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A high-resolution ultraviolet (UV)-to-visible image conversion microscope using photoluminescence emitted from self-assembled CdSe/ZnCdMgSe quantum dots (QDs) and quantum wells has been developed. This novel microscope exhibits a 1 [micro]m lateral resolution with possible estimated lateral resolution of 200 nm using defect-free QD samples and UV micro-objective with higher numerical aperture and field of view. OCIS codes: 110.0110, 180.0180, 350.0350.

Cypate-octreote peptide analogue conjugate (Cytate) was investigated as a prostate cancer receptor-targeted contrast agent. The absorption and fluorescence spectra of Cytate were ranged in the near-infrared 'tissue optical window.' Time-resolved investigation of polarization-dependent fluorescence emitted from Cytate in solution as well as in cancerous and normal prostate tissues was conducted. Polarization preservation characteristics of Cytate in solution and tissues were studied. Fluorescence intensity emitted from the Cytate-stained cancerous prostate tissue was round to be much stronger than that from the Cytate-stained normal prostate tissue, indicating more Cytate uptake in the former tissue type. The polarization anisotropy of Cytate contained in cancerous prostate tissue was found to be larger than that in the normal prostate tissue, indicating a larger degree of polarization preservation in Cytate-stained cancerous tissue. The temporal profiles of fluorescence from Cytate solution and from Cytate-stained prostate tissue were fitted using a time-dependent fluorescence depolarization model. The photoluminescence imaging of Cytate-stained cancerous and normal prostate tissues was accomplished, showing the potential of Cytate as a fluorescence marker for prostate cancer detection. OCIS codes: 300.6280, 110.3080.

A new type of computer-controlled optical scanning, high-magnification imaging system with a large field of view is described that overcomes the commonly believed incompatibility of achieving both high magnification and a large field of view. The new system incorporates galvanometer scanners, a CCD camera, and a high-brightness LED source for the fast acquisition of a large number of a high-resolution segmented tile images with a magnification of 800x for each tile. The captured segmented tile images are combined to create an effective enlarged view of a target totaling 1.6 mm x 1.2 mm in area. The speed and sensitivity of the system make it suitable for high-resolution imaging and monitoring of a small segmented area of 320 [micro]m x 240 [micro]m with 4 [micro]m resolution. Each tile segment of the target can be zoomed up without loss of the high resolution. This new microscope imaging system gives both high magnification and a large field of view. This microscope can be utilized in medicine, biology, semiconductor inspection, device analysis, and quality control. OCIS codes: 180.0180, 110.0180, 180.5810.

UV fluorescence and absorption spectroscopy from Bacillus subtilis spores detected proteins and dipicolinic acid (DPA) released into the supernatant after heat treatments ranging from 20[degrees] to 90[degrees]C. The protein and DPA concentration in the supernatant was greater with higher heat treatment temperatures, undergoing a substantial increase for T [greater than or equal to] 60[degrees]C, and supporting the theory that spores undergo a phase transition from a glassylike to a rubberylike state at 56[degrees]C. Gel electrophoresis detected several small proteins with molecular weights between 6 and 11 kDa. These proteins may be small acid-soluble spore proteins that are present in spores but break down during germination. A 30 kDa protein extracted above 60[degrees]C is related to the rubber-glass phase transition. OCIS codes: 170.6280, 010.1100.

A new approach for optical imaging and localization of objects in turbid media that makes use of the independent component analysis (ICA) from information theory is demonstrated. Experimental arrangement realizes a multisource illumination of a turbid medium with embedded objects and a multidetector acquisition of transmitted light on the medium boundary. The resulting spatial diversity and multiple angular observations provide robust data for three-dimensional localization and characterization of absorbing and scattering inhomogeneities embedded in a turbid medium. ICA of the perturbations in the spatial intensity distribution on the medium boundary sorts out the embedded objects, and their locations are obtained from Green's function analysis based on any appropriate light propagation model. Imaging experiments were carried out on two highly scattering samples of thickness approximately 50 times the transport mean-free path of the respective medium. One turbid medium had two embedded absorptive objects, and the other had four scattering objects. An independent component separation of the signal, in conjunction with diffusive photon migration theory, was used to locate the embedded inhomogeneities. In both cases, improved lateral and axial localizations of the objects over the result obtained by use of common photon migration reconstruction algorithms were achieved. The approach is applicable to different medium geometries, can be used with any suitable photon propagation model, and is amenable to near-real-time imaging applications. OCIS codes: 170.7050, 170.5280, 170.3660, 100.3190, 100.3010.

We describe the use of space and polarization gates in a study of free-space optical communication of a coded pulse train as it passes through turbid media. The propagation of coded signals at 10 GHz through adverse environmental conditions is demonstrated. Polarization and space-gating techniques are used to improve the signal-to-noise ratio and to enhance the information fidelity of high-bit-rate transmitted signals, which shows potential improvement for cloud, fog, and smog applications. OCIS codes: 060.4510, 260.5430, 290.4210.

A new study investigates an analytical solution of the elastic Boltzmann transport equation in an infinite uniform medium.

Electroreflectance (ER), piezoreflectance (PZR) and secondary ion mass spectrometry (SIMS) were employed to analyze two In1-xGaxAsyP1-y/InP p-i-n multiple quantum well (MQW) solar cell structures with intrinsic (1)-InP spacers and two InP p-i-n samples. The composition, strain and well width of the MQWs were described by comparing the rich ER/PZR spectra from the MQW regions with an envelope function computation. From the electric fields coming from the i-InP region of the two InP p-i-n control samples, the amount of p-dopant interdiffusion was assessed based on the SIMS data. The results are discussed.

InGaAsP/InP multiple quantum well (MQW) solar cell structures with sequential resonant tunneling between adjacent wells are studied. Results show that the photovoltaic efficiency of the MQW cell has an average 11% increase compared to the control InP samples. The bias voltage and excitation wavelength dependence of photoluminescence and photocurrent for were also determined for the MQW and control samples.

Transillumination images of objects hidden in normal and cancerous human breast tissues and bovine, porcine, and gallinaceous (chicken) tissues as well as model-random-scattering media were recorded with 1250-nm light from a chromium-doped forsterite laser. A Fourier space gate and a polarization gate were used to sort out image-bearing photons and discriminate against multiply scattered image-blurring photons. Better contrast, higher spatial resolution, and deeper penetration of samples were achieved for imaging with 1250-nm light than those obtained at shorter wavelengths, such as 1064 nm from a neodymium-doped yttrium aluminum garnet (YAG) laser. Better contrast and higher resolution were also obtained when the object was imaged through normal human breast tissue than through cancerous breast tissue. Images with marked distinction between fatty and fibrous human breast tissues were obtained when the Cr:forsterite laser was tuned to 1225 nm, a wavelength that resonates with an optical absorption band of breast fat tissues. Imaging with linearly polarized light revealed that the image quality depends significantly on the orientation of the polarization of the incident light with respect to the fibers in the bovine tissue.

A method for fluorescence polarization difference imaging is demonstrated for enhancing the image quality of a luminous object embedded in a random medium. The polarization preservation of light propagating in the scattering medium leads to partially polarized light emission by a contrast-agent dye located inside the object. Subtraction of the images of the luminous object detected at two orthogonal polarization directions improves the image resolution compared with a conventional optical imaging approach. OCIS codes: 290.0290, 260.2510, 260.5430.

A method to digitize the intensity of ultrashort laser pulses for high-speed optical signal processing is described. This digitization was based on the spectral broadening of a weak probe (carrier) pulse by a more intense pump (signal) pulse through the nonlinear optical process of cross-phase modulation (XPM). The signal pulse intensity was varied to generate different spectral widths that can be encoded into digital form. Using a 50-ps time-divided multiplexing pulse train with a waveguide splitter, combiner, and an array of fibers with variable lengths, a unary XPM encoding approach is demonstrated. The spectral encoding scheme can be used to achieve a 5-GHz sampling rate at a 16-level accuracy. Key words: Cross-phase modulation, ultrafast optical digitization, unary encoding.

The use of the polarization of light as a parameter to discriminate against multiple-scattered light for transillumination imaging through random scattering media is examined. Time-resolved two-dimensional images of submillimeter test bars immersed in 5-cm-thick Intralipid solutions with different micelle dilutions were measured for two orthogonal polarizations (parallel and perpendicular) of light emerging from the turbid medium by using a picosecond Kerr-Fourier (KF) imaging system. The measured contrast and intensity of parallel-polarized KF shadowgrams decreased as the concentration of the scattering medium was increased, whereas the behavior of the perpendicular-polarized KF shadowgrams varied in an opposite matter to the micelle concentration. Key words: Time-resolved imaging, Fourier optical filtering, ultrafast laser spectroscopy, polarization, turbid media.

Ultrafast time-gated optical imaging and computational image-enhancement techniques were combined to produce a robust system for viewing objects in turbid media. Image enhancement was implemented by use of images from the early light with a histogram contrast-enhancement algorithm. Image quality was assessed by use of the contrast radius of gyration and the contrast-to-noise ratio. The technique was applied to viewing the dispersion of water droplets emanating from a jet spray and to pictures of an object embedded in turbid media. In all instances there were substantial improvements in image quality at a given time delay. Key words: Optical imaging, turbid media, time resolved, image enhancement.

The temporal profiles of the parallel and perpendicular polarization components of a light pulse back-scattered from a scattering medium are different. The depth of penetration into the tissue and depolarization of the backscattered light depend on the scattering and absorption characteristics of the tissue. Based on these facts, a novel technique is demonstrated for noninvasive surface and beneath-the-surface imaging of biological systems. Key words: Optical imaging, polarization.

Multiple quantum well InGaAsP/InP p-i-n laser heterostructures with various barrier thicknesses were studied by photoluminescence (PL) and photocurrent (PC) measurements. The PL spectrum and peak positions obtained were in good agreement with those derived from transfer matrix computations. Comparison of the measured quantum well PC with computed carrier escape rates showed that the photocurrent is controlled by the temperature dependence of the electron escape time.

Second- and third-harmonic generations of femtosecond and picosecond laser pulses have been measured from chicken skin, muscle, and fat tissues. The magnitude of the harmonic signals showed a strong structural dependence with the signal from skin interface being the strongest. The polarization dependence of the signal was also measured and found to be consistent with the fact that the tissue samples were highly scattering random media. The second-harmonic- and third-harmonic-generation conversion efficiencies were found to be in the range of [approximately][10.sup.-7] to [approximately][10.sup.-10].

The image of an object hidden in highly scattering media was reconstructed using a fast, noise-resistant algorithm newly applied to diffusion tomography. A pulsed light source producing scattered and transmitted light is examined at multiple times. Multiple source detector pairs around the medium are used to obtain data in many different directions. An inverse scattering algorithm with nonuniform regularization achieves rapid inversion convergence.

Use of traveling wave equations in the analysis of the production and amplification of picosecond optical pulses in a field-effect GaAs-AlGaAs laser diode shows that the transfer of hot electrons from satellite to central valley enhances the gain of the diodes. Synchronous modulation of the electric field of the diodes using input pulses results in a single pass gain of 10 to the 5th power and in the production of high peak power picosecond optical pulses. Saturable photon absorption in the active region of the laser results in the production of ultrashort optical pulses in the presence of an applied electric field.

The absorption, fluorescence, and excitation spectra of a dye in a highly scattering random medium were studied experimentally. The intrinsic absorption spectrum of the dye does not change in the presence of scatterers, but the presence of scatterers in the media will change the observed fluorescence spectra. The observation is accounted for the change in the photon trajectory path length for the fluorescence emission.

The optical density of breast tissues without blood is found to be relatively constant from 320 to 800 nm, indicating a relatively independent scattering cross section over this wavelength region.

The transmission of 100-fs ultrafast laser pulses through biological tissues was measured by using femtosecond and picosecond time-resolved detection techniques. The broadening of transmitted pulses was found to increase as the thickness of the biological tissue increases. The absence of a distinct ballistic pulse transmitted through a relatively thin tissue is in sharp contrast with the pulse transmission through a random medium of discrete scatterers. Because of the continuous variation of the dielectric constant in tissue, the photons undergo scattering through the tissue, travel in various small zigzag least optical paths, and form a broadened early-arriving portion of the transmitted pulse. Even in the absence of a well-defined ballistic pulse, we can image an opaque object hidden inside a tissue as thick as 6.5 mm with submillimeter resolution by selecting the early-arriving portion of the transmitted pulse.

We demonstrate that use of a picosecond double-stage Kerr gate system results in a 3-orders-of-magnitude improvements in signal-to-noise ratio and a threefold improvement in shutter speed compared with those of a single-stage Kerr gate.

The native fluorescence spectra, intensity dependence on sperm density, relaxation decay time, and polarization were investigated on spermatozoa and their components (sperm heads and sperm tails) under laser excitation.

Nonlinear optical imaging with femtosecond ([10.sup.-15]-second) laser technology was used to evaluate the subsurface tumor progression in control, dysplasia, and cancerous 7,12-dimethylbenz[a]anthracene-treated hamster cheek pouch mucosa tissues. Two-dimensional images of hamster cheek pouch mucosa tissues were obtained by scanning the second harmonic signal at various sagittal and axial positions. The spatial mapping of the second harmonic signals showed depth differentiation between normal, dysplasia, and a more advanced cancerous state. This nonlinear optical method offers a noninvasive in situ imaging tool to the medical community.

We have measured UV fluorescence excited through two-photon absorption from native chicken tissue, using 600-nm, 500-fs pulses from a R6G dye laser. The observed emission signal was found to depend quadratically on the excitation intensity. The two-photon excitation-induced fluorescence spectrum is attributed to tryptophan residues in proteins. Key words: Two-photon excitation-induced fluorescence, tissue, spectroscopy.

The spatial distribution of small translucent droplets inside a 50-millimeter-thick Intralipid solution was imaged with a picosecond time and spatial-gated Kerr-Fourier imaging system at a signal level of about 10-10 of the incident illumination intensity., Early ballistic and snake light imaging (1-9) offers a nondestructive and noninvasive method to observe translucent objects inside a highly scattering environment. With recent advances in the development of ultrafast [...]

RECENT REPORTS [1, 2] SHOW THAT one in ten women will develop breast cancer, which is the number one killer for women over 40 years old. A significant reduction in [...]

Temperature-dependent time-resolved photoluminescence spectroscopy is used to investigate the carrier recombination through radiative and nonradiative processes in lattice-matched ZnCdSe/ZnCdMgSe multi-quantum-wells (MQWs). The carrier recombination processes found in these samples are attributed to the interplay between the free carrier recombination and hole capture through multiphonon emission.

Terahertz time-domain spectroscopy was used to measure the absorption of water vapor from low to high humidity at room temperature. The unexpected decrease in absorption intensity for ortho rotational transitions with increasing concentration is attributed to the interactions between monomers, dimers, and clusters in the terahertz beam path.