G. K. Kostyuk

Peculiarities of the formation of planar micro-optic elements on porous glass substrates under the effect of laser radiation followed by sintering

The theoretical and practical approaches to the formation of micro-optic elements (MOE) for the integrated optical communication on substrates made of different materials, including silicate glasses, have been reviewed. The applicability of high-silica porous glasses (PG) fabricated by a homogeneous acid leaching of two-phase alkali borosilicate glasses as basic matrices for laser formation of MOE of different types (microlenses and microchannels) has been discussed. It has been demonstrated that sintering laser-modified PGs at temperatures ensuring the collapse of the pore can be used to stabilize MOE optical properties. The results of choosing the time-temperature mode for sintering PG substrates with a planar MOE-strip waveguide (SW) providing the SW fixation on a completely sintered substrate were presented.

Surface Sintering of Porous Glass Plates under Laser Radiation

The kinetics of surface sintering of flat plates of the 96SiO2 · 3.8B2O3 · 0.2Na2O (mol %) porous glass exposed to CO2 laser radiation is investigated under conditions when either the irradiation time is varied at a constant radiation power density or the radiation power density is varied at a constant irradiation time. It is established that the irradiation time is the most appropriate controlled parameter in the process of sintering. A decrease in the thickness of the porous layer sintered on the plate surface is accompanied by an increase in the radii of curvature of the interfaces of this layer.

Local laser-induced change of optical properties in the bulk of photochromic porous silicate glass doped by silver and copper halides

The principles of the formation of modified areas of a spherical shape and complex structure in porous glass plates doped by silver and copper halides under the continuous radiation of a fiber laser focused inside the plate have been formulated. The results of the study of the obtained modified areas are given.

Laser induced structural changes in porous glass due to hot and cold compaction

A comparison is presented of the structural changes occurring in porous glass during laser-induced hot and cold compaction. The changes occurring in modified regions of different compaction processes when a porous-glass plate with a micro-region is sintered in a furnace are also compared.

Laser-induced local change in optical properties of alkaline-borosilicate glasses

The process of the formation of microregions (MRs) in the volume of alkaline-borosilicate glasses using the method which includes the production of porous glass (PG) by leaching two-phase alkaline-borosilicate glass in acid and the action on PG of laser radiation of a wavelength practically not absorbed by glass has been studied. The optical properties of MRs and the possibility of their preservation after PG sintering in a furnace to obtain a quartzoid glass are studied.

Laser-induced passivation of porous glass to protect it from chemical degradation and aging

A technique for forming thermally densified layers on opposite wafer surfaces so as to retain a complex well-developed structure of porous glass wafers is proposed. These thermally densified layers passivate and protect porous glass from chemical degradation and aging. The process involves the formation of thermally densified layers and removal of graphite particles from these layers. The formation of a thermally densified layer on the surface of a porous glass wafer was induced by an ytterbium fiber laser with wavelength λ = 1.06 μm, pulse duration τ = 100 ns, and pulse repetition frequency ν = 30–50 kHz. Graphite particles were removed from the surface of porous glass wafers on the same laser setup model. Even 10 months after the thermally densified layers had been formed, loss in transmittance in the entire wavelength range was less than 5–7%. The results of examining the surface relief of porous glass wafers before and after a thermally densified layer had been formed on a scanning probe microscope with an arbitrary selection of 500 × 500-nm scanning areas are presented.

Fast and reversible phase-structure modifications of glass-ceramic materials under CO2-laser action

The reversibility of phase-structure modifications of glass-ceramics (photosensitive and in-photosensitive) has already been experimentally demonstrated with the use of CO2-laser. It has been demonstrated that CO2-laser radiation resulted in a crystallization of glass and a subsequent reverse amorphization of as FS-1 and ST-50 glass-ceramics. The rates of such structural modification under laser heating are about 102 − 103 times higher than under conventional heating with the use of a furnace. The laser technology of structural modification of glass-ceramics is very attractive for development and fabrication of new optical components, different microstructures and microdevices.

Laser-induced microplasma as a tool for microstructuring transparent media*

We have studied the properties of laser-induced microplasma (LIMP) emerging in the ablation of a strongly light-absorbing target in the regime of confinement of spatial plasma expansion. The LIMP particle temperature is shown to be higher in this case than in the free expansion. It is found that the amplitude of the pressure pulse in the regime of spatial LIMP confinement is an order of magnitude higher than in the open surface case. The feasibility of writing microstructures on transparent dielectrics with the use of LIMP is demonstrated: microlens arrays and different diffraction elements are made.

Determination of the Optical Characteristics of Complexly Structured, Locally Modified Regions in Quartzoid Glass

The focal length and numerical aperture of a complexly structured modified region in a plate of porous glass are determined. It is shown that when a plate of porous glass with a modified region is baked the complex structure of the modified region remains. The focal length and numerical aperture of the complexly structure modified region in the quartzoid glass plate are determined. It is found that baking a porous glass plate with a modified region in a furnace considerably reduces the focal length and increases the numerical aperture to 0.9.

Laser technologies for miniature optical elements: approaches and solutions

The field of mini- and micro-optics is stimulated by the development of optical fibers and optical systems for communication, cable television, medicine, diode lasers devices, optical disc memory and optical computers, etc. Such variety of the application directions demands a new more variable components base which cannot be realized by the traditional methods of optical technology. We summarize current theories of physical essence and technical opportunities of different laser technologies for MOC fabrication.