Zhiguang Zhou

Intense 2.7 µm emission of Er 3+ -doped water-free fluorotellurite glasses

By physical and chemical dehydration techniques, a group of Er3+-doped water-free fluorotellurite glasses with a composition of 60TeO2-30ZnF2-10NaF(TZNF60,mol%)+x Er2O3(wt%,x=0~1.5) were fabricated. Under 978 nm excitation, the 4I(11/2)→4I(13/2) emission of Er3+ ions in TZNF60-glass was investigated: τ(f) is of 1.07~1.93 ms and emission bandwidth is about 163 nm at 2.71 µm, which benefits from the absence of OH groups and the decreased phonon energy with the addition of fluorides. In contrast, 1.25Er-TZNF60 glass is proposed to be a promising material for mid-infrared fiber lasers at around 2.7 µm.

High birefringent rhombic-hole photonic crystal fibers

High birefringence induced by rhombic air-hole photonic crystal fibers (PCFs) is numerically analyzed by using the finite-element method. The birefringence of a few kinds of PCFs was investigated with different parameters related to rhombic holes, including the rhombic-hole shape, size, and spacing. It was found that the birefringence of the proposed rhombic-hole PCF in this study is relatively larger than that of an elliptical-hole PCF with the same air-filling fraction (f=0.0375) when the ratio of the rhombic-hole diagonal length is equal to the elliptical-hole ellipticity.

Ytterbium-doped large-mode-area silica fiber fabricated by using chelate precursor doping technique

We reported on a highly effective chelate precursor doping technique for Yb-doped large-mode-area (LMA) fiber manufacture. By accurately controlling the evaporation temperature and flow rate of carrier gas, the chelate precursor doping technique is capable of making Yb-doped LMA silica fiber with good uniformity free of center dip, low numerical aperture of ~0.056, large preform core size of 4.46 mm, and appropriate cladding absorption of 1.17  dB/m at 976.4 nm. Based on a single-end-pump all-fiber oscillator laser setup, the laser output at 1080 nm reached 700 W with slope efficiency of 54.2%.

Third-order nonlinear optical properties of GeS 2 -Sb 2 S 3 -CdS chalcogenide glasses

The third-order nonlinear optical properties of GeS(2)-Sb(2)S(3)-CdS chalcogenide glasses were investigated utilizing the Z-scan and femtosecond time-resolved optical Kerr effect (OKE) methods at the wavelength of 800 nm, respectively. The compositional dependences were analyzed and the influencing factors including the linear refractive index, the concentration of lone electron pairs, the optical bandgap and the amount of weak covalent/ homopolar bonds were discussed. A glass, i.e. 76GeS(2)·19Sb(2)S()·5CdS, with large nonlinear refrative index (n(2) = 5.63 × 10(-14) cm(2)/W), low nonlinear absorption coefficient (β = 0.88 cm/GW) and minimum figure of merit (FOM = 2βλ/n(2) = 2.51) was finally prepared. The electronic contribution in weak heterpolar covalent and homopolar bonds are responsible for large n(2) in chalcogenide glass, and the Sheik-Bahae rule combining the Moss rule are proved to be an effective guidance for estimating the third-order nonlinearities and further optimizing the compositions in chalcogenide glasses.

Third-order nonlinear optical properties of GeS2-Sb2S3-CdS chalcogenide glasses

The third-order nonlinear optical properties of GeS(2)-Sb(2)S(3)-CdS chalcogenide glasses were investigated utilizing the Z-scan and femtosecond time-resolved optical Kerr effect (OKE) methods at the wavelength of 800 nm, respectively. The compositional dependences were analyzed and the influencing factors including the linear refractive index, the concentration of lone electron pairs, the optical bandgap and the amount of weak covalent/ homopolar bonds were discussed. A glass, i.e. 76GeS(2)·19Sb(2)S()·5CdS, with large nonlinear refrative index (n(2) = 5.63 × 10(-14) cm(2)/W), low nonlinear absorption coefficient (β = 0.88 cm/GW) and minimum figure of merit (FOM = 2βλ/n(2) = 2.51) was finally prepared. The electronic contribution in weak heterpolar covalent and homopolar bonds are responsible for large n(2) in chalcogenide glass, and the Sheik-Bahae rule combining the Moss rule are proved to be an effective guidance for estimating the third-order nonlinearities and further optimizing the compositions in chalcogenide glasses.

High contrast ballistic imaging using femtosecond optical Kerr gate of tellurite glass

We investigated the ballistic imaging technique using femtosecond optical Kerr gate of a tellurite glass. High contrast images of an object hidden behind turbid media were obtained. Compared to the conventional femtosecond optical Kerr gate using fused quartz, the optical Kerr gate using tellurite glass has more capacity to acquire high quality images of the object hidden behind a high optical density turbid medium. The experimental results indicated that the tellurite glass is a good candidate as the optical Kerr material for the ballistic imaging technique due to its large optical nonlinearity.

Efficient optical Kerr gate of tellurite glass for acquiring ultrafast fluorescence

We investigated the ultrafast optical Kerr effect of tellurite glass (Te glass) by the femtosecond time-resolved pump?probe technique. The Kerr-gated spectra from a chirped supercontinuum (SC) obtained by a Te glass optical Kerr gate (OKG) were of a narrow bandwidth and wide range of transmittance spectra. Time-resolved violet fluorescence of a ZnO thin film with high temporal resolution was measured using the Te glass OKG. Experimental results showed that Te glass was a good candidate for an OKG medium due to its ultrafast response, large transmittance window, and large nonlinear refractive index.

Fabrication and characterization of carbon/oxygen-implanted waveguides in Nd3+-doped phosphate glasses

Abstract. Optical planar waveguides in Nd3+-doped phosphate glasses are fabricated by a 6.0-MeV carbon ion implantation with a dose of 6.0×1014 ions/cm2 and a 6.0-MeV oxygen ion implantation at a fluence of 6.0×1014 ions/cm2, respectively. The guided modes and the corresponding effective refractive indices were measured by a modal 2010 prism coupler. The refractive index profiles of the waveguides were analyzed based on the stopping and range of ions in matter and the RCM reflectivity calculation method. The near-field light intensity distributions were measured and simulated by an end-face coupling method and a finite-difference beam propagation method, respectively. The comparison of optical properties between the carbon-implanted waveguide and the oxygen-implanted waveguide was carried out. The microluminescence and Raman spectroscopy investigations reveal that fluorescent properties of Nd3+ ions and glass microstructure are well preserved in the waveguide region, which suggests that the carbon/oxygen-implanted waveguide is a good candidate for integrated photonic devices.

Chirp structure measurement of a supercontinuum pulse based on transient lens effect in tellurite glass

We demonstrated the controllable acquisition of optical gated spectra from a chirped supercontinuum (SC) pulse based on ultrafast transient lens (TrL) effect. Comparing with CS2, the gated spectra had much narrower spectral bandwidths using tellurite glass (Te glass) as the nonlinear medium due to its ultrafast nonlinear response. Experimental results showed that the chirp structure of the SC pulse measured by TrL method was quite accordant with that measured by femtosecond optical Kerr gate method

1.23 μm emission of Er/Pr-doped water-free fluorotellurite glasses

To investigate the relatively unexplored 1.2 μm region, we identified a near-infrared emission at around 1.23 μm from Er3+/Pr3+-codoped water-free fluorotellurite glass with a composition of 60TeO2-30ZnF2-10NaF (TZNF60, mol. %). Under the condition of pumping with the 488 nm optical parametric oscillator (OPO) laser system, the directly measured lifetime (τ(f)) at 1.23 μm in Er/Pr-codoped fluorotellurite glasses is about 111.2 μs, much longer than that of Er-doped fluorotellurite glass (80.1 μs). The stimulated emission cross section (σ(em)) and quantum efficiency (η) for Er3+:4S3/2→4I11/2 transition are greatly enhanced when appropriate Pr3+ ions are incorporated. These advances arise partially from the absence of the hydroxyl (OH) group and low phonon energy with the addition of a large amount of fluorides into oxide-based host glasses. With high quantum efficiency (56.2%) and a large stimulated cross section (4.03×10(-21) cm2), Er3+/Pr3+-codoped TZNF60 glass is regarded as promising material for the development of optical amplification and laser operation at the relatively unexplored 1.2 μm region.