The Visible and Infrared Survey Telescope for Astronomy (VISTA) is the 4-m wide-field survey telescope at ESO’s Paranal Observatory, equipped with the world’s largest near-infrared imaging camera (VISTA IR Camera, VIRCAM), with 1.65 degree diameter field of view, and 67 Mpixels giving 0.6 deg2 active pixel area, operating at wavelengths 0.8−2.3 μ m. We provide a short history of the project, and an overview of the technical details of the full system including the optical design, mirrors, telescope structure, IR camera, active optics, enclosure and software. The system includes several innovative design features such as the f /1 primary mirror, thedichroic cold-baffle camera design and the sophisticated wavefront sensing system delivering closed-loop 5-axis alignment of the secondary mirror. We conclude with a summary of the delivered performance, and a short overview of the six ESO public surveys in progress on VISTA.

/pdf/the-visible-and-infrared-survey-telescope-for-astronomy-5czsktv06r.pdf

The Visible and Infrared Survey Telescope for Astronomy (VISTA): Design, technical overview, and performance

Nanofabrication of structures with a feature size of sub-50 nm with ultrashort-laser based two-photon polymerization (2PP) technique is presented. The spatial resolution of the 2PP structures depends on the characteristics of the polymer material and the laser system used for fabrication. Here we compare the successful creation of sub-100 nm structures with two different few-cycle laser systems and chemically modified zirconium-based sol-gel composite material using cross-linker for resolution enhancement.

Two-photon polymerization technique with sub-50 nm resolution by sub-10 fs laser pulses

Investigations of two-photon polymerization (TPP) with sub-100 nm in the structuring resolution are presented by using photosensitive sol-gel material. The high photosensitivity of this material allows for TPP using a large variety in laser pulse durations covering a range between sub-10 fs and ≈140 fs. In this study, the authors demonstrate TPP structuring to obtain sub-100 nm in resolution by different approaches, namely, by adding a cross-linker to the material and polymerization with sub-10 fs short pulses. Additionally, a simulation and model based characterization method for periodic sub-100 nm structures was implemented and applied in an experimental white light interference Fourier-Scatterometry setup.

/pdf/development-of-functional-sub-100-nm-structures-with-3d-two-11hac2bmnw.pdf

Development of functional sub-100 nm structures with 3D two-photon polymerization technique and optical methods for characterization

In 1832 Hamilton predicted that a collimated light beam propagating through a biaxial crystal parallel to one of its optical axes refracts as a slanted cone within the crystal and emerges as a hollow light cylinder, this optical effect being named as conical refraction (CR). The diffractive solution of CR presented by Belsky and Khapalyuk in 1978 and the corresponding re-formulation carried out by Berry in 2004 rekindled this old and almost forgotten phenomenon. In this article, we review the CR phenomenon following different approaches that allow understanding light propagation in biaxial crystals, including the case of multiple crystals in cascade. We then focus on the description of the singular properties of the CR beams, presenting some examples such as optical bottle beams and beams carrying orbital angular momentum. All these features are used to introduce some of the most appealing applications of CR in the fields of optical trapping, free-space optical communications, polarization metrology, super-resolution imaging, two-photon polymerization, and lasers.

Conical refraction: fundamentals and applications

We report on the creation and use of a unique object of scientific infrastructure – a technological line designed to create and study diffractive optical elements (DOEs). The technological line is a key element of the Center for Collective Use of Equipment "Diffractive Optics and Nanophotonics", created by joint efforts of scientists of Samara University and the Image Processing Systems Institute of the Russian Academy of Sciences. The line includes both the purchased equipment and software, and unique in-house developments. The line covers all stages of DOE creation: from calculation and modeling to experimental research, including development and testing of DOE-based devices.

Technological line for creation and research of diffractive optical elements

Enhancing the diffraction efficiency of continuous-relief diffractive optical elements fabricated by direct laser writing is discussed. A new method of zone-boundary optimization is proposed to correct exposure data only in narrow areas along the boundaries of diffractive zones. The optimization decreases the loss of diffraction efficiency related to convolution of a desired phase profile with a writing-beam intensity distribution. A simplified stepped transition function that describes optimized exposure data near zone boundaries can be made universal for a wide range of zone periods. The approach permits a similar increase in the diffraction efficiency as an individual-pixel optimization but with fewer computation efforts. Computer simulations demonstrated that the zone-boundary optimization for a 6 microm period grating increases the efficiency by 7% and 14.5% for 0.6 microm and 1.65 microm writing-spot diameters, respectively. The diffraction efficiency of as much as 65%-90% for 4-10 microm zone periods was obtained experimentally with this method.

Zone-boundary optimization for direct laser writing of continuous-relief diffractive optical elements.

A novel type of a combined (or multiplex) computer-generated hologram (CGH) and a method for interferometric testing of steep axially symmetric aspheres is presented. The method is based on a hybrid CGH containing two different diffractive structures. The presented new type of Diffractive Fizeau Null Lens (DFNL) design eliminates the transmitted wavefront distortion (TWD) of the CGH substrate and increases the accuracy of the surface test. The method was approved by testing a spherical reference mirror with an f-number of f/0.65.

Combined computer-generated hologram for testing steep aspheric surfaces

An overview of recent results in fabrication and application of new types of high precision CGHs for interferometric aspherical testing is presented.

Computer generated holograms: fabrication and application for precision optical testing

/pdf/methods-for-on-line-testing-of-characteristics-of-5ef6lv9s76.pdf

Methods for On-Line Testing of Characteristics of Diffractive and Conformal Optical Elements during the Manufacturing Process

A Shack-Hartmann type wavefront sensor designed on the basis of a low-aperture off-axis diffraction lens array is described. Tests experiments showed that the sensor is capable of measuring wavefront slopes at array subapertures of size 640×640 µm with an error not exceeding 4.80 arcseconds (0.15 pixel), which corresponds to the standard deviation (SD) (SD = 0.0170λ) at the reconstructed wavefront. Advantages of the array used in the sensor and the technology of its manufacture are discussed. The sensor tested in the experiments can be used to measure atmospheric turbulence parameters and as an element of adaptive optical imaging systems.

Ruslan K. Nasyrov

Papers

Zone-boundary optimization for direct laser writing of continuous-relief diffractive optical elements.

Combined computer-generated hologram for testing steep aspheric surfaces

Computer generated holograms: fabrication and application for precision optical testing

Methods for On-Line Testing of Characteristics of Diffractive and Conformal Optical Elements during the Manufacturing Process

Shack-Hartmann sensor based on a low-aperture off-axis diffraction lens array