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Thin arsenic trisulfide films were deposited by thermal evaporation and thermally activated silver diffusion into these films was studied. UV–vis transmission and Rutherford backscattering spectrometry (RBS) was used for characterization of film property changes with Ag incorporation. The straightforward analysis proposed by Swanepoel, which allows determination of the dispersion relation and the film thickness from the optical transmission spectrum, was extended and applied to the chalcogenide thin films. RBS shows that silver diffusion mechanism depends strongly on an eventual annealing between the chalcogenide and silver deposition step. Without annealing the silver diffusion takes place by exchange between silver and arsenic atoms whereby sulfur atoms remain stationary, and arsenic accumulation occurs at the surface. For annealed samples silver diffuses without changing the film stoichiometry. In this case, the diffusion is much slower and the profile is more step-like. The possibility of using this technique for channel waveguide fabrication is demonstrated.

A detailed study of multiphoton lithography (MPL) in arsenic trisulfide (As2S3) films and the effects on nanoscale morphology, chemical networking, and the appearance of the resulting features by the chemical composition, deposition rate, etch processing, and inclusion of an antireflection (AR) layer of As2Se3 between the substrate and the As2S3 layer is reported. MPL was used to photo-pattern nanostructured arrays in single- and multilayer films. The variation in chemical composition for laser-exposed, UV-exposed, and unexposed films is correlated with the etch response, nanostructure formation, and deposition conditions. Reflection of the focused beam at the substrate back into the film produces standing wave interference that modulates the exposure with distance from the substrate and produces nanobead structures. The interference and the modulation can be controlled by the addition of an AR layer of As2Se3 deposited between the substrate and the As2S3 film. Relative to structures produced in a single-layer As2S3 film having no AR layer, photo-patterning in the multilayer As2S3-on-As2Se3 film yields pillar-shaped structures that are closer to the targeted shape and are narrower (120 versus 320 nm), more uniform, and better adhering to the substrate. Processing methods are demonstrated for fabricating large-area arrays with diffractive optical function.

Arsenic trisulfide (As2S3) is a transparent material from ~620 nm to 11 μm with direct applications in sensors, photonic waveguides, and acousto-optics. As2S3 may be thermally deposited to form glassy films of molecular chalcogenide (ChG) clusters. It has been shown that linear and multi-photon exposure can be used to photo-pattern thermally deposited As2S3. Photo-exposure cross-links the film into a network solid. Treating the photo-patterned material with a polarsolvent removes the unexposed material leaving behind a structure that is a negative-tone replica of the photo-pattern. In this work, nano-structure arrays were photo-patterned in As2S3 films by multi-photon direct laser writing (DLW) and the resulting structure, morphology, and chemical composition were characterized and correlated with the conditions of the thermal deposition, patterned irradiation, and etch processing. Raman spectroscopy was used to characterize the chemical structure of the unexposed and photo-exposed material, and near infrared ellipsometry was used to measure the refractive index. Physical characterization including structure size and surface adhesion of nano-scale features is related to the processing conditions.

Chiral gyroid photonic crystals are fabricated in the high refractive index chalcogenide glass arsenic trisulfide with an adaptive optics enhanced direct laser writing system. The severe spherical aberration imparted when focusing into the arsenic trisulfide is mitigated with a defocus decoupled aberration compensation technique that reduces the level of aberration that must be compensated by over an order of magnitude. The fabricated gyroids are shown to have excellent uniformity after our adaptive optics method is employed, and the transmission spectra of the gyroids are shown to have good agreement with numerical simulations that are based on a uniform and diffraction limited fabrication resolution.

Arsenic trisulfide (As2S3) thin films were deposited by a relatively new and simple successive ionic layer adsorption and reaction (SILAR) method using As2O3 and Na2S2O3 as arsenic and sulfide ion sources, respectively. The films were deposited on glass and silicon(111) wafer substrates. The concentration, pH, and temperature of anionic and cationic precursor solutions, immersion and rinsing times, and number of immersions have been optimized for obtaining good-quality As2S3 thin films. X-ray diffraction, optical absorption, and electrical resistivity techniques were used for characterization of the As2S3 thin films.

Optical recording in amorphous arsenic trisulfide was investigated for amplitude to phase conversion to be exploited in applications such as holographic recording and the fabrication of diffractive optical elements. The main result of this study is the demonstration that it is possible to obtain a linear relation between the spatial variation of the recording intensity and the recorded phase modulation. The extent of the linear recording region depends strongly on the recording wavelength. At short wavelength (458 nm in these experiments), where the rate of the photoinduced structural changes is strong, the recording is practically linear from zero exposure up to about 25% of the maximum value of the refractive index change. With higher exposure, saturation effects start to play an important role and degrade the linearity of the response. Recording with longer wavelength (488 and 514.5 nm) is less effective (absorption becomes weaker) and then relaxation processes in the material become significant. If the competition between photoinduced processes and relaxation processes is strong, the linear relationship between exposure and refractive index change can no longer be linear. Nevertheless, even for recording with the longer wavelengths, a region of exposures can be found within which variations of intensity can be converted into variations of phase with a linear relationship.

We present a theoretical background and experimental verification of holographic recording in nano-sized films. The interference pattern is created by a total internal reflected (TIR) reference wave and normally incident plane one. Due to a surface-propagating evanescent wave, the holographic recording is stored in 39 nm arsenic trisulfide film. The exposure and modulation dependence on the diffraction efficiency is investigated. The angular and wavelength selectivity of the thin TIR hologram is shown to be similar to that of thick Bragg gratings.

Fully crystalline samples of high-purity arsenic trisulfide have been prepared for the first time. Comparison of X-ray diffraction spectrum (XRD) of prepared crystals with XRD spectrum of natural orpiment, as well as Raman scattering experiments, confirmed the crystallinity of the prepared sample. Using differential scanning calorimetry, the melting enthalpy (78 J/g) and apparent activation energy of the melting process (306 kJ/mol) were found. A kinetic analysis of the peaks, as the melting process took place, showed that melting can be described well by the Johnson–Mehl–Avrami equation with a kinetic exponent slightly more than 1. A detailed computer fit of Raman spectrum is described.

We present a study of the photoresponse spectrum of heterojunctions ofn-GaAs with amorphous As2S3 films with various thicknesses of the glassy chalcogenide semiconducting film. We obtain an expression to calculate the fraction of the light absorbed in the glassy semiconductor, the fraction of the light absorbed in GaAs, taking into account the multiple reflections at the interfaces in the structure under study, and also their ratio. We present an analysis of the absorption of light in the structure. The calculated results show good agreement with experiment.

Differential scanning calorimetry (DSC) measurements were performed at different heating rates under nonisothermal conditions to probe the glass transition kinetics of As2S3 bulk glass and thick films. We found that, for films, the glass transition temperature (Tg) increases with increasing annealing temperature, and sharp crystalline-like melting endothermic peaks appear in samples annealed at 160°C. Such sharp endothermic peaks could also be found for samples annealed at 140°C for 300 h, indicating a very slow crystallization process. The activation energy for the molecular motions and rearrangements around Tg could be estimated as 2.12 eV for films and 2.3 eV for the bulk, respectively.

The dependence of the electron-induced dichroism effect in vitreous As2S3 on the photon energy of the probe radiation and on the temperature of subsequent thermal anneals is investigated. The effect is observed to be completely suppressed after prolonged storage of the samples (10–15 days) following electron irradiation. It is shown by induced-reflection Fourier-transform IR spectroscopy that the observed effect is associated with processes involving the formation of oriented defects in the form of undercoordinated atomic pairs in the glass structural matrix.

Dissolution kinetics of glassy and crystalline As2S3 in aqueous sodium sulfide and hydroxide solutions was investigated. Glass, produced by rapid quenching contains frozen products of arsenic trisulfide dissociation — As4S4 and S. A strong change in the chemical behavior of g- and c-As2S3 has been found in its interaction with hydroxide ions. A mechanism of dissolving has been suggested.

The dispersion characteristics of Arsenic Trisulfide As2S3 chalcogenide glass were analyzed and a kind of As 2 S 3 microstructured optical fiber was designed to shift the zero dispersion wavelength from longer than 4 µm to around 2 µm. The supercontinuum generation in the designed fiber with selected pump wavelengths and pulse durations were simulated through numerically solving the Generalized Nonlinear Schrodinger Equation. The results reveal that the broadest supercontinuum covering 1.1 µm to 5.5 µm can be obtained with pump laser with duration 150 fs centered at 2.0 µm which is slightly longer than the first zero dispersion wavelength. When the pump wavelength is around the zero dispersion wavelength apparent dispersive waves which are significant for spectral broadening can be observed.

The intra/extracellular beta-amyloid (Aβ) of neuron has been known as the most representative hallmark of Alzheimer's disease (AD). Recently, the clinical diagnosis of AD has been significantly issued with early detection of Aβ. For further accurate quantification of Aβ compared to current techniques, we suggest a new technical concept that enables the evaluation of as small as a few femtomolar Aβ peptide by using photo-sensitive field-effect transistor (p-FET) coated with selectively transmissible optical filter for a particular range of wavelengths of excitation beam. The photo-current generated by p-FET with arsenic trisulfide (As2S3) filter is as much apparent as about 76 nA for a small amount of Aβ-conjugated fluorescent particles. This result indicates that even with slightly small amount of Aβ peptides the As2S3 coated p-FET is applicable to recognizing optically tenuous fluorescence.

Chalcogenide glasses are composed of two or more chalcogen elements normally selected from the small group including As, Ge, Sb, P, Te, Se, and S. When these elemental materials are heated and mixed in an oxygen-free environment, some very stable and simple glasses can result. One of the oldest chalcogenide glasses studied is the binary glass arsenic trisulfide, As2S3. This glass is deep red in color, and it is very stable. In the mid 1960s, this glass was drawn into the first IR fiber by N. S. Kapany. In his 1967 book on fiber optics, Kapany includes a discussion of As2S3 fibers and some of their potential applications. It was not until some 10 to 15 years later, however, that these materials were studied seriously as viable IR fiber candidates. The reticence to pursue these materials in the early days came in part from the toxic nature of some of the elements used in the glasses. Today they are a popular IR fiber material as they are readily drawn into fiber with a broadband IR transmission. While they are much more delicate in nature than the oxide glass fibers, they are finding many applications in chemical and temperature sensor systems and as IR image bundles. Chalcogenide fibers fall into three categories: sulfide, selenide, and telluride. Within these categories, one usually finds that the binary and ternary glasses are excellent choices for fiberization. That is, unlike the fluoride glasses where it is commonplace to have five or more components, most chalcogenide glasses have only two or three elemental components. In general, these glasses have softening temperatures comparable to fluoride glass. They are very stable, durable, and largely insensitive to moisture. A distinctive difference between these glasses and the other IR fiber glasses is that they do not transmit well in the visible region and their refractive indices are quite high. Additionally, most of the chalcogenide glasses, except for As2S3, have a rather large value of dn/ˆ•dT. This fact limits the laser power handling capability of the fibers.

Arsenic trisulfide (As 2 S 3 ) glass is an interesting material for photonic integrated circuits (PICs) as infrared (IR) or nonlinear optical components. In this paper, direct laser writing was applied to engineer the refractive index of As 2 S 3 thin film. Film samples were exposed to focused above bandgap light with wavelength at 405nm using different fluence adjusted by laser power and exposure time. The index of refraction before and after laser irradiation was calculated by fitting the experimental data obtained from Spectroscopic Ellipsometer (SE) measurement to Tauc-Lorenz dispersion formula. A positive change in refractive index (Δn=0.19 at 1.55μm) as well as an enhancement in anisotropy was achieved in As 2 S 3 film by using 10mW, 0.3μs laser irradiation. With further increasing the fluence, refractive index increased while anisotropic property weakened. Due to the rapid and large photo-induced modification of refractive index obtainable with high spatial resolution, this process is promising for integrated optic device fabrication.

It is shown that the linear recording of holographic gratings can be obtained at 514 nm in the amorphous arsenic trisulfide films. While strong nonlinearity was observed during recording at room temperature, these effects were eliminated when the recording was performed at temperatures below 275 K. To verify the linearity of the recording, the first- and second-order diffraction of a recorded grating were monitored during exposure. Since temperature appeared to be an important factor in obtaining the linearity of the recording, the experimental results support our qualitative model in which photoinduced structural changes, the main recording process, are deteriorated by a competitive relaxation process.

We previously reported on the deposition, absorption, and CO 2 -laser damage threshold for As 2 S 3 , As 2 Se 3 , and NaF coatings. It was shown that the damage threshold was much lower for coated than uncoated substrates and that the mechanism for damage was different in the coatings than in the substrates. We speculated that the damage in the coatings was related to the presence of micron-sized crystalline defects distributed in the amorphous chalcogenide matrix. In this paper we report the results of damage measurements on these materials at 2.8 and 3.8 μm and identify two operating damage processes: "uniform" damage, which we associate with the amorphous chalcogenide matrix, and "selective" damage, which we associate with the crystalline defects. For single-layer films, we find that N/1 conditioning generally produces an increase in the damage thresholds. The wavelength dependence of multithreshold results in single-layer coatings of As 2 S 3 and NaF suggests that improvement in threshold results from the thermal desorption of contaminating layers of water at 2.7 μm. However, for a dielectrically enhanced reflector containing quarter-wave layers of As 2 Se 3 and NaF, N/1 conditioning promoted crystallite growth which resulted in a definite deterioration of N/1 thresholds.

We present a novel high-index-of-refraction (2.45) photoresist material based on erbium doped arsenic trisulfide. It shows room temperature photoluminescence at 1.5 microns wavelength, and can directly be used for direct laser writing.

The diverse applications of chalcogenide glassy semiconductors (CGSs) are based on the unique possibility of making photo-induced changes (PIC) in their physical and chemical properties. The laws of reversible (i.e., reversible with annealing up to temperatures 20-30 K lower than Tg) PIC, discovered over the last 10-15 years, have served as a basis for the development of systems for recording, storing, and transmitting optical information based on thin semiconductor layers of arsenic, antimony, bismuth, germanium, etc., chalcogenides [i, 2].

The development and use of arsenic trisulfide glass in infrared systems began in 1950. The glass was produced commercially in ton quantities by a number of companies in the US and Europe and used in NIR and MWIR systems mostly for commercial use. In the 60's, it became apparent that new optical materials capable of longer wavelength transmission would be needed for thermal imaging systems beginning to be considered. The government sponsored exploratory development programs aimed at providing selenium and tellurium containing glasses. By mid 1970's, two selenium based glass compositions had been developed and were in production in the U.S. Many tons of these two glasses have been produced and used in the 1980's, 1990's and present day for thermal imaging systems both military and commercial. The fact that only two glass compositions have been used so extensively for such a long period is due in part to the size of the effort required to identify, characterize and produce a new glass to a state where it will be considered by the optical designer for use in new systems. But new compositions may be needed to provide a glass better suited for a different application. Glasses developed by Amorphous Materials for different applications will be described.

This letter describes the passivation of an n‐type GaAs surface using an arsenic trisulfide (As2S3) film. Metal–insulator—semiconductor diodes were fabricated with an evaporated As2S3 film as an insulator. In the inversion region, the capacitance–voltage curve shows deep depletion, that coincides with the depletion theory. In the accumulation region, surface Fermi level movement is blocked 0.25 eV below the conduction‐band minimum due to a high density of interface states. The minimum interface state density is found to be about 1–2×1011 eV−1 cm−2.

A temperature-dependent, sub-band-gap, light-scattering study of the vibrational modes of vitreous As 2 S 3 fibers during the photoinduced fluidity effect is reported. The structural changes that give rise to the effect are detected mainly through variations in the degree of polarization of the scattered light. The results show a nonmonotonic behavior in the observed structural changes interpreted as a reduction in the flow ability of the glass a few degrees above room temperature followed by a subsequent increased ability to plastic deformation at higher temperatures, but still well below the glass-transition temperature. Studies on the nonstoichiometric concentration As 2 5 S 7 5 at room temperature revealed noticeable differences with arsenic trisulfide. The relation between the illuminating energy and the band gap of the glass has also been investigated. An account for the possible nature of these experimental facts is attempted in terms of the specific structural units constituting the glass structure.

The fabrication and performance of an optically addressed spatial light modulator (OASLM) based on nematic liquid crystal and nanodimensional amorphous arsenic trisulfide (a-As2S3) chalcogenide glassy films are described. The photoconductive a-As2S3 layers are used both as photoalignment material and as a photosensor. The use of the OASLM as a color converter is demonstrated in the transmission mode. The phase retardation dynamic range is over 3π. Diffraction efficiency measurements show a high resolution (150 lp/mm at 50% MTF). A wide variety of materials from the chalcogenide glass (ChG) family are useful for simple fabrication of high-resolution OASLMs depending on the desired wavelength.

A subbandgap light scattering investigation of vitreous arsenic trisulfide, $v\ensuremath{-}{\mathrm{As}}_{2}{\mathrm{S}}_{3},$ fibers subjected to external elongation stress has been undertaken in order to elucidate the photoinduced fluidity effect [H. Hisakuni and K. Tanaka, Science 270, 974 (1995)] in a microscopic scale. Orientational changes in the short-range order (intramolecular vibrations) caused by the presence of the illuminating visible light are detected. Subtle but noteworthy alterations are revealed in the intermediate range order, manifested as the increase of the magnitude and the modification of the frequency dependence of the depolarization ratio---in the low frequency part of the spectrum---as a function of the applied stress. The results are discussed alongside with old and recent structural models that have been employed to account for light-induced changes in amorphous semiconductors and low-energy modes in amorphous solids.

In this report we study the formation of surface relief in arsenic trisulfide films under laser light radiation with modulated polarization direction. The formation of surface relief is obtained with method what is different from holographic recording – only one laser beam with modulated polarization direction was used. Samples with different thickness were made using vacuum evaporation. The photo-induced changes on the surface were initiated by DPSS laser light (λ = 532nm). Profiles of surface reliefs were observed and relief depth dependence on film thickness and exposure was studied.

Amorphous Materials (AMI) has been engaged for several years in developing a process suitable for forming coherent imaging bundles from small diameter chalcogenide glass fibers. Currently, in a SBIR II program funded by the Navy Air Warfare Center at Patuxent River, Md., efforts are directed towards forming a bundle 10 meters in length from arsenic trisulfide glass fibers using the stacked ribbon method. A drum 10 meters in circumference was constructed on which to wind the ribbons. The fiber core diameter goal is 50 micrometer. The bundle will be 7 mm square with an active fiber area greater than 50% and an overall transmission goal of 50%. Anti-reflection coatings on both ends are provided using the AMI coating facility. A unique method of forming imaging bundles will be discussed. Images formed during evaluation will be shown.

We describe instrumentation that has been constructed at the National Institute of Standards and Technology (NIST) for measurement of the index of refraction of solid materials in the spectral region from 0.5 micrometer to 1000 micrometer using Fourier-transform based spectrophotometers and etalon samples. Preliminary index of refraction measurements have been performed on fused silica and arsenic trisulfide glass samples from 0.5 micrometer to 12 micrometer, and the results are compared to tabulated values on these materials.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

At one time, arsenic trisulfide (As2S3) glass was the only IR optical material produced commercially for infrared optical systems. The glass was produced by the tons from the 50s into the 70s. However, as the emphasis shifted to the long wavelength 8 - 12 micrometer passive optical systems, the glass fell out of favor and production worldwide ceased. The production processes used were open systems which led to environmental concerns that also contributed to the decisions to cease production. In the 1990s, Amorphous Materials (AMI) became interested in the glass in part because of the reported ability of As2S3 glass fibers to transmit large amounts (greater than 100 watts) of laser power. A closed process which eliminated environmental concerns was developed to produce the glass. Major emphasis was in producing glass for IR fibers. Use for imaging systems was limited. Now, however, a trend has developed to produce imaging systems based on focal plane array technology which operate in the 3 - 5 micrometer wavelength region. A demand once again has been created for the glass. The method used at AMI to produce the glass is presented. Efforts to reduce absorption through purification of the elements are described. Properties of the glass are reviewed.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A newly discovered bacterium, Desulfotomaculum auripigmentum, precipitates arsenic trisulfide (As(inf2)S(inf3)). Precipitation of As(inf2)S(inf3) by this organism results from its reduction of As(V) to As(III) and S(VI) to S(-II). At the As(III) concentration range of interest (0.1 to 1 mM), the stability of As(inf2)S(inf3) is highly sensitive to pH and [S(-II)]. Thus, the relative rates at which D. auripigmentum reduces As(V) and S(VI) are critical to its formation of As(inf2)S(inf3). Other As(V)- or S(VI)-reducing bacteria are unable to precipitate As(inf2)S(inf3) either due to their inability to reduce both As(V) and S(VI) or because they reduce S(VI) too rapidly. Electron microscopy of thin sections showed that the precipitate forms both intra- and extracellularly. Microbial As(inf2)S(inf3) formation nucleates precipitation of the mineral in the bulk milieu, whereas heat-killed cells alone do not serve as templates for its formation. Precipitation of As(inf2)S(inf3) by D. auripigmentum suggests that As(inf2)S(inf3) formation may be important in the biogeochemical cycle of arsenic.

The importance of early Alzheimer's disease (AD) detection has been recognized to diagnose people at high risk of AD. The existence of intra/extracellular beta-amyloid (Aβ) of brain neurons has been regarded as the most archetypal hallmark of AD. The existing computed-image-based methods have limitations on accurate quantification of nanoscale Aβ peptides due to optical diffraction during the imaging process. Therefore, we propose a new method that is capable of evaluating a small amount of Aβ peptides by using photo-sensitive field-effect transistor (p-FET) integrated with a single layer on-chip optical filter. Arsenic trisulfide (As2S3) layer has adequate optical functions that reflect the unwanted ranges ( 480 nm) from fluorochromes widely used for labeling Aβ peptides.We measured destructively decayed photo-currents from As2S3-coated p-FET compared with those from bare p-FET. We also measured the elevated photo-currents generated by the transmitted fluorescent emission when a small amount of fluorescein isothiocyanate (FITC) were placed on As2S3-coated p-FET, indicating that the As2S3 filtered p-FET would differentiate the optically tenuous fluorescent beam. Furthermore, we measured the photo-currents generated by FITC conjugated with Aβ peptides expressed on a cell line to investigate the applicability of our p-FET sensor to the actual detection of Aβ peptides existing in a biological material.

Titanium-diffused lithium niobate (Ti:LiNbO(3)) waveguides are widely used in current fiber optic networks because of their high-speed, electro-optic modulation, and low-loss integration with standard single-mode fibers. However, they cannot achieve small ring resonators owing to their lack of a high core-to-cladding index contrast. To overcome this challenge, we vertically integrate an emerging chalcogenide glass waveguide technology on well-established Ti:LiNbO(3) waveguides. We present, to our knowledge, the first arsenic trisulfide (As(2)S(3)) race-track ring resonator with a 290.8 microm bend radius in an all-pass filter configuration, integrated on a Ti:LiNbO(3) waveguide. Vertical coupling is achieved using a unique taper design. Experimental results are shown for 10.6% coupling, 2.08 dB roundtrip loss, and a 25.4 GHz free-spectral range.

This research was supported by the Australian Research Council through its Centres of Excellence and Federation Fellow Programs.

Single-channel waveguides and Y couplers were fabricated in chalcogenide thin films by use of femtosecond laser pulses from a 25-MHz repetition rate Ti:sapphire laser. Refractive-index differentials (delta n > 10(-2)) were measured through interferometric microscopy and are higher than the typical values reported for oxide glasses. The dependence of the index differential on the peak intensity reveals the nonlinear nature of the photosensitivity in arsenic trisulfide below its bandgap energy, and the refractive-index change is correlated to the photoinduced structural changes inferred by Raman spectroscopy data. A free-electron model to predict the parametric dependence of delta n is proposed.

We report the creation of microchannels in a photosensitive material, the arsenic trisulfide As2S3. We show that microchannels are created through the process of self-writing and are highly sensitive to the photosensitivity of the material as well as the quality of the incident wave front. The very high photosensitivity of As2S3 allows the self-written waveguide to become much smaller than the incident beam. We present a numerical analysis based on the nonlinear Schrodinger equation that accounts well for the diversity of the microchannels that were experimentally observed and shows that they can actually guide light.

The luminescence of a neodymium-doped arsenic trisulfide planar waveguide at 1083 nm is reported. The dopant was introduced into the chalcogenide glass by ion implantation. The dopant distribution following ion implantation was predicted by molecular dynamic simulation and measured by Rutherford backscattering spectrometry. The most efficient pump wavelength was determined to be 818 nm. This observation of luminescence from rare-earth-ion implantation into chalcogenide glass, for the first time to the authors’ knowledge, suggests that this technique can be useful for rare-earth-doped devices.

The relaxation processes in As(2)S(3) films related to the self-enhancement effect of holographic gratings with low initial diffraction efficiencies are examined. It is demonstrated that the dark relaxation plays a noticeable role in the self-enhancement.