Time resolved backscattering to monitor different stages of eye cataract.

We show that measurement of the temporal profile of the backscattered pulse has the potential to monitor the extent of cataract development in the eye.

Determination of the scattering and absorption lengths from the temporal profile of a backscattered pulse.

The temporal profiles of the backscattered pulse from random media are studied experimentally with femtosecond laser and streak-camera technologies. For a weakly scattering medium, the temporal profile of a backscattered pulse can be described by a simple exponential function. In the strongly scattering regime the temporal profile becomes nonexponential.

Nonlinear-optical response in polythiophene films using four-wave mixing techniques.

We report measurement of X(3) in polythiophene and a homologous series of polycondensed thiophene-based polymers above and below the absorption edge using the folded-boxcar four-wave mixing technique. Above gap the nonlinear coefficient X(3) was found to be one of the largest and fastest in a polymer.

Search for the effect of weak photon localization in second-harmonic waves generated in a disordered anisotropic nonlinear medium.

The possibility of observing the effect of weak photon localization in the second-harmonic waves generated in KH(2)PO(4) (KDP) powder is investigated and discussed. The two primary factors for the negative observation are that the second-harmonic waves are generated by different primary wave vectors because of multiple scattering of the primary wave in the disordered medium and that the scattering amplitude for the two counterpropagating second-harmonic waves are different because of the anisotropy of the KDP microcrystals.

Implementation of a binary optical full adder using a Venn diagram and optical phase conjugation.

Conventional optical pattern logic schemes can only process two input variables at a time. We propose a new optical spatial encoding scheme that is capable of simultaneously processing multiple input variables. Based on this new scheme an optical full adder was experimentally demonstrated using a picosecond optical phase-conjugation device.

Alkali D-line absorption in the luminescence spectrum of solid-fluid interfaces under high-intensity laser excitation.

Photoluminescence spectra from the high-T(c) superconductor YBa(2)Cu(3)O(7-x), the semiconductor GaAs, and GaP under intense picosecond laser excitation were studied with their surfaces exposed to different alkali solutions. Strong absorption of D lines of neutral-alkali atoms was observed in these spectra. These absorption lines indicate that free ground-state alkali atoms were formed by recombination of the sublimated alkali ions with photoelectrons through various processes.

Broad bandwidth mirror with random layer thicknesses.

A broad bandwidth high reflecting multilayered mirror can be fabricated by randomizing the optical thicknesses and refractive indices of the layers. The performance of this mirror improves with the larger number of layers and larger fluctuation of optical thicknesses and refractive indices. A broad bandwidth of reflection found at a shorter wavelength may be important for fabricating broad bandwidth x-ray mirrors.

Dynamic effect of weak localization on the light scattering from random media using ultrafast laser technology.

Angle and time resolved experiments on the backscattering of light from model random media are presented. Weak localization was observed using 30-fs laser pulses, where this time scale is shorter than the scattering mean free time of the light in the random medium. This observation implies that the coherent peak is due to interference between the scattered light at the point of observation.

Pulsed and cw laser fluorescence spectra from cancerous, normal, and chemically treated normal human breast and lung tissues.

The origin of the differences in the fluorescence spectra obtained from cancerous and normal human breast and lung tissues is explored experimentally. The fluorescence spectra from chemically treated normal tissues were measured to give information on the source of the spectral differences. The pulsed fluorescence spectra photoexcited by the second and third harmonic of a 10-ps pulse from Nd:glass laser are reported for normal and cancerous tissues of breast and lung.

Time dynamics of photon migration in semiopaque random media.

The temporal behavior of femtosecond laser pulses propagating and scattering in random media was studied using an optical fiber probe and a streak camera. Information on the temporal profile of laser pulse scattering at 90 degrees in semiopaque media was analyzed. Apparent ballistic transport was observed for both single and multiple scattering regimes.

Continuous-wave laser operation of chromium-doped forsterite.

Room-temperature continuous-wave laser action in chromium-activated forsterite (Cr:Mg(2)SiO(4)) has been achieved for longitudinal pumping in a nearly concentric cavity by the 1064-nm radiation from a cw Nd:YAG laser. The laser emission is centered at 1244 nm and has a spectral bandwidth of 12 nm. An output-power slope efficiency of 6.

Self-phase modulation in multimode optical fibers produced by moderately high-powered picosecond pulses.

The spectral distributions of 8-psec ultrashort laser pulses propagating through multimode glass fibers were measured and compared with those of single-mode fibers at comparable intensities. In multimode optical fibers the spectral broadening arising from self-phase modulation was found to be asymmetric to the Stokes side owing to modal dispersion.

15-THz pulse generation arising from modulation instability oscillation in a colliding-pulse mode-locking dye laser.

15-THz trains of a few-tens-of-femtoseconds optical pulses were generated by modulation instability oscillation in a colliding-pulse mode-locked dye laser. A repeatable and stable modulation instability regime was obtained with the laser operating in the anomalous-dispersion regime and with a low saturable-absorber concentration. Autocorrelation measurements indicate that subpulses were completely separated in real time.

Near infrared tunable operation of chromium doped forsterite laser.

Tunable, room temperature pulsed laser operation of a chromium-doped forsterite laser for 1064-nm pumping is reported. Using different sets of mirrors and a single birefringent plate as the intracavity wavelength selecting element, tunability over the 1167-1345-nm spectral range has been demonstrated.

Ultrafast noncollinear second-harmonic-generation-based 4 x 4 optical switching array.

A noncollinear second-harmonic-generation-based 4 x 4 switchable computational array is experimentally demonstrated. Picosecond binary scalar and vector-matrix multiplication results are presented.

Compact picosecond Nd:glass mode-locked laser with variable cavity length from 5 to 21 m.

The design, performance, and characteristics of a compact mode-locked laser with effective cavity length from 5 to 21 m is described. The overall size of the laser is 1.7 m.

Optical wave breaking and pulse compression due to cross-phase modulation in optical fibers.

When a probe pulse copropagates with a pump pulse inside an optical fiber, the two can interact through cross-phase modulation. It is shown that an interplay between the effects of group-velocity dispersion and cross-phase modulation can lead to optical wave breaking that manifests as rapid oscillations near the leading or the trailing side of the probe pulse. Qualitative features of this new kind of optical wave breaking are discussed, as well as the conditions under which it can be observed experimentally.

Spectroscopic differences between human cancer and normal lung and breast tissues.

Steady-state spectra, time-resolved spectroscopic, and excitation spectra from human cancer and normal tissues have been measured. Spectroscopic differences between normal and cancerous tissues have been found that could be used as a basis for an instrument for the early detection of cancer.