The first direct detection of gravitational waves opens a vast new frontier in astronomy

The first direct detection of gravitational waves (GWs), announced on 11 February 2016, has opened a vast new frontier in astronomy. Albert Einstein predicted the existence of these waves about a century ago as a consequence of his general theory of relativity. Radio astronomy observations of the binary pulsar system PSR 1913 + 16 over a 20 year period beginning in 1975 provided strong observational evidence that gravitational waves carried energy away from the orbits of neutron stars at precisely the level predicted by general relativity (GR). This relentless conversion of orbital energy into gravitational wave energy causes binary orbits to decay until the objects eventually collide and merge. The frontier of precision measurement science, using laser interferometers, was pushed for more than four decades to achieve this first direct detection, marking a milestone in experimental physics and engineering. Even more significantly, this milestone also opens a new window onto our universe and a completely new kind of astronomy to explore

Photoinduced time-resolved electrodynamics of superconducting metals and alloys

The photoexcited state in superconducting metals and alloys was studied via pump-probe spectroscopy. A pulsed Ti:sapphire laser was used to create the non-equilibrium state and the far-infrared pulses of a synchrotron storage ring, to which the laser is synchronized, measured the changes in the material optical properties. Both the time- and frequency- dependent photoinduced spectra of Pb, Nb, NbN, Nb{0.5}Ti{0.5}N, and Pb{0.75}Bi{0.25} superconducting thin films were measured in the low-fluence regime. The time dependent data establish the regions where the relaxation rate is dominated either by the phonon escape time (phonon bottleneck effect) or by the intrinsic quasiparticle recombination time. The photoinduced spectra measure directly the reduction of the superconducting gap due to an excess number of quasiparticles created by the short laser pulses. This gap shift allows us to establish the temperature range over which the low fluence approximation is valid.Comment: 12 pages with 10 figure

Parallel phase modulation scheme for interferometric gravitational-wave detectors

Advanced LIGO (aLIGO) requires multiple frequency sidebands to disentangle all of the main interferometer’s length signals. This paper presents the results of a risk reduction experiment to produce two sets of frequency sidebands in parallel, avoiding mixed ‘sidebands on sidebands’. Two phase modulation frequencies are applied to separate Electro-Optic Modulators (EOMs), with one EOM in each of the two arms of a Mach-Zehnder interferometer. In this system the Mach-Zehnder’s arm lengths are stabilized to reduce relative intensity noise in the recombined carrier beam by feeding a corrective control signal back to the Rubidium Titanyl Phosphate (RTP) EOM crystals to drive the optical path length difference to zero. This setup’s use of the RTP crystals as length actuators provides enough bandwidth in the feedback to meet arm length stability requirements for aLIGO

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 $\mu$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

The first direct detection of gravitational waves opens a vast new frontier in astronomy

The first direct detection of gravitational waves (GWs), announced on 11 February 2016, has opened a vast new frontier in astronomy. Albert Einstein predicted the existence of these waves about a century ago as a consequence of his general theory of relativity. Radio astronomy observations of the binary pulsar system PSR 1913 + 16 over a 20 year period beginning in 1975 provided strong observational evidence that gravitational waves carried energy away from the orbits of neutron stars at precisely the level predicted by general relativity (GR). This relentless conversion of orbital energy into gravitational wave energy causes binary orbits to decay until the objects eventually collide and merge. The frontier of precision measurement science, using laser interferometers, was pushed for more than four decades to achieve this first direct detection, marking a milestone in experimental physics and engineering. Even more significantly, this milestone also opens a new window onto our universe and a completely new kind of astronomy to explore

High-power femtosecond optical pulse compression by using spatial solitons

We demonstrate a novel pulse-compression technique that uses the self-confinement of two-dimensional spatial solitons propagating in bulk nonlinear media to increase the spectral bandwidth followed by a grating pair for recompression. Output pulses of 19-fs duration with 0.6-,J energies are routinely obtained at a repetition rate of 8.6 kHz. Unlike other high-energy compression methods, soliton compression offers both high repetition rates and a potentially unlimited wavelength range. Femtosecond pulse compression techniques that employ self-phase modulation in an optical fiber to generate spectral bandwidth have developed to the point where it is now possible to generate optical pulses as short as 6 fs.1 However, fiber damage thresholds and parasitic higher-order nonlinear processes typically limit the amount of energy that can effectively be compressed to less than 10 nJ. Applications such as mode-selective excitation of coherent phonons by means of impulsive stimulated Raman scattering 2 and strong-field physics'-' require new methods of compression that produce shortduration optical pulses while maintaining high energies. In recent years progress has been made in extending the energy range of compressed pulses. Efforts by Rolland and Corkum, who used self-phase modulation in bulk materials, have succeeded in generating 100-,J, 24-fs pulses. In this Letter we report on a new method of pulse compression, which produces 19-fs, 0.6-,uJ optical pulses at a repetition rate of 8.6 kHz. Our method relies on the self-trapping and stable propagation of two-dimensional bright spatial optical solitons in bulk nonlinear media. In close analogy with temporal solitons, in which the balancing of group-velocity dispersion and self-phase modulation lead to dispersion-free propagation, 9 the balancing of diffraction by the spatial nonlinear index profile results in diffraction-free propagation.' 0 Although selftrapping of beams in three dimensions is unstable and leads to catastrophic self-focusing, recent experiments have demonstrated the stable propagation of two-dimensional spatial solitons in CS 2 liquid"' and in guided-wave geometries.12l' 4 The self-trapped propagation of the spatial soliton itself maintains the high intensity necessary for large phase modulation, which generates the necessary bandwidth for pulse compression. Unlike other high-energy compression methods, soliton compression offers both high repetition rates and a potentially unlimited wavelength range. The basic experimental apparatus for generating and compressing spatial solitons is as follows. Pulses of 75-fs duration and 0.1-nJ energies from a balanced colliding-pulse mode-locked ring dye laser operating at 620 nm were amplified to 30 /.tJ at a repetition rate of 8.6 kHz in a two-stage optical amplifier pumped by a 20-W copper-vapor laser. To achieve these pulse energies, we used a dye cell in the second stage.' 5 Following recompression to 75 fs with a two-prism sequence in a double-pass geometry, the pulses were spatially filtered to improve beam quality and ensure the formation of clean spatial solitons. The energy throughput of the prism sequence-spatial filter was 11 /%J. We chose an 8-mm-thick piece of bulk fused silica as the nonlinear medium, which has a positive nonlinear index (n 2 = 2.7 x 10-16 cm 2 /W), as required for bright spatial solitons as well as minimal linear and twophoton absorption. Pulses were focused on the front face of the glass in an elliptical profile by a cylindrical-spherical lens combination. We used beam diameters of w = 900 gum (l/e peak intensity) in the long dimension (which we denote x; see the graph o

Sub-nanosecond, time-resolved, broadband infrared spectroscopy using synchrotron radiation

A facility for sub-nanosecond time-resolved (pump-probe) infrared spectroscopy has been developed at the National Synchrotron Light Source of Brookhaven National Laboratory. A mode-locked Ti:sapphire laser produces 2 ps duration, tunable near-IR pump pulses synchronized to probe pulses from a synchrotron storage ring. The facility is unique on account of the broadband infrared from the synchrotron, which allows the entire spectral range from 2 cm-1 (0.25 meV) to 20,000 cm-1 (2.5 eV) to be probed. A temporal resolution of 200 ps, limited by the infrared synchrotron-pulse duration, is achieved. A maximum time delay of 170 ns is available without gating the infrared detector. To illustrate the performance of the facility, a measurement of electron-hole recombination dynamics for an HgCdTe semiconductor film in the far- and mid infrared range is presented.Comment: 11 pages with 9 figures include

Time-resolved spectroscopy using synchrotron infrared pulses

Electron synchrotron storage rings, such as the VUV ring at the National Synchrotron Light Source (NSLS), produce short pulses of infrared (IR) radiation suitable for investigating the time-dependent phenomena in a variety of interesting experimental systems. In contrast to other pulses sources of IR, the synchrotron produces a continuum spectral output over the entire IR (and beyond), though at power levels typically below those obtained from laser systems. The infrared synchrotron radiation (IRSR) source is therefore well-suited as a probe using standard FTIR spectroscopic techniques. Here the authors describe the pump-probe spectroscopy facility being established at the NSLS and demonstrate the technique by measuring the photocarrier decay in a semiconductor

Small optic suspensions for Advanced LIGO input optics and other precision optical experiments

We report on the design and performance of small optic suspensions developed to suppress seismic motion of out-of-cavity optics in the Input Optics subsystem of the Advanced LIGO interferometric gravitational wave detector. These compact single stage suspensions provide isolation in all six degrees of freedom of the optic, local sensing and actuation in three of them, and passive damping for the other three

Characterization of thermal effects in the Enhanced LIGO Input Optics

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. At four times the power of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved performance including better optical isolation, less thermal drift, minimal thermal lensing and higher optical efficiency. The success of the Input Optics design fosters confidence for its ability to perform well in Advanced LIGO