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Selected Topics in Quantum Electronics, IEEE Journal of

Issue 4 • Date July-Aug. 1999

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Displaying Results 1 - 25 of 43
  • In memoriam - Robert T. Wangemann

    Page(s): 891 - 892
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    Freely Available from IEEE
  • Introduction to the issue on lasers in medicine and biology

    Page(s): 893 - 894
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    Freely Available from IEEE
  • Clinical optical tomography and NIR spectroscopy for breast cancer detection

    Page(s): 1143 - 1158
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    The results of the first set of clinical trials with the Philips optical mammography prototype system are summarized. This optical mammo prototype is designed to image the interior of the female breast with the help of near-infrared (NIR) laser light transmission measurements. This study is expected to lead to optical tomography systems for breast cancer detection. This paper presents information on the design of the optical mammo system, the clinical measurements and the imaging results from an initial group of ten patients, and discussions about ongoing research on optical tomography. View full abstract»

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  • Sensitivity of laser opto-acoustic imaging in detection of small deeply embedded tumors

    Page(s): 981 - 988
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    Current imaging modalities fail to detect small tumors in the breast. Opto-acoustic tomography is a novel technique for early cancer detection with promising diagnostic capability. The experimental limit of sensitivity and maximal depth of the laser opto-acoustic detection for small model tumors located within bulk phantom tissue were studied. Two phantoms with optical properties similar to that of breast tissue in the near infrared spectral range were used in these studies: turbid gelatin slabs with the thickness of 100 mm and chicken breast muscle slabs with the thickness of up to 80 mm. Gelatin spheres with enhanced absorption coefficient relative to the background absorption and liver tissue were used to simulate small tumors. The experiments demonstrated the capability of laser optoacoustic imaging to detect and localize phantom tumors with the diameter of 2 mm at a depth of up to 60 mm within the gelatin phantoms and 3×2×0.6-mm piece of liver tissue within 80-mm chicken breast tissue. Theoretical studies on sensitivity of opto-acoustic detection at various diameters, depths of location, and absorption coefficients of small tumors were performed using the experimental data. Our results suggest that the opto-acoustic imaging may occupy a significant niche in early detection of cancer in the breast and other organs View full abstract»

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  • The effect of light losses in double integrating spheres on optical properties estimation

    Page(s): 944 - 947
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    The double integrating sphere setup (DIS) measures diffuse reflectance, diffuse transmittance and collimated transmittance, from which the optical properties of tissue (the absorption coefficient μ a, the scattering coefficient μs and the anisotropy of scattering g) are estimated. The effect of light losses in the DIS and optical thickness on optical properties estimation by the inverse adding doubling algorithm (IAD) and uniqueness of measurement have been investigated using a Monte Carlo method. Results were obtained for optical properties in turbid tissues (0.80⩽albedo⩽0.99, 0.80⩽anisotropy⩽ 0.99, 1.5⩽optical thickness⩽7.5) sandwiched between glass slides. At optical thickness=6.0 the loss of light through the glass slides is ranging from 13%±0.5% (at albedo=0.80) to 15%±0.5% (at albedo=0.98) of the incident power. The loss of light at the exit port in the transmittance sphere is increasing up to 50% of the incident power at highly forward scattering. These losses result in a dependency on optical thickness of the optical properties estimation by the IAD algorithm. Furthermore, because of these losses, the DIS setup measurement is found to be fundamentally nonunique, when simultaneously measuring the diffuse reflectance, diffuse transmittance and collimated transmittance View full abstract»

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  • Laser tissue welding: laser spot size and beam profile studies

    Page(s): 1004 - 1012
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    Evaluates the effect of laser spot diameter and beam profile on the shape of the thermal denaturation zone produced during laser tissue welding, 2-cm-long full thickness incisions were made on the epilated backs of guinea pigs in vivo. India ink was used as an absorber and clamps were used to appose the incision edges. Welding was performed using continuous-wave 1.06-μm, Nd:YAG laser radiation scanned over the incisions to produce ~100-ms pulses. Laser spot diameters of 1, 2, 4, and 6 mm were studied, with powers of 1, 4, 16, and 36 W, respectively. The irradiance remained constant at 127 W/cm2. Monte Carlo simulations were also conducted to examine the effect of laser spot size and beam profile on the distribution of photons absorbed in the tissue. The laser spot diameter was varied from 1 to 6 mm, Gaussian, flat-top, dual Gaussian, and dual flat-top beam profiles were studied. The experimental results showed that 1-, 2-, 4-, and 6 mm-diameter spots produced thermal denaturation to an average depth of 570, 970, 1470, and 1900 μm, respectively. Monte Carlo simulations demonstrated that the most uniform distribution of photon absorption is achieved using large diameter dual flat-top beams View full abstract»

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  • Estimation of internal skin temperatures in response to cryogen spray cooling: implications for laser therapy of port wine stains

    Page(s): 1058 - 1066
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    In many port wine stain (PWS) patients, successful clearing is not achieved even after multiple laser treatments because of inadequate heat generation within the targeted blood vessels. Use of higher radiant exposures has been suggested to improve lesion clearing, but risk of epidermal injury due to nonspecific absorption by melanin increases. It has been demonstrated that cryogen spray cooling (CSC) can protect the epidermis from nonspecific thermal injury during laser treatment of PWS. Inasmuch as epidermal melanin concentration and blood vessel depth vary among patients, evaluation of internal skin temperatures in response to CSC is essential for further development and optimization of treatment parameters on an individual patient basis. We present internal temperature measurements in an epoxy resin phantom in response to CSC and use the results in conjunction with a mathematical model to predict the temperature distribution within human skin for various cooling parameters. Measurements on the epoxy resin phantom show that cryogen film temperature is well below the cryogen boiling point, but a poor thermal contact exists at the cryogen-phantom interface. Based on phantom measurements and model predictions, internal skin temperature reduction remains confined to the upper 400 μm for spurt durations as long as 200 ms. At the end of a 100 ms spurt, our results show a 31°C temperature reduction at the surface, 12°C at a depth of 100 μm, and 4°C at a depth of 200 μm in human skin. Analysis of estimated temperature distributions in response to CSC and temperature profiles obtained by pulsed photothermal radiometry indicates that a significant protective effect is achieved at the surface of laser irradiated PWS skin. Protection of the epidermal basal layer, however, poses a greater challenge when high radiant exposures are used View full abstract»

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  • Double-pass fiber Raman laser-a powerful and widely tunable in the ultraviolet, visible, and near-infrared fiber Raman laser for biomedical investigations

    Page(s): 1013 - 1018
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    We present the operating principle, general features, and advantages of a novel concept for the development of powerful and widely tunable fiber Raman lasers (FRL's), based on the high-power pumping of large-core low-loss multimode fibers using a simple double-pass laser arrangement with Littrow-prism-tuned emission. Basic experimental results obtained with various modification double-pass FRL schemes, which provide the generation of both discretely tunable emission in the UV/blue (360-493 nm) at λp=355 nm and continuously tunable emission in the visible/near-IR (0.54-1.01 μm) at λ p=532 nm, are reported. The double-pass FRL schemes permit powerful and widely tunable spectral components to be generated, due to the double passing of nonlinear-converted laser emission through the optical fiber, maximum cavity feedback, the use of multimode fibers, and high-power pumping View full abstract»

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  • Characterization of temperature-dependent biophysical properties during laser mediated cartilage reshaping

    Page(s): 1095 - 1102
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    Laser radiation can be used to reshape cartilage tissue into new morphologic configurations. When a critical temperature is attained, mechanically deformed cartilage becomes malleable and may be reshaped into new geometric configurations that harden as the tissue cools. This temperature dependent process results in mechanical stress relaxation and is characteristic of a phase transformation. The principal advantages of using laser radiation for the generation of thermal energy in tissue are precise control of both the space-time temperature distribution and time-dependent thermal denaturation kinetics. We illustrate the utility of laser mediated cartilage reshaping in ex vivo porcine model of reconstructive nasal and laryngeal surgery, and attempt to determine the temperature range in which accelerated stress relaxation occurs during laser mediated cartilage reshaping. Optimization of the reshaping process requires identification of the temperature dependence of this phase transformation and its relationship to observed changes in cartilage optical (diffuse scattering), mechanical (internal stress), and thermodynamic properties (heat capacity). Light scattering, infrared radiometry, and modulated differential scanning calorimetry were used to measure temperature-dependent changes in the biophysical properties of cartilage tissue during fast (laser mediated) and slow heating (conventional calorimetric beating). Our studies using MDSC and laser probe techniques have identified changes in tissue thermodynamic and optical properties suggestive of a phase transformation occurring near 60°C. Clinically, reshaped cartilage tissue can be used to recreate the underlying cartilaginous framework of structures in the head and neck such as the ear, larynx, trachea, and nose View full abstract»

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  • Polarized light scattering spectroscopy for quantitative measurement of epithelial cellular structures in situ

    Page(s): 1019 - 1026
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    We report an in situ method of probing the structure of living epithelial cells, based on light scattering spectroscopy with polarized light. The method makes it possible to distinguish between single backscattering from uppermost epithelial cells and multiply scattered light. The spectrum of the single backscattering component can be further analyzed to provide histological information about the epithelial cells such as the size distribution of the cell nuclei and their refractive index. These are valuable quantities' to detect and diagnose precancerous changes in human tissues View full abstract»

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  • Corneal refractive surgery with femtosecond lasers

    Page(s): 902 - 910
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    We investigated the use of ultrashort pulsed (femtosecond) laser technology in corneal refractive surgery. When compared to longer pulsewidth nanosecond or picosecond laser pulses, femtosecond laser-tissue interactions are characterized by significantly smaller and more deterministic photodisruptive energy thresholds, as well as reduced shock waves and smaller cavitation bubbles. We utilized a highly reliable all-solid-state femtosecond laser system for all studies to demonstrate practicality in real-world operating conditions. Contiguous tissue effects were achieved by scanning a 5-μm focused laser spot below the corneal surface at pulse energies of approximately 2-4 μJ. A variety of scanning patterns was used to perform three prototype procedures in animal eyes; corneal flap cutting, keratomileusis, and intrastromal vision correction. Superior dissection and surface quality results were obtained for lamellar procedures (corneal flap cutting and keratornileusis). Preliminary in vivo studies of intrastromal vision correction suggest that consistent refractive changes can also be achieved with this method. We conclude that femtosecond laser technology may be able to perform a variety of corneal refractive procedures with high precision, offering advantages over current mechanical and laser devices and techniques View full abstract»

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  • Tunable diode laser spectroscopy at 1.6 and 2 μm for detection of Helicobacter pylori infection using 13C-urea breath test

    Page(s): 1040 - 1048
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    Tunable diode laser spectroscopy has been applied to diagnosis of Helicobacter pylori by detecting the 13CO2 to isotope ratio in human breath. A number of line pairs in the 1.6- and 2.0-μm band suitable for isotope ratio detection has been investigated in terms of temperature and pressure stability of the detected isotope ratio. Two wavelength modulated diode laser absorption spectrometers (WMS), one in each band, were set up to find the detection limit in isotope abundance difference. Isotope ratio measurements have been performed on 13CO2 enriched gases with isotope ratios calibrated against an isotope ratio mass spectrometer (IRMS). The agreement between the delta values measured with the WMS technique and the IRMS was excellent. Eight breath samples from otherwise healthy volunteers were simultaneously analyzed by IRMS and the present method for possible infection with Helicobacter pylori View full abstract»

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  • Dynamic optical-thermal modeling of laser tissue soldering with a scanning source

    Page(s): 1072 - 1082
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    A transient two-dimensional optical-thermal model that accounts for dynamic changes in optical and thermal properties with temperature was developed to investigate the mechanisms leading to thermal damage during laser tissue soldering. The model was implemented using the electrical circuit simulator simulation program with integrated circuit emphasis (SPICE). Electrical analogies for the optical and thermal behavior of the solder and tissue mere established. With these analogies, light was propagated using a flux representation of the light and the electrical simulator mas used to calculate heat transfer with an algorithm based on the finite difference technique. Thermal damage was calculated using the Arrhenius rate process relation. Temperature-dependent absorption and scattering coefficients, thermal conductivity and thermal diffusivity, mere incorporated in the SPice optical-thermal simulation (SPOTS), as well as the time domain behavior of a scanning laser source. Experimental results from an in vitro study performed using an 808-nm diode laser in conjunction with indocyanine green-doped albumin protein solders to repair bovine aorta specimens compared favorably with numerical results obtained from SPOTS using dynamic optical and thermal properties. The maximum surface temperature was over-estimated by almost 10% when dynamic properties were not taken into account. This difference corresponds to over two orders of magnitude difference in terms of the Arrhenius tissue damage integral. The incorporation of dynamic changes in optical and thermal properties of tissue during laser-induced heating represents a significant advance in computer modeling of laser tissue interactions View full abstract»

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  • Polarization effects in optical coherence tomography of various biological tissues

    Page(s): 1200 - 1204
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    Polarization sensitive optical coherence tomography (PS-OCT) was used to obtain spatially resolved ex vivo images of polarization changes in skeletal muscle, bone, skin and brain. Through coherent detection of two orthogonal polarization states of the signal formed by interference of light reflected from the biological sample and a mirror in the reference arm of a Michelson interferometer, the depth resolved change in polarization was measured. Inasmuch as any fibrous structure will influence the polarization of light, PS-OCT is a potentially powerful technique investigating tissue structural properties. In addition, the effects of single polarization state detection on OCT image formation is demonstrated View full abstract»

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  • Depth profiling of absorbing soft materials using photoacoustic methods

    Page(s): 989 - 996
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    A Q-switched, frequency doubled, Nd:YAG laser coupled to an optical parametric oscillator generated 4.75-ns laser pulses at 726 nm to create subsurface acoustic waves in India ink solutions, India ink acrylamide gels, and in flat segments of elastin biomaterial stained with India ink. The acoustic waves traveled through the target and were detected by a piezoelectric transducer. The waveforms were converted to measurements of initial laser induced pressure and temperature as functions of depth in the material. An algorithm based on Beer's Law was developed and applied to the acoustic signals to extract information about the absorption coefficient as a function of depth in the samples View full abstract»

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  • Optical Doppler tomography

    Page(s): 1134 - 1142
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    Optical Doppler tomography (ODT) is an imaging modality that takes advantage of the short coherence length of a broad-band light sources to perform micrometer-scale, cross-sectional imaging of tissue structure and blood flow dynamics simultaneously. The authors review in this paper the principal of ODT and its applications. Results from in vitro and in vivo model studies demonstrated that ODT can map the blood flow velocity profile with high spatial resolution in scattering medium. ODT detection mechanisms are illustrated using Monte Carlo simulations. The application of ODT to image brain hemodynamics is demonstrated. Finally, the authors discuss the limitations of the current technology and application of a phase resolved technique to improve image speed and quality View full abstract»

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  • Fluorescence lifetime imaging: an application to the detection of skin tumors

    Page(s): 923 - 929
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    A portable system based on fluorescence lifetime imaging has been developed and tested for the detection of skin tumors in humans. The Heme precursor δ-aminolevulinic acid, which promotes the preferential accumulation of the endogenous Protoporphyrin IX (PpIX) in proliferative tissues, is used as an exogenous marker to target the tumor, δ-aminolevulinic acid is topically administered to the patient 1 h before the measurement. Then, using a gated intensified camera, two or more images of the sample are acquired after different delays with respect to the excitation pulses. The images are processed in real time in order to calculate the spatial map of the fluorescence decay time of the sample. The localization of the tumor is based on the longer decay time detected in neoplastic tissues as a result of the stronger emission of PpIX, which has a long decay time, and the reduction in the short living natural tissue fluorescence View full abstract»

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  • Evaluation of four different laser systems for a minimally invasive scoliosis treatment

    Page(s): 1067 - 1071
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    Today most surgical treatment of spinal deformations is concentrated on invasive techniques with long operation times and major effects on the patient's mobility. The proposed minimally invasive technique using laser light for tissue ablation offers a possibility of gentle scoliosis treatment. Four different laser systems including argon, Nd:YAG (Q-switched), Nd:YAG (CW) and Ho:YAG were compared with respect to thermal damage to adjacent tissue, ablation rates, efficiency and laser handling. For in vitro investigation, fresh lamb spine was used. Comparison showed that the Ho:YAG laser is the most appropriate laser for the given goal, however, heating of adjacent tissue had to be minimized by intermediate laser action and irrigation View full abstract»

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  • Thermographic and histological evaluation of laser skin resurfacing scans

    Page(s): 1116 - 1126
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    In general, ablative laser skin resurfacing procedures have shown good short-term efficacy. However, the mechanisms underlying laser skin resurfacing remain poorly understood. We performed a quantitative study to investigate the thermal response of skin to CO2 laser irradiation. Raster scans were performed on an in vivo rat model and radiometric surface temperatures measured using a thermal camera. Temperatures approaching 400°C were measured during the scans and remained above the initial skin temperature for durations longer than ten seconds. Analysis of histology sections showed that the epidermis remained partially intact after three passes. To explain the observed trends in the temperature response and histology, the dynamics of optical and thermal parameters were investigated. Water vaporization played a key role in governing the response of the skin to subsequent laser passes. Char formation and pulse stacking altered the thermal effects View full abstract»

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  • Experimental validation of a backpropagation algorithm for three-dimensional breast tumor localization

    Page(s): 1049 - 1057
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    To validate a new backpropagation algorithm for three-dimensional (3-D) tumor localization in breast tissue with a two-dimensional measurement, we performed experiments on breast phantoms using a heterodyne, frequency-domain photon migration system. The near-infrared (680 or 780 nm) laser diode used to provide illumination was intensity modulated at both megahertz (20-60 MHz) and kilohertz (10 kHz) frequencies. The breast phantoms were made of plastic resin with a variety of simulated tumors imbedded inside and then scanned with the system in a planar geometry. With megahertz modulation signals, both of the amplitude and phase of the transmitted light were used in the data reduction process, whereas with kilohertz modulation signals only the amplitudes were used for the reconstruction. In both cases, the backpropagation reconstruction algorithm was used to accomplish 3-D localization of the imbedded tumors. In all cases, the reconstructed locations for the hidden objects are in good agreement with the true values. Our current work demonstrates the possibility and potential of developing low-cost optical tomographic instruments View full abstract»

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  • Optical coherence tomography (OCT): a review

    Page(s): 1205 - 1215
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    This paper reviews the state of the art of optical coherence tomography (OCT), an interferometric imaging technique that provides cross-sectional views of the subsurface microstructure of biological tissue. Following a discussion of the basic theory of OCT, an overview of the issues involved in the design of the main components of OCT systems is presented. The review concludes by introducing new imaging modes being developed to extract additional diagnostic information View full abstract»

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  • Tissue welding using near-infrared forsterite and cunyite tunable lasers

    Page(s): 1103 - 1106
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    Two new near-infrared (NIR) tunable lasers were used to investigate weld repair strength. The tensile strengths of the shell membrane of hen eggs and the Wistar rat skin welding model were measured for the varying laser wavelengths: 1220, 1240, 1270, 1300 nm (from the forsterite laser) and 1360, 1430 nm (from the cunyite laser). The tensile strength was measured with a digital force gauge. The highest tensile strength was achieved at 1430 nm in the shell membrane of 0.81±0.11 N and in the skin welding model of 0.64±0.16 N. The weld strength follows the absorption spectrum of water View full abstract»

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  • Picosecond electronic time-gated imaging of bones in tissues

    Page(s): 916 - 922
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    Two-dimensional in vivo optical images of metacarpal bones of a human palm and in vitro images of turkey and chicken bones embedded in tissues were obtained in the near-infrared region using femtosecond pulse transillumination and picosecond electronic time-sliced detection technique. A small hole drilled in chicken bone and embedded in chicken breast tissue was imaged using early arriving light. Time-gated fluorescence images of an interior marrow region of a bone injected with a fluorescent dye were recorded. The techniques have potential for monitoring bone fracture, bone diseases such as, osteoporosis and arthritis, and diseases that originate in or affect bone marrow View full abstract»

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  • Laser-induced photodecomposition of amino acids and peptides: extrapolation to corneal collagen

    Page(s): 1107 - 1115
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    Recent studies on the laser photochemistry of aromatic and aliphatic amino acids and small peptides in neutral aqueous solution are described. We report on major parameters such as photoionization and photodecomposition quantum yields for the cases of direct (and indirect) photolysis. Although four different UV laser sources were used, the impact is made on 193-nm-induced photoprocesses. The relative probabilities of photochemical damage of specific residues are estimated. It is shown that the peptide bond is likely to be the main target in collagen. Its scission could be the most important photochemical reaction taking place at 193-nm laser irradiation of the cornea. We have found strong arguments in favor of the ablative photodecomposition mechanism of photorefractive keratectomy View full abstract»

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  • Time-gated transillumination of objects in highly scattering media using a subpicosecond optical amplifier

    Page(s): 895 - 901
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    We have developed an optical system that simultaneously selects and amplifies photons in a time window of less than 10 ps. This new subpicosecond optical amplifier allowed us to realize one-dimensional images of a striped pattern with a spatial resolution of 200-μm through a 30-mm liquid scattering medium. Monte Carlo simulations were performed to study the relative importance of parameters characterizing the medium and the time-gated amplifying system in relation to the image sharpness. The potential application of this system in medical imaging is discussed View full abstract»

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Aims & Scope

Papers published in the IEEE Journal of Selected Topics in Quantum Electronics fall within the broad field of science and technology of quantum electronics of a device, subsystem, or system-oriented nature.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
John Cartledge
Queen's University