The resolution with which the synchronous picosecond flashes of acoustically generated light can be measured has been improved. The flash widths are now found to be considerably less than 50 ps and the jitter in the time between flashes can also be substantially less than 50 ps. The flashes of sonoluminescence appear to turn off very sharply without ringing or after pulsing. PACS numbers: 43.35.Sx, 43.35.EiSonoluminescence is the phenomenon whereby nonlinear effects cause the energy in a sound field to self-focus to such an extent that light is emitted. Since the photons must originate from a region of molecular dimensions and since photon energies are measured in eV whereas sound energies are measured in ergs/cc, sonoluminescence involves a spontaneous amplification that spans 12 orders of magnitude. Although sonoluminescence (SL) was discovered over 50 yr ago it is only recently that the dynamical properties of the acoustically generated flashes of light were measured. • In those experiments it was found that the light is emitted in spherically symmetric flashes that are less than 100 ps in width and which repeat with a rate given by the acoustic frequency. The jitter in the time between flashes was also found to be less than 200 ps. Each flash comprises over 105 photons and originates from a trapped cavity (bubble) at the pressure antinode.We have now used the fastest available microchannel plate photomultiplier tube (PMT) to further resolve SL flashes. We now find that the flash widths are less than 50 ps and that the jitter in the time between flashes is also less than 50 ps. Furthermore the SL flashes appear to turn off abruptly. This point is made clear by Fig. 1, which shows the voltage versus time curves that are measured at the output of the PMT for an SL flash as well as the flash that is generated by a 34-ps laser pulser (Hamamatsu PLP01 ). The laser operates at 410 nm, which matches the blue color of the SL. The overlay of these traces indicates that the SL flash turnsoff well before the laser flash. The cleaner turn off of SL is probably due to the absence of the after pulsing (or ringing) which characterizes the laser pulser.The experimental arrangement (Fig. 2) consists of a deciliter spherical pyrex flask that is filled with degassed distilled water and then driven at its fundamental acoustic resonance. 1 The light originates from a trapped cavity at the pressure antinode and is detected by a Hamamatsu R2809U two-stage microchannel plate PMT. The rated rise time of Department of Electrical Engineering. the tube is 170 ps. The output of the PMT is fed into a sampling oscilloscope (HP 54124T) which yields traces that become Fig. 1 after Fourier analysis is used to remove the scatter. The scope creates a trace by averaging (and piecing together) the digitized response that is obtained from many repetitive samplings of the signal (single shot oscilloscopes do not operate at 50 GHz). For this means of signal acquisition the raw trace shows a scatter or noise of about 5% around the line drawn in Fig. 1...

Abstract-Stable operation in a single mode is an important goal of high-power gyrotrons. Both multimoding and switching into ynwanted modes can lead to lower efficiency and undesirable heating of components not designed to accommodate parasitic modes. We have extensively studied mode behavior in a pulsed 100-kW, 140-GHz gyrotron using a variety of

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We have made heterodyne radiometric measurements with GaAs Schottky diode mixers, mounted in a corner-reflector configuration, over the spectral range 170 μm to 1 mm. At 400 μm, system noise temperatures of 9700 K DSB (NEP=1.4×10−19 W/Hz) and mixer noise temperatures of 5900 K have been achieved. This same quasioptical mixer has also been used to generate 10−7 W of tunable radiation suitable for spectroscopic applications.

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We report the results of a demonstration of a real time delay, optically controlled phased array radar receiver. This implementation employed a free space configuration based upon an optical switching network using liquid crystal spatial light modulators (SLM's). A three-delay unit, two-antenna array receiver was implemented at an optical wavelength of 1.3 pm and demonstrated "squint-free" operation over the entire X-band (8-12 GHz) with an angular accuracy of 1.4". Finally, a novel configuration for the two-antenna element SLM architecture was proposed and demonstrated equivalent system performance with a reduction in the number of components.

Microwave phase conjugation was observed in a liquid suspension of elongated microparticles via degenerate four-wave mixing in a collinear waveguide geometry. Longitudinal phase corrections of a double-passed phase shifter were demonstrated by interferometry. Nondegenerate four-wave mixing was demonstrated with a FWHM bandwidth of 70 MHz. The 10% scattering from the induced grating indicates that high conversion efficiency and gain can be achieved with higher pump power.

Electron paramagnetic resonance of divalent nickel in the low temperature phases of magnesium fluosilicate and magnesium fluotitanate J. Chem. Phys. 66, 3948 (1977); 10.1063/1.434445 Electron paramagnetic resonance of divalent nickel in zinc fluosilicate J. Chem. Phys. 66, 3297 (1977); 10.1063/1.434305 Electron paramagnetic resonance of divalent nickel in ferrous fluosilicateThe electron paramagnetic resonance spectrum of FeSiF 6 ·6H 2 0 was studied at 4.2 K in the parallel orientation using the I mm radiation from a CSF carcinotron. the 337 and 311 p.m radiation from an HCN laser and the 195 and 190 p.m radiation from a DCN laser. In addition, the submillimeter spectrum was measured at zero-field. A good fit of the data was obtained using the spin-Hamiltonian, H = DS; + E(S; -S;) + gl{3HS" with D = 11.88 cm-1 , E = 0.67 cm-1 , and gil = 1.96. The fit of the two highest field lines could be improved slightly by assuming that e, the angle between the z axis of a magnetic site and the crystallographic c axis. was about 4'.