arXiv subjects

Guido Mueller

Publications and source records attributed to Guido Mueller.

44 records · Page 3Linked to original sources

arXiv2016

The Advanced LIGO Input Optics

The Advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions required every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design.

physics.ins-det↗

arXiv2015

In-situ characterization of the thermal state of resonant optical interferometers via tracking of their higher-order mode resonances

Thermal lensing in resonant optical interferometers such as those used for gravitational wave detection is a concern due to the negative impact on control signals and instrument sensitivity. In this paper we describe a method for monitoring the thermal state of such interferometers by probing the higher-order spatial mode resonances of the cavities within them. We demonstrate the use of this technique to measure changes in the Advanced LIGO input mode cleaner cavity geometry as a function of input power, and subsequently infer the optical absorption at the mirror surfaces at the level of 1 ppm per mirror. We also demonstrate the generation of a useful error signal for thermal state of the Advanced LIGO power recycling cavity by continuously tracking the first order spatial mode resonance frequency. Such an error signal could be used as an input to thermal compensation systems to maintain the interferometer cavity geometries in the presence of transients in circulating light power levels, thereby maintaining optimal sensitivity and maximizing the duty-cycle of the detectors.

gr-qc↗

arXiv2014

Arm locking for space-based laser interferometry gravitational wave observatories

Laser frequency stabilization is a critical part of the interferometry measurement system of space-based gravitational wave observatories such as the Laser Interferometer Space Antenna (LISA). Arm locking as a proposed frequency stabilization technique, transfers the stability of the long arm lengths to the laser frequency. The arm locking sensor synthesizes an adequately filtered linear combination of the inter-spacecraft phase measurements to estimate the laser frequency noise, which can be used to control the laser frequency. At the University of Florida we developed the hardware-based University of Florida LISA Interferometer Simulator (UFLIS) to study and verify laser frequency noise reduction and suppression techniques under realistic LISA-like conditions. These conditions include the variable Doppler shifts between the spacecraft, LISA-like signal travel times, optical transponders, realistic laser frequency and timing noise. We review the different types of arm locking sensors and discuss their expected performance in LISA. The presented results are supported by results obtained during experimental studies of arm locking under relevant LISA-like conditions. We measured the noise suppression as well as initial transients and frequency pulling in the presence of Doppler frequency errors. This work has demonstrated the validity and \ feasibility of arm locking in LISA.

gr-qc↗

arXiv2013

Feedback control of optical beam spatial profiles using thermal lensing

A method for active control of the spatial profile of a laser beam using adaptive thermal lensing is described. A segmented electrical heater was used to generate thermal gradients across a transmissive optical element, resulting in a controllable thermal lens. The segmented heater also allows the generation of cylindrical lenses, and provides the capability to steer the beam in both horizontal and vertical planes. Using this device as an actuator, a feedback control loop was developed to stabilize the beam size and position.

physics.optics↗

arXiv2012

Demonstration of Time Delay Interferometry and Spacecraft Ranging in a Space-based Gravitational Wave Detector using the UF-LISA Interferometry Simulator

Space-based gravitational-wave observatories such as the Laser Interferometer Space Antenna (LISA) use time-shifted and time-scaled linear combinations of differential laser-phase beat signals to cancel the otherwise overwhelming laser frequency noise. Nanosecond timing precision is needed to accurately form these Time-Delay Interferometry (TDI) combinations which defines a ~1 meter requirement on the inter-spacecraft ranging capability. The University of Florida Hardware-in-the-loop LISA Interferometry Simulator (UFLIS) has been used to test Time-Delay Interferometry in a configuration which incorporates variable delays, realistic Doppler shifts, and simulated gravitational-wave signals. The TDI 2.0 combinations are exploited to determine the time-changing delays with nanosecond accuracy using a TDI-ranging reference tone. These variable delays are used in forming the TDI combinations to achieve the LISA interferometry sensitivity resulting from 10 orders of magnitude laser frequency noise cancellation.

astro-ph.IM↗

arXiv2011

Near-field radiative heat transfer between macroscopic planar surfaces

Near-field radiative heat transfer allows heat to propagate across a small vacuum gap in quantities that are several orders of magnitude greater then the heat transfer by far-field, blackbody radiation. Although heat transfer via near-field effects has been discussed for many years, experimental verification of this theory has been very limited. We have measured the heat transfer between two macroscopic sapphire plates, finding an increase in agreement with expectations from theory. These experiments, conducted near 300 K, have measured the heat transfer as a function of separation over mm to $μ$m and as a function of temperature differences between 2.5 and 30 K. The experiments demonstrate that evanescence can be put to work to transfer heat from an object without actually touching it.

physics.optics↗

arXiv2009

Detailed design of a resonantly-enhanced axion-photon regeneration experiment

A resonantly-enhanced photon-regeneration experiment to search for the axion or axion-like particles is described. This experiment is a shining light through walls study, where photons travelling through a strong magnetic field are (in part) converted to axions; the axions can pass through an opaque wall and convert (in part) back to photons in a second region of strong magnetic field. The photon regeneration is enhanced by employing matched Fabry-Perot optical cavities, with one cavity within the axion generation magnet and the second within the photon regeneration magnet. Compared to simple single-pass photon regeneration, this technique would result in a gain of (F/pi)^2, where F is the finesse of each cavity. This gain could feasibly be as high as 10^(10), corresponding to an improvement in the sensitivity to the axion-photon coupling, g_(agg), of order (F/pi)^(1/2) ~ 300. This improvement would enable, for the first time, a purely laboratory experiment to probe axion-photon couplings at a level competitive with, or superior to, limits from stellar evolution or solar axion searches. This report gives a detailed discussion of the scheme for actively controlling the two Fabry-Perot cavities and the laser frequencies, and describes the heterodyne signal detection system, with limits ultimately imposed by shot noise.

hep-ph↗

arXiv1999

Virtual photons to fourth order CHPT with nucleons

I discuss the whole mechanism to calculate isospin violation effects in the framework of CHPT. In order to get the correct size of isospin violation one has to include all non-isospin symmetric sources like the electromagnetic interaction, the quark mass difference ($π_0 - η$ mixing), explicit photon loops. As examples I discuss the electromagnetic contributions to the pion nucleon sigma term and to the S-wave pion nucleon scattering length.

hep-ph↗