultiplexers for optical communication networks. Two specific mounts and their performance are presented.
ABSTRACT
The general equations for parameters of concave grating mounts that provide stationary and superstationary astigmatism at the wavelength of correction are derived for the first time, to the best of our knowledge. These can be used to design grating multi/demultiplexers for wavelength-division multiplexed optical communication systems and high-resolution, narrow-band spectrographs. Important special cases of stationary anastigmatic mounts and their performance are presented.
ABSTRACT
The concave grating stationary anastigmatic spectrograph has been modified into a novel retroreflective scheme by introducing a convex mirror concentric to the intermediate image. This provides double dispersion, diffraction-limited imaging of a long entrance slit, and substantial compensation of the stationary chromatic astigmatism. One can realize 140 independent multi/demultiplexers with 160 channels each simultaneously in the described device for optical network applications. Ray-tracing spot diagrams are presented.
ABSTRACT
A simple equation for the parameters of the Rowland circle grating mount is derived that ensures that the astigmatism and the meridional spherical aberration are stationary at the wavelength of correction. This is important in optimizing the design of grating multiplexers-demultiplexers and cross connects in wavelengthdivision multiplexed networks and high-resolution narrow-band spectrographs. An analysis of aberrations in three-dimensional and planar two-dimensional optical schemes is presented, and it is shown that in the wavelength range of 1530-1570 nm diffraction-limited performance can be achieved for 160 channels in a three-dimensional multiplexer-demultiplexer and for more than 800 channels for a planar free-space scheme.
ABSTRACT
A diffractive optical element has been synthesized with laser phototechnology. It can transform a point source into a bright caustic (a light line) stretched along the optical axis. The element transforms a spherical wave into a conic and a point source in the object space to a ring structure in the image space. We investigated how the parameters of the light line (the length and the effective diameter) depend on the wavelength of the light source and the movement of the source along the optical axis. Also the interference field outside the caustic (Fresnel and Poisson fringes) was investigated. For an explanation of experimental data the geometrical theory of interferometers was used. The conditions for the appearance of fringes in white light are given. A device for rectilinear control of large tool beds and for centering machine components was manufactured. Experiments on determining the macroshape and the microshape of objects were performed.