Laser modification and ablation of substance

Irreversible impact of laser radiation on substances (laser destruction of dielectrics, pulse laser polymerization, and others) has been a traditional object of interest for researchers at IAP RAS. The present-day studies are concerned with major modification of substances, primarily polymers, under the action of laser radiation in the ultraviolet and visible wavelength ranges. Investigation of these phenomena is interesting for both fundamental science and possible applications. For example, use of laser radiation for producing regions of different optical or electrical properties in a sample of a homogeneous material is attractive for microfabrication technologies. Primary attention is focused on experimental and theoretical investigation of the effects of spatial localization of modification processes caused by various positive feedbacks, as well as of photomodification of thin films followed by surface etching and/or bulk contraction. An analytical theory of these processes has been constructed. The effect of spatial localization (peaking) as a result of developing optical thermochemical instability in a polymer film and the nonlinear effect of formation of a strongly modified layer in a polymer film irradiated by intense UV laser radiation have been observed in experiment.

Recently, the attention of researchers worldwide has been attracted to the phenomena related to laser ablation – removal (by evaporation) of substance from the surface of a solid under the action of powerful pulse laser radiation. Research in this field is carried out in IAP RAS in close collaboration with the Institute of General Physics RAS, the Institute of Theoretical Physics RAS and the Institute of Applied Physics at the J. Kepler University of Lintz (Austria). The main line of activity is development of the theory of this phenomenon in a wide range of light pulse durations. A photophysical model of laser ablation taking into consideration the role of electron-excited states and processes of electron relaxation and explaining a number of experimental facts has been constructed. Research on consistent allowance for the role of bulk effects and substance modification at laser ablation of dielectrics is carried out. Work on laser modification of substances is currently under way in laboratory 332 of IAP RAS.

Laser ablation is the main building block for using lasers in surgery. Advanced research on application of IR and UV lasers in ophthalmology is carried out. Cooperative efforts with researchers at the Institute of Chemistry of High-Purity Substances RAS demonstrated that it is possible to surgically remove a cataract by means of an Er:YAG laser with simultaneous monitoring by a laser tomograph. Application of lasers for such operations is extremely important as they allow minimal invasion of the surrounding tissues and, thus, implantation without loss of ability for the intraocular lens to accommodate. Capabilities of solid-state UV (5-th harmonic of Nd:YA1O 3) and IR (Er:YAG) lasers for corneal vision correction surgery (laser photorefractive keratechtomy) are studied in collaboration with S.N. Fedorov’s clinic.

Appearance of powerful lasers generating light pulses of femtosecond duration stimulated investigation of the radiation–substance interaction in these extreme conditions. The Department of Ultrafast Processes at IAP RAS is equipped with modern femtosecond lasers, which allows not only advanced theoretical research but also experiments on laser ablation within new time intervals. Femtosecond lasers provide basically new opportunities for volume information recording. Possibilities of using nonlinear processes at laser ablation of transparent media for volume information recording are investigated.