The fabrication of submicron-height sine-like relief of a trifocal diffractive zone plate using a nanoimprinting technique is studied. The zone plate is intended for use in combined trifocal diffractive–refractive lenses and provides the possibility to form trifocal intraocular lenses with predetermined light intensity distribution between foci. The optical properties of the designed zone plate having the optical powers 3 D, 0, −3 D in the three main diffraction orders are theoretically and experimentally investigated. The results of the theoretical investigations are in good agreement with experimental measurements. The effects of the pupil size (lens diameter) as well as the wavelength-dependent behavior of the zone plate are also discussed.
It is described the express optical method of evaluation of thin-film coatings, deposited on metal or semiconductor
surface. For the tested samples of enamel-covered duralumin it is found the linear dependence of maximal intensity and
half-width of secondary radiation on the thickness of the coating.
There are shown the results of experimental investigation of parameters of laser-formed periodic nanostructuring of metal film by means of intracavity processing in the resonator of ruby laser with laser radiation wavelength 0.69 micrometers. AFM-treatment of formed nanostructures profiles has shown the possibility to form multiple periodic structures with characteristic sizes less 200 nanometers during one laser pulse.
The temporal shape of ruby laser pulse is experimentally investigated in the cavity typical for the intracavity processing of Al-film evaporated on the glass substrate. This results in forming of the train of nanosecond pulses with nearly 100% modulation. It is shown the possibility to form nano-sized periodic surface structures by single-pulse ruby laser treatment.
By observing the TEA CO2 laser generation dynamics during the intracavity processing of reflecting surfaces, physical mechanisms responsible for the fabrication of periodic sub-micrometer structures are studied.
The analytical and experimental investigations describing the intracavity processing of different solid-sate materials (Al, Cr, Ge, Si) are presented. New designs of the laser cavity were explored to facilitate the fabrication of structures composed of a system of equidistant parallel 250 nm-sized grooves and periodic micro-dots on massive samples of metals and semiconductors, as well as micro-holes in thin film metallic samples.
In this work it is shown the possibility of the nano-size periodic structures forming on the surface of semiconductor monocrystals with low reflectivity by means of the intracavity laser processing. For this aim the special laser resonator has been designed, which allows to produce extremely narrow high-quality periodic surface structures, looking as equidistant parallel grooves, micro grids, systems of periodically located micro-craters, as well as nano-size structures of other form. The experiments have shown that this resonator makes it possible to fabricate such nano-size structures on the processed samples of monocrystals of germanium and silicon, which have the Fresnel reflectivity coefficient less than 40 percent.
In this work there is described the improved construction of laser cavity which makes possible to form submicron periodic structures on the surface of such perspective but not high- reflective materials as semiconductor single-crystals. The experimental investigation of the intracavity processing of the pure single-crystalline surface of germanium and silicon by means of 1.06-micrometer radiation of neodymium glass laser shows that 0.3-micrometer width periodic structures may be formed even on the surfaces with the reflection coefficient lower than 40 percent.
The one-pulse intracavity processing of the solid-state surface by the radiation of the 150-ns TEA carbon dioxide laser allowed to form the system of supernarrow (less than 0.3 micrometer) equidistant parallel grooves on thin metallic films, evaporated on glass substrates. Later, the more complicated structures, looking as the grids and the regular systems of submicron hollows, were formed by means of only one laser pulse on the basis of the modified laser resonator. The final view of the system of microstructures, which can be formed by the intracavity method, substantially depends on the laser resonator parameters as well the characteristics of the laser impulse (energy, wavelength, duration, mode structure, etc.).
There are shown the basic experimental result, achieved by the 1.06-micrometer intracavity laser processing of the 800 angstrom aluminum film evaporated on the optical glass substrate. There is described the nw laser cavity geometry, which allows to form 2D submicron-size image on the solid- state surface by means of one pulse of laser radiation.
There are discovered physical aspects of one-pulse laser forming of 2D periodical surface microstructures with the characteristic sizes about 30 times less than the used laser radiation wavelength. It is experimentally shown that by means of TEA carbon dioxide laser treatment of the 800 Ao-aluminum film, evaporated on the K8-glass substrate, the periodical system of microhollows with the diameter about 0.5 micron can be formed. The proposed method may be useful for surface microstructures producing in microelectronics or precise filters fabrication.
In this work it is reported about the further development of the intracavity method of the solid state surface processing by the laser radiation. It is experimentally shown the possibility to form 2D periodical micron and submicron surface structures, looking as a system of squares, rectangles and parallelograms. A new type of the laser cavity allowed to fabricate a system of regular microhollows with submicron characteristic sizes even by means of the carbon dioxide laser treatment (10.6-micron radiation wavelength).
The aim of this paper is the theoretical and experimental study of the mode structure laser radiation influence on the basic parameters of the sharp periodical submicron structures (grooves) system which is formed on the solid-state surface by means ofthe intracavity method. It is shown that the longitudinal resonator mode influence is one of the important factors determining the groove width. This factor may be the main one for wide-range infrared lasers with short cavities such as high-pressure carbon dioxide lasers. The comparison of the theoretical analysis with the experimental data enables to conclude that the treated surface damage looking like the sharp equidistant grooves system is formed only when the transverse mode TEM is used. The higher order transverse modes lead to the chaotically located microcraters producing. It is achieved that the grooves system contrast depends on the laser radiation spectrum width, the cavity length, the mirrors reflectivities and practically doesn't depend on the laser beam turn angle.
Key words: Intracavity laser treatment of the surface, laser radiation mode structure, submicron periodical structures forming.
A method of producing submicron (hundreds of nanometers and less) periodical structures on the solid state surface by means of one-pulse laser radiation treatment is developed. The resulting structures look like a system of narrow parallel equidistant grooves. Before a treatment the surface may be covered by one of several thin layers to be destroyed. It is possible to obtain the grooves, a width of which is from 10 to 100 times less than the wavelength of used laser radiation. It is possible to vary the distance between the grooves in a wide range. When a carbon dioxide TEA-laser (0.2 joule-energy, 10.6 micron-wavelength) was used for the treatment of samples (800 angstrom-aluminum film evaporated on the optical glass plates) periodical structures looking like a system of narrow parallel equidistant grooves were produced on an area with a diameter of about 2 mm. The width of the grooves was less than 0.3 micron and a distance between the grooves varied from 7 to 500 microns. Therefore this method has enabled us to obtain grooves with a width about 30 times less than the wavelength of the laser radiation used.
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