Time resolved measuring of laser induced acoustic transients is a good possibility for the determination of optical properties of tissue and tissue like samples. Laser radiation with perpendicular incidence upon the sample-air boundary causes a thermoelastic pressure distribution, which corresponds to the distribution of the absorbed energy in the sample. The knowledge of this distribution allows the determination of optical parameters. Acoustic transients are measured with an aluminum coated film of polyvinylidene fluoride (25 micrometers thickness). The geometric dimensions of the experimental set-up, such as the laser beam diameter, radial profile of the laser beam, penetration depth of radiation, position and size of the sensors are significantly influencing the profile of the measured transients. By using samples consisting of layers with different absorption coefficients, we can analyze the influence of diffraction on the profile of the acoustic signal. For simple geometric configurations it is possible to calculate the thermoelastic wave analytically, but for arbitrary configurations we are using a numerical procedure. The experimental results are qualitatively in good coincidence with our calculations.

A versatile confocal microscope has been developed that combines the optical sectioning properties of a confocal microscope with the chemical identification characteristics offered by Raman spectroscopy to yield a high performance imaging instrument. The apparatus is described and general alignment procedures discussed for optimum performance. An axial resolution of 1.8 micrometer has been determined experimentally for Raman active planar structure and its form compared to theory, A broad range of applications are envisaged in areas of biology, geology and other areas of microscopic analysis. A study is presented showing its applicability to photodynamic therapy for the localization of specific dyes within cells.

A repetitively pumped ruby laser including long (16 m) intracavity optical delay line is described emitting microsecond pulses. A prototype model of laser lithotriptor was made using this laser, and histological and clinical studies were made.

The results of experimental study on a focusing of laser- induced submicrosecond pressure pulses and destruction of solids subjected to them are presented. It was studied how the source distribution of pressure pulse amplitude influences upon the focusing in water. The means for the focusing improvement have been developed. The high focal pressure (approximately 40 MPa) localized in a small spatial region (approximately 10 multiplied by 1 mm) was achieved. The destruction of solids loaded by the trains of shock pulses was studied also. It has been found that much more effective disintegration takes place under a quasi-resonance loading. The results show that efficiency of extracorporeal lithotripsy may be significantly increased when using laser- induced submicrosecond pressure pulses.

The existing laboratory optical methods do not fulfill in full measure the modern accuracy and operational requirements. Primarily this is due to the high sensitivity of the methods to the changes of the optical and electronic signals passing condition, to the optical elements and cuvettes pollution, etc. These drawbacks can be eliminated at the elimination of the dependence of the methods error on the apparatus constants of emitting-receiving and measuring blocks, optics pollution, etc. Below the description is being given to the variant of methodological errors elimination technique in the laboratory optical investigations (illustrated by the example of attenuation coefficient (transparency) determination of optically transparent biological objects).

Miniaturized fiber optic sensor probes continue to be developed in a number of research laboratories around the world. Such fiber optic probes originate from work undertaken on the development of nanometric probes used in scanning near-field optical microscopes. The probes can be converted to sensors for highly localized chemical measurements by attaching the appropriate chemical indicators to the probe tips. We use the term 'micro- optrode' to describe fiber-optic chemical sensors possessing such high spatial resolution. This paper presents a brief summary of the progress that has taken place in the development of the micro-optrode and includes recent results obtained in our laboratory with such sensors.

For integrated optical immunosensors, a much more reliable interpretation of the sensor output signal can be achieved by introducing reference pads located near the sensing pads, in order to separate specific from nonspecific effects. Results of theoretical and experimental investigations are reported for immunosensors based on measuring changes of the effective refractive index due to the binding of analyte molecules. The emphasis is on the correction for temperature variations which is an important example of compensation for nonspecific effects. Using the binding of rabbit immunoglobulin to immobilized protein A as a regenerable model bioaffinity system, the influence of consecutive assay cycles on the two pads has been investigated. Experiments have been performed using sensor chips consisting of TiO₂ waveguiding films on fused silica and replicated polycarbonate substrates.

First results with a new generation of bioaffinity sensors based on luminescence excitation using single-mode planar waveguides are presented. Planar waveguides show superior physical characteristics, concerning sensitivity and required sample volumes, and can principally be fabricated in low-costs mass production processes. Additionally, they allow for different detection geometries, e.g., different configurations of fluorescence detection and simultaneous determination of the transmitted excitation light. The transducer characteristics, possible detection geometries and our present experimental configuration are explained. Results with different bioaffinity systems applied on the novel transducer generation are presented, demonstrating the capability of detecting attomole amounts of analytes within a few minutes.

A miniaturized optical fiber probe for measuring the esophageal pressure, making use of biconically tapered fibers, has been built and characterized. The operation of the probe is based on the decrease of the transmitted power from a biconical fiber when it is bent, in its biconical part, under the action of pressure. The necessary sensitivity is about 1 divided by 2 mm Hg in the range between 0 and 50 mm Hg. To obtain it we have fabricated and tested some probes using different fibers (four-mode, two- mode and monomode) and different values of tapering. Our best result has been achieved with a probe made with a monomode fiber of waist 36 micrometer whose sensitivity is 2 mm Hg in the range between 5 and 55 mm Hg.

An optical-fiber strain-gauge based on Fabry-Perot interferometric principles together with a novel signal processing technique has been developed. Although the originally intended area of usage was aero-engineering, this paper describes its use as an aid to bone fracture fixation. Some trial results are presented and our further development strategies are discussed, in particular, the replacement of dielectric thin mirrors with fiber gratings.

The dynamic sensors for speed and flow are applied in pathological physiological research of the cardiovascular system and for the study of blood flow in the capillaries. The use of laser Doppler anemometry (LDA) method is considered the major prospective for this application. This method is based on the Doppler shift of the frequency of laser radiation scattered by blood particles in movement. However, to have access to inner organs, a small-size delivery system and optical probe are necessary. In this paper, we report a novel miniature optical probe for the differential-type LDA, suitable for use in small blood vessels and in other small channels. For the construction of the probe, two-core single mode optical fiber was used. This fiber had two anisotropic 8 (mu) cores, located symmetrically with respect to the fiber axis. The separation between them was 25 (mu) . In the fiber, a directional coupler was integrated near the fiber's remote end. The coupler was fabricated by heating of a small section of the fiber, with simultaneous elongation of this section. For heating, the carbon-dioxide laser was utilized. The carbon-dioxide laser was also used to fabricate a lens at the fiber tip. At the fiber entrance, the laser light was launched in one of the fiber's cores. The fiber was typically of several meters long. Near the fiber end, this radiation was splitted by the directional coupler, and the second core was excited too. At the fiber tip, the fused lens provided collimation of the emerging beams and secured their intersection in front of the fiber tip. In this intersection volume, the interference field was formed. In the flow, this periodic pattern resulted in Doppler frequency shift of the light scattered by moving particles. This probe was successfully used together with the LDA signal processing equipment for velocity measurement in small tubes for blood-flow simulation experiments. In the probe, the two cores are identical, and the between the directional coupler and the fiber tip is very small. Thereafter, all extrinsic fields and effects have identical influence on the propagation constant of each core. Hence, the resultant parasitic phase modulation, that is the main problem in the fiber-based differential LDA, is negligible in this probe. This is the principal advantage of this probe. However, its small size and integrated nature are also of value for biomedical applications.

The fiberoptic evanescent wave Fourier transform IR spectroscopy (FEWS) using fiberoptic sensors operated in the attenuated total reflection (ATR) regime in the mid-IR region of the spectrum (4 to 16 micrometer) has recently found application in the diagnostics of biotissues. The silver halide fibers used are non-toxic, non-hygroscopic, flexible and soft and are characterized by a low optical loss. The method allows for non-invasive and rapid (seconds) direct measurements of the spectra of normal and pathological tissues in vitro, ex vivo and in vivo with the aim of express testing of various tumor tissues at the early stages of their development. The method is expected to be further developed for endoscopic and biopsy applications.

A fiber optic pulsed photothermal radiometric prototype system was constructed. The radiometric system includes a carbon dioxide laser, an infrared detector and two infrared transmitting silver-halide optical fibers for radiation delivery to and from the target. We used the pulsed photothermal radiometric system to heat up a sample by a short duration laser pulse and measured the decay time of the photothermal infrared signal emitted from a sample due to the absorption of the laser pulse in the sample. The fiber optic radiometric system was used to establish the feasibility of using the pulsed photothermal radiometric method for diagnosis of thermal damage in tissue.

A feasibility study of performing radiation dosimetry using a radiochromic film fitted in an optical fiber link is presented. The radio-transducer is the transparent Gafchromic^TM film, exhibiting a non-reversible blue coloration when exposed to ionizing radiation. Samples of a Gafchromic^TM sheet have been firstly exposed to different 6 MV X-radiation doses in the 0 - 100 Gy range, and then optically characterized by means of absorption, transmittance and reflectance measurement in the 400 - 900 nm spectral range, in order to choose the best fiber/sensor link assembly. The films showed a usual radiation-modulation absorption spectrum with two main peaks at 614 and 670 nm and null response above approximately 750 nm allowing for two-wavelength differential-attenuation measurements in order to compensate cable and connector losses. As a first approach an optical fiber link has been realized, made of multimode fibers and GRIN-rods, allowing the film insertion in a sleeve between the GRINs. The optical link is connected to an electro-optical unit providing illumination by two LEDs emitting at 655 nm (sensing signal) and 840 nm (reference signal), and detection by a single PIN. The interrogation scheme is based on LED time-domain modulation and subsequent Fourier analysis of the detected signal. Measurements have been performed sequentially inserting the previously radio-exposed films between the GRINs and measuring the ratio between the sensing and reference signals. System output exhibits a dynamics of 14 dB for exposures to doses in the 0 - 100 Gy range, with a dynamics of 2.5 dB and a fairly linear behavior in the 0 - 10 Gy range. The feasibility of using Gafchromic^TM film for radiation dosimetry in combination with optical fibers has been well documented.

Spectral analysis of human blood serum was carried out by fiberoptic evanescent wave spectroscopy (FEWS) and Fourier transform infra red (FTIR) spectrometer, with a silver- halide fiber as the sensing element. The concentrations of three blood components were predicted simultaneously using neural network (NN) models. In order to overcome the problem of fiber deterioration caused by interaction with serum salts, the fiber was coated with a plastic layer. The coating was tested and found to provide excellent protection to the fiber placed in a 3.5% salt solution. This method may be used for in-situ real time and long-lasting measurements.

Biomedical science and practical medicine need special techniques for reliable real-time remote detection and determination information from human tissue. Most applications of these techniques in interior organs are based on optical fibers which should not only be able to deliver excitation light with minimal loss but provide effective light gathering from tissue being under the test. As emitted from tissue optical signal is often weak especially if autofluorescence spectroscopy is chosen for diagnostics, an efficient collection by fiber optics probe became essential. The main part of the proposed fiber optics probes is a specially designed tapered tip with one flat surface and another spherical one. This tip operates as a collector, transmitter and coupler to deliver light to the tissue and backward to the detector simultaneously. To find geometrical dimensions of tips optimized for these purposes calculating formulas have been adduced. These optimized tips could collect fluorescence signal from biological sites in wide angular aperture region and could transport light without leakage on tapered surface. When delivery fibers are placed at the focal plane of tip spherical surface an efficient optical coupling with them is achieved. Ray tracing of the tapered tips has been performed on sapphire and quartz tip materials in air and in saline to determine the best sensor design.

During the laser treatments in biomedical fields the patient must not run any risk due to a damage of the fiber delivery systems. Such damages are usually monitored by backscattering. Here an investigation of backscattered signals due to flat, bulb and damaged fiber tips is reported. A fiber directional coupler was employed which has shown noticeable advantages with respect to the conventional beam splitter technique (BST). These results have been exploited to design a practical monitoring device which has been inserted int a fiber-optic delivery system, fed by a Nd:YAG laser.

The maximal laser power transmitted through polycrystalline silver halide fibers is limited by their IR absorption and optical strength. The mechanisms of the IR absorption and laser-induced breakdown (LIB) thresholds P_c in AgCl_xBr_1-x crystals and polycrystalline fibers were studied. Investigations, including mechanical treatments, heat treatments, and luminescence properties were performed to clarify the reason for the IR absorption and LIB in silver halide crystals and fibers. From these experiments we concluded that one of the reasons for LIB may be the avalanche of electrons in the conduction band of the crystal. These seed electrons are produced by the IR absorption of the cation vacancies in these crystals. A simple annealing procedure for reduction of the IR absorption of fibers is proposed.

Design and fabrication of silver hollow nickel waveguides have been conducted based on the outer-coating method with three inner dielectric layers composed of two zinc sulfide layers and a germanium layer. The sputtering conditions are optimized experimentally for depositing silver, germanium, and zinc sulfide layers and a low-loss waveguide with multiple inner dielectric layers has been fabricated, for the fist time, for Er:YAG laser light transmission.

Hollow flexible copper waveguides were developed with two types of dielectric layers (Cu₂O and ZnS). Measurements of transmission as a function of coupled power have shown that scattering appears in the Cu₂O dielectric waveguides which give losses affecting the time of the outlet power which can be maintained constant. Beam profile measurements were performed using the perspex cubes and Spiricon beam profile methods. It was shown that the type of dielectric layer and wavelength of transmitted energy have an influence on the beam profile. The ZnS dielectric layer waveguides have a beam profile with larger average amplitude and less modes as compared to that of Cu₂O dielectric layer. The smaller energy per mode of the Cu₂O waveguides compared to that for ZnS makes the application of the perspex cubes method not applicable for beam profile measurements for the Er-YAG laser where the average transmitted energy is smaller than that of the CO₂ laser, since the energy per mode is not enough to produce traces. It was shown, from the beam profile measurements made with perspex and Spiricon methods on ZnS dielectric waveguides, that when ER-YAG laser radiation is used, by increasing the energy per pulse, is obtained longer traces in perspex or larger energy per pulse than by increasing the time of irradiation. This can have practical applications for the operation of removing tissue with Er-YAG laser. A method of detection if the maximum average transmitted energy is coupled to the center of cross section of waveguide was developed based on beam profile measurements.

Copper hollow waveguides with an inner dielectric layer have been developed by using simple techniques of chemical etching and oxidation for the inner wall of the copper tubes. Transmission properties of hollow waveguides have been measured. It is shown, for the first time that a thin Cu₂O layer is obtained by using chemical oxidation techniques. It is also shown that the thickness of a Cu₂O layer can be controlled by the oxidation time.

The paper deals with a problem of light focusing on the tissue for laser surgery, diagnostic and therapeutics with assistance by tapered tips. Optimization of the shape and geometrical dimensions of laser scalpels sought to minimize tissue damage by means of exception of light leaking through the tapered surface and decrease of distal end inner reflection. These results can be achieved by simultaneous attaching,spherical shape to the front surface of tapered tip also optimization of fiber-tip distance and tip dimensions. Analytical and ray-tracing calculations have been performed for sapphire (n equals 1.75) and silica (n equals 1.45) tip materials and air or saline (n equals 1.33) mediums. The diameter of aperture diaphragm and reflection number of incident beam in the tip have been varied from 1 to 5 fiber core diameter and from 1 to 10, respectively. Several numerical methods for evaluation of tip efficiency for optimized and conventional tips were discussed. Some versions of commercially available tip modernization have been presented. Modification of front surface of the tapered tip increased the angular aperture from 4 degrees to 12 degrees (in air) and from 8 degrees to 15 degrees (in saline) with obviating light leaking in commercial tip by Hans Sttetler SA, Switzerland. Replacement of the contact flat laser scalpel (surgical laser technologies, Malvern, PA) to an optimized one allowed us to increase the taper angle from 1.9 degrees to 10 degrees and produced, therefore, shorter and stronger tip without reducing its optical properties.

We have succeeded in fabricating low-loss fluorocarbon polymer (FCP)-coated silver hollow glass waveguides by using a liquid-flow coating method. The thickness of a FCP film is strongly dependent on the flow speed and the concentration of FCP solution. It is shown that the optimum condition exists for depositing the polymer to reduce the roughness of layer. The transmission loss of the fabricated waveguide with inner diameter of 700 micrometers is about 0.2 dB/m for Er:YAG laser light. An efficient tapered coupler with a lens is also investigated to couple the laser beam with large diameter to small-bore waveguides.

Our attention was focused on chalcogenide, heavy metal oxide glasses (TeO_{2/ - PbO, PbCl(subscript 2}) and sapphire fibers. Improving of the purity of these glasses was achieved by their preparation in a halogen reactive atmosphere, the concentration of hydride impurities were diminished below 10^-4 mol%. The values of optical losses are below 1 dB/m at 3 and 5 micrometer. The attention was focused on sapphire fibers too. The fibers about 1 mm in diameter and 200 - 300 mm in length were prepared. Their optical losses are below 1 dB/m at 3 micrometer.

A new technique for the absorption of cells is presented. A NIR diode laser (810 nm) and an absorption enhancing dye (indocyanine green, ICG) are used. Localized heating of ICG aggregates close to the cell surface generates bubbles inside the cells. Expansion and emergence of these bubbles cause the cells to open, thus creating the condition for successful transfection. Successful application to plant (tomato) cells is reported for the first time. The experimental results are directly linked both to the absorption characteristics of the dye employed and to the nature of the wall. Optoporation was achieved only by the use of the dye. Laser powers were employed comparable to those used for animal cells.

Haematic cells, excited with radiation of suitable wavelength, give rise to a natural fluorescence (NF) emission. This paper investigates NF to develop new techniques for applications in both basic research and medical diagnostics. Results show that the cell populations examined exhibit peculiar emission bands. The intracellular fluorescence pattern reveals that flouresence is mainly located at cytoplasmic-level, thus related to the metabolic processes of the cells. The photophysical properties of cells appear different among the normal populations and between normal and leukaemic ones. Therefore the recognition of the various cellular elements, according to their fluorescence emission, is possible.

Complete handling of single DNA molecules and their enzymatic restriction are described. For that purpose a microsphere was bound to a DNA molecule and trapped by optical tweezers. It could be moved in any direction. For stretching or rotating the molecule an electrical field was applied while the bead was fixed by the optical tweezers. In a near-equilibrium state of the resulting forces, the DNA remained stretched. Subsequently, a restriction endonuclease was activated by liberating Mg²⁺ from a caged compound. The enzymatic reaction could be directly observed in the light microscope. While the bead remained in the focus of the laser trap the other restricted part of the DNA molecule is pulled away in the electrical field. The reaction was directly monitored and recorded on videotape.

Various techniques, including coherence gating have been employed to discriminate against scattered light when imaging objects in a diffusing medium. We demonstrate a coherence gate using a photorefractive holographic imaging system. Using ultrashort pulse illumination, depth resolved images of three dimensional objects embedded in such a scattering medium have been obtained. We have investigated the use of bulk photorefractive crystals (Rh:BaTiO₃) and photorefractive multiple quantum well (MQW) devices as the hologram recording medium. Using a long integration time in bulk Rh:BaTiO₃, an image of a test chart has been obtained through up to 16 mean free paths (mfp) of scattering medium. Conversely a fast response time (less than 0.4 ms) has been demonstrated in the MQW device when imaging through 8 mfp of scattering medium.

System miniaturization is a key issue in further development of integrated optical sensors. We present an integrated optical GaAs/AlGaAs-based Mach-Zehnder interferometer with a 2 mm long TiO₂ on SiO₂ embedded waveguide sensor pad and its performance as a bioaffinity sensor. Preliminary experiments to evaluate the performance of our Mach-Zehnder interferometer device were done by studying the binding of immunoglobulin (IgG) to protein A. The current resolution limit of IgG surface coverage is 3 pg/mm², corresponding to less than 1/1600 of a saturated IgG monolayer. Since the design of the basic GaAs/AlGaAs waveguide structure is fully compatible with monolithic integration of lasers, modulators and detectors, improved performance can be expected from integration of these optoelectronic components on the same chip.

Optical sensors based on the utilization of the evanescent field arising at the interface between two media in the case of total internal reflection are an excellent tool for the reduction of time consuming and complex chemical analysis. We developed a fiber-optic based set-up with visible diode lasers as excitation sources. As recognition element an optical fiber covered with a photopolymerized antibody monolayer was used. Beside the commercially available cyanine fluorescent dye Cy 5, newly developed fluorescent dyes in the red spectral region were coupled to antibodies. In order to test the set-up in a clinically relevant system the antibodies BM-2 and BM-7 were chosen. With this antibody system the tumor marker mucine in a sandwich immunoassay was investigated. This protein shows increased concentrations in serum and ascites in the case of breast cancer. The combination of semiconductor devices and ultrathin antibody layers together with an antibody system directed against mucine offers the possibility of an on-line detection of the tumor marker.

The immobilization techniques presented represent an innovative method for the highly specific determination of antigens and other proteins in a very short time and may be a useful tool for the industrial preparation of highly sensitive biosensors. Non amphiphilic alkylated cellulose films are used as matrices to reduce non-specific interactions with biomolecules. These films are transferred onto waveguides by using the Langmuir-Blodgett- technique. After photochemical stabilization the cellulose films serve as excellent matrices for the immobilization of proteins at high density. Furthermore, one-step immobilization of a mixed photopolymer antibody film with a continuously operating LB-trough is demonstrated. The activity and specificity of immobilized antibodies and streptavidin is controlled by an enzyme-linked immunosorbent assay (ELISA) and an evanescent wave immunosensor.

Preliminary investigations into the design of an affinity sensor using evanescent wave technology concentrate upon the means of immobilization of the receptor molecules. In this work DNA served as the selective recognition element. The molecular principle of a sequence-selective biosensor for DNA is based on a sandwich-hybridization assay wherein the analyte, a single-stranded (ss)DNA, bound specifically to both an immobilized capture probe and a dye-labeled oligonucleotide in free solution. The efficiency of the capture array depends on the density of highly organized oligonucleotides on the waveguide surface and correlates therefore directly with the specificity and the sensitivity of the sensor. In the present approach using the Langmuir- Blodgett technique cinnamoylbutylether-cellulose monolayers were transferred onto optical fibers or planar waveguides. These films served as matrices for the immobilization of biotinylated oligonucleotides via streptavidin. For the first time streptavidin was immobilized by that manner. The specificity of the streptavidin layer or the following bounded nucleic acid molecules were controlled by an enzyme- linked immunosorbent assay (ELISA). Finally, this application has also shown to be suitable for the detection of Salmonella, which is an important pathogen associated with acute gastroenteritidis and food borne diseases.