Liangbi Su

Bi-doped BaF2 crystal for broadband near-infrared light source

Bi-doped BaF(2) crystal was grown by the temperature gradient technique and its spectral properties were investigated. The absorption, emission and excitation spectra were measured at room temperature. Two broadband emissions centered at 1070 and 1500 nm were observed in Bi-doped BaF(2) crystal. This extraordinary luminescence should be ascribed to Bi-related centers at distinct sites. We suggest Bi(2+) or Bi(+) centers adjacent to F vacancy defects are the origins of the observed NIR emissions.

Spectroscopic properties and CW laser operation of Nd, Y-codoped CaF2 single crystals

Spectroscopic properties of Nd:CaF2 crystals with different doping concentrations of Nd3+ and codoping concentrations of Y3+ were investigated. The effect of codoping with Y3+ ions on the absorption and emission spectra, emission lifetimes, quantum efficiency, and emission cross sections of Nd3+ were studied. In particular, codoping with Y3+ ions increases the width of the emission lines over that found with Nd-doped glasses, and allows true CW laser operation around 1.06 μm.

Diode-pumped Yb:GSO femtosecond laser.

Compact femtosecond laser operation of Yb:Gd(2)SiO(5) (Yb:GSO) crystal was demonstrated under high-brightness diode-end-pumping. A semiconductor saturable absorption mirror was used to start passive mode-locking. Stable mode-locking could be realized near the emission bands around 1031, 1048, and 1088 nm, respectively. The mode-locked Yb:GSO laser could be tuned from one stable mode-locking band to another with adjustable pulse durations in the range 1~100 ps by slightly aligning laser cavity to allow laser oscillations at different central wavelengths. A pair of SF10 prisms was inserted into the laser cavity to compensate for the group velocity dispersion. The mode-locked pulses centered at 1031 nm were compressed to 343 fs under a typical operation situation with a maximum output power of 396 mW.

Broadband near-infrared luminescence in γ-irradiated Bi-doped α-BaB 2 O 4 single crystals

Spectroscopic properties of as-grown and gamma-irradiated undoped and Bi-doped alpha-BBO (BaB(2)O(4)) single crystals were investigated. Bi(2+) and color centers in Bi:alpha-BBO crystals were investigated to be nonluminescent in the near-infrared (NIR) region. Broadband NIR luminescence at 1139 nm with a FWHM of 108 nm and a decay time of 526 mus was realized in Bi:alpha-BBO crystal through gamma irradiation. Bi(+) was attributed to be responsible for the NIR emission, which can be bleached by thermal annealing. The involved physical processes in Bi:alpha-BBO crystal during the courses of irradiation and heat annealing were tentatively established.

Near-infrared ultrabroadband luminescence spectra properties of subvalent bismuth in CsI halide crystals

We observed two ultrabroadband near-infrared (NIR) luminescence bands around 1.2 and 1.5 μm in as-grown bismuth-doped CsI halide crystals, without additional aftertreatment. Dependence of the NIR emission properties on the excitation wavelength and measurement temperature was studied. Two kinds of NIR active centers of subvalent bismuth and color centers were demonstrated to coexist in Bi:CsI crystal. The eye-safe 1.5 μm emission band with an FWHM of 140 nm and lifetime of 213 μs at room temperature makes Bi:CsI crystal promising in the applications of the ultrafast laser and ultrabroadband amplifier.

Study on the effect of heat-annealing and irradiation on spectroscopic properties of Bi:α-BaB 2 O 4 single crystal

The absorption, excitation, and ultrabroadband near-infrared luminescence spectra of Bismuth were investigated in H(2)-annealed and gamma-irradiated Bi:alpha-BaB(2)O(4)(alpha-BBO) single crystals, respectively. Energy-level diagrams of the near-infrared luminescent centers were fixed. The electronic transition energies of near-infrared active centers are basically consistent with the multiplets of free Bi(+) ions. The minor difference of the energy-level diagrams of Bi(+) ions in H(2)-annealed and gamma-irradiated Bi:alpha-BaB(2)O(4) crystals can be ascribed to the difference of the local lattice environments. The involved physical and chemical processes were discussed. The effect of Ar-, air-annealing and electron-irradiation on Bi:alpha-BaB(2)O(4) crystal were also investigated.

Spectroscopic properties and near-infrared broadband luminescence of Bi-doped SrB4O7 glasses and crystalline materials.

Spectroscopic properties of Bi-doped SrB(4)O(7) glasses, sintered compounds, polycrystalline materials, and single crystals were investigated. Broadband near-infrared luminescence was realized in Bi-doped SrB(4)O(7) glasses with basicity and polycrystalline materials with non-bridging oxygens. In Bi:SrB(4)O(7) single crystals, only visible luminescence of Bi(3+) and Bi(2+) was observed, but no near-infrared. The rigid three-dimensional network of SrB(4)O(7) crystal is proved to be unfavorable for accommodation of Bi(+) ions.

Low-threshold diode-pumped Yb3+, Na+: CaF2 self-Q-switched laser

For the first time to our knowledge, the laser performance of Yb3+, Na+-codoped CaF2 single crystals was demonstrated. Self-Q-switched laser operation at 1050nm was observed for 976 nm diode pumping at room temperature. On 5 W of incident power, the repetition rate and width of the self-Q-switched pulses reached 28 kHz and 1.5 micros, respectively. A maximal slope efficiency of 20.3% and minimal threshold absorbed pump power of 30 mW were respectively achieved with different output couplers, showing the promising application of Yb3+, Na+-codoped CaF2 crystals as compact and efficient solid-state lasers.

Growth and spectroscopic characteristics of Yb:GSO single crystal

For the first time, a high optical quality 10 at.% Yb3+-doped gadolinium oxyorthosilicate laser crystal Gd2SiO5 (GSO) was grown by the Czochralski (Cz) method. The segregation coefficient of Yb3+ was studied by the inductively coupled plasma atomic emission spectrometer (ICP-AES) method. The crystal structure has monoclinic symmetry with space group P 21/c; this was determined by means of an x-ray diffraction analysis. The absorption spectra, fluorescence spectra and fluorescence decay curves of Yb3+ ions in a GSO crystal at room temperature were also studied. Then, the spectroscopic parameters of Yb:GSO were calculated. The advantages of the Yb:GSO crystal include high crystal quality, quasi-four-level laser operating scheme, high absorption cross-sections and particularly broad emission bandwidth (~72 nm). The results indicated that the Yb:GSO crystal seemed to be a very promising laser gain medium in diode-pumped femtosecond laser and tunable solid state laser applications when LD pumped at 940 and 980 nm.

Generation of 210 fs laser pulses at 1093 nm by a self-starting mode-locked Yb:GYSO laser

We report the first demonstration, to our knowledge, of the femtosecond laser operation by using a new alloyed Yb:GYSO crystal as the gain medium. With a 5 at. %Yb(3+)-doped sample and chirped mirrors for dispersion compensation, we obtained pulses as short as 210 fs at the center wavelength of 1093 nm. The average mode-locking power is 300 mW, and the pulse repetition frequency is 80 MHz.