Janis Teteris

Holographic recording in amorphous chalcogenide semiconductor thin films

Abstract A detailed study of the amorphous As–S–Se and As2S3 films as recording media for optical holography and electron beam lithography is presented. The results of R&D on resist based on the amorphous As–S–Se thin films for manufacturing of embossed holographic labels are discussed. The holographic recording of transmission and Bragg gratings was studied.

Amorphous As–S–Se semiconductor resists for holography and lithography

Abstract The photo- and electron-beam induced changes in solubility of thin films of the amorphous chalcogenide semiconductors As–S–Se and As 2 S 3 have been studied. The possibilities of practical application of these materials as resists for the production of relief holograms and holographic optical elements are discussed. It is shown that the self-enhancement (SE) phenomenon of holographic recording in amorphous chalcogenide semiconductor films by light or thermal treatment can be used to increase the diffraction efficiency (DE) of the holograms.

Relaxation process of holographic gratings in amorphous As 2 S 3 films

A detailed study of the relaxation self-enhancement (RSE) of the holographic gratings in amorphous As2S3 films is presented. The changes of the diffraction efficiency have been measured as functions of the aging time and the recording light intensity. The role of the internal mechanical stress of the films in the self-enhancement phenomenon has been discussed. It is shown that the RSE has a vectorial character owing to the uniaxial periodically distributed stress relaxation. A model based on the photoinduced stress relaxation and viscous flow of amorphous film is proposed to explain the experiments qualitatively. It is further shown that the stress-induced optical anisotropy of the films is responsible for the RSE.

On thermal influence of laser beam irradiation on optical absorption of amorphous as-evaporated As2S3 films

Abstract Photoinduced changes of the optical absorption in amorphous as-evaporated As 2 S 3 thin films are studied. Before the measurements films were kept at dark for more than two years. The long storage time ensured that the relaxational structural changes caused by the deposition process were absent. As a light source a CW unfocused 488.0 nm Ar laser line was used. The intensity of the laser beam was varied from rather low intensity values up to intensities which raised the temperature of the films above the glass transition temperature. Based on the behavior of the saturation values of the absorption we were able to state that the exposed As 2 S 3 films started to polymerize at 63–69°C which corresponds to the light intensity level of ∼4 W cm −2 .

Photoinduced changes of refractive index in amorphous arsenic and antimony chalcogenides

The maximum values of the light induced refractive index changes in amorphous As-Se and Sb-Se are 0.78 and 0.66, respectively. These results were used for a refractometric estimation of the first coordination radius Δr/r change. The maximum values of Δr/r are 9.4% in As60Se40 and 6.6% in Sb45Se55.

Investigations of As-S-Se thin films for use as inorganic photoresist for digital image-matrix holography

As-S-Se chalcogenide thin films are successfully employed in classical and dot-matrix holography as inorganic photoresists for obtaining a relief-phase hologram. However using these films for image-matrix hologram recording has not been studied due to some features of image-matrix technology. For the applied research of the optical properties of As-S-Se films an experimental device of digital image-matrix holographic recording based on 100 mW 405 nm semi-conductor laser and Spatial Light Modulator (SLM) has been created. The device has the following main parameters: 140 × 105 µm frame size; laser intensity during exposure 10 W/cm2. With the help of this device diffraction grating and security holograms were recorded on As-S-Se thin films. The work reported herein presents results of an experimental study of how diffraction efficiency (DE) of the received relief-phase holographic gratings depends on an exposure and period. Diffraction grating profiles and speed of etching corresponding to different exposure doses are shown. Hologram samples with DE = 65% have been received which allows for using chalcogenide film as alternative to organic photoresists in applied dot-matrix and image-matrix holography.

Holographic recording in amorphous chalcogenide semiconductor photoresists

The properties and mechanism of relaxation processes of holographic gratings in amorphous chalcogenide semiconductor films have been studied. The possibilities of the practical applications of these materials as the photoresists for the production of the relief holograms and holographic optical elements are discussed. It is shown that the self- enhancement phenomenon of holographic recording in amorphous chalcogenide semiconductor films by light or thermal treatment can be used to increase the diffraction efficiency of the holograms.

Photoinduced mass transport in soft materials

The surface relief grating formation in amorphous As2S3 and azo-benzene polymer films strongly depends on the polarization state of recording beams. The surface relief grating formation efficiency of s-s and p-p recording beam combination can be essentially enhanced by additional illumination with orthogonal polarization. It is shown that the direction of mass transport on the film surface is determined by the direction of light electric vector.

Dot-matrix holographic recording in amorphous chalcogenide films

We have developed PC controlled dot-matrix holographic recording system based on the CW diode pumped YAG:Nd SHG laser (wavelength 532 nm, power 30mW,) modulated electronically with TTL signals. Two-beam technique has been used with convergence angle 30o and PC controlled incident beam plane rotation 0-360o. Optical system consists of beam splitter, 40mm focus length forming cylindrical lens and 40mm focusing lens. Characteristic parameters of experimental equipment are following: spot size - 50-200 micrometers, direct laser writing area, limited by x-y positioning system, was 70mm x 70mm, number of writing head rotation positions up to 256 (8 bit), time of each exposure - 1-1000 msec. As the recording material we have used AsxSySe1-x chalcogenide glass material. Diffraction efficiency of written gratings in the material in dot-matrix regime exceeds 25%. Original method for surface relief enhancement by etching and subsequent electroplating has been developed. Special PC controlled device for thermal imprinting of relief holograms on the metallized polyamide film has been built. Measurements of light transmission, reflection, and diffraction phenomena of laser beams in processed chalcogenide materials are discussed.

Light-induced relaxation of holographic gratings in amorphous As2S3 films

Abstract The dependence of the holographic recording self-enhancement on the illumination intensity of the holographic gratings has been experimentally studied in amorphous as-evaporated As 2 S 3 films. The relaxation time of the self-enhancement was found to decrease exponentially as a function of the exciting laser beam intensity. Results are explained by assuming that light induces the decrease of the viscosity.