6 research outputs found
On fundamental diffraction limitation of finesse of a Fabry-Perot cavity
We perform a theoretical study of finesse limitations of a Fabry-Perot (FP)
cavity occurring due to finite size, asymmetry, as well as imperfections of the
cavity mirrors. A method of numerical simulations of the eigenvalue problem
applicable for both the fundamental and high order cavity modes is suggested.
Using this technique we find spatial profile of the modes and their round-trip
diffraction loss. The results of the numerical simulations and analytical
calculations are nearly identical when we consider a conventional FP cavity.
The proposed numerical technique has much broader applicability range and is
valid for any FP cavity with arbitrary non-spherical mirrors which have
cylindrical symmetry but disturbed in an asymmetric way, for example, by tilt
or roughness of their mirrors.Comment: 15 pages, 10 figure
Optical Gravitational Wave Antenna with Increased Power Handling Capability
Fundamental sensitivity of an optical interferometric gravitational wave
detector increases with increase of the optical power which, in turn, limited
because of the opto-mechanical parametric instabilities of the interferometer.
We propose to optimize geometrical shape of the mirrors of the detector to
reduce the diffraction-limited finesse of unessential optical modes of the
interferometer resulting in increase of the threshold of the opto-mechanical
instabilities and subsequent increase of the measurement sensitivity. Utilizing
parameters of the LIGO interferometer we found that the proposed technique
allows constructing a Fabry-Perot interferometer with round trip diffraction
loss of the fundamental mode not exceeding ~ppm, whereas the loss of the
first dipole as well as the other high order modes exceed ~ppm and
~ppm, respectively. The optimization comes at the price of tighter
tolerances on the mirror tilt stability, but does not result in a significant
modification of the optical beam profile and does not require changes in the
the gravity detector read-out system. The cavity with proposed mirrors is also
stable with respect to the slight modification of the mirror shape.Comment: 5 pages, 4 figure
Diffraction losses of a Fabry-Perot cavity with nonidentical non-spherical mirrors
Optical cavities, with both optimized resonant conditions and high quality factors, are important metrological tools. In particular, they are used for laser gravitational wave (GW) detectors. In order to have high cavity powers in GW detectors, it is necessary to suppress the parametric instability and to reduce the loss in the arm caused by point absorbers by damping the resonant conditions of harmful higher order optical modes (HOOM). This can be achieved effectively by using non spherical mirrors in symmetric Fabry–Perot (FP) cavities by increasing roundtrip losses of HOOMs Ferdous F et al 2014 Phys. Rev. A 90 033826; Matsko A et al 2016 Phys. Rev. D 93 083010. FP cavities in most of the GW detectors have non-identical mirrors to optimize clipping losses and reduce thermal noise by reducing the beam size on one side of the cavity facing to the beam splitter and recycling cavities. We present here a general method to design non spherical non-identical mirrors in non-symmetric FP cavities to damp HOOMs. The proposed design allows us to suppress the loss of the arm power caused by point absorbers on test masses
Diffraction losses of a Fabry-Perot cavity with nonidentical non-spherical mirrors
Optical cavities with both optimized resonant conditions and high quality
factors are important metrological tools. In particular, they are used for
laser gravitational wave (GW) detectors. It is necessary to suppress the
parametric instability by damping the resonant conditions of harmful higher
order optical modes (HOOM) in order to have high cavity powers in GW detectors.
This can be achieved effectively by using non spherical mirrors in symmetric
Fabry-Perot (FP) cavities by increasing roundtrip losses of HOOMs. Fabry-Perot
cavities in most of the GW detectors have non-identical mirrors to optimize
clipping losses and reduce thermal noise by reducing the beam size on one side
of the cavity facing to the beam splitter and recycling cavities. We here
present a general method to design non spherical non-identical mirrors in
non-symmetric FP cavities to damp HOOMs. The proposed design allows to the
suppress the loss of the arm power caused by point absorbers on test masses.Comment: 12 pages, 10 figure