Mirror In Vacuum Research Articles

First- and Second-Order Forces in the Asymmetric Dynamical Casimir Effect for a Single δ − δ′ Mirror

Here, we consider an asymmetric δ−δ′ mirror undergoing time-dependent interactions with a massless scalar field in 1 + 1 dimensions. Using fluctuation-dissipation theory for a mirror in vacuum, we compute the force on a moving δ−δ′ mirror with time-dependent material properties. We investigate the first-order forces arising from the two distinct fluctuation sources and calculate the linear susceptibility in each case. We then plot the resulting forces. At the second order, we also find the independent contributions to the total force as well as the force that arises from the interference phenomena between the two fluctuation sources.

Characterization of laser thermal loading on microelectromechanical systems-based fast steering mirror in vacuum

Microelectromechanical systems (MEMS) have produced high-quality, high-bandwidth, small form factor, and inexpensive fast steering mirror (FSM) devices potentially suitable for a large variety of applications, such as image stabilization and beam pointing in satellite-based and ground-based, free-space optical communication systems. However, one outstanding question for this application is power handling. The absorption of the mirror substrate is low, but non-negligible, so the question remains of whether thermal loading from laser radiation on a MEMS mirror will deform its surface and, if so, to what extent. We show experimental results of optical performance changes due to thermal loading for MEMS two-axis FSM devices from Mirrorcle Technologies, Inc. Results and reproducible behavior are reported and compared in ambient versus vacuum conditions, where the benefits of convective cooling are absent. Finite element analyses corroborate the experimental results and show that the mirror substrate can deform due to thermal expansion imbalances. The deformation changes the focusing characteristics of the mirror, with a peak to valley defocus (second-order Zernike mode) of up to 50 nm when the mirrors are tested in ambient and up to approximately 450 nm when under vacuum. Such defocusing negatively impacts the link budget for laser-based satellite communications.

Wide-angle ITER-prototype tangential infrared and visible viewing system for DIII-D.

An imaging system with a wide-angle tangential view of the full poloidal cross-section of the tokamak in simultaneous infrared and visible light has been installed on DIII-D. The optical train includes three polished stainless steel mirrors in vacuum, which view the tokamak through an aperture in the first mirror, similar to the design concept proposed for ITER. A dichroic beam splitter outside the vacuum separates visible and infrared (IR) light. Spatial calibration is accomplished by warping a CAD-rendered image to align with landmarks in a data image. The IR camera provides scrape-off layer heat flux profile deposition features in diverted and inner-wall-limited plasmas, such as heat flux reduction in pumped radiative divertor shots. Demonstration of the system to date includes observation of fast-ion losses to the outer wall during neutral beam injection, and shows reduced peak wall heat loading with disruption mitigation by injection of a massive gas puff.

The parametric doppler effect upon oblique radiation incidence in quartz glass

Frequency and reflection angle of probe radiation from a refractive-index inhomogeneity induced by an intense pumping pulse in quartz glass and moving with a relativistic velocity are calculated. Conditions under which the normal component of the wave vector of the reflected wave is directed to the opposite or to the same direction as the same component for the incident wave are determined. Comparison with the case of radiation reflection from a relativistic mirror in vacuum is performed. Conditions of the appearance of the Vavilov-Cherenkov radiation from a relativistic refractive-index inhomogeneity induced in the medium by an intense laser pulse are discussed.

Aerial imaging technology for photomask qualification: from a microscope to a metrology tool

Abstract Photomasks carry the structured information of the chip designs printed with lithography scanners onto wafers. These structures, for the most modern technologies, are enlarged by a factor of 4 with respect to the final circuit design, and 20–60 of these photomasks are needed for the production of a single completed chip used, for example, in computers or cell phones. Lately, designs have been reported to be on the drawing board with close to 100 of these layers. Each of these photomasks will be reproduced onto the wafer several hundred times and typically 5000–50 000 wafers will be produced with each of them. Hence, the photomasks need to be absolutely defect-free to avoid any fatal electrical shortcut in the design or drastic performance degradation. One well-known method in the semiconductor industry is to analyze the aerial image of the photomask in a dedicated tool referred to as Aerial Imaging Measurement System, which emulates the behavior of the respective lithography scanner used for the imaging of the mask. High-end lithography scanners use light with a wavelength of 193 nm and high numerical apertures (NAs) of 1.35 utilizing a water film between the last lens and the resist to be illuminated (immersion scanners). Complex illumination shapes enable the imaging of structures well below the wavelength used. Future lithography scanners will work at a wavelength of 13.5 nm [extreme ultraviolet (EUV)] and require the optical system to work with mirrors in vacuum instead of the classical lenses used in current systems. The exact behavior of these systems is emulated by the Aerial Image Measurement System (AIMS™; a Trademark of Carl Zeiss). With these systems, any position of the photomask can be imaged under the same illumination condition used by the scanners, and hence, a prediction of the printing behavior of any structure can be derived. This system is used by mask manufacturers in their process flow to review critical defects or verify defect repair success. In this paper, we give a short introduction into the lithography roadmap driving the development cycles of the AIMS systems focusing primarily on the complexity of the structures to be reviewed. Second, we describe the basic principle of the AIMS technology and how it is used. The last section is dedicated to the development of the latest generation of the AIMS for EUV, which is cofinanced by several semiconductor companies in order to close a major gap in the mask manufacturing infrastructure and the challenges to be met.

Quantum dissipative effects in moving imperfect mirrors: Sidewise and normal motions

We extend our previous work on the functional approach to the dynamical Casimir effect, to compute dissipative effects due to the relative motion of two flat, parallel, imperfect mirrors in vacuum. The interaction between the internal degrees of freedom of the mirrors and the vacuum field is modeled with a nonlocal term in the vacuum field action. We consider two different situations: either the motion is `normal', i.e., the mirrors advance or recede changing the distance $a(t)$ between them; or it is `parallel', namely, $a$ remains constant, but there is a relative sliding motion of the mirrors' planes. For the latter, we show explicitly that there is a non-vanishing frictional force, even for a constant shifting speed.

Quantum fluctuations of mass for a mirror in vacuum

A mirror in vacuum is coupled to fluctuating quantum fields. As a result, its energy-momentum and mass fluctuate. We compute that correlation spectra of force and mass fluctuations for a mirror at rest in vacuum (of a scalar field in a two-dimensional space-time). The obtained expressions agree with a mass correction equal to a vacuum energy stored by the mirror. We introduce a Lagrangian model which consistently describes a scalar field coupled to a scatterer, with inertial mass being a quantum variable.

1H NMR spectra and electronic structure of reduced iron porphyrins: Fe(II), Fe(I) and Fe(0) porphyrins

Fe(II), Fe(I) and Fe(0) porphyrins have been generated by stepwise reduction with a sodium mirror in vacuum and their 1H NMR spectra have been recorded and analyzed. Fe(II) porphyrins (Fe(II)P) have been examined in three spin states, an S = 0 state in pyridine- d 8, an S = 1 state in benzene- d 6 and an S = 2 state in tetrahydrofuran- d 8 (THF- d 8). The analysis of isotropic shifts for low-spin Fe(II)P ( S = 0) has indicated that no charge transfer has been observed. The ground state configuration is (d xy) 2 (d xz,d yx) 4. The contact shifts for intermediate-spin Fe(II)P ( S = 1) reflect P → Fe π charge transfer. The proposed electron configuration is (d xy) 2 (d z2) 2 (d xz, d yz) 2, which agrees with Mössbauer data. The pattern of contact shifts for high-spin Fe(II)P ( S = 2) is consistent with σ spin transfer, which suggests that the d x2-y2 orbital possesses an unpaired spin. The electron configuration is (d xy) 2 (d xz, d yz 2 (d z2) 1 (d x2-y2) 1. Our results for Fe(II)P ( S = 1,2) agree with the literature 1H NMR data . In the case of Fe(I)P in THF, the separation of isotropic shifts into the dipolar and contact contributions has shown the dominance of the latter. The observed shifts indicate negative π spin density on pyrrole and meso carbon atoms of the ligand, which seems to be due to a strong π-π spin polarization effect. When this fact is taken into account the pattern of contact shifts is consistent with π spin transmission involving both P → Fe π charge transfer out of the ligand-filled molecular (3e(π)) orbital and Fe → P π * charge transfer into the ligand highest unoccupied (4e(π *)) molecular orbital. The occurrence of the unpaired spin in this molecular orbital is consistent with π-radical anion formulation which was found by X-ray crystallography. An S = 1/2 spin state determined by magnetic moment measurements agrees with the most probable electron configuration (d xy) 2 (d xz, d yz 3 (d z2) 2. In the case of Fe(0)P, the isotropic shifts were found to be small, providing evidence of some spin transfer. The ground state configuration is (d xy) 2 (d xz, d yz) 4 (d z2) 2.

Quantum fluctuations of position of a mirror in vacuum

A mirror scattering vacuum fields is submitted to a quantum fluctuating radiation pressure. It also experiences a motional force, related to force fluctuations through fluctuation-dissipation relations. The resulting position fluctuations of the coupled mirror are related to the dissipative part of the mechanical admittance. We compute the time dependent position commutator, which makes apparent the difference between the low-frequency and high-frequency masses, and the anticommutator noise spectrum, which describes the ultimate sensitivity in a length measurement using mirrors.

Causality, stability and passivity for a mirror in vacuum

The mean force exerted upon a perfect mirror moving in vacuum (in a two-dimensional spacetime) has the same expressions as the radiation reaction force computed in classical electron theory. It follows that unacceptable runaway solutions are predicted. We show that this instability problem does not appear when partially transmitting mirrors are studied. The mechanical impedance describing the mirror coupled to vacuum radiation pressure is computed explicitly (recoil is neglected). It is found to be a passive function, so that stability is ensured. This is connected to the fact that no energy can be extracted from the vacuum state.

Fluctuations and dissipation for a mirror in vacuum

A mirror in the vacuum is submitted to a radiation pressure exerted by scattered fields. It is known that the resulting mean force is zero for a motionless mirror, but not for a mirror moving with a non-uniform acceleration. We show here that this force results from a motional modification of the field scattering while being associated with the fluctuations of the radiation pressure on a motionless mirror. We consider the case of a scalar field in a two-dimensional spacetime and characterize the scattering upon the mirror by frequency dependent transmissivity and reflectivity functions obeying unitarity, causality and high frequency transparency conditions. We derive causal expressions for dissipation and fluctuations and exhibit their relation for any stationary input. We recover the known damping force at the limit of a perfect mirror in vacuum. Finally, we interpret the force as a mechanical signature of the squeezing effect associated with the mirror's motion.