GaAs monolithic frequency doublers with series connected varactor diodes

GaAs monolithic frequency doublers using series connected varactor diodes have been fabricated for the first time. Output powers of 150 mW at 36.9 GHz with 24% efficiency and 300 mW at 24.8 GHz with 18% efficiency have been obtained. Peak efficiencies of 35% at output power levels near 100 mW have been achieved at both frequencies. Both K-band and Ka-band frequency doublers are derived from a lower power, single-diode design by series connection of two diodes and scaling to achieve different power and frequency specifications. Their fabrication was accomplished using the same process sequence

Atom lithography using MRI-type feature placement

We demonstrate the use of frequency-encoded light masks in neutral atom lithography. We demonstrate that multiple features can be patterned across a monotonic potential gradient. Features as narrow as 0.9 microns are fabricated on silicon substrates with a metastable argon beam. Internal state manipulation with such a mask enables continuously adjustable feature positions and feature densities not limited by the optical wavelength, unlike previous light masks.Comment: 4 pages, 4 figure

Photothermal Fluctuations as a Fundamental Limit to Low-Frequency Squeezing in a Degenerate Optical Parametric Amplifier

We study the effect of photothermal fluctuations on squeezed states of light through the photo-refractive effect and thermal expansion in a degenerate optical parametric amplifier (OPA). We also discuss the effect of the photothermal noise in various cases and how to minimize its undesirable consequences. We find that the photothermal noise in the OPA introduces a significant amount of noise on phase squeezed beams, making them less than ideal for low frequency applications such as gravitational wave (GW) interferometers, whereas amplitude squeezed beams are relatively immune to the photothermal noise and may represent the best choice for application in GW interferometers

Human μ-calpain: Simple isolation from erythrocytes and characterization of autolysis fragments

Heterodimeric μ-calpain, consisting of the large (80 kDa) and the small (30 kDa) subunit, was isolated and purified from human erythrocytes by a highly reproducible four-step purification procedure. Obtained material is more than 95% pure and has a specific activity of 6 - 7 mU/mg. Presence of contaminating proteins could not be detected by HPLC and sequence analysis. During storage at -80 °C the enzyme remains fully activatable by Ca²⁺, although the small subunit is partially processed to a 22 kDa fragment. This novel autolysis product of the small subunit starts with the sequence (60)RILG and is further processed to the known 18 kDa fragment. Active forms and typical transient and stable autolysis products of the large subunit were identified by protein sequencing. In casein-zymograms only the activatable forms 80 kDa+30 kDa, 80 kDa+22 kDa and 80 kDa+18 kDa displayed caseinolysis

Sensing and control in dual-recycling laser interferometer gravitational-wave detectors

We introduce length-sensing and control schemes for the dual-recycled cavity-enhanced Michelson interferometer configuration proposed for the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO). We discuss the principles of this scheme and show methods that allow sensing and control signals to be derived. Experimental verification was carried out in three benchtop experiments that are introduced. We present the implications of the results from these experiments for Advanced LIGO and other future interferometric gravitational-wave detectors

Experiments with Lasers and Frequency Doublers

Solid state laser sources, such as diode-pumped Nd:YAG lasers, have given us CW laser light of high power with unprecedented stability and low noise performance. In these lasers most of the technical sources of noise can be eliminated allowing them to be operated close to the theoretical noise limit set by the quantum properties of light. The next step of reducing the noise below the standard limit is known as squeezing. We present experimental progress in generating reliably squeezed light using the process of frequency doubling. We emphasize the long term stability that makes this a truly practical source of squeezed light. Our experimental results match noise spectra calculated with our recently developed models of coupled systems which include the noise generated inside the laser and its interaction with the frequency doubler. We conclude with some observations on evaluating quadrature squeezed states of light

Polarization speed meter for gravitational-wave detection

We propose a modified configuration of an advanced gravitational-wave detector that is a speed-meter-type interferometer with improved sensitivity with respect to quantum noise. With the addition of polarization-controlling components to the output of an arm cavity Michelson interferometer, an orthogonal polarization state of the interferometer can be used to store signal, returning it later with opposite phase to cancel position information below the storage bandwidth of the opposite mode. This modification provides an alternative to an external kilometer-scale Fabry-Pérot cavity, as presented in earlier work of Purdue and Chen [Phys. Rev. D 66, 122004 (2002)]. The new configuration requires significantly less physical infrastructure to achieve speed meter operation. The quantity of length and alignment degrees of freedom is also reduced. We present theoretical calculations to show that such a speed meter detector is capable of beating the strain sensitivity imposed by the standard quantum limit over a broad range of frequencies for Advanced Laser Interferometer Gravitational-wave Observatory-like parameters. The benefits and possible difficulties of implementing such a scheme are outlined. We also present results for tuning of the speed meter by adjusting the degree of polarization coupling, a novel possibility that does not exist in previously proposed designs, showing that there is a smooth transition from speed meter operation to that of a signal-recycling Michelson behavior