Quantum noise in gravitational-wave interferometers: Overview and recent developments

We present an overview of quantum noise in gravitational wave interferometers. Gravitational wave detectors are extensively modified variants of a Michelson interferometer and the quantum noise couplings are strongly influenced by the interferometer configuration. We describe recent developments in the treatment of quantum noise in the complex interferometer configurations of present-day and future gravitational-wave detectors. In addition, we explore prospects for the use of squeezed light in future interferometers, including consideration of the effects of losses, and the choice of optimal readout schemes.Comment: 13 pages, 5 figure

Mathematical framework for simulation of quantum fields in complex interferometers using the two-photon formalism

We present a mathematical framework for simulation of optical fields in complex gravitational-wave interferometers. The simulation framework uses the two-photon formalism for optical fields and includes radiation pressure effects, an important addition required for simulating signal and noise fields in next-generation interferometers with high circulating power. We present a comparison of results from the simulation with analytical calculation and show that accurate agreement is achieved

Antibacterial activity of conjugated electrolytes

A series of water soluble, cationic, anionic and zwitterionic conjugated polyelectrolytes (CPEs) with main chains based on an arylene ethynylene repeat unit structure with tetraalkylammonium and/or alkylsulfonate side groups were found to exhibit significant antibacterial activity. A number of these complexes also showed pronounced light-induced modulation of their effectiveness, with either biocidal enhancement or suppression, depending on such properties as singlet oxygen sensitization potential and lipophilicity. These collected studies examine the biocidal activity of the CPEs, as determined by Confocal Laser Scanning Microscopy (CLSM) and Flow Cytometry, correlating this activity with the photophysical properties of the polymers. We demonstrate biocidal activity, both in solution and immobilized, of similar ionic conjugated polyelectrolytes. These polymers were tested and shown to be effective in solution, physisorbed or surface grafted on non-porous borosilicate microspheres and grafted on fabrics. Also, studies with templated hollow spheres formed from polymer multilayers show considerable bacterial sequestration and significant biocidal activity, especially upon light exposure. The effective killing of Cobetia marina, Pseudomonas aeruginosa and Bacillus atrophaeus in these systems is also correlated with a requirement for oxygen suggesting that interfacial generation of singlet oxygen is the crucial step in the light-induced biocidal activity. This document begins with an introduction to the problem, including a review of literature. This is followed by an experimental section describing in detail the selection, growth and harvesting parameters for the bacteria and a summary of substrate preparation protocols. A number of biocidal experiments using a variety of compounds and substrates and evaluated with confocal microscopy and flow cytometry are then covered, followed by conclusions and future directions

A Stable Optical Trap from a Single Optical Field Utilizing Birefringence

We report a stable double optical spring effect in an optical cavity pumped with a single optical field that arises as a result of birefringence. One end of the cavity is formed by a multilayer Al$_{0.92}$Ga$_{0.08}$As/GaAs stack supported by a microfabricated cantilever, with a natural mode frequency of $274$ Hz. The optical spring shifts the resonance to $21$ kHz, corresponding to a suppression of low frequency vibrations by a factor of more than $10^{4}$. The stable nature of the optical trap allows the cavity to be operated without any external feedback and with only a single optical field incident

Frequency-Dependent Squeeze Amplitude Attenuation and Squeeze Angle Rotation by Electromagnetically Induced Transparency for Gravitational Wave Interferometers

We study the effects of frequency-dependent squeeze amplitude attenuation and squeeze angle rotation by electromagnetically induced transparency (EIT) on gravitational wave (GW) interferometers. We propose the use of low-pass, band-pass, and high-pass EIT filters, an S-shaped EIT filter, and an intra-cavity EIT filter to generate frequency-dependent squeezing for injection into the antisymmetric port of GW interferometers. We find that the EIT filters have several advantages over the previous filter designs with regard to optical losses, compactness, and the tunability of the filter linewidth.Comment: 4 page

A route to observing ponderomotive entanglement with optically trapped mirrors

The radiation pressure of two detuned laser beams can create a stable trap for a suspended cavity mirror; here it is shown that such a configuration entangles the output light fields via interaction with the mirror. Intra-cavity, the opto-mechanical system can become entangled also. The degree of entanglement is quantified spectrally using the logarithmic negativity. Entanglement survives in the experimentally accessible regime of gram-scale masses subject to thermal noise at room temperature.Comment: 4 pages, 4 figure

Optical dilution and feedback cooling of a gram-scale oscillator to 6.9 mK

We report on use of a radiation pressure induced restoring force, the optical spring effect, to optically dilute the mechanical damping of a 1 gram suspended mirror, which is then cooled by active feedback (cold damping). Optical dilution relaxes the limit on cooling imposed by mechanical losses, allowing the oscillator mode to reach a minimum temperature of 6.9 mK, a factor of ~40000 below the environmental temperature. A further advantage of the optical spring effect is that it can increase the number of oscillations before decoherence by several orders of magnitude. In the present experiment we infer an increase in the dynamical lifetime of the state by a factor of ~200

Quantum noise and radiation pressure effects in high power optical interferometers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.Includes bibliographical references (p. 181-189).In recent years, a variety of mechanical systems have been approaching quantum limits to their sensitivity of continuous position measurements imposed by the Heisenberg Uncertainty Principle. Most notably, gravitational wave interferometers, such as the Laser Interferometer Gravitational wave Observatory (LIGO), operate within a factor of 10 of the standard quantum limit. Here we characterize and manipulate quantum noise in a variety of alternative topologies which may lead to higher sensitivity GW detectors, and also provide an excellent testbed for fundamental quantum mechanics. Techniques considered include injection and generation of non-classical (squeezed) states of light, and cooling and trapping of macroscopic mirror degrees of freedom by manipulation of the optomechanical coupling between radiation pressure and mirror motion. A computational tool is developed to model complex optomechanical systems in which these effects arise. The simulation tool is used to design an apparatus capable of demonstrating a variety of radiation pressure effects, most notably ponderomotive squeezing and the optical spring effect. A series of experiments were performed, designed to approach measurement of these effects. The experiments use a 1 gram mirror to show progressively stronger radiation pressure effects, but only in the classical regime. The most significant result of these experiments is that we use radiation pressure from two" optical fields to shift the mechanical resonant frequency of a suspended mirror from 172 Hz to 1.8 kHz, while simultaneously damping its motion. The technique could prove useful in advanced gravitational wave interferometers by easing control issues, and also has the side effect of effectively cooling the mirror by removing its thermal energy. We show that with improvements, the technique may allow the quantum ground state of the mirror to be approached. Finally, we discuss future prospects for approaching quantum effects in the experiments.by Thomas Randall Corbitt.Ph.D

Measurement of radiation-pressure-induced optomechanical dynamics in a suspended Fabry-Perot cavity

We report on experimental observation of radiation-pressure induced effects in a high-power optical cavity. These effects play an important role in next generation gravitational wave (GW) detectors, as well as in quantum non-demolition (QND) interferometers. We measure the properties of an optical spring, created by coupling of an intense laser field to the pendulum mode of a suspended mirror; and also the parametric instability (PI) that arises from the nonlinear coupling between acoustic modes of the cavity mirrors and the cavity optical mode. Specifically, we measure an optical rigidity of $K = 3 \times 10^4$ N/m, and PI value $R = 3$.Comment: 4 pages, 3 figure