A novel approach to creating long-range Structured Laser Beams (SLB) using optical aberrations is described. By combining optical elements that produce significant spherical and defocus aberrations, it is possible to generate an interference field with both transverse and longitudinal local polarization. This creates an SLB that can propagate as a wave to infinity with an invariant transverse profile, different from Bessel Beams (BB). The size and divergence of the central part of the SLB can be much smaller than those observed in Gaussian beams. Experimental confirmation showed a divergence of 0.01 mrad for the central part of the SLB, from a diameter of less than 10 μm. This method makes it possible to form a hollow beam, where non-perpendicular electric and magnetic fields exist in the central part of the beam. An overview of the properties of these SLBs is presented.
The Structured Laser Beam (SLB) is a pseudo-non-diffracting laser beam that shares many characteristics with a Bessel beam. However, it can theoretically propagate over an unlimited distance while maintaining an extremely low inner core divergence of only 0.01 mrad. This makes it a promising candidate for precise longdistance alignment applications such as the alignment of particle accelerator components at CERN. In this work, a novel method to detect low-order wavefront aberrations induced by an SLB generator, that can affect the referential straightness of the beam, is presented. Our approach is based on the analysis of a single intensity distribution of an SLB. The coefficients of the Zernike polynomials are estimated using artificial intelligence before least-squares fitting is used to refine the result. This approach ensures that the fitting avoids local minima. This method provides a novel way to analyze the optical aberrations induced by the SLB generator and estimate the quality of the beam. Furthermore, it has the potential to be used for the alignment of complex lens systems, where an SLB can serve as a reference optical axis to which the other optical elements can be aligned.
This paper treats the issue of locking a solid state laser, pumped by high power diodes (Verdi V5), to a twenty meter long optical resonator for OSQAR LSW - light shining through the wall, dark matter search experiment. In this paper the optical design and a possible locking scheme are presented. The environmental conditions in SM18 testing hall at CERN, where OSQAR experiment is based, are discussed. The main focus is put on the vibration analysis, cavity transversal modes behaviour, possible clipping in the anticryostat of LHC – Large Hadron Collider magnet bore and locking loop parameters required for future experimental testing. The expected finesse of resonator will be presented and discussed in the sense of OSQAR LSW; its impact on possible new exclusion limits is discussed.
Modified folded Jamin interferometer for on-line measurement of refractive index of gases was designed, constructed and tested. The accuracy of this interferometer is better than 10-6 and can be still approved about two orders by appropriate mathematical method. Interferometer is almost vibration insensitive with vibration noise equivalent to refractive index variation 2•10-9. The interferometer qualities were tested by air refractive index monitoring.
This paper describes a quest to find simple technique to superpolish Zerodur asphere (55μm departure from best fit sphere) that could be employed on old fashion way 1-excenter optical polishing machine. The work focuses on selection of polishing technology, study of different polishing slurries and optimization of polishing setup. It is demonstrated that either by use of fine colloidal CeO2 slurry or by use of bowl-feed polishing setup with CeO2 charged pitch we could reach 0.4nm RMS roughness while removing <30nm of surface layer. This technique, although not optimized, was successfully used to improve surface roughness on already prepolished Zerodur aspheres without necessity to involve sophisticated super-polishing technology and highly trained manpower.
A sensitive method for optical birefringence measurement is presented. To optimize the signal over the noise ratio, the polarization of the laser beam is modulated exceptionally with a high frequency electro-optical modulator. The specially developed optical apparatus exhibits high sensitivity and accuracy, which were checked by measuring the Cotton-Mouton effect in nitrogen as a function of the pressure. It is able to measure the retardance down to 2x10-4 rad. This apparatus will be used with the locked optical cavity. The optical cavity will serve as an optical path multiplier for increasing the sensitivity. This proposed set-up will be able to measure the Cotton-Mouton effect in helium, where the birefringence effect is Δn ≈ 2.4x10-16.
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.
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.
Linear electro-optic coefficients r13 and r33 of LiNbO3 crystal were measured in the setup of Mach-Zehnder interferometer with He-Ne laser. Sample was placed in closed circuit He cryostat, so temperature dependency was investigated from 150K to 330K. Electro-optical coefficients r33 and r13 were constant in this temperature range. In the measured frequency range 200 Hz-10 kHz, there is no change of the E-O coefficients with frequency.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.