Optical interferometry-based array of seafloor environmental sensors using a transoceanic submarine cable.

Optical fiber-based sensing technology can drastically improve Earth observations by enabling the use of existing submarine communication cables as seafloor sensors. Previous interferometric and polarization-based techniques demonstrated environmental sensing over cable lengths up to 10,500 kilometers. However, measurements were limited to the integrated changes over the entire length of the cable. We demonstrate the detection of earthquakes and ocean signals on individual spans between repeaters of a 5860-kilometer-long transatlantic cable rather than the whole cable. By applying this technique to the existing undersea communication cables, which have a repeater-to-repeater span length of 45 to 90 kilometers, the largely unmonitored ocean floor could be instrumented with thousands of permanent real-time environmental sensors without changes to the underwater infrastructure.

Optical rotation of the second harmonic radiation from retinal in bacteriorhodopsin monomers in Langmuir-Blodgett film: evidence for nonplanar retinal structure.

We observed optical rotation of the plane of polarization of the second harmonic (SH) radiation at 532 nm (in resonance with the retinal absorption) generated in reflection geometry in Langmuir-Blodgett film of bacteriorhodopsin (bR). The analysis of the experimental data showed that this effect arises from the nonvanishing contribution of the antisymmetrical part of the hyperpolarizability tensor. This requires that the dipole moment of the resonant electronic transition, the change of the dipole moment upon electronic excitation, and the long axis of the retinal not be coplanar. Such conditions are satisfied only if the retinal has a nonplanar geometry, a conclusion that could lend support to the heterogeneity model of the origin of the biphasic band shape of the linear CD spectrum of the retinal in bR. On the basis of our theoretical analysis, we were able to estimate the angle between the induced dipole moment and the plan that contains the long axis of the chromophore and the transition dipole moment of the retinal absorption.

Cavity-dumped femtosecond Kerr-lens mode locking in a chromium-doped forsterite laser.

We report the operation of a cavity-dumped self-mode-locked chromium-doped forsterite laser with pulse energies exceeding 30 nJ and pulse durations as short as 54 fs (FWHM) at 1260 nm. By frequency doubling in a beta-barium borate crystal, pulse energies as high as 3 nJ and pulse durations as short as 49 fs (FWHM) at 630 nm were generated. The high stability and ultrashort pulse widths with a variable repetition rate in both the infrared (1260 nm) and the red (630 nm) make this system an attractive light source for ultrafast spectroscopy.

Cubic optical nonlinearity of free electrons in bulk gold.

A fast (Tau(response) <90 fs) free-electron spin-f lipping frequency-degenerate nonlinearity with a signif icant value of|chi((3))(xxyy)(omega,omega,omega,-omega)chi((3))(xxyy)(omega,omega,omega,-omega)|~10(-)(8)esu has been observed in bulk gold at 1260 nm by use of a new pump-probe polarization-sensitive technique.

Time-resolved fluorescence of crown ether styrul dyes.

Photophsical processes are studied in a new class of dyes contining a chromophoric part and a crown ether part. Fluorescence decays were oebserved to be strongly dependent on temperature in the range from 294 to 4 K. Photoinduced isomerization and electron transfer are considered as possible mechanisms to explain the results.

Resonance-enhanced time-resolved optical Kerr effect of beta-carotene in solution.

A sharp resonant amplification of the third-order susceptibility of a diluted beta-carotene solution in dodecane is observed by means of the time-resolved optical Kerr effect when the wavelength of the probe is tuned in the range of 490-570 nm. The resonance is well in the red with respect to the 0-0 first electronic transition; some evidence is given of the possible role of higher excited states and of two-photon resonance.

Laser picosecond microspectrofluorometry of haematoporphyrin in cells and liposomes.

The results of a laser picosecond microspectrofluorometric study of the spectral and kinetic characteristics of haematoporphyrin (Hp) fluorescence at various sites in cultured SPEV cells and phosphatidylcholine liposomes are presented. The computer-controlled detection system is based on the single-photon counting method with picosecond time resolution. In aqueous medium, the Hp fluorescence spectrum is characterized by two bands at 615 and 675 nm. In living cells and liposomes, Hp fluorescence is red shifted to 630 and 690 nm. In addition a new band at 665 nm is detected. The dependence of this band on the incubation time and Hp concentration was investigated. The fluorescence decay kinetics of Hp in a culture medium, liposome and a cell nuclear membrane were measured. Possible Hp aggregate formation in the lipid bilayer and its implications are discussed.

The movement of melanosomes in melanophore fragments obtained by laser microbeam irradiation.

The melanophores of the teleost Gymnocorymbus ternetzi are filled with pigment granules, melanosomes, which in response to appropriate treatments, can disperse throughout the cytoplasm or form an aggregate in the cell center. Melanophores with the dispersed pigment were irradiated by a laser microbeam, focused on the cell center by the microscope objective. If the average energy of the microbeam was 6-7 microJ, either the center of the melanophore was damaged and a single ring-shaped fragment was formed, or the cell was broken into several fragments of smaller size. The fragments retained their ability to move the pigment granules. In ring-shaped fragments, after adrenaline treatment, the melanosomes formed a ring-shaped aggregate moving away from both outer and inner (irradiation-produced) margins of the fragment. The smaller fragments treated with adrenaline moved the pigment to their centers. Both small and ring-shaped fragments could aggregate melanosomes as soon as 5 minutes after irradiation.