Guowu Tang

Tm 3+ doped barium gallo-germanate glass single-mode fibers for 2.0 μm laser

Tm³⁺ doped barium gallo-germanate (BGG) glass has emerged as a promising 2.0 μm laser material offering excellent optical property. Unfortunately, low anti-crystallization ability and high OH⁻ content of the glass have hindered the fabrication of high-quality optical fibers. In this paper, La₂O₃ and Y₂O₃ were added into BGG glass to enhance the glass anti-crystallization ability. Additionally, the optimized Reaction Atmosphere Procedure (RAP) was utilized to minimize OH⁻ content. Continuous Tm³⁺ doped BGG glass single-mode (SM) fibers were successfully obtained by the rod-in-tube technique for the first time to our best knowledge. A 140 mW all-fiber laser at 1.95 μm was demonstrated using a 9.7-cm-long as-drawn Tm³⁺ doped BGG glass SM fiber upon excitation of a home-made 1568 nm fiber laser.

Highly Tm(3+) doped germanate glass and its single mode fiber for 2.0 μm laser.

Highly Tm3+ doped optical fibers are urgently desirable for 2.0 μm compact single-frequency fiber laser and high-repetition-rate mode-locked fiber laser. Here, we systematically investigated the optical parameters, energy transfer processes and thermal properties of Tm3+ doped barium gallo-germanate (BGG) glasses. Highly Tm3+ doped BGG glass single mode (SM) fibers were fabricated by the rod-in-tube technique. The Tm3+ doping concentration reaches 7.6 × 1020 ions/cm3, being the reported highest level in Tm3+ doped BGG SM fibers. Using ultra short (1.6 cm) as-drawn highly Tm3+ doped BGG SM fiber, a single-frequency fiber laser at 1.95 μm has been demonstrated with a maximum output power of 35 mW when in-band pumped by a home-made 1568 nm fiber laser. Additionally, a multilongitudinal-mode fiber laser at 1.95 μm has also been achieved in a 10 cm long as-drawn active fiber, yielding a maximum laser output power of 165 mW and a slope efficiency of 17%. The results confirm that the as-drawn highly Tm3+ doped BGG SM fibers are promising in applications that require high gain and high power from a short piece of active optical fiber.

Reactive molten core fabrication of glass-clad Se(0.8)Te(0.2) semiconductor core optical fibers.

Phosphate glass-clad optical fibers comprising amorphous Se(0.8)Te(0.2) semiconductor core were fabricated by a reactive molten core approach. The Se(0.8)Te(0.2) crystals were precipitated in core region by a postdrawing annealing process, which were confirmed by X-ray diffraction, micro-Raman spectra, electron probe X-ray micro-analyzer, and transmission electron microscope measurement results. A two-cm-long crystalline Se(0.8)Te(0.2) semiconductor core optical fiber, electrically contacted to external circuitry through the fiber end facets, exhibits a two-orders-of-magnitude change in conductivity between dark and illuminated states. The great discrepancy in light and dark conductivity suggests that such crystalline Se(0.8)Te(0.2) semiconductor core optical fibers have promising applications in optical switch and photoconductivity of optical fiber array.

Tm 3+ doped lead silicate glass single mode fibers for 2.0 μm laser applications

Tm3+ doped lead silicate glasses with good thermal stability were prepared by the melt-quenching method. Based on the absorption and emission spectra, Judd-Ofelt intensity parameters, absorption and emission cross sections, gain spectra, and σe × FWHM were calculated and analyzed. These results suggest that Tm3+ doped lead silicate glasses are promising as mid-infrared laser materials. Tm3+ doped lead silicate glass single mode (SM) fibers with cladding diameter of 125 μm and core diameter of 8.5 μm were then fabricated by the rod-in-tube technique. The Tm3+ doping concentration reached as high as 4.545 × 1020 ions/cm3. ~2.0 μm amplified spontaneous emission (ASE) was realized in a 3.5-cm-long as-drawn SM fiber when pumped by a homemade single mode 1560 nm fiber laser. The results indicate that these Tm3+ doped lead silicate glass single mode fibers are promising fiber material for 2.0 μm fiber laser applications.

Selenium semiconductor core optical fibers

Phosphate glass-clad optical fibers containing selenium (Se) semiconductor core were fabricated using a molten core method. The cores were found to be amorphous as evidenced by X-ray diffraction and corroborated by Micro-Raman spectrum. Elemental analysis across the core/clad interface suggests that there is some diffusion of about 3 wt % oxygen in the core region. Phosphate glass-clad crystalline selenium core optical fibers were obtained by a postdrawing annealing process. A two-cm-long crystalline selenium semiconductor core optical fibers, electrically contacted to external circuitry through the fiber end facets, exhibit a three times change in conductivity between dark and illuminated states. Such crystalline selenium semiconductor core optical fibers have promising utility in optical switch and photoconductivity of optical fiber array.

Silver nanoparticles enhanced near-infrared luminescence of Er3+/Yb3+ co-doped multicomponent phosphate glasses

Abstract A new way to improve the 1.53 μm emission in Er 3+ /Yb 3+ co-doped multicomponent phosphate glass was demonstrated by introducing silver nanoparticles (NPs) in rare-earth doped glass. The existence of Ag NPs was confirmed by absorption spectra and transmission electron microscopy (TEM) measurements. The homogeneous distribution of silver NPs could be observed by the TEM images. UV-Vis-NIR absorption spectra revealed that the surface plasmon band was centered at about 420 nm. The photoluminescence spectra of glass samples were used to investigate the effect of silver NPs on the fluorescence properties of Er 3+ . Efficient 1.53 μm emission was obtained in prepared samples when pumped at 980 nm laser diode (LD). The 1.53 μm emission intensity could be enhanced 87% by doping 2 mol.% AgCl due to the increased localized field effect in the vicinity of NPs and the possible energy transfer from silver NPs to Er 3+ ions. Our present work may point out one way to enhance the gain coefficient of Er 3+ /Yb 3+ co-doped glass fiber.

Enhanced 1.8 μm emission in Er3+/Tm3+ co-doped lead silicate glasses under different excitations for near infrared laser

Abstract A detailed study of the fluorescence emission properties and energy transfer mechanism in Er 3+ /Tm 3+ co-doped lead silicate glasses was reported. Enhanced near infrared 1.8 μm and visible up-conversion emissions were investigated under 808 and 980 nm excitations, respectively. The energy transfer mechanism between Er 3+ and Tm 3+ was analyzed according to the absorption spectra, the emission spectra and the level structures of Er 3+ and Tm 3+ . The energy transfer efficiency between Er 3+ and Tm 3+ reached 68.1% in the Er 3+ /Tm 3+ co-doped lead silicate glasses when pumped by 808 nm laser diode. Based on the absorption spectra, the Judd-Ofelt parameters, spontaneous emission probability, absorption and emission cross sections, gain coefficients were calculated and analyzed. It was found that the calculated emission cross section and the maximum gain coefficient around 1.8 μm were 4.9×10 −21 cm 2 and 1.12 cm −1 , respectively. These results indicated that the Er 3+ /Tm 3+ co-doped lead-silicate glasses had potential application in near infrared lasers.

Enhanced thermoelectric properties of polycrystalline Bi2Te3 core fibers with preferentially oriented nanosheets

Bi2Te3-based materials have been reported to be one of the best room-temperature thermoelectric materials, and it is a challenge to substantially improve their thermoelectric properties. Here novel Bi2Te3 core fibers with borosilicate glass cladding were fabricated utilizing a modified molten core drawing method. The Bi2Te3 core of the fiber was found to consist of hexagonal polycrystalline nanosheets, and polycrystalline nanosheets had a preferential orientation; in other words, the hexagonal Bi2Te3 lamellar cleavage more tended to be parallel to the symmetry axis of the fibers. Compared with a homemade 3-mm-diameter Bi2Te3 rod, the polycrystalline nanosheets’ preferential orientation in the 89-μm-diameter Bi2Te3 core increased its electrical conductivity, but deduced its Seebeck coefficient. The Bi2Te3 core exhibits an ultrahigh ZT of 0.73 at 300 K, which is 232% higher than that of the Bi2Te3 rod. The demonstration of fibers with oriented nano-polycrystalline core and the integration with an efficient fabrication technique will pave the way for the fabrication of high-performance thermoelectric fibers.Bi2Te3-based materials have been reported to be one of the best room-temperature thermoelectric materials, and it is a challenge to substantially improve their thermoelectric properties. Here novel Bi2Te3 core fibers with borosilicate glass cladding were fabricated utilizing a modified molten core drawing method. The Bi2Te3 core of the fiber was found to consist of hexagonal polycrystalline nanosheets, and polycrystalline nanosheets had a preferential orientation; in other words, the hexagonal Bi2Te3 lamellar cleavage more tended to be parallel to the symmetry axis of the fibers. Compared with a homemade 3-mm-diameter Bi2Te3 rod, the polycrystalline nanosheets’ preferential orientation in the 89-μm-diameter Bi2Te3 core increased its electrical conductivity, but deduced its Seebeck coefficient. The Bi2Te3 core exhibits an ultrahigh ZT of 0.73 at 300 K, which is 232% higher than that of the Bi2Te3 rod. The demonstration of fibers with oriented nano-polycrystalline core and the integration with an efficient ...

Crystalline selenium core optical fibers with low optical loss

Amorphous selenium (a-Se) core fibers with glass cladding have immediately been fabricated using the molten core method. The high aspect ratio of the a-Se core fibers and the presence of the glass cladding surrounding the Se core make it convenient to convert the a-Se core into a polycrystalline structure. It is found that the two-step thermal annealing process allows for the increase of crystal grain size and decrease of the structure defects in the Se core. Therefore, a low propagation loss of 1.5 dB/cm at 1310 nm has been realized for the polycrystalline selenium (c-Se) core optical fibers obtained by the wo-step annealing a-Se core fibers, first at a 80 °C low temperature annealing followed by a 207 °C high temperature annealing, which is much lower than that reported for c-Se core optical fibers (2.6 dB/cm).

Efficient 1.6 μm linearly-polarized single-frequency phosphate glass fiber laser

Based on the heavily Er3+/Yb3+ co-doped phosphate glass fiber (EYPF) with a larger emission cross-section, an efficient linearly-polarized single-frequency distributed Bragg reflector fiber laser at 1603 nm is demonstrated. By balancing the cavity length against the longitudinal mode spacing, a stable single-longitudinal-mode laser with more than 20 mW is generated from a 16-mm-long EYPF. The measured relative intensity noise of the fiber laser is less than –140 dB/Hz at frequencies of over 5 MHz. The signal-to-noise ratio is greater than 62 dB and the linewidth is less than 1.9 kHz, while the obtained polarization extinction ratio is higher than 25 dB. The L-band operating combined with the narrow linewidth and low noise characteristic makes this laser an ideal candidate for high-resolution molecular spectroscopy and coherent lidar applications.