For the first time of our knowledge, we demonstrate the graphene oxide as a saturable absorber (SA) in the passive mode-locking of a diode pumped Tm 3+ -doped laser. Broadly spectral region sub-10 ps mode-locking in a Tm:YAlO3 (Tm:YAP) laser near 2 µm were obtained. With a pump power of 8.64 W, the average output power of 268 mW with the maximum pulse energy of 3.7 nJ at the pulse repetition frequency (PRF) of 71.8 MHz was obtained.

A bulk crystal of Yb:Sc 2 SiO 5 (Yb:SSO) with favorable thermal properties was successfully obtained by the Czochralski method. The energy level diagrams for Yb:SSO crystal were determined by optical spectroscopic analysis and semi-empirical crystal-field calculations using the simple overlap model. The full width at half maximum of the absorption band centering at 976 nm was calculated to be 24 nm with a peak absorption cross-section of 9. Table 1.As indicated in Table 1, Sc 2 SiO 5 crystal with characterizations of high thermal conductivity and negative refractive index is an excellent laser host [6]. However, the growth of Yb:Sc 2 SiO 5 single crystal with a large size is rather difficult mainly due to crystal diameter controlling [7,8]. Ivanov reported a transparent crystal slice with a diameter of 4 mm grown by the Czochralski method [9]. Furthermore, no laser action was reported on Yb:Sc 2 SiO 5 until now.In this letter, we report on the growth of 5 at. % Yb: Sc 2 SiO 5 with a large size of 25 mm in diameter, by imu Fax: +86-21-69987109, E-mail: xujun@mail.shcnc.ac.cn proving the growth conditions. The laser performances under diode-pumping are also presented. The segregation coefficient of Yb 3+ ion was detected by inductively coupled plasma atomic emission spectrometry (ICP-AES). Crystal structure was identified by X-ray diffractometry (Cu target, K α , X-pert, Hollland). The unpolarized absorption spectrum was measured with a UV/Vis/NIR spectrophotometer (Model V-570, JASCO) using Xe light as the pump source. The fluorescence spectrum was measured with a 940 nm pumping source (Jobin-Yvon TRIAX 550 spectrophotometer). A fluorescence lifetime measurement was carried out by a computer-controlled transient digitizer decay curve of emission. All measurements were performed at room temperature.

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.