Eximer Laser pra-0084

Full Title Eximer Laser — a Universal Instrument For Investigations in Microelectronics, Photochemistry, X-Ray Spectroscopy and Other Sciences Tech Area / Field

PHY-OPL: Physics / Optics and Lasers

CHE-RAD: Chemistry / Photo and Radiation Chemistry

INF-ELE: Information and Communications / Microelectronics and Optoelectronics

Brief Description of Technology Lasers based on eximer molecules that generate a radiation wavelenth range of 190-350 nm are developed and produced by a number of companies. This is due to the fact that the lasers’ parameters (radiation spectrum, average power, pulse energy) make them attractive for many applications in microelectronics, photochemistry and generation of x-ray radiation. However, the complexities and difficulties caused by their service impede their competition when compared to garnet lasers with frequency conversion.

Analysis of published data and our own experiences show that the greatest difficulties are due to the brief time of inversion existence in an eximer laser. This makes it necessary to use complicated schemes of the generation spectrum selection. An essential disadvantage of eximer lasers is the requirement of a regular change of operating gases and considerable sizes (small stored energy in an active medium).

An eximer laser has been developed in IAP RAS in which the mentioned disadvantages are eliminated, or greatly diminished.

The laboratory laser model has the following parameters: a wavelenth of 308 nm, a pulse duration varying from 1-40 ns for the spectrum width of 0.02 cm^-1, a divergence close to the diffraction, and an output energy of 0.1 J.

When the spectrum width grows to 1 cm^-1, the pulse duration can be increased to 200 ns. It is planned in the near future to raise the energy output to 1 J. For the given radiation parameters, the laser has high stability.

By employing special technology in the discharge electrode preparation, we managed to decrease the longitudinal sizes of amplifying moduli to 0.4 m instead of the conventional 1 m, which permitted us to diminish the laser sizes and reduce the active mixture consumption. The setup also included a dye laser with eximer laser pump. The output radiation wavelength of this attachment (adapter) can vary from 350-800 nm.

Legal Aspects Patents were not sought.

Special Facilities in Use and Their Specifications None.

Scientific Papers Nikolay I.Polushkin, S.A.Gusev, M.N.Drozdov, Yu.K.Verevkin, V.N.Petryakov., “Arrays of magnetic wires created in phase separating Fe-containing alloys by interference laser irradiation,” J.Appl.Phys. v.81, N 8, pp.1-3 (1997).

Yu.K.Verevkin, E.Ya.Daume, V.N.Petryakov, A.D.Tertyshnik, “The use of SMBS in xenon for compensating the distortions of the radiation space structure in XeCl gas-discharge plasma,” Proceedings SPIE. Phase Conjugation and Adaptive Optics v.2771, pp.22-27 (1995).

Optical Coherence Tomography of Human Biotissues pra-0085

Full Title Optical Coherence Tomography of Human Biotissues Tech Area / Field

PHY-OPL: Physics / Optics and Lasers

BIO-PAB: Biotechnology and Life Sciences / Public Health

INS-MEA: Instrumentation / Measuring Instruments

Brief Description of Technology Optical imaging of biological microstructures within tissue interiors is a challenging and medically important scientific problem. Radiation in the “therapeutic window” (0.6 - 1.3 m) is ideal for non-invasive optical monitoring, plus detection of biological objects and tissues owing to minimal tissue absorption. Nonetheless, the use of traditional methods of transillumination for biological imaging employing continuous wave or long pulsewidth sources of coherent radiation is ineffective due to multiple light scattering with tissue and poor spatial resolution, resulting in poor image quality and spatial smearing of even coarse (> 1 mm) features.

Optical coherence tomography (OCT) is a relatively new coherence-domain technique for optical imaging of biological tissues. Pioneered by Fujimoto and coworkers, as well as others within the past five years, OCT is now widely recognized as a very promising tool for providing non-invasive clinical diagnostic information of eye structures, skin, internal organs and other tissues. Based on low-coherence reflectometry, OCT provides high spatial resolution (~10 m) while allowing for two- and three-dimensional images of the internal structures of biotissue without solving an image reconstruction problem. OCT enables one to follow the pulse-to-pulse kinetics of laser interactions with turbid biological tissues. An advantage of OCT in these investigations is the possibility to follow the transformations of not only surface layers, but also inner layers that are hidden from usual optical observation. The state-of-the-art in OCT development is described by J.Izatt in the May 1997 issue of Optics and Photonics News. The Nizhny Novgorod research team is widely recognized to be among leading groups in OCT development. The following world-class achievements can be mentioned: — invention and implementation of fast piezo-optic, in-depth scanning (Russian patent granted, US patent pending) — creation of a compact OCT device, with a flexible fiber cable, based on unique self-made polarization-maintaining (PM) single-mode fiber elements — creation of a dual-wavelength OCT device for simultaneous biotissue imaging — world first in vitro and in vivo observation of OCT images of mucous membranes — observation of pulse-to-pulse kinetics of ablation crater growth during irradiation of cataracted lens by mid-infrared laser.

Legal Aspects A Russian patent for a fast piezo-optical in-depth scanner and low coherence interferometer with such a scanner was granted (priority date 1 Mar 1995); US patent pending, PCT application submitted (covering Europe and Japan) and preliminary international expertise has been carried out.

Special Facilities in Use and Their Specifications A unique OCT device designed and produced by the applicant group monitors biotissues in laboratory and clinical environments. An optical workshop produces unique, polished fiber optic elements with record parameters.

Scientific Papers A.Sergeev, V.Gelikonov, G.Gelikonov, F.Feldchtein, et.al. “In Vivo Optical Coherence Tomography Of Human Skin Microstructure In Biomedical optoelectronic devices and systems II,” Proc. SPIE 2328, p.144 (1994).

V.M.Gelikonov, G.V.Gelikonov,R.V.Kuranov, K.I.Pravdenko, A.M.Sergeev, F.I.Fel’dstein, Ya.I.Khanin, D.V.Shabanov, N.D.Gladkova, N.K.Nikulin, G.A.Petrova, and V.V.Pochinco. Coherent optical tomography of microscopic inhomogeneities in biological tissues. Piz’ma Zh. Eksp. Teor. Fiz. 61, No.2, pp.149-153 (1995).

A.Sergeev, V.Gelikonov, V.Gelikonov, F.Feldchtein, et al, “High-spatial resolution optical-coherence tomography of human skin and mucous membranes,” in: CLEO’95 Technical Digest, p.349 (1995).

Sergeev A.M., Gelikonov V.M., Gelikonov G.V., Feldchtein F.I., Gladkova N.D., Kamensky V.A., “Biomedical diagnostics using optical coherence tomography,” OSA TOPS on Advances in Optical Imaging and Photon Migration, v.2, p.196-199 (1996).

Gelikonov V.M., Sergeev A.M., Gelikonov G.V., Feldchtein F.I., Gladkova N.D., Ioannovich J., Fragia K., Pirza T, “Compact fast-scanning OCT device for in vivo biotissue imaging,” Conference on Lasers and Electro-optics, OSA Technical digest series, v.16, p.58 (1996).

F.Feldchtein, V.Gelikonov, G.Gelikonov, N.Gladkova, V.Leonov, A.Sergeev, “Optical fiber interferometer and piezoelectric modulator,” International application PCT/RU96/00045 (1995).

G.Gelikonov, V.Gelikonov, F.Feldchtein, J.Stepanov, A.Sergeev, I.Antoniou, J Ioannovich, D.Reitze, W.Dawson, “Two-Color-in-One-Interferometer OCT System for Bioimaging,” CLEO’97 Technical Digest, p.210 (1997).

V. Kamensky, V.Gelikonov, G.Gelikonov, F.Feldchtein, A.Sergeev, K.Pravdenko, N.Artemiev, N.Bityurin, I.Skripachev, A.Pushkin, G. Snopatin, “In situ monitoring of the middle IR laser ablation of cataract-suffered human lens by optical coherent tomography,” Proc. SPIE, v.2930, p.222 (1996).

V. Kamensky, V.Gelikonov, G.Gelikonov, F.Feldchtein, A.Sergeev, K.Pravdenko, N.Artemiev, N.Bityurin, I.Skripachev, G. Snopatin, “YAG:Er laser system for microsurgery treatment of cataract-suffered human lens,” Proc. SPIE, v.3091, paper 19 (1997).

V. Kamensky, F. Feldchtein, K. Pravdenko, V. Gelikonov, G. Gelikonov, A. Sergeev, and N. Bityurin, “Monitoring and animation of laser ablation process in cataracted eye lens using coherence tomography,” Proc. SPIE (in press).