483,251 research outputs found
The Casimir force for passive mirrors
We show that the Casimir force between mirrors with arbitrary frequency
dependent reflectivities obeys bounds due to causality and passivity
properties. The force is always smaller than the Casimir force between two
perfectly reflecting mirrors. For narrow-band mirrors in particular, the force
is found to decrease with the mirrors bandwidth.Comment: 12 pages, 2 figures, LaTe
Estimate of Tilt Instability of Mesa-Beam and Gaussian-Beam Modes for Advanced LIGO
Sidles and Sigg have shown that advanced LIGO interferometers will encounter
a serious tilt instability, in which symmetric tilts of the mirrors of an arm
cavity cause the cavity's light beam to slide sideways, so its radiation
pressure exerts a torque that increases the tilt. Sidles and Sigg showed that
the strength T of this torque is 26.2 times greater for advanced LIGO's
baseline cavities -- nearly flat spherical mirrors which support Gaussian beams
(``FG'' cavities), than for nearly concentric spherical mirrors which support
Gaussian beams with the same diffraction losses as the baseline case -- ``CG''
cavities: T^{FG}/T^{CG} = 26.2. This has motivated a proposal to change the
baseline design to nearly concentric, spherical mirrors. In order to reduce
thermoelastic noise in advanced LIGO, O'Shaughnessy and Thorne have proposed
replacing the spherical mirrors and their Gaussian beams by ``Mexican-Hat''
(MH) shaped mirrors which support flat-topped, ``mesa'' shaped beams. In this
paper we compute the tilt-instability torque for advanced-LIGO cavities with
nearly flat MH mirrors and mesa beams (``FM'' cavities) and nearly concentric
MH mirrors and mesa beams (``CM'' cavities), with the same diffraction losses
as in the baseline FG case. We find that the relative sizes of the restoring
torques are T^{CM}/T^{CG} = 0.91, T^{FM}/T^{CG} = 96, T^{FM}/T^{FG} = 3.67.
Thus, the nearly concentric MH mirrors have a weaker tilt instability than any
other configuration. Their thermoelastic noise is the same as for nearly flat
MH mirrors, and is much lower than for spherical mirrors.Comment: 10 pages, 3 figures, 4 table
Conicoid Mirrors
The first order equation relating object and image location for a mirror of
arbitrary conic-sectional shape is derived. It is also shown that the parabolic
reflecting surface is the only one free of aberration and only in the limiting
case of distant sources.Comment: 9 page
AlGaAs lasers with micro-cleaved mirrors suitable for monolithic integration
A technique has been developed for cleaving the mirrors of AlGaAs lasers without cleaving the
substrate. Micro-cleaving involves cleaving a suspended heterostructure cantilever by ultrasonic
vibrations. Lasers with microcleaved mirrors have threshold currents and quantum efficiencies
identical to those of similar devices with conventionally cleaved mirrors
A new sputtering apparatus
The writer, in sputtering a large number of mirrors, has found that the apparatus and methods to be described have several advantages, particularly where very large and perfect mirrors are desired. The accompanying diagram will be self explanatory, and the dimensions given have been found convenient for mirrors up to 10 cm diameter
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