In this work spectroscopic and laser characteristic of photo-thermo-refractive (PTR) glasses doped with different concentrations of rare-earth ions (ytterbium-erbium and Neodymium) were comprehensively carried out. Spectroscopic parameters were obtained using some theoretical techniques like Judd-Ofelt theory and Fuchtbauer-Landenburg (F-L) theory. Results show that the optimal concentration of neodymium oxide in PTR is 0.5 mol%, at which the glass demonstrates the best spectral characteristics. It was found that PTR glass doped with 0.1 mol% of erbium oxide and codoped with 2 mol% of ytterbium oxide also shows good spectral-luminescent properties. Laser action on those two samples was demonstrated. optical losses were found to be 0.34 % for neodymium- doped PTR active element and 0.28 % in the case of erbium and ytterbium co-doped active element. These values are quite low and compared to that obtained in commercial laser glasses. It was concluded that the rare-earth ions doped PTR glass isIn this work spectroscopic and laser characteristic of photo-thermo-refractive (PTR) glasses doped with different concentrations of rare-earth ions (ytterbium-erbium and Neodymium) were comprehensively carried out. Spectroscopic parameters were obtained using some theoretical techniques like Judd-Ofelt theory and Fuchtbauer-Landenburg (F-L) theory. Results show that the optimal concentration of neodymium oxide in PTR is 0.5 mol%, at which the glass demonstrates the best spectral characteristics. It was found that PTR glass doped with 0.1 mol% of erbium oxide and codoped with 2 mol% of ytterbium oxide also shows good spectral-luminescent properties. Laser action on those two samples was demonstrated. optical losses were found to be 0.34 % for neodymium- doped PTR active element and 0.28 % in the case of erbium and ytterbium co-doped active element. These values are quite low and compared to that obtained in commercial laser glasses. It was concluded that the rare-earth ions doped PTR glass is a promising material that can be a good candidate for producing the DFB lasers. a promising material that can be a good candidate for producing the DFB lasers.
In present work we perform analysis of the recorded Bragg gratings on the PTR glass. The analysis includes rigorous couple wave theory and Kogelnik’s theory. Rigorous coupled wave analysis of the recorded gratings includes up to 11 waves. This analysis allows us to retrieve the phase and the amplitude of the Fourier coefficients of a 1-D grating. Which in turns allow to reconstruct the profile of the grating inside the glass volume. Reconstructed profiles of the refractive index inside the gratings explained by the photo-thermo-induced crystallization mechanism.
New application of photo-thermo-refractive glass (PTR) named “holographic prism” is presented. In the holographic prism angles between directions are set by the holograms which create “fan” of signal beams. This kind of prism creates several signal beams which are equal to the reflections from facets of the conventional silica prism. Implementation of PTR glass as a holographic medium for this device brought us several advantages and new features. First it leads to decrease in overall size of the prism that positively affects the identification process of the beam's crosspoint. Thus, it increases sensitivity and accuracy of the measure. Second, greater value of the refractive index change in PTR glass in comparison with calcium fluoride crystal allows us to increase quantity of the recorded reference beams for the measure which leads to sensitivity increase. During this work, it was found that with uneven exposures the refractive index distribution between the gratings is proportional to their irradiation. Also, we demonstrated various geometries of diffraction responses for a new modification of the holographic prism, with two perpendicular "fans".
In present paper we report a study and demonstration of rare earth doped photo-thermo-refractive glasses for monolithic integration of laser sources/amplifiers and volume Bragg gratings. Namely, we demonstrated laser action of neodymium and ytterbium-erbium doped photo-thermo-refractive glasses. In addition, we studied the influence of the rare earth dopants on the photosensitivity of photo-thermo-refractive glass. It was shown that introduction of rare earth dopants not only increase the viscosity of the glass that leading to the longer heat treatment time, but also decrease the ability of fluorine to form sodium fluorine nanocrystals in the glass host. In accordance with this data we developed and demonstrated a new glass composition which overcomes these drawbacks and can act as both holographic and laser active medium. Thus new rare earth doped photo-thermo-refractive glass can be very attractive and promising medium for monolithic integration of lasers/amplifiers and volume Bragg gratings on the united laser-holographic substrate.
We report the results of a thorough investigation into the initial stages of the photo-thermo-induced crystallization process in photo-thermo-refractive glass. The spectral location of the absorption peak characteristic of the surface plasmon resonance in the silver nanoparticles is known to be highly sensitive to the dielectric parameters of the nanoparticle surrounding. We have studied the evolution of the peak location in the course of PTI crystallization process and shown that the red shift of the peak in glass is caused by the occurrence, around the silver nanoparticles, of highly-refractive shell of a mixed nature. The blue shift of the peak that can be observed under the reduced speed of the process was shown to be inflicted by the precipitation of sodium fluoride crystals. During further analysis was proven that shell is of 5.7 angstrom thickness. A couple of models examining shell possible evolution was proposed, namely sodium bromide and silver bromide crystal solid solution and silver bromide inclusions into the surrounding glass layer. Both approaches were modeled to obtain surface plasmon resonance shifts equal to experimentally observed ones. It was shown also that the observed blue shift of the plasmon resonance peak at the later stage of PTI crystallization is due to the NaF precipitation.
The paper is aimed at the development of multi-valued holographic plane angle measure, so called, holographic prism. The holographic prism serves as a base of a device for calibration of equipment (swinging platforms) for navigation apparatus test on influence of rolling. The holographic prism is a small specimen of photosensitive material which a system of superimposed holographic gratings is written in, and a laser used for the gratings readout. Under the influence of the laser, a fan of diffracted beams is induced in the specimen. Consisting of the test device, the holographic prism is mounted on the platform, and while as it swings the fan moves along a photo-detector, for instance, CCD-sensor. First, fluorite was selected as a photosensitive material for the holographic prism. But it had several major drawbacks. Application of photothermo- refractive glass as the photo-sensitive material for the holographic prism manufacture permits to overcome these drawbacks. The hologram number is increased up to twenty-one. The fan proves to be very plane. The fan center is located in a domain which is of small size equal to some part of the specimen thickness (1-2 mm). The fan beams are energy-wise uniform, and every beam can be identified by using the fan in the test equipment. For instance, the beam can be coded, for its identification, by known angles between that beam and the adjacent ones. At last, the hologram recording in photothermo- refractive glass is much easier than that in fluorite.
New application of photo-thermo-refractive glass (PTR) named “holographic prism” is presented. In the
holographic prism angles between directions are set by the holograms which create “fan” of signal beams. This kind of
prism creates several signal beams which are equal to the reflections from facets of the conventional silica prism.
Implementation of PTR glass as a holographic medium for this device brought us several advantages and new features.
First it leads to decrease in overall size of the prism that positively affects the identification process of the beam's crosspoint.
Thus, it increases sensitivity and accuracy of the measure. Second, greater value of the refractive index change in
PTR glass in comparison with calcium fluoride crystal allows us to increase quantity of the recorded reference beams for
the measure which leads to sensitivity increase. During this work, we established recording schedule for the PTR glass in
case of the superimposed gratings recording. Was found that exposure for each grating should be equal to the 1/N fraction
of the optimal exposure where N is the number of multiplexed gratings. We proved that in this case the total value of the
refractive index modulation amplitude is equal to that for the single grating with optimal exposure. Considering obtained
data we successfully performed recording of the holographic prism of the second modification with 14 channels.
In this research, we present new holographic material based on fluoride photo-thermo-refractive glass(PTR) - chloride PTR glass. One of the benefit of this type of PTR glass is positive refractive index change. During this work, for the first-time volume Bragg gratings were recorded in this kind of material. The first experiments revealed that such gratings are mixed i.e. possess both absorption and phase components. Complex analysis shows that both refractive index and absorption coefficient are modulated inside the grating structure. We found out that at first there is no strict dependence of the refractive index change from dosage, but as we continue the process of thermal treatment – dependence is appear. Exposure influence on the refractive index change for this glass differs from fluoride one and shows some sort of saturation after the exposure of 4-6 J/cm2 . We distinguished refractive index change and absorption coefficient change and observed both behavior with increasing thermal treatment time. We found out that the increase of thermal treatment time results in the significant refractive index change. At the same time the absorption does ‘not practically change. It was found that maximum modulation of refractive index is comparable with fluoride PTR glass and achieves value of 1600 ppm. The modulation of absorption is equal to induced absorption caused by silver nanoparticles and depends from reading wavelength. Our study shows that almost all absorption is modulated inside the grating.
In present paper, we represent a study on the effect of RE dopants (lanthanum, erbium, ytterbium, and neodymium) on the process of the photo-thermo-induced (PTI) crystallization. During this work, we investigated each step of the PTI crystallization process including silver particle formation, growth of shell and nanocrystal. To perform these observations, we reduced the temperature of thermal treatment below the glass transition temperature to slow down all processes inside the glass. We found out that the silver nanoparticles formation process does not depend from the concentration of RE ions and is the same as in case of the parent PTR glass. In other hand the growth kinetics of AgBr-NaBr shell and NaF nanocrystals differ from the parent glass and depend on RE concentration. Our observations show no difference in final position of plasmon resonance, which means that the PTI crystallization process itself stays the same and is not affected by the RE dopants. Further study shows that utmost achievable refractive index change falls off with rare earth dopant concentration increase mainly due to the bond formed between dopant and fluorine. This bond prevents fluorine from participation in crystallization process thus overall volume fraction of the crystalline phase decreases. This effect can be corrected by addition of fluorine in the chemical composition of the glass at the synthesis. In conclusion, we show that refractive index change in doped glass with appropriate concentration of additional fluorine is same as in the parent glass (1500 ppm).
The novel photo-thermo-refractive (PTR) glass developed in ITMO University is a very promising optical material for photonic and plasmonic applications. In this paper authors represent study of tin influence on photo thermo inducted crystallization process and make a comparison of the optical and holographic properties of the new and classic composition of glass. Also during this work was made overall optimization of chemical composition namely was optimized concentration of halides, fluorides, bromides which are responsible for crystalline phase properties. Ions of antimony, which playing key role in catching and transferring electrons emitted during the UV exposure and subsequent heating. Also was lowered the concentration of stray impurity ions which a capable to catch photo-electrons. Optical spectra show that new composition of PTR glass has no absorption band in visible range caused by metal nano particles of silver. That allows recording of pure phase holograms in wide spectral range. Furthermore new PTR glass allows receiving refractive index modulation up to 1500 ppm. And the UV exposures needed to achieve maximum changes in refraction index are 6-7 times lower than in classic glass.
Holographic sight was successfully recorded and observed. All necessary properties of recorded sight were confirmed. Optimal parameters for holographic sight recording were calculated. Were shown advantages of PTR glass application as a holographic medium for holographic gun sights. Obtained holograms have high visibility, diffraction efficiency, spectral selectivity and transparency.
First step of Er-Yb laser based on PTR glass creation was made. Complex study of luminescent characteristics of PTR glass doped with Er-Yb with recorded holograms was made. Direct measurements of population inversion of main Erbium level 4I13/2 for different Erbium concentrations and pumping power was made. Was shown that spectral and luminescent characteristics of poly-functional PTR glass doped with Er-Yb and recorded holograms are comparable to the traditional laser barium phosphate glass.
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