Dapeng Jiang

Generation of 103 fs mode-locked pulses by a gain linewidth-variable Nd,Y:CaF 2 disordered crystal

We have demonstrated a diode-pumped passively mode-locked femtosecond Nd,Y:CaF2 disordered crystal laser for the first time to our knowledge. By choosing appropriate Y-doping concentration, a broad fluorescence linewidth of 31 nm has been obtained from the gain linewidth-variable Nd,Y:CaF2 crystal. With the Nd,Y:CaF2 disordered crystal as gain medium, the mode-locked laser generated pulses with pulse duration as short as 103 fs, average output power of 89 mW, and repetition rate of 100 MHz. To our best knowledge, this is the shortest pulse generated from Nd-doped crystal lasers so far. The research results show that the Nd,Y:CaF2 disordered crystal will be a potential alternative as gain medium of repetitive chirped pulse amplification for high-peak-power lasers.

Nd,Y:CaF2 laser crystals: novel spectral properties and laser performance from a controlled local structure

A series of Nd,Y:CaF2 single crystals grown using the TGT method were studied systematically by absorption, excitation and luminescence spectroscopy, and the extended X-ray absorption fine structure (EXAFS) technique. The incorporation of Y3+ substantially manipulated the local structure of Nd ions in the CaF2 crystal lattice. Subsequently, the changes in the local structure of the Nd3+ ions induced substantial variations of the photoluminescence parameters, including FWHM, cross sections, lifetimes and quantum efficiency. Preliminary laser experiments were carried out with 0.5% Nd,10% Y:CaF2, 0.8% Nd,5% Y:CaF2 and 0.8% Nd,10% Y:CaF2 crystals under LD pumping; true CW laser operation was achieved with slope efficiencies of 30.1%, 19.3% and 24.9%, respectively.

Characteristics of a diode-pumped Yb:CaF2-SrF2 mode-locked laser using a carbon nanotube absorber

Yb:CaF2–SrF2 disordered crystals are successfully grown by the TGT method. By using a double-walled carbon nanotube saturable absorber (DWCNT-SA), the continuous-wave mode-locked (CWML) laser properties of Yb:CaF2–SrF2 crystals are demonstrated under diode pumping for the first time. The mode-locked laser delivers pulses as short as 5 ps at a center wavelength of 1045.5 nm without any dispersion compensation. The oscillator operating at a repetition rate of ~87 MHz delivers 292 mW average output power.

Laser performance of diode-pumped Nd, Y-codoped CaF 2–SrF 2 mixed crystal

A disordered Nd, Y-codoped CaF2?SrF2 mixed crystal was obtained by the temperature gradient technique (TGT). The absorption and fluorescence spectra of the crystal were measured at room temperature. Diode-pumped continuous-wave (CW) and Q-switched laser operations were demonstrated at 1056?nm with a 0.65?at.% Nd, 10?at.% Y-codoped crystal, for the first time to our knowledge. The CW output power of 724?mW was obtained in a compact linear cavity. Also the Q-switched pulse characteristics of Nd, Y:CaF2?SrF2 laser crystal were reported based on Cr4+:YAG saturable absorbers in a folded cavity. The shortest pulse width of 110?ns and the highest peak power of 383?W were obtained when the initial transmission of the Cr4+:YAG crystals was 90%. The dependence of the operational parameters on the pump power was also investigated experimentally.

Spectroscopic, dielectric properties and local structure observation by EXAFS for Nd,Y:CaF2 crystal

Trivalent impurity ions are clustered easily in fluoride crystals. With the addition of Y3+ spectral properties are greatly enhanced. Low temperature absorption and emission spectra are performed to unfold the optical centers in Nd3+,Y3+:CaF2 crystals. The strongest absorption line at around 790 nm belongs to M luminescence quenched centers in 1%Nd3+:CaF2; and at 797 nm to L centers for a codoped one. For emission spectra 1049.3 nm and 1068.7 nm are attributed to M and N non quenched centers; 1054.6 nm to an L site in a 1%Nd3+,5%Y3+:CaF2 sample. EXAFS spectra, an intuitive approach, are applied to reveal that the first coordination number of Nd3+ increased from 9.2 to 10.7 with the addition of Y3+ ions, and the local lattice expanded.

Spectral properties and highly efficient continuous-wave laser operation in Nd-doped Sr(1-x)Y(x)F(2+x) crystals.

Spectral properties of Nd:Sr(1-x)Y(x)F(2+x) crystals were investigated. Compared with Nd:SrF2, the spectral parameters of Nd:Sr(1-x)Y(x)F(2+x) (x=0.05,0.1) were altered in a large scale. LD-pumped true CW laser has been demonstrated in the crystals. The slope efficiency up to 43.5% in 0.43% Nd:Sr0.95Y0.05F2.05 was achieved. The system is a promising candidate for highly efficient lasers.

Operational characteristics of a LD-pumped novel Yb,Y:CaF2 mode-locked laser using a SESAM

A LD-pumped novel Yb,Y:CaF2 femtosecond laser is demonstrated for the first time. The continuous-wave and mode-locked operational characteristics of the co-doped fluoride crystal are described in detail. With intracavity dispersion management using a prism-pair, a 330 fs pulse at a centre wavelength of 1049 nm is obtained. The average output power is 224 mW at a repetition rate of ~83 MHz.