We report recent progress in design and testing of a distribution system for high-power laser beam delivery
developed within the HiLASE project of the IOP in the Czech Republic. Laser beam distribution system is a
technical system allowing safe and precise distribution of different laser beams from laboratories to several
experimental stations. The unique nature of HiLASE lasers requires new approach, which makes design of the
distribution system a state-of-the-art challenge.
We present recent progress in design of innovative versatile laser head for lasers based on thin-disk architecture which are being constructed at the HiLASE centre of the IOP in the Czech Republic. Concept of thin-disk laser technology allows construction of lasers providing excellent beam quality with high average output power and optical efficiency. Our newly designed thin-disk carrier and pump module comes from optical scheme consisting of a parabolic mirror and roof mirrors proposed in 90’s. However, mechanical parts and a cooling system were in-house simplified and tailor-made to medium power lasers since no suitable setup was commercially available. Proposed opto-mechanical design is based on stable yet easily adjustable mechanics. The only water nozzle-cooled component is a room-temperature-operated thindisk mounted on a special cooling finger. Cooling of pump optics was replaced by heat conductive transfer from mirrors made of special Al alloy to a massive brass baseplate. Such mirrors are easy to manufacture and very cheap. Presented laser head was manufactured and tested in construction of Er and Yb doped disk lasers. Details of the latest design will be presented.
The measurement of spatially varying surface reflectance is required for faithful reproduction of real world to allow for predictive look of computer generated images. One such proposed method uses a rotational kaleidoscopic imaging, where illumination and imaging paths are realized by subimages on kaleidoscopic mirrors and illumination is carried out by a DLP projector. We describe a novel geometric calibration method for a rotational kaleidoscope that is necessary to get aligned and accurate data from measurement. The calibration has two stages. The first stage mechanically adjusts the camera, the projector, and the autocollimator against the kaleidoscope mirrors. The second stage is based on the software. By random perturbation of camera and projector in corresponding mathematical model of the kaleidoscope we estimate better real positions of camera and projector in a physical setup, comparing the computed images from the software simulator and the acquired images from the physical setup.
Realistic reproduction of appearance of real-world materials by means of computer graphics requires accurate measurement and reconstruction of surface reflectance properties. We propose an interactive software simulation tool for modeling properties of a kaleidoscopic optical system for surface reflectance measurement. We use ray tracing to obtain fine grain simulation results corresponding to the resolution of a simulated image sensor and computing the reflections inside this system based on planar mirrors. We allow for a simulation of different geometric configurations of a kaleidoscope such as the number of mirrors, the length, and the taper angle. For accelerating the computation and delivering interactivity we use parallel processing of large groups of rays. Apart from the interactive mode our tool also features batch optimization suitable for automatic search for optimized kaleidoscope designs. We discuss the possibilities of the simulation and present some preliminary results obtained by using it in practice.
Imaging of surface textures requires many combinations of incident illumination angles and detector angles of view.
Kaleidoscope is one of the means for measurement of bidirectional texture function of various sample surfaces.
An optical system featuring the kaleidoscope is proposed in the paper. Optical parameters of such an imaging system are
described and evaluated. We also discuss the optimization process of these parameters which influences the overall
imaging performance of a kaleidoscope device. We provide the visualization of various kaleidoscope designs.
This paper gives short overview of laser-based experiment OSQAR at CERN which is focused on search of axions and
axion-like particles. The OSQAR experiment uses two experimental methods for axion search – measurement of the
ultra-fine vacuum magnetic birefringence and a method based on the “Light shining through the wall” experiment.
Because both experimental methods have reached its attainable limits of sensitivity we have focused on designing a
vacuum laser resonator. The resonator will increase the number of convertible photons and their endurance time within
the magnetic field. This paper presents an opto-mechanical design of a two component transportable vacuum laser
resonator. Developed optical resonator mechanical design allows to be used as a 0.8 meter long prototype laser resonator
for laboratory testing and after transportation and replacement of the mirrors it can be mounted on the LHC magnet in
CERN to form a 20 meter long vacuum laser resonator.
This paper covers a description and a technique of a possible optical method of mode locking within a laser resonator.
The measurement system is a part of instrumentation of laser-based experiment OSQAR at CERN. The OSQAR
experiment aims at search of axions, axion-like particles and measuring of ultra-fine vacuum magnetic birefringence.
It uses a laser resonator to enhance the coupling constant of hypothetical photon-to-axion conversion. The developed
locking-in technique is based on differential interferometry. Signal obtained from the measurement provide crucial
information for adaptive control of the locking-in of the resonator in real time. In this paper we propose several optical
setups used for measurement and analysis of mutual position of the resonator mirrors. We have set up a differential
interferometer under our laboratory conditions. We have done measurements with hemi-spherical cavity resonator
detuned with piezo crystals. The measurement was set up in a single plane. Laser light was directed through half-wave
retarder to a polarizing beam splitter and then converted to circular polarization by lambda/4 plates. After reflection
at the mirrors, the beam is recombined in a beam splitter, sent to analyser and non-polarizing beam splitter and then
inspected by two detectors with mutually perpendicular polarizers. The 90 degrees phase shift between the two arms
allows precise analysis of a mutual distance change of the mirrors. Because our setup was sufficiently stable, we were
able to measure the piezo constant and piezo hysteresis. The final goal is to adapt the first prototype to 23 m resonator
and measure the displacement in two planes.
Two optical methods are used in the laser-based experiment OSQAR at CERN for the search of axions and axion-like
particles. The first method looks as light shining through the wall. The second one wants to measure the ultra-fine
vacuum magnetic birefringence. Both methods have reached its attainable limits of sensitivity. Present work is focused
on increasing the number of photons and their endurance time within the magnetic field using a laser cavity. Presented
paper covers recent state of development of a prototype of a 1 meter long laser cavity which is the prerequisite of further
development of the experiment.
This paper presents a short analysis of possible techniques for fusion targets tracking in rep-rate regime. Target tracking
solution is limited with necessity of high speed, high precise and long-distance measurement combined with a harsh
environment of the vacuum fusion chamber. The only optical measurement seems to be usable to meet required
conditions to measurement system. Few standards and less traditional methods are presented in this paper. Its possibility
to meet the target goal resolution is discussed. Preparation of experimental techniques for verification of measurement
conditions of suggested methods is shown too.