Solution Doping Technique Research Articles

Fabrication and Spectroscopic Analysis of Yb–Tm Co-Doped Nano-Phase Separated Yttrium–Germanium–Aluminium–Phospho–Silicate Composite Glass Optical Fibers

A new class of Yb-Tm co-doped nano-phase separated yttrium germanium aluminium phospho silica composite optical fiber has been fabricated using a modified chemical vapour deposition process with a solution doping technique in order to achieve more intense up-conversion luminescence in visible region. A strong 474 nm up-conversion luminescence, along with three peaks at 364, 650 and 790 nm of Tm3+, have been detected under excitation at 975 nm. The observation of a 474 nm strong up-conversion emission in comparison with other three emission peaks is explained using energy transfer coefficient values obtained from kinetic model of energy transfer up-conversion process. The strong up-conversion emission (474 nm) of yttrium-germanium-aluminium-phospho-silica composite optical fibers compared to yttrium aluminium silicate composite fiber is detected due to the high value of third energy transfer coefficient (W-3) associated with the 474 nm emission. Tm-Yb doped nano-engineered optical fibers would be suitable for efficient power tunable 474 nm light source for several applications.

Fabrication and characterization of chromium-doped nanophase separated yttria-alumina-silica glass-based optical fibers

The basic material and optical properties of chromium-doped nanophase-separated yttria–alumina–silica (YAS) glass based optical preforms and fibers, fabricated through the modified chemical vapor deposition process in conjunction with solution doping technique under suitable thermal annealing conditions are reported. The size of the phase-separated particles within the core of the annealed preform is around 20–30 nm which is significantly reduced to around 5.0 nm in the drawn fiber. The absorption spectra of fibers drawn from the annealed and non-annealed preform samples revealed the presence of Cr4+, Cr3+, and Cr6+ specie. Numerically, extinction of absorption drops ∼3–3.5 times for the annealed sample as a result of nano-phase restructuration during annealing process. Intense broadband emission (within 500–800 nm) in case of the annealed preform sample is observed as compared to the non-annealed one and is associated with the presence of Cr3+ ions in nanostructured environment inside the YAS core glass. The final fibers show broadband emission ranging from 900 to 1400 nm under pumping at 1064 nm which is attributed mainly to the presence of Cr3+/Cr4+ ions. The fabricated fibers seem to be a potential candidate for the development of fiber laser sources for the visible and near-infra ranges and for effective Q-switching units for ∼1–1.1 μm all-fiber ytterbium lasers.

Experimental demonstration of optical fiber laser with octagonal-shaped core

Double-cladding Yb3+-doped fiber with octagonal core is designed and fabricated using solution doping techniques. According to the simulated results, the octagonal-core fiber with core/cladding diameter of 30/250 μm has decreased the number of mode supported from 6 to 4, and the fiber with core/cladding diameter of 10/130 μm exhibits single-mode performance. Additionally, to confirm that the octagonal core does not influence the laser power and efficiency, CW and AO Q-switched pulsed fiber lasers using the 10/130 μm fiber are presented. The CW fiber laser has a single-mode output of 7.25 W with a slope efficiency of 80 %. For a pulsed fiber laser, an average power of 1.5 W, pulse width of 245 ns, is amplified to 18 W.

Tm-Yb Doped Optical Fiber Performance with Variation of Host-Glass Composition

The fabrication process of Thulium-Ytterbium doped optical fiber comprising different host glass through the Modified Chemical Vapor Deposition (MCVD) coupled with solution doping technique is presented. The material and optical performance of different fibers are compared with special emphasis on their lasing efficiency for 2 µm application.

Highly fluorescent silver nanoclusters in alumina-silica composite optical fiber

An efficient visible fluorescent optical fiber embedded with silver nanoclusters (Ag-NCs) having size ∼1 nm, uniformly distributed in alumina-silica composite core glass, is reported. Fibers are fabricated in a repetitive controlled way through modified chemical vapour deposition process associated with solution doping technique. Fibers are drawn from the transparent preforms by conventional fiber drawing process. Structural characteristics of the doped fibers are studied using transmission electron microscopy and electron probe micro analysis. The oxidation state of Ag within Ag-NCs is investigated by X-ray photo electron spectroscopy. The observed significant fluorescence of the metal clusters in fabricated fibers is correlated with electronic model. The experimentally observed size dependent absorption of the metal clusters in fabricated fibers is explained with the help of reported results calculated by ab-initio density functional theory. These optical fibers may open up an opportunity of realizing tunable wavelength fiber laser without the help of rare earth elements.

Fabrication of a Novel Nano-engineered Glass Based Optical Fiber for Radiation Sensor Application

The fabrication of a new class of cerium (Ce) and Ce/Au co-doped nano-phase separated alumina-phospho-silica glass based optical fibres through modified chemical vapour deposition (MCVD) process coupled with solution doping technique is presented along with study of their radiation response behavior under 60Co-gamma radiation source at 635nm wavelength. The sensitivity of both Ce doped and Ce/Au co-doped fibres are found to be 0.4643dB/m/Gy and 0.4360dB/m/Gy, respectively. The experimental results show that Ce doped and Ce/Au co-doped optical fibres have good response to radiation exposure which can be useful as a radiation sensor for fibre optic based personal dosimetry applications.

Development of Nano-engineered Thulium-doped Fiber Laser With Low Threshold Pump Power and Tunable Operating Wavelength

A tunable and low-threshold thulium (Tm)-doped fiber (TDF) laser is demonstrated using a new silica-based nanoengineered TDF in a linear configuration, in conjunction with 1552-nm pumping. The TDF used in these experiments had a Tm-doped nanoengineering yttrium-alumina-silica glass core with a diameter of 13.43 μm and 0.21 NA, which is surrounded by a pure silica inner cladding with normal acrylate polymer resin coating. The nanoengineered TDF was fabricated using a modified chemical vapor deposition (MCVD) process, in conjunction with a solution-doping technique. The fabricated fiber shows an absorption loss of 165 dB/m at 793 nm. A maximum lasing slope efficiency of 26.2% was obtained at a 1910-nm wavelength using the fabricated fiber with an optimum length of 5 m. The maximum output power of 138 mW was achieved at the maximum pump power of 1100 mW. The lowest pump power threshold of 693 mW for a 1552-nm wavelength was obtained at a TDF length of 7 m. The operating wavelength of the laser could be continuously tuned from 1890 to 1910 nm with an optical signal-to-noise ratio better than 43 dB, whereas the slope efficiency of the laser varies from 16.4% to 19.7%.

Thermal regenerated grating operation at temperatures up to 1400°C using new class of multimaterial glass-based photosensitive fiber.

The work demonstrates for the first time a thermal regenerated grating (RG) operating at an ultra-high temperature up to 1400°C. A new class of photosensitive optical fiber based on erbium-doped yttrium stabilized zirconia-calcium-alumina-phospho silica (Er-YZCAPS) glass is fabricated using modified chemical vapor deposition (MCVD) process, followed by solution doping technique and conventional fiber drawing. A type-I seed grating inscribed in this fiber is thermal regenerated based on the conventional thermal annealing technique. The investigation result indicates that the produced RG has an ultrahigh temperature sustainability up to 1400°C. The measured temperature sensitivities are 14.1 and 15.1 pm/°C for the temperature ranges of 25°C-1000°C and 1000°C-1400°C, respectively.

Thulium Bismuth Co-Doped Fiber Lasers at 1901 nm by 802 nm Pumping

We demonstrate an efficient fiber laser operating at 1901.6 nm using a new Thulium Bismuth co-doped fiber (TBF) under 802 nm pumping. The TBF was fabricated using modified chemical vapor deposition process associated with optimized solution doping techniques. The TBF lasers at 1901.6 nm are obtained at a noticeably low threshold pump power of 75–92 mW using two fiber Bragg gratings in a Fabry–Perot cavity. The highest efficiency of 42.2% is achieved using a 0.4 m long TBF fiber with a core dopant concentrations (in wt%) of 0.35 Bi <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> O <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex></formula> , 0.9 Tm <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex> </formula> O <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex></formula> , 3.0 Al <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$ </tex></formula> O <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex></formula> and 4.0 GeO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$_{2}$</tex></formula> . Compared to the laser from a commercially available Thulium-doped fiber, the proposed laser has a significantly higher efficiency and lower threshold pump power. This is attributed to the incorporation of Bi ions in the gain medium which helps to increase the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${}^{3}$</tex></formula> F <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{4}$</tex></formula> population through energy transfer processes. The maximum output power of 52.7 mW is achieved at the pump power of 195 mW.

Photoluminescence in Ga/Bi co-doped silica glass

Bismuth-Gallium co-doped silica glass fiber preform was prepared from nano-porous silica xerogels using a conventional solution doping technique with a heterotrinuclear complex and subsequent sintering. Ga-connected optical Bismuth active center (BAC) was identified as the analogue of Al-connected BAC. Visible and infrared photoluminescence (PL) were investigated in a wide temperature range of 1.46 - 300 K. Based on the results of the continuous wave (CW) and time resolved (TR) spectroscopy we identify the centers emitting in the spectral region of 480 - 820 nm as Bi(+) ions. The near infrared (NIR) PL around 1100 nm consists of two bands. While the first one can be ascribed to the transition in Bi(+) ion, the second band is presumably associated to defects. We put in evidence the energy transfer (ET) between Bi(+) ions and the second NIR emitting center via quadrupole-quadrupole and dipole-quadrupole mechanisms of interactions. Finally, we propose the energy level diagram of Bi(+) ion interacting with this defect.

Multiple Soaking with Different Solution Concentration in Doped Silica Preform Fabrication Using Modified Chemical Vapor Deposition and Solution Doping

Incorporation of alumina (Al2O3) into a silica matrix by modified chemical vapor deposition and a solution doping technique is investigated in this study. Multiple soaking cycles were used to increase the aluminum content in the core layer. The effect of alumina retention in silica matrix soot is focused by multiple cycles of soaking with different solution concentrations, while the effect of the adsorption mechanism is fixed by maintaining the soot deposition process (such as temperature [1,800°C], precursor, total gas flow, and soaking time). The deposited soot is examined for porosity characteristics and effective surface area by a gas adsorption technique with Brunauer–Emett–Teller surface area analysis and the surface and cross-section morphology using scanning electron microscopy. Three different concentrations are used in this work (0.3, 0.7, and 1.2 M) with multiple cycles of soaking. Sintering and the collapsing process is controlled for each preform. The result shows that the alumina content is increased substantially as the number of soaking processes is increased, which may be due to the retention effect as only a small amount of adsorption process takes place as indicated by the slight decrease in the surface area of soot. The collapsed preforms are analyzed using a preform analyzer. Energy dispersive x-ray spectrometry is used to check aluminum content and distribution into the core layer.

Double-clad thulium/ytterbium co-doped octagonal-shaped fibre for fibre laser applications

We investigate the lasing performance of a new double-clad thuli- um/ytterbium co-doped octagonal-shaped fibre, basing on a cladding pump techni- que. The fibre is fabricated with the aid of a modified chemical vapour deposition combined with a solution doping technique. It is characterized by the Tm 3+ - and Yb 3+ -cladding absorptions equal to 0.325 and 3.3 dB/m respectively at 790 and 976 nm. A triple-wavelength fibre laser operating at 1914.5, 1934.7 and 1953.6 nm is built that uses a 5 m long fibre in a ring configuration as a gain medium. With the fibre as long as 15 m, the ring laser produces the highest output power of 21.9 mW at the pump power of 3600 mW, with the lowest threshold pump power being equal to 1000 mW. When operating at 1961.4 nm, the maximal efficiency of 0.88 per cent is achieved for the gain medium length fixed at 10 m. We also demonstrate a Q-switched thulium/ytterbium-doped fibre laser that operates at 1977.5 nm and utili- zes multi-walled carbon nanotubes as a gain medium. By varying the multimode 905 nm pump power from 1591.3 to 2261.5 mW, one can increase the pulse repetiti- on rate from 18.8 to 50.6 kHz, while the pulse width then decreases from 8.6 to 1.0 µs. The maximum pulse energy 5.71 nJ is obtained at the pump power 2100 mW.

Radiation Response Behavior of Carbon Co-Doped Aluminosilicate Glass Based Optical Fibre for Use as Radiation Sensor

Carbon co-doped alumino-silicate glass based step index multimode optical fibres (SIMM) embedded with SiC and Al4C3 crystals into silica glass were fabricated successfully through a combination of modified chemical vapour deposition (MCVD) process and solution doping technique with variation of the doping levels of carbon and Al2O3 content. The radiation response behavior of such kind of optical fibre was investigated at room temperature using Co-60-gamma radiation source of 1.25 Mev energy. Such kind of carbon alumino-silicate (CAS) glass based step index multimode (SIMM) fibre shows an excellent linear radiation response behavior with sensitivity around 0.01 dB/m/Gy at 1300 nm wavelength as well as very low recovery at room temperature which enable its practical application as radiation sensor.

${\rm Yb}^{3+}$ Concentration Effects in Novel Yb Doped Lanthano-Alumino-Silicate Fibers: Experimental Study

Novel lanthano-alumino-silicate optical fibers doped with ytterbium (Yb) in a wide concentration range are obtained through the conventional modified chemical vapor deposition process and solution doping technique. The featuring fibers' characteristics are determined, applying a routine that involves the spectroscopic, nonlinear-optical, and laser methods as well as photodarkening tests. Special attention is paid to address thoroughly the effect of ${\rm Yb}^{3+}$ concentration upon the fibers' properties.

Silicon Nano-Particles Doped Optical Fiber: Fabrication, Characterization, and Application

The fabrication of a new-type of Silicon nanoparticles (Si-n/p) doped silica fiber is reported. The method is entirely based on the MCVD process, with no solution-doping technique being required. The TEM, EPMA, EDX, and electron diffraction analyses as well as the Raman, optical absorption, and fluorescence spectra’ measurements confirm the formation of Si-n/p in the fiber. When pumped at 406 nm, this fiber fluoresces mainly in the VIS to near-IR spectral range and the fluorescence shows a multi-peak spectral structure in several wide bands. As a consequence of the high nonlinearity $n_{2}$ of the fiber, effective supercontinuum generation at 1.6- $\mu{\rm m}$ excitation by tens ns-range, kW-level pulses is demonstrated.

Fabrication and Properties of Er-Doped Nanocrystalline Phase-Seperated Optical Fibers

The fabrication of Er-doped ZrO 2 -based nanocrystalline phase-separated optical fiber preforms using the MCVD and solution doping techniques is presented and discussed in details in the paper. Preforms with nearly transparent cores containing Er-doped nanocrystals with dimensions mainly within 20-80 nm have been prepared. Fibers drawn from the preforms exhibit good luminescent properties around 1550 nm suitable for applications in lasers and amplifiers.

A graphene-based mode-locked nano-engineered zirconia–yttria–aluminosilicate glass-based erbium-doped fiber laser

We demonstrate a simple, compact and low cost graphene-based mode-locked nano-engineered erbium-doped zirconia–yttria–aluminosilicate (ZYA-EDF) glass-based fiber laser. The fiber preform in a quaternary glass host of silica–zirconia–yttria–aluminum was made through the modified chemical vapor deposition (MCVD) process followed by the solution doping technique. The core glass is made of 0.40 mol% of Al2O3, 3.0 mol% of ZrO2 and 0.25 mol% of Er2O3, which give rise to a peak absorption of 30.0 dB m−1 at 978 nm and a fluorescence lifetime of 10.65 ms. Such a doping host provides the high concentration of erbium ions of 4500 ppm without any clustering. Such an active fiber was used as a gain medium for an ultra-fast femtosecond fiber laser, mode locked by a graphene oxide (GO) saturable absorber. This paper describes geometrical and optical characterization of the nano-engineered glass-based erbium-doped optical fiber (ZYA-EDF) as well as the performance of the mode-locked femtosecond laser based on the developed fiber. The all-anomalous cavity laser generated soliton pulses with 8.5 nm bandwidth, 50 MHz repetition frequency and nearly transform-limited 400 fs duration at 1561 nm center wavelength using a new class of EDF.

Effects of Yb/Tm Concentration and Pump Wavelength on the Performance of Ytterbium-Sensitized Thulium-Doped Fiber Laser

A 1901.6-nm laser is demonstrated using the newly developed double-clad ytterbium-thulium-doped fiber (YTDF) samples in conjunction with 931-nm pumping through the transition of thulium ion from 3F4 to 3H6 with the assistance of ytterbium to thulium-ion energy transfer. The YTDF used was drawn from a D-shape preform, which was fabricated using the modified chemical vapor deposition and solution-doping technique. The laser operates at 1901.6 nm with an efficiency of 2.47% using 2-m-long YTDF in a Fabry-Perot cavity with two fiber Bragg gratings. It is found that the higher ytterbium-to-thulium concentration ratio contributes to more efficient energy transfer between the sensitizer and acceptor ions in YTDF, which in turn lowers the threshold of the proposed ytterbium-thulium-doped fiber laser (YTFL). The lowest threshold pump power of the proposed YTFL is around 961 mW. The use of multimode pump with a wavelength slightly lower than 931 nm is also observed to improve both the laser's threshold and efficiency of the YTFL.

1880-nm Broadband ASE Generation With Bismuth–Thulium Codoped Fiber

A broadband amplified spontaneous emission (ASE) generation in 1880-nm region is demonstrated by employing a newly developed single-mode Tm-Bi codoped fiber (TBF) in conjunction with 793-nm pumping for the first time. The TBF was obtained by drawing a preform, which was fabricated using a deposition of porous layer by the modified chemical vapor deposition (MCVD) process in conjunction with solution doping technique. The highest Bi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Tm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> concentrations of 0.35 wt.% and 0.9 wt.%, respectively, were successfully achieved to generate ASE centered at 1880-nm region. The ASE peaked at - 47.2 dBm with 3-dB spectral width ranging from 1817 to 1984 nm with 1.0-m-long TBF and 200-mW 793-nm pump power, which was generated due to the transition of thulium ions from <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> to <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> with some assistance from bismuth to thulium ion energy transfer. The use of a secondary pump of 1550 nm is also shown to improve the ASE generation.

Passively mode-locked erbium doped zirconia fiber laser using a nonlinear polarisation rotation technique

A nonlinear polarization rotation (NPR) based mode-locked fiber laser is demonstrated using a 2m long erbium-doped Zirconia–Yttria–Allumino Silicate fiber (EDZF) as the gain medium. The EDZF is drawn from a silica preform fabricated using the Modified Chemical Vapor Deposition (MCVD) method in which glass modifiers and nucleating agents are added using the solution doping technique. The fabricated EDZF has a core with dopant concentrations of 0.25mol% of Al2O3, 2.10mol% of ZrO2 and 0.23mol% of Er2O3, peak absorption of 22.0dB/m at 978nm and the fluorescence life-time of 10.86ms. A stable picosecond laser is succesfully obtained with pulse width of 0.32ps and the repetition rate of 50MHz using a simple ring cavity.