Germano-silicate Glass Optical Fiber Research Articles

Effect of Temperature and Gamma-Ray Irradiation on Optical Characteristics of Fiber Bragg Grating Inscribed Radiation-Resistant Optical Fiber

A new radiation-hard germano-silicate glass optical fiber with a pure silica glass buffer and a boron-doped silica glass inner cladding was fabricated for temperature sensor application based on the fiber Bragg grating (FBG) under γ-ray irradiation environment. The temperature dependences of optical attenuation at 1550.5 nm and Bragg reflection wavelength shift from 18 °C to 40 °C before the γ-ray irradiation were about 4.57×10−4 dB/ °C and 5.48 pm/ °C, respectively. The radiation-induced optical attenuation at 1550.5 nm and the radiation-induced Bragg reflection wavelength shift under the γ-ray irradiation with the total dose of 22.85kGy at 35 °C were about 0.03dB/m and 0.12nm, respectively, with the γ-ray irradiation sensitivity of 5.25×10−3 pm/Gy. The temperature and the γ-ray irradiation dependence of optical attenuation at 1550.5nm in the FBG written fiber with boron-doped silica glass inner cladding were about 6 times and 4 times lower than that in the FBG written fiber without boron-doped silica glass inner cladding under a temperature change from 18 °C to 40 °C and the γ-ray irradiation with the total dose of 22.85 kGy at 35 °C, respectively. Furthermore, the effect of temperature increase on the Bragg reflection wavelength of the FBG written fiber with boron-doped silica inner cladding was much larger about 1000 times than that of the γ-ray irradiation. However, no influence on the reflection power of the Bragg wavelengths and the full width at half maximum (FWHM) bandwidth under temperature and the γ-ray irradiation change was found. Also, after the γ-ray irradiation with the dose of 22.85kGy, no significant change in the refractive index was found but the residual stresses developed in the fiber were slightly relaxed or retained.

Upconversion luminescence in bismuth-doped germano-silicate glass optical fiber

We report, for the first time, a broadband upconversion emission (800–1000 nm) in Bi-doped germano-silicate glass optical fibers with excitation in the range of 1515–1585 nm, which can explain the low laser efficiency at wavelengths longer than 1500 nm. The mechanism responsible for the emission is two-step upconversion process. The origin of this upconversion luminescence is discussed and new energy transition schemes are proposed. • We fabricated bismuth-doped germane-silicate glass optical fibers. • New upconversion emission band was observed by pumping around 1.5 μm. • Both emissions at 837 and 945 nm depend quadratically on the incident power. • Two-step upconversion process and new energy transition scheme was proposed.

Fabrication of highly nonlinear germano-silicate glass optical fiber incorporated with PbTe semiconductor quantum dots using atomization doping process and its optical nonlinearity

Germano-silicate glass optical fiber incorporated with PbTe semiconductor quantum dots (SQDs) in the core was fabricated by using the atomization process in modified chemical vapor deposition (MCVD) process. The absorption bands attributed to PbTe semiconductor quantum dots in the fiber core were found to appear at around 687 nm and 1055 nm. The nonlinear refractive index measured by the long-period fiber grating (LPG) pair method upon pumping with laser diode at 976.4 nm was estimated to be ~1.5 × 10(-16) m2/W.

NONLINEAR OPTICAL PROPERTIES OF ZINC DOPED GERMANO-SILICATE GLASS OPTICAL FIBER

Zinc doped germano-silicate glass optical fiber was developed by using the modified chemical vapor deposition and the drawing tower process. Absorption peaks of the germano-silicate glass optical fiber preform appeared at 240 nm and 330 nm were due to the incorporated Zn metal nano-particles (MNPs) and ZnO semiconductor nano-particles (SNPs), respectively and the average diameter of nano-particles (NPs) was estimated to be about 2 nm by transmission electron microscopy. However, the absorption peak of the zinc doped optical fiber due to ZnO SNPs was found to appear at 490 nm red-shifted from 330 nm can be explained by the increase in average size of ZnO SNPs in the fiber core due to growth or recrystallization of ZnO SNPs during the fiber drawing process about 2150°C. The nonlinear refractive index coefficient, n2, of the fiber was estimated to be 5.62 × 10-20 m2/W due to the stable dispersion of ZnO SNPs using the continuous-wave self-phase modulation method.

Particle size control of PbTe quantum dots incorporated in the germano-silicate glass optical fiber by heat treatment

The effect of heat treatment of the germano-silicate glass optical fiber incorporated with PbTe quantum dots on the absorption characteristics was investigated. Incorporation of the PbTe QDs in the fiber core was confirmed by the absorption peaks that appeared at 687 nm and 1055 nm and their shift upon heat treatment. The absorption peak was found to shift linearly toward a longer wavelength after heat treatment at 700 °C, 1000 °C, and 1100 °C for 1 h. The red shift of the excitonic absorption peak was attributed to the increase in the average size of the PbTe QDs in the fiber core.

Au-nanoparticle-incorporated germano-silicate glass fiber with high resonant nonlinearity

To investigate the nonlinear optical properties of metallic nanoparticles in dielectric composite materials, germano-silicate glass optical fibers incorporated with gold nanoparticles were made by using modified chemical vapor deposition technique and solution doping process. The incorporation of the gold nanoparticles was confirmed by the sharp absorption peak appeared near 498.4nm, which was due to the surface plasmon resonance absorption of Au nanoparticles. Resonant optical nonlinearities of the fibers were estimated by measuring the peak shift of the fringes obtained from the long-period fiber grating pair upon pumping with Argon laser at 488nm. The resonant nonlinearity was found to be 5.00×10 -16 m 2 /W by the incorporation of the gold metal concentration and with the addition of Al 3+ ions.

Formation of Tm 2+ ions in germanosilicate glass optical fibers

For the first time, we have developed Tm 2+–Tm 3+ co-doped germanosilicate glass optical fibers by providing a strong reduction environment based on a solution doping technique in a modified chemical vapor deposition process. The incorporation of the Tm 2+ ions into the fiber core was identified by a broad optical absorption band appearing from 350 to ∼900 nm, which was due to 4f–5d electronic transitions of the Tm 2+ ions. The electron paramagnetic resonance spectrum was also measured to confirm the formation of the Tm 2+ ions in the fiber preform by addition of a reducing agent during the preform preparation. The concentration of the Tm 2+ ions in the fiber core was found to increase with the increase of heat treatment temperature just after drying the soaked porous core layers.

Fabrication of Germanosilicate glass optical fibers containing Tm/sup 2+/ ions and their nonlinear optical properties

Germanosilicate glass optical fibers incorporated with the Tm/sup 2+/ ions were fabricated to enhance optical nonlinearity by providing a strong reduction environment based on the solution doping technique in the modified chemical vapor deposition (MCVD) process. The incorporation of the Tm/sup 2+/ ions into the fiber core was identified by the electron paramagnetic resonance (EPR) spectrum in the fiber preform, and the absorption and emission properties between 350 and 1600 nm of the Tm/sup 2+/ ions in optical fibers and the fiber preform. A strong broad absorption band due to the Tm/sup 2+/ ions appeared from 350 to /spl sim/900 nm, and a broad emission from /spl sim/600 to /spl sim/1050 nm and the other emission from /spl sim/1050 to /spl sim/1300 nm, which were not shown in the Tm/sup 3+/ ions, were found upon Ar-ion laser pumping at 515 nm. Both absorption and emission results confirm that the Tm/sup 2+/ ions in the germanosilicate glass have the 4f-5d energy band from 350 to /spl sim/900 nm and the 4f-4f energy level at /spl sim/1115 nm. Also, the resonant nonlinearity at /spl sim/1310 and /spl sim/1530 nm due to the Tm/sup 2+/ ions in the fiber was measured upon the 515 nm optical pumping by using a long-period fiber grating (LPG) pair method. The nonlinear refractive index n/sub 2/ at /spl sim/1310 and /spl sim/1530 nm was found to be /spl sim/4/spl times/10/sup -15/ m/sup 2//W, where 70% and 30% of the n/sub 2/ are attributed to the nonradiative transitions and the radiative transitions, respectively.