45 research outputs found
Stable optical spring in aLIGO detector with unbalanced arms and in Michelson-Sagnac interferometer
Optical rigidity in aLIGO gravitational-wave detector, operated on dark port
regime, is unstable. We show that the same interferometer with excluded
symmetric mechanical mode but with unbalanced arms allows to get stable optical
spring for antisymmetric mechanical mode. Arm detuning necessary to get
stability is shown to be a small one - it corresponds to small power in signal
port. We show that stable optical spring may be also obtained in
Michelson-Sagnac interferometer with both power and signal recycling mirrors
and unbalanced arms
Accurate calculation of thermal noise in multilayer coating
We derive accurate formulas for thermal fluctuations in multilayer
interferometric coating taking into account light propagation inside the
coating. In particular, we calculate the reflected wave phase as a function of
small displacements of the boundaries between the layers using transmission
line model for interferometric coating and derive formula for spectral density
of reflected phase in accordance with Fluctuation-Dissipation Theorem. We apply
the developed approach for calculation of the spectral density of coating
Brownian noise.Comment: 10 pages, 9 figure
Stable Optical Rigidity Based on Dissipative Coupling
We show that the stable optical rigidity can be obtained in a Fabry-Perot
cavity with dissipative optomechanical coupling and with detuned pump,
corresponding conditions are formulated. An optical detection of a weak
classical mechanical force with usage of this rigidity is analyzed. The
sensitivity of small force measurement can be better than the standard quantum
limit (SQL).Comment: 10 pages, 6 figure
Squeezing of optomechanical modes in detuned Fabry-Perot interferometer
We carry out analysis of optomechanical system formed by moveable mirror of
Fabry-Perot cavity pumped by detuned laser. Optical spring arising from detuned
pump creates in the system several eigen modes which could be treated as high-Q
oscillators. Modulation of laser power results in parametric modulation of
oscillators spring constants thus allowing to squeeze noise in quadratures of
the modes. Evidence of the squeezing could be found in the light reflected from
the cavity.Comment: 8 pages, 2 figure
Displacement-noise-free gravitational-wave detection with two Fabry-Perot cavities
We propose two detuned Fabry-Perot cavities, each pumped through both the
mirrors, positioned in line as a toy model of the gravitational-wave (GW)
detector free from displacement noise of the test masses. It is demonstrated
that the noise of cavity mirrors can be completely excluded in a proper linear
combination of the cavities output signals. This model is illustrated by a
simplified round trip model (without Fabry-Perot cavities). We show that in
low-frequency region the obtained displacement-noise-free response signal is
stronger than the one of the interferometer recently proposed by S.Kawamura and
Y.Chen.Comment: 10 pages, 5 figure
Back action cancellation in resolved sideband regime
We consider the simple model of measurement of mechanical oscillator position
via Fabry-Pero cavity pumped by detuned laser (end mirror of cavity is mass of
oscillator) in resolved sideband regime when laser is detuned from cavity's
frequency by frequency of mechanical oscillator and relaxation
rate of cavity is small: . We demonstrate
fluctuation back action cancellation in reflected wave. However, it does not
allow to circumvent Standard Quantum Limit, the reason of it is the dynamic
back action.Comment: 5 pages, 1 figur
Electromagnetic Continuum Induced Nonlinearity
A nonrelativistic Hamiltonian describing interaction between a mechanical
degree of freedom and radiation pressure is commonly used as an ultimate tool
for studying system behavior in opto-mechanics. This Hamiltonian is derived
from the equation of motion of a mechanical degree of freedom and the optical
wave equation with time-varying boundary conditions. We show that this approach
is deficient for studying higher order nonlinear effects in an open resonant
opto-mechanical system. Opto-mechanical interaction induces a large mechanical
nonlinearity resulting from a strong dependence of the power of the light
confined in the optical cavity on the mechanical degrees of freedom of the
cavity due to coupling with electromagnetic continuum. This dissipative
nonlinearity cannot be inferred from the standard Hamiltonian formalism.Comment: 5 pages, 1 figur
On sensitivity limitations of a dichromatic optical detection of a classical mechanical force
We apply the strategy of the back action evading measurement of a quadrature
component of mechanical motion of a test mass to detection of a classical force
acting on the mass (Science, 209, (1980) 547) and study both classical and
quantum limitations of the technique. We are considering a resonant
displacement transducer interrogated with a dichromatic optical pump as a model
system in this study. The transducer is represented by a Fabry Perot cavity
with a totally reflecting movable end mirror the resonant force of interest
acts upon. The cavity is pumped with two coherent optical carriers equally
detuned from one of the cavity resonances. We show that the quantum back action
cannot be completely excluded from the measurement result due to the dynamic
instability of the opto-mechanical system that either limits the allowable
power of the optical pump or calls for introducing an asymmetry to the pump
configuration destroying the quantum nondemolition nature of the measurement.Comment: 8 pages, 1 figur
Displacement- and laser-noise-free gravitational-wave detection with two Fabry-Perot cavities
We propose two Fabry-Perot cavities, each pumped through both the mirrors,
positioned in line as a toy model of the gravitational-wave (GW) detector free
from displacement noise of the test masses. It is demonstrated that the
displacement noise of cavity mirrors as well as laser noise can be completely
excluded in a proper linear combination of the cavities output signals. We show
that in low-frequency approximation (gravitational wave length
is much greater than distance between mirrors
) the decrease of response signal is about
, i.e. signal is stronger than the one of the
interferometer recently proposed by S. Kawamura and Y. Chen.Comment: 7 pages, 4 figur
Polarization loss in reflecting coating
In laser gravitational waves detectors optical loss restricts sensitivity. We
discuss polarization scattering as one more possible mechanism of optical
losses. Circulated inside interferometer light is polarized and after
reflection its plane of polarization can turn a little due to reflecting
coating of mirror can have slightly different refraction index along axes in plane of mirror surface (optical anisotropy). This anisotropy can be
produced during manufacture of coating (elasto-optic effect). This orthogonal
polarized light, enhanced in cavity, produces polarization optical loss.
Polarization map of mirrors is very important and we propose to measure it.
Polarization loss can be important in different precision optical experiments
based on usage of polarized light, for example, in quantum speed meter