Phase-locking of the 2D structures.

Experimental results on 1D and 2D phase-locking of laser diode arrays are presented. Attention is paid to the employment of the arrays consisting of wide aperture lasers diodes. Selection of the "in-phase" supermode, preferable for most of the cases, is attained in the external quarter Talbot (Lc=ZT/4=d 2 /2l) cavity due to the output mirror tilt at the angle jm=l/2d. Analysis of the parameters that influence on the phase-locking is given. Our experiments confirm theoretical predictions of the system stability and adequate selectivity for the laser diode array fill factor (FF) FF=0.6.

Modeling of fiber-optic sensors based on micromechanical vibrations in liquid.

Fiber-optic chemical sensors based on optical power absorption or wavelength changes are well known. A new type of sensing element is considered. A micromechanical vibrated fiber-optic tip changes its resonance frequency during its operation. Sensors of this type are simple and convenient and do not require adjustment while in use. They are useful in industry and in medical applications. The action of this sensitive element in a liquid is considered.

[Clinical fluorescent diagnosis of tumors using photosensitizer photogem]. / Klinicheskaia fliuorestsentnaia diagnostika opukholei s fotosensibilizatorom fotogemom.

During clinical trials of photodynamic therapy (PDT) the tissue fluorescence spectra under 510 nm laser excitation were recorded in 22 patients with tumors of the lungs, larynx, skin, gastric and esophageal carcinoma, and cancer of the gynecological organs before (autofluorescence) and after drug administration. A spectroscopic fluorescence detection system, developed at the General Physics Institute, Russian Academy of Sciences, was applied for tumor diagnostics. The system has been used for clinical fluorescence diagnostics with the aid of HPD-type photosensitizer Photogem (Moscow Institute of High Chemical Technologies) marked by selective retention in malignant tumors. Methods and equipment for spectra analysis aimed at estimating drug distribution in the near-surface layers of tissues, determining the tumor boundaries before photodynamic treatment, as well as studying drug pharmaco kinetics have been developed and tested. The results demonstrate the possibility of tumor detection by fluorescence even in low selectivity of drug accumulation which appears to be dependent on the stage and type of the disease and the organ involved.

[The experimental validation of the clinical use of new surgical lasers]. / Eksperimental'noe obosnovanie primeneniia v klinike novykh khirurgicheskikh lazerov.

A comparative evaluation has been carried out between the effects of surgical CO2-laser (lambda = 10.6 mcm) and lasers previously unused in medicine: Yag-erbium (lambda = 2.94 mcm) and YAG-erbium-in-glass lasers on biological tissue. The cutting properties of the lasers, nature of their effect on tissue and the period of healing of laser injury were studied morphologically. Effects of radiation on the energetic, biosynthetic and proliferative processes in the liver tissue, as well as the activity of transamination enzymes have been investigated. It has been shown that laser radiation of lambda = 1.54 and lambda = 2.94 mcm can destroy biological tissue with minimum inflammatory reaction as compared to CO2-laser. It has been ascertained that better marked changes in bioenergetics, aminotransferase activity, RNA and DNA contents are observed under the influence of CO2 and YAG-erbium lasers. Exposure of liver to YAG-erbium-in-glass laser radiation produced minimum changes in cells of the tissue contiguous to the injury. Thus, under its influence the majority of the investigated indices either changed insignificantly or improved. This might account for a positive effect of this laser on the dynamics and quality of the injury healing. The experimental studies gave basis for creation of working models of laser devices (lambda = 1.54 mcm) which are undergoing successful clinical trials at present.

Generation of a high-repetition-rate train of practically noninteracting solitons by using the induced modulational instability and Raman self-scattering effects.

A new method for high-repetition-rate (approximately terahertz) soliton train generation in optical fibers from a cw signal is suggested. The method permits the conversion of all the signal energy into the soliton train energy without the appearance of a pedestal.

Kinetic model of bacteriorhodopsin photocycle: pathway from M state to bR.

A model of the last parts of the bacteriorhodopsin (bR) photocycle is proposed on the basis of experimental data for the kinetic behavior of the 'O' intermediate during a temperature pulse in distilled water suspension. The model includes the previously proposed (but not well characterized) intermediate 'N' between the 'M' and 'O' states of bR. This intermediate exists in fast temperature-dependent quasi-stationary equilibrium with the red-shifted intermediate 'O' and has a maximum of absorption close to the bR spectrum.

Possible mechanism for laser-induced two-dimensional periodic structures by analogy with the Bénard effect.

An explanation is presented for the formation of periodic structures on solid surfaces under powerful laser irradiation through an analogy to the Bénard effect.

Generation of a train of fundamental solitons at a high repetition rate in optical fibers.

By adiabatic amplification of a periodically modulated cw signal in an optical fiber, a train of approximately independent solitons can be generated at a high repetition rate (up to the terahertz range). These pulse trains can be produced with fibers having slowly varying dispersion as well.

Fiber external-cavity injection laser with a dispersive single-mode coupler.

An injection laser with an external dispersive cavity, which uses a selective single-mode coupler as a mode discriminator, has been designed. Narrow-linewidth operation has been achieved with an output power of 5 mW.

Wavelength- and polarization-selective fused single-mode couplers.

Analytical results are presented that describe the characteristics of fused single-mode tapered couplers. The influence of coupler geometry on polarization splitting and spectral selectivity is investigated. A selective fused coupler has been made that exhibits a channel separation of Deltalambda = 0.6 nm, an insertion loss of 1 dB, and an extinction ratio of 20 dB. Polarization selectivity of 20 dB has also been achieved.

Projection system with brightness amplifier for biology and medicine.

Some results of investigation of biological systems using laser projection microscope is given. The scheme permitted to work both in reflected and transmitting light. The image of a living cell on a large screen was observed.

Laser isotope separation of rare earth elements.

The experimental results on the laser isotope separation of the neodimium, samarium, europium, gadolinium, dysprosium, and erbium by the selective two-step photoionization are given. The rare earth elements have been chosen for the investigation because they constitute a good series of the very similar but different atoms that are heavy enough and allow experiments to be carried out that are representative enough. The experimental technique developed for the laser isotope separation experiments has been applied to measure the excitation energy transfer cross sections at the collisions in the gas of the same atoms ((153)Eu ? (151)Eu, sigma = 1.4 x 10(-13) cm(2)). The combination of the selective two-step photoionization and ion mass filtration allowed us to develop a very convenient technique for the precise measurement of hyperfine structure in the spectrum of odd isotopes. The examples of dysprosium and erbium are given. The technique is good for the rare and unstable isotopes as well. The ionization cross sections for the transition starting off the excited level have been estimated ( approximately 10(-17) cm(2)). For the example of gadolinium the possibility of creating neutral atomic vapor dense enough for laser isotope separation by the electron-beam evaporation technique has been demonstrated.