Design and performance of the ALPS II regeneration cavity.

The regeneration cavity (RC) is a critical component of the Any Light Particle Search II (ALPS II) experiment. It increases the signal from possible axions and axion-like particles in the experiment by nearly four orders of magnitude. The total round-trip optical losses of the power circulating in the cavity must be minimized in order to maximize the resonant enhancement of the cavity, which is an important figure of merit for ALPS II.

Optimized dielectric mirror coating designs for quasi-harmonic cavity resonance.

High-finesse optical cavities have a wide range of applications, some of which are bichromatic. The successful operation of high-finesse bichromatic cavities can demand careful control on the temperature dependence of the wavelength-dependent reflection phase from the dielectric mirror coatings that constitute the optical cavity. We present dielectric coating designs that are optimized for minimal differential change in the reflection phase between a quasi-second-harmonic field and its fundamental field under temperature changes.

Prospective evaluation of functional outcomes in 395 patients with an ileal neobladder 1 year after radical cystectomy.

Purpose: This study aims to report on functional outcomes in a large cohort of patients who underwent inpatient rehabilitation (IR) in a highly specialized, high-volume German urologic rehabilitation center after radical cystectomy (RC) and creation of an ileal neobladder (INB).

Methods: Data for 842 patients, who underwent three weeks of IR after RC and urinary diversion between April 2018 and December 2019 were prospectively collected. INB patients were surveyed on continence and sexual function.

Design and performance characterization of a new LISA-like (laser interferometer space antenna-like) gravitational reference sensor and torsion pendulum testbed.

In this paper, we present the design and performance of the upgraded University of Florida torsion pendulum facility for testing inertial sensor technology related to space-based gravitational wave observatories and geodesy missions. In particular, much work has been conducted on inertial sensor technology related to the Laser Interferometer Space Antenna (LISA) space gravitational wave observatory mission. A significant upgrade to the facility was the incorporation of a newly designed and fabricated LISA-like gravitational reference sensor (GRS) based on the LISA Pathfinder GRS.

High volume UV LED performance testing.

There is increasing interest in deep UV Light-Emitting Diodes (LEDs) for applications in water purification, virus inactivation, sterilization, bioagent detection, and UV curing, as well as charge management control in the Laser Interferometer Space Antenna (LISA), which will be the first gravitational wave detector in space. To fully understand the current state of commercial UV LEDs and assess their performance for use on LISA, large numbers of UV LEDs need to be tested across a range of temperatures while operating in air or in a vacuum. We describe a new hardware system designed to accommodate a high volume of UV LED performance tests and present the performance testing results from over 200 UV LEDs with wavelengths in the 250 nm range.

The missing link in gravitational-wave astronomy: A summary of discoveries waiting in the decihertz range.

Since 2015 the gravitational-wave observations of LIGO and Virgo have transformed our understanding of compact-object binaries. In the years to come, ground-based gravitational-wave observatories such as LIGO, Virgo, and their successors will increase in sensitivity, discovering thousands of stellar-mass binaries. In the 2030s, the space-based will provide gravitational-wave observations of massive black holes binaries.

Probing the nature of black holes: Deep in the mHz gravitational-wave sky.

Black holes are unique among astrophysical sources: they are the simplest macroscopic objects in the Universe, and they are extraordinary in terms of their ability to convert energy into electromagnetic and gravitational radiation. Our capacity to probe their nature is limited by the sensitivity of our detectors. The LIGO/Virgo interferometers are the gravitational-wave equivalent of Galileo's telescope.

Ultrastable optical components using adjustable commercial mirror mounts anchored in a ULE spacer.

This paper describes a novel, to the best of our knowledge, approach to build ultrastable interferometers using commercial mirror mounts anchored in an ultralow expansion (ULE) base. These components will play a critical role in any light particle search (ALPS) and will also be included in ground testing equipment for the upcoming laser interferometer space antenna (LISA) mission. Contrary to the standard ultrastable designs where mirrors are bonded to the spacers, ruling out any later modifications and alignments, our design remains flexible and allows the alignment of optical components at all stages to be optimized and changed.

A new torsion pendulum for gravitational reference sensor technology development.

We report on the design and sensitivity of a new torsion pendulum for measuring the performance of ultra-precise inertial sensors and for the development of associated technologies for space-based gravitational wave observatories and geodesy missions. The apparatus comprises a 1 m-long, 50 μm-diameter tungsten fiber that supports an inertial member inside a vacuum system. The inertial member is an aluminum crossbar with four hollow cubic test masses at each end.

Overview of Advanced LIGO adaptive optics.

This is an overview of the adaptive optics used in Advanced LIGO (aLIGO), known as the thermal compensation system (TCS). The TCS was designed to minimize thermally induced spatial distortions in the interferometer optical modes and to provide some correction for static curvature errors in the core optics of aLIGO. The TCS is comprised of ring heater actuators, spatially tunable CO laser projectors, and Hartmann wavefront sensors.

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.

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.

Experimental verification of clock noise transfer and components for space based gravitational wave detectors.

The Laser Interferometer Space Antenna (LISA) and other space based gravitational wave detector designs require a laser communication subsystem to, among other things, transfer clock signals between spacecraft (SC) in order to cancel clock noise in post-processing. The original LISA baseline design requires frequency synthesizers to convert each SC clock into a 2 GHz signal, and electro-optic modulators (EOMs) to modulate this 2 GHz clock signal onto the laser light. Both the frequency synthesizers and the EOMs must operate with a phase fidelity of 2×10(-4)cycles/√Hz.

Thermal effects in the Input Optics of the Enhanced Laser Interferometer Gravitational-Wave Observatory interferometers.

We present the design and performance of the LIGO Input Optics subsystem as implemented for the sixth science run of the LIGO interferometers. The Initial LIGO Input Optics experienced thermal side effects when operating with 7 W input power. We designed, built, and implemented improved versions of the Input Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO interferometers, designed to run with 30 W input power.

On the interference of two Gaussian beams and their ABCD matrix representation.

Gaussian beam propagation is well described by the q-parameter and the ABCD matrices. A variety of ABCD matrices are available that represent commonly occurring scenarios/components in optics. One important phenomenon that has not been studied in detail is the interference of two optical beams with different q-parameters undergoing interference.

Adaptive control of modal properties of optical beams using photothermal effects.

We present an experimental demonstration of adaptive control of modal properties of optical beams. The control is achieved via heat-induced photothermal actuation of transmissive optical elements. We apply the heat using four electrical heaters in thermal contact with the element.

Optical design of the proposed Australian International Gravitational Observatory.

Marginally stable power recycling cavities are being used by nearly all interferometric gravitational wave detectors.With stability factors very close to unity the frequency separation of the higher order optical modes is smaller than the cavity bandwidth. As a consequence these higher order modes will resonate inside the cavity distorting the spatial mode of the interferometer control sidebands.

Design of the Advanced LIGO recycling cavities.

The current LIGO detectors will undergo an upgrade which is expected to improve their sensitivity and bandwidth significantly. These advanced gravitational-wave detectors will employ stable recycling cavities to better confine their spatial eigenmodes instead of the currently installed marginally stable power recycling cavity. In this letter we describe the general layout of the recycling cavities and give specific values for a first possible design.

Adaptive beam shaping by controlled thermal lensing in optical elements.

We describe an adaptive optical system for use as a tunable focusing element. The system provides adaptive beam shaping via controlled thermal lensing in the optical elements. The system is agile, remotely controllable, touch free, and vacuum compatible; it offers a wide dynamic range, aberration-free focal length tuning, and can provide both positive and negative lensing effects.

Beam jitter coupling in advanced LIGO.

Fluctuations in the position or propagation direction of the laser beam (beam jitter) is one of the most critical technical noise sources in an interferometric gravitational wave detector. These fluctuations couple to spurious misalignments of the mirrors forming the interferometer and potentially decrease the sensitivity. In this paper we calculate the transfer function of beam jitter into the gravitational wave channel for the Advanced LIGO detector and derive a first expression for the requirements on beam jitter for Advanced LIGO.

First step toward a benchtop model of the Laser Interferometer Space Antenna.

A technique for simulating large optical path lengths by use of digital delay buffers is presented. This technique is used to generate a synthetic interferometer with one arm having an arbitrary length. The response of the interferometer to phase and frequency modulation is measured and found to be in agreement with predictions.