A study of the electrical and optical properties of the GeO2-TeO2 glass system

Results of measurements of the d.c. electrical conductivity, optical absorption edge and infrared optical absorption of GeO₂-TeO₂ glasses are reported. Conduction in these glasses is found to be electronic and the hopping of polarons seems to be the dominant process in the transport mechanism. The electrical activation energy decreases with the increase of tellurium content and this decrease corresponds to a decrease in the optical energy gap. The optical gap is of the order of 2.74 eV, somewhat lower than for many other oxide based glasses. Most of the sharp absorption bands characteristic of the basic materials GeO₂ and TeO₂ are modified with the formation of broad and strong absorption bands in the process of going from the crystalline to the amorphous state. Density measurements show the glasses to have a compact structure.     

Effect of core glass composition on the optical properties of active fibers

We optimized the composition of core glass for active fibers. Using solution doping, we obtained aluminogermanosilicate core fibers containing up to 0.6 mol % Yb₂O₃ with optical losses within 10 dB/km.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 4, 2005, pp. 508–512.Original Russian Text Copyright © 2005 by Khopin, Umnikov, Vechkanov, Rozental, Guryanov, Bubnov, Rybaltovskii, Belov, Dianov.Deceased.     

Optical and physical properties of solgel-derived GeO2:SiO2 films in photonic applications

The functionality of optical components relies heavily on the composition-dependent properties of germanosilicate materials, which include the refractive index, photosensitivity, and microstructural properties. Recent studies and parallel developments are presented of germanosilicate films with composition x of Ge content (i.e., xGeO(2):(1-x)SiO(2)) that were synthesized by the solgel process for various integrated photonic applications undertaken. The following novel aspects are discussed with respect to the effect of composition of the glassy films (0.05相似文献   

Optical transmission of hollow glass photonic-crystal fibers

A photonic-crystal fiber (PCF) with a forbidden photon band (FPB) in the visible spectral range has been created for the first time. The PCF shell comprises concentric layers of hollow circular air-filled channels with variable diameters. The optical transmission of the proposed PCF and the influence of the geometric parameters on the FPB width and position in the visible spectral range have been studied. By varying the PCF structure and geometry, it is possible to change the FPB characteristics, which offers broad possibilities of output light control.     

Study of optical properties of GeO2 nanocrystals as synthesized by hydrothermal technique

The GeO₂ nanocrystals (α-quartz type structure) with β-phase are synthesized at relatively lower temperature by hydrothermal route using autoclave. All samples are characterized by XRD, FESEM, EDS, TEM, photoluminescence (PL) and UV–vis absorption spectroscopy techniques. Synthesized nanocrystals have uniform shape and uniform size distribution for a particular synthesis condition, which is about 30–300 nm depending on synthesis conditions. The XRD results indicate that grown GeO₂ crystals only shows peak related to α-quartz structure with lattice parameters a = 4.985 Å and c = 5.648 Å. UV–vis absorption spectroscopy measurements reveal the bandgap energies corresponding to the GeO₂ α-quartz structure. Synthesized nanocrystals are capable to emit strong blue light around 425–435 nm under excitation of 300 nm and 325 nm and consequently the as synthesized material can be used in integrated optical devices.     

空芯光纤中沉积多晶态GeO2薄膜的实验研究

通过缩短高温炉冷却器的距离,使化学反应与沉积区的温度梯度增加到约9℃／mm,进而使GeCl4与O2可在内径为1.0mm的空芯石英管内壁沉积上颗粒度约0.1um,厚度为3.0um的多晶态GeO2介质膜,使表面更加光滑,提高了光纤的传输性能,光纤的传输损耗小于0.8dB／m.     

Optical properties of single-crystal sapphire fibers

Single-crystal sapphire fibers have been grown with the laser-heated pedestal-growth method with losses as low as 0.3 dB /m at 2.94 ?m. With the incorporation of a computer-controlled feedback system, fibers have been grown with less than +/-0.5 % diameter variation, or +/-1.5 ?m for a 300- ?m fiber. The losses in these fibers have been reduced further through a postgrowth anneal at 1000 degrees C in air, from 5.4 to 1.5 dB /m at 543 nm and from 0.4 -0.3 dB /m at 2.94 ?m. These fibers delivered 4.7 W at 10 Hz of Er:YAG laser power.     

Optical properties of end-sealed hollow fibers

We propose sealing techniques for medical hollow fibers to protect the inner surface of fibers from debris or water that scatters from targets. First, hollow fibers are sealed with a film of polymer that is easily formed by use of a dipping technique. The transmission loss of 20-microm-thick sealing film was 0.2 dB for Er:YAG laser light, and the maximum energy that is available for the film was 180 mJ. Second, a sealed glass cap was applied to the output end of hollow fiber. The silica-glass cap with a wall thickness of 400 microm shows a transmission loss of 0.5 dB and was not damaged by radiation of 400-mJ energy pulses.     

Hydroxyl groups in phosphosilicate glass for optical fibers

To gain insight into the local environment of impurity hydroxyl groups in phosphosilicate glass and determine its signatures in the vibration spectrum, the IR absorption spectra of phosphosilicate glasses containing up to 20 mol % P₂O₅ were analyzed. The interaction of hydroxyl groups with phosphorus-containing centers was studied with the use of a cluster model and the PM3 and MNDO quantum-chemical methods. The observed changes in the OH-stretching region of the absorption spectrum were interpreted using the modeling results.     

Optical time-domain reflectometry of bent plastic optical fibers

Optical time-domain reflectometry (OTDR) signals of step-index plastic optical fibers (POF's) and graded-index POF's were measured with a laser diode and an avalanche photodiode. When bent step-index and graded-index POF's were used, the OTDR signal behavior differed. The OTDR signal of the bent graded-index POF's had a step that corresponds to a curvature loss, but the step-index POF's had a spike signal at a bend, which indicated the occurrence of backscattering. The peak intensity was proportional to the square of the curvature. The refractive-index variation of the bent step-index POF's was measured, and the dependence of the peak intensity on the curvature was shown to agree with that predicted by the scattering from the refractive-index perturbation.     

Electron spin resonance and some electrical and optical properties of GeO2/SiO x thin films

Electron spin resonance measurements show a reduction in the spin density associated with unpaired electron dangling bonds of a mixed complex of co-evaporated GeO₂/SiO _x films compared with that of SiO _x films investigated under similar conditions. Unlike the behaviour of BaO/GeO₂ complex films, these samples show a decrease in the optical gap as the thickness increases for films of fixed compositions. However, it increases as the SiO percentage increases in films of the same thickness. D.C. measurements at low applied fields below 10⁵ V cm^–1 agree well with the spin density results.     

The photosensitivity of ytterbium-doped optical fibers with aluminophosphosilicate glass cores

The phenomenon of photoinduced refractive index change in active optical fibers with Al₂O₃/P₂O₅/Yb₂O₃/SiO₂ core composition has been observed under the action of UV laser radiation with 193-nm wavelength. It is established that hydrogen treatment of active fibers plays a key role in ensuring a radical (about two orders of magnitude) increase in their photosensitivity. It is shown that intrafiber Bragg gratings with reflection coefficients above 99% can be formed, which are promising mirror reflectors for fiber laser cavities.     

Optical properties of small-bore hollow glass waveguides

Hollow glass waveguides with a 250-μm i.d. have been fabricated with a liquid-phase deposition technique that uses silica tubing as a base material. The losses of the 250-μm-bore guide measured at CO(2) laser wavelengths are as low as 2.0 dB/m. The straight losses for the hollow guides are in good agreement with theoretically predicted losses as a result of the nearly ideal structure of the guides. It is also shown that the guides have low bending losses, a nearly pure-mode delivery, and good high-power laser transmission. By proper design of the dielectric thickness, the guide is also able to deliver Er:YAG laser energy with a low loss of 1.2 dB/m for the 320-μm-bore waveguide. Because the hollow glass waveguide is very flexible and robust, it is quite suitable for medical applications.     

Optical properties of SrAl2O4: Eu2+ phosphor in glass

Phosphor-in-glass (PiG) typed robust color converters were fabricated using pb-free silicate glasses for luminescence materials applications. The PiG based on a SiO₂–B₂O₃–BaCO₃ ternary system and SrAl₂O₄: Eu²⁺ phosphor showed good transparency reached 99.50%, even if the GTP ratio is 25:1. By simply changing the mixing ratio of glass to SrAl₂O₄: Eu²⁺ phosphor, the emission color of PiG can be controlled from blue to bluish green. The results reveal that the luminescence properties of SrAl₂O₄: Eu²⁺ distinct from the phosphor in glass significantly. These suggest that PiG could provide potential application in a variety of luminescence materials.     

Suspended core tellurite glass optical fibers for infrared supercontinuum generation

We report the fabrication and characterization of tellurite TeO₂-ZnO-Na₂O (TZN) microstructured suspended core optical fibers (MOFs). These fibers are designed for infrared supercontinuum generation with zero dispersion wavelength (ZDW) at 1.45 μm. The measured losses at this wavelength are approximately 6 dB/m for a MOF with a 2.2 μm diameter core. The effective area of a particular fiber is 3.5 μm² and the nonlinear coefficient is calculated to be 437 W⁻¹km⁻¹. By pumping a 20 cm long fiber at 1.56 μm with a sub-nJ femtosecond laser source, we generate a supercontinuum (SC) spanning over 800 nm in the 1-2 μm wavelength range.     

Thermal properties of highly birefringent optical fibers and preforms

Temperature cycling of highly birefringent optical fibers and preforms has been used to investigate the thermal properties of bow-tie and elliptically clad structures. The thermal hysteresis of the birefringence is shown to be a direct consequence of the thermal history of the fiber or preform and has been related to volume changes in the stress-producing borosilicate sections. Annealing increases the axial stress as well as the stress anisotropy and hence the birefringence. Increases of up to a factor of 2 in the birefringence on suitable thermal treatment indicate a new method for further improvement of high birefringence fibers. The implications of the results in the design, fabrication, and use of such fibers are discussed.