Development of displacement- and frequency-noise-free interferometer in 3-D configuration for gravitational wave detection

The displacement- and frequency-noise-free interferometer (DFI) is a multiple laser interferometer array for gravitational wave detection free from both the displacement noise of optics and laser frequency noise. So far, partial experimental demonstrations of DFI have been done in 2-D table top experiments. In this paper, we report the complete demonstration of a 3-D DFI. The DFI consists of four Mach-Zehnder interferometers with four mirrors and two beamsplitters. The displacement noises both of mirrors and beamsplitters were suppressed by up to 40 dB. The non-vanishing DFI response to a gravitational wave was successfully confirmed using multiple electro-optic modulators and computing methods

Nutritional Status, Activity Pattern, and Dietary Intake among the Baka Hunter-gatherers in the Village Camps in Cameroon

The nutritional status of 75 male and 73female pygmy hunter-gatheres were surveyed as well as the daily physical activity, energy and intake of major nutrients, and total energy expenditure were examined for two married couples of the Baka hunter-gatherers in Cameroon. The average stature was intermediate relative to other Pygmy hunter-gatherers, and the subjects were generally well nourished. Despite the limited sample size and survey duration, the results indicated that the energy intake and energy expenditure of Cameroonian Baka hunter-gatherers were relatively low, which may enable them to adapt to low food availability in the village camps during the rainy season

Fabrication of exchange-coupled α-Fe/L1₀-FePd nanocomposite isolated particles

The fabrication of exchange-coupled α-Fe/L10-FePd nanocomposite particles, by annealing the Fe/Pd nanocomplex particles, was analyzed. It was observed that two regions composed of α-Fe and L1 0-FePd coexisted in each nanoparticle separated by a diffusion boundary. It was also observed that there was a gradual increase in the saturation magnetization with increase in the volume ratio of the α-Fe region. The results show that an exchange coupling existed between α-Fe and L10-FePd crystallites connected coherently with each other within the nanoparticles.Junichi Kawamura, Kazuhisa Sato, and Yoshihiko Hirotsu, "Fabrication of exchange-coupled α-Fe/L1₀-FePd nanocomposite isolated particles", Journal of Applied Physics 96, 3906-3911 (2004) https://doi.org/10.1063/1.1782963

Demonstration of displacement-noise-free interferometry using bi-directional Mach–Zehnder interferometers

We have demonstrated displacement- and frequency-noise-free laser interferometry (DFI) by partially implementing a recently proposed optical configuration using bi-directional Mach–Zehnder interferometers (MZIs). This partial implementation, the minimum necessary to be called DFI, has confirmed the essential feature of DFI: the combination of two MZI signals can be carried out in a way that cancels the displacement noise of the mirrors and beam splitters while maintaining gravitational-wave signals. The attained maximum displacement noise suppression was 45 dB

The Experimental plan of the 4m Resonant Sideband Extraction Prototype for The LCGT

The 4m Resonant Sideband Extraction (RSE) interferometer is a planned prototype of the LCGT interferometer. The aim of the experiment is to operate a powerrecycled Broadband RSE interferometer with suspended optics and to achieve diagonalization of length signals of the central part of the interferometer directly through the optical setup. Details of the 4m RSE interferometer control method as well as the design of the experimental setup will be presented

The experimental plan of displacement- and frequency-noise free laser interferometer

We present the partial demonstration of displacement- and laser-noise free interferometer (DFI) and the next experimental plan to examine the complete configuration. A part of the full implementation of DFI has been demonstrated to confirm the cancellation of beamsplitter displacements. The displacements were suppressed by about two orders of magnitude. The aim of the next experiment is to operate the system and to confirm the cancellation of all displacement noises, while the gravitational wave (GW) signals survive. The optical displacements will be simulated by electro-optic modulators (EOM). To simulate the GW contribution to laser lights, we will use multiple EOMs

Development of a frequency-detuned interferometer as a prototype experiment for next-generation gravitational-wave detectors

We report on our prototype experiment that uses a 4-m detuned resonant sideband extraction interferometer with suspended mirrors, which has almost the same configuration as the next-generation, gravitational-wave detectors. We have developed a new control scheme and have succeeded in the operation of such an interferometer with suspended mirrors for the first time ever as far as we know. We believe that this is the first such instrument that can see the radiation pressure signal enhancement, which can improve the sensitivity of next-generation gravitational-wave detectors

Interferometers for Displacement-Noise-Free Gravitational-Wave Detection

We propose a class of displacement- and laser-noise free gravitational-wave-interferometer configurations, which does not sense non-geodesic mirror motions and laser noises, but provides non-vanishing gravitational-wave signal. Our interferometer consists of 4 mirrors and 2 beamsplitters, which form 4 Mach-Zehnder interferometers. By contrast to previous works, no composite mirrors are required. Each mirror in our configuration is sensed redundantly, by at least two pairs of incident and reflected beams. Displacement- and laser-noise free detection is achieved when output signals from these 4 interferometers are combined appropriately. Our 3-dimensional interferometer configuration has a low-frequency response proportional to f^2, which is better than the f^3 achievable by previous 2-dimensional configurations.Comment: 5 pages, 4 figure