Supermirror phase anisotropy measurement (original) (raw)
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Layer-by-layer magnetometry of polarizing supermirrors
Applied Physics A: Materials Science & Processing, 2002
We investigate the remagnetization behaviour of remanent polarizing supermirrors by polarized neutron reflectometry. Such a mirror can be remagnetized in a magnetic field of 30 mT. It is shown, that at lower fields, the mirror is not completely remagnetized, but the magnetization of the thinner layers can be flipped more easily than the magnetization of the thicker layers. With polarized neutron reflectometry, we are able to find out exactly how many layers are magnetized parallel and how many are magnetized antiparallel to the external field. Furthermore, information about structural and magnetic imperfections (roughness, domain formation) is available.
Near-infrared scanning cavity ringdown for optical loss characterization of supermirrors
Optics Express
A cavity ringdown system for probing the spatial variation of optical loss across high-reflectivity mirrors is described. This system is employed to examine substrate-transferred crystalline supermirrors and quantify the effect of manufacturing process imperfections. Excellent agreement is observed between the ringdown-generated spatial measurements and differential interference contrast microscopy images. A 2 mm diameter ringdown scan in the center of a crystalline supermirror reveals highly uniform coating properties with excess loss variations below 1 ppm.
Applied Optics, 2008
In cavity ring-down spectroscopy (CRDS), residual or stress-induced birefringence (10 −7 -10 −6 rad) of supermirrors will lift the polarization degeneracy of TEM 00 modes and generate two new polarization eigenstates in the cavity with small resonant frequency splitting (∼0:1 kHz); the new eigenstates are nearly linearly polarized. When both modes are excited simultaneously, the intracavity polarization state will evolve as the energy decays in the cavity. Without polarization analysis, such mode beating would not be observable. However, real supermirrors have a linear polarization-dependent loss (dichroism) that leads to a change in the loss rate as the polarization state evolves and thus to deviation from the expected single-exponential decay. We develop a model for the evolution of the intracavity polarization state and intensity for a cavity with both birefringence and polarization-dependent loss in the mirrors. We demonstrate, experimentally, that these parameters (both magnitudes and directions) can be extracted from a series of measurements of the cavity decay and depolarization of the transmitted light.
A new type of wide-angle supermirror analyzer of neutron polarization
Journal of Physics: Conference Series, 2014
We describe here a new type of wide-angle supermirror-based multichannel analyzer configured in the fan orientation. The increased channel width allows for reflections only from one of the channel's walls, so that the overlap of beams propagating through neighboring channels is avoided. However the straight beam, which is unavoidably propagating through the channels with the increased width, is blocked by an absorbing mask at the entrance of the analyzer. The neutron transmission of such analyzer is 22% higher and the number of the supermirrors needed to cover the same beam cross section is 16% less in comparison with a conventional fan analyzer. Results of the calculations and first tests of the analyzer at the Magnetism Reflectometer at Oak Ridge National Laboratory, USA, are presented.
Stable fiber-based Fabry-Pérot cavity
We report the development of a fiber-based, tunable optical cavity with open access. The cavity is of the Fabry-Perot type and is formed with miniature spherical mirrors positioned on the end of single-or multi-mode optical fibers by a transfer technique which involves lifting a high-quality mirror from a smooth convex substrate, either a ball lens or micro-lens. The cavities typically have a finesse of ∼ 1, 000 and a mode volume of 600 µm 3 . We demonstrate the detection of small ensembles of cold Rb atoms guided through such a cavity on an atom chip. PACS numbers: 1 An optical cavity amplifies the interaction between light and matter by recirculation of the light at a resonant frequency. This feature is exploited in a number of fields, notably lasers and optical sensors. Furthermore, it is crucial to experiments and possible technologies based on exploiting the quantum mechanical properties of individual atoms and photons. In this field of cavity quantum electrodynamics (CQED), the crucial features of the cavity are a small mode waist and/or mode volume V m , and a high finesse F = ∆ν/δν (where ∆ν is the free spectral range and δν the linewidth of the cavity), equivalently a high Q factor Q = ν/δν [1]. The "gold standard" for CQED cavities is still being set by macroscopic Fabry-Perot (FP) cavities with superpolished, concave mirrors. These mirrors have relatively large radii of curvature (R = 20 cm is typical) and achieve record finesse values of F > 2 × 10 6 [2]. However, there are situations where
On measuring birefringences and dichroisms using Fabry–Pérot cavities
Applied Physics B, 2006
When measuring very small ellipticities or rotations induced on a polarized beam of light, Fabry-Pérot cavities are often used to increase the number of passes within the region of interest. In this paper we show that due to the intrinsic birefringence of the reflective surface of the cavity mirrors, a cross talk between dichroism and ellipticity is induced. We also show how such a cross talk may be measured and kept under control by means of an adequate phase locking scheme of the laser to the cavity.
Fabrication and characterization of multilayer supermirrors for hard X-ray optics
Journal of Synchrotron Radiation, 1998
We report on a novel fabrication approach to build multilayered optical tissue phantoms that serve as independently validated test targets for axial resolution and contrast in scattering measurements by depth-resolving optical coherent tomography (OCT) with general applicability to a variety of three-dimensional optical sectioning platforms. We implement a combinatorial bottom-up approach to prepare monolayers of light-scattering microspheres with interspersed layers of transparent polymer. A dense monolayer assembly of monodispersed microspheres is achieved via a combined methodology of polyelectrolyte multilayers (PEMs) for particlesubstrate binding and convective particle flux for two-dimensional crystal array formation on a glass substrate. Modifications of key parameters in the layer-by-layer polyelectrolyte deposition approach are applied to optimize particle monolayer transfer from a glass substrate into an elastomer while preserving the relative axial positioning in the particle monolayer. Varying the dimensions of the scattering microspheres and the thickness of the intervening transparent polymer layers enables different spatial frequencies to be realized in the transverse dimension of the solid phantoms.
Physical Review A, 2001
An extensive characterization of high finesse optical cavities used in cavity QED experiments is described. Different techniques in the measurement of the loss and phase shifts associated with the mirror coatings are discussed and their agreement shown. Issues of cavity field mode structure supported by the dielectric coatings are related to our effort to achieve the strongest possible coupling between an atom and the cavity.
High-performance Kirkpatrick-Baez supermirrors for neutron milli- and micro-beams
Materials Science and Engineering: A, 2006
High-performance Kirkpatrick-Baez (KB) neutron supermirror optics can nondispersively image neutrons to small spots. Ray tracing finds that under many conditions, KB mirrors work near the theoretical limit set by source brilliance and can deliver orders of magnitude greater intensities than is possible with conventional (nonfocusing) neutron optics. In general, KB neutron supermirrors are preferred when the required beam size at the sample is small and when the distance between the optics and the sample is not small. Waveguides with beam definings slits are preferred for very short wavelengths, for big beams and when the slits can be placed very close to the sample. For example, for λ ∼ 0.1 nm, if the distance from the last optical element to the sample is ∼100 mm, almost two orders of magnitude greater intensity can be focused onto a 100 m spot with M = 3 KB supermirrors than with a beam guide and symmetric slits. This is independent of whether the beam guide collimates or condenses the beam so long as without slits the beam is larger than the acceptable beam size at the sample. We describe the ray tracing and phase space arguments that support the use of KB supermirrors for producing intense small beams and describe the performance of a prototype KB device which achieved a 89 m × 90 m focus. We briefly describe even more advanced methods that can increase the beam divergence on the sample while maintaining a small beam.
Optics Express, 2014
This study explores how interference manipulation breaks through the diffraction limit and induces super-resolution nano-optical hot spots through the nonlinear Fabry-Perot cavity structure. The theoretical analytical model is established, and the numerical simulation results show that when the thickness of the nonlinear thin film inside the nonlinear Fabry-Perot cavity structure is adjusted to centain value, the constructive interference effect can be formed in the central point of the spot, which causes the nanoscale optical hot spot in the central region to be produced. The simulation results also tell us that the hot spot size is sensitive to nonlinear thin film thickness, and the accuracy is required to be up to nanometer or even subnanometer scale, which is very large challenging for thin film deposition technique, however, slightly changing the incident laser power can compensate for drawbacks of low thickness accuracy of nonlinear thin films. Taking As 2 S 3 as the nonlinear thin film, the central hot spot with a size of 40nm is obtained at suitable nonlinear thin film thickness and incident laser power. The central hot spot size is only about /16 λ , which is very useful in super-high density optical recording, nanolithography, and high-resolving optical surface imaging.