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Transparent Sm:Y 2 O 3 ceramics were fabricated by spark plasma sintering (SPS). The effects of LiF additive and sintering temperature on the microstructure and optical transmittance of the Sm:Y 2 O 3 ceramics were investigated. The optimal content of LiF additive and sintering temperature was found to be 0.3 wt% and 1500 ℃. The transmittance of Sm:Y 2 O 3 ceramics with a thickness of 1.7 mm reached 75.3% at 609 nm, which is about 94% of the theoretical value. The average grain size of the sample was about 50 µm. [ABSTRACT FROM AUTHOR]

Cr4+:YbAG (Cr4+:Yb3Al5O12) crystal with a size up to Φ24 mm×30 mm was grown by the Czochralski method. In the absorption spectrum, there are two absorption bands at 939 and 969 nm, respectively, which are suitable for InGaAs diode laser pumping, and there is an absorption band at 1030 nm, which is suitable for passive Q-switched laser output at 1.03 μm. A broad emission spectrum from 970 to 1100 nm was exhibited from 940 nm wavelength pumping. This crystal is promising as a self-Q-switched laser crystal used for compact, efficient, highly stable, passive self-Q-switched thin chip solid-state lasers. [Copyright &y& Elsevier]

The absorption spectra, emission under 940 nm excitation by laser diode, and fluorescence lifetimes of as-grown and annealed Cr,Yb:YAG crystal have been investigated at room temperature. The increase of absorption coefficients at 941 and 1030 nm and the quenching of Yb3+ emission intensity and fluorescence lifetime after annealing are due to the increase of the concentration of Cr4+ ions. The data of thermal expansion and specific heat of the crystal have been measured. The thermal expansion coefficient is α=8.71×10−6 /K. The specific heat is 89.9 cal/mol K at 320.5 K. [Copyright &y& Elsevier]

In this paper, we demonstrate a SESAM mode-locked Tm:CaYLuAlO4 (a-cut) laser in the 2-μm spectral range. A birefringent filter (BF) is employed to shift the emission wavelength above 2 μm to support the stable mode locking through avoiding the structured water vapor absorption. Pulses as short as 288 fs are generated with a central wavelength of 2037 nm and an average power of 166 mW at a repetition rate of ~ 77.6 MHz. Moreover, wavelength tunable femtosecond laser with a tuning range from 2031.8 to 2081.1 nm is realized simply by rotating the birefringent filter around its surface normal. This work experimentally shows that birefringent filter is a simple and low-cost way to support the stable mode locking of Tm-bulk femtosecond lasers with an emission peak in the water vapor absorption region. [ABSTRACT FROM AUTHOR]

• The performance of passively mode-locked Nd:LMA laser was achieved for the first time. • A continuous wide tuning range of roughly 38 nm was obtained for the tuning operation. • The highest output power of Nd:LMA ultrafast laser was achieved. A 5 at.% Nd:LaMgAl 11 O 19 (Nd:LMA) disordered crystal was successfully fabricated by the Czochralski method. A continuous wide tuning range of roughly 38 nm (1051 nm ∼ 1089 nm) was obtained for the tuning operation. The performance of diode-pumped passively mode-locked Nd:LMA laser was successfully achieved for the first time. By employing a semiconductor saturable absorber mirror (SESAM), a continuous-wave mode-locked (CWML) laser with pulse duration of 11.2 ps was delivered, corresponding repetition rate was 55 MHz. The maximum average output power was 122 mW at a central wavelength of 1054.7 nm. These results indicated that the Nd:LMA was a promising laser material. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, single crystal of ytterbium (Yb) doped Ca5(PO4)3F (FAP) has been grown along the c-axis by using the Czochralski method. The segregation coefficients of Yb3+ in the Yb:FAP crystal has been determined by ICP-AES method. The absorption spectrum, fluorescence spectrum and fluorescence lifetime of the Yb:FAP crystal has been also measured at room temperature. In the absorption spectra, there are two absorption bands at 904 and 982nm, respectively, which are suitable for InGaAs diode laser pumping. The absorption cross-section (σ abs) is 5.117×10−20 cm2 with an FWHM of 4nm at 982nm. The emission cross-section (σ em) is 3.678×10−20 cm2 at 1042nm. Favorable values of the absorption cross-section at about 982nm are promising candidates for laser diode (LD) pumping. [Copyright &y& Elsevier]

Abstract: A large and transparent Yb:FAP crystal with dimensions up to ∅30mm×85mm has been grown by the Czochralski method. The preparation of the raw material has been investigated. X-ray power diffraction studies of Yb:FAP crystal confirm that the as-grown crystal is isostructural with the FAP crystal. The crystalline quality has been studied using X-ray rocking curve analysis. The segregation coefficient of Yb3+ in the Yb:FAP crystal has been also determined. Linear thermal expansion coefficients in [001] and [100] directions have been measured in the 30–800°C temperature range. [Copyright &y& Elsevier]

We report on a high-power Ho:YAG single-crystal fiber (SCF) laser inband pumped by a high-brightness Tm-fiber laser at 1908 nm. The Ho:YAG SCF grown by the micro-pulling-down technique exhibits a propagation loss of $0.05\pm 0.005~\text{cm}^{-1}$ at $2.09~\unicode[STIX]{x03BC}\text{m}$. A continuous-wave output power of 35.2 W is achieved with a slope efficiency of 42.7%, which is to the best of our knowledge the highest power ever reported from an SCF-based laser in the 2 $\unicode[STIX]{x03BC}\text{m}$ spectral range. [ABSTRACT FROM AUTHOR]

Pr3+-doped Sr 0.5 La 0.5 Mg 0.5 Al 11.5 O 19 (ASL) crystal along 〈100〉 direction was successfully grown using the Czochralski technique under azote atmosphere. Absorption and emission spectra of Pr:ASL crystal have been measured at room temperature. Continuous-wave laser operation of the a-cut and c-cut Pr:ASL samples under InGaN laser diode pumping has been demonstrated. For deep red laser operation at about 726 nm, the maximum output powers achieved from a-cut sample was 92.8 mW with slope efficiency of about 11.9%, while 46.6 mW with slope efficiency of 8.0% for the c-cut sample. For red laser at about 645 nm, maximum output powers of 49.2 mW and 42.8 mW were obtained for the a-cut sample and c-cut sample, corresponding to a slope efficiency of 6.7% and 8.5%, respectively. • Pr:Sr 0.5 La 0.5 Mg 0.5 Al 11.5 O 19 crystal was successfully grown using the Czochralski method. • Spectral parameters of Pr:Sr 0.5 La 0.5 Mg 0.5 Al 11.5 O 19 crystal were obtained. • Red and deep red laser were demonstrated in Pr:Sr 0.5 La 0.5 Mg 0.5 Al 11.5 O 19 crystal. [ABSTRACT FROM AUTHOR]

A diode-end-pumped continuous-wave and passively Q-switched mode-locked Nd:(Gd0.3Y0.7)2SiO5 laser was designed. At a pump power of 0.8W, we achieve dual-wavelength continuous-wave (CW) laser generation at wavelengths around 1,073.26 and 1,076.62 nm. Using a semiconductor saturable absorber mirror (SESAM), we obtain passively Q-switched mode-locked (QML) operation. A maximum average output power of 171 mW is obtained under a pump power of 5 W. The optical conversion efficiency for the QML laser is 3.4%. The duration of the mode-locked pulse is estimated to be about 649 ps at a repetition rate of 101.34 MHz. [ABSTRACT FROM AUTHOR]

• Spectral properties and high-efficiency broadband laser operation of Tm:CYGA crystal at 2 μm were demonstrated. • The maximum continuous-wave output power of 1.43 W was obtained. • A 284.7 nm tuning coverage was realized with a BF. We report on spectral properties and a high-efficiency broadband laser operation of Tm:CaY 0.9 Gd 0.1 AlO 4 (Tm:CYGA) crystal. The polarized absorption and emission spectra, gain cross sections and fluorescence lifetime are systematically studied, presenting a broad absorption and emission spectra and thus a smooth gain band. Furthermore, under an absorbed pump power of 4.35 W, a maximum continuous-wave (CW) laser output power of 1.43 W at 1967.8 nm is obtained, corresponding to a slope efficiency of 42.2 %. The beam quality factors (M2) in X-axis and Y-axis are measured to be 1.011 and 1.027, respectively. A tunable Tm:CYGA laser with a tuning range of 284.7 nm from 1837.5 to 2122.2 nm is achieved employing a birefringent filter (BF). The results indicate that the Tm:CYGA crystal is an excellent laser medium for generating high-efficiency broadband CW laser, indicating its potential for ultrashort pulse generation in the 2-μm spectral range. [ABSTRACT FROM AUTHOR]

Tb 3+ -doped YAlO 3 (YAP) single crystal was grown by Czochralski (Cz) method. Based on the polarized absorption spectra, the spectroscopic parameters were calculated to be Ω 2 = 3.49 × 10 −20 cm 2 , Ω 4 = 5.87 × 10 −20 cm 2 and Ω 6 = 2.55 × 10 −20 cm 2 , and then the spontaneous transition rate, fluorescent branching ratio and radiative lifetime of 5 D 4 multiplet were obtained. The yellow emission cross sections of 5 D 4 → 7 F 4 transition were calculated to be 1.72 × 10 −22 cm 2 , 2.73 × 10 −22 cm 2 and 2.65 × 10 −22 cm 2 for a, b and c polarization, respectively. The fluorescence lifetime of the 5 D 4 multiplet was fitted to be 1.72 ms. All the data indicate that Tb:YAP crystal is a promising candidate for yellow laser operation. [ABSTRACT FROM AUTHOR]

• We report the highest output power (12.36 W) of diode-pumped Tm:CALYO laser at 1938 nm with a slope efficiency of 53.9%. • We report the broadest tunability (271 nm) for Tm:CALYO lasers. • Passively Q-switched operation was also achieved with a maximum average output power of 3.81 W and pulse width of 25.9 ns. We report on the recent progress on high-power and broadband wavelength tunability of diode-pumped Tm:CaYAlO 4 (Tm:CALYO) lasers. Using a double-end pumping geometry, we have achieved a maximum output power of 12.36 W at 1938 nm, which is believed to be the highest power that have ever achieved for Tm:CALYO lasers. Moreover, we have operated 1861 nm, 1982 nm and 2032 nm lasers with maximum output powers of 8.73 W, 5.36 W and 0.73 W, respectively, by using differently coated end-face cavity mirrors. Furthermore, using a MgF 2 birefringent filter, we have tuned the lasing wavelengths from 1807 nm to 2078 nm. The 271 nm wavelength range is also believed to be the broadest tunability for Tm:CALYO lasers. Passively Q-switched Tm:CALYO laser has also been demonstrated with a maximum average output power of 3.81 W. The shortest pulse width reached 25.9 ns at a repetition rate of 10.1 kHz, which led to a pulse energy of 377.22 μJ and a peak power of 14.56 kW. These results indicate clearly that the Tm:CALYO crystal is excellent as a high-power and broadband laser gain medium operating at the important 2 μm wavelength region. [ABSTRACT FROM AUTHOR]

Nd-doped PbClF crystals were grown with modified Bridgman method. Broad and flat emission band at 1.0 μm was observed. The FWHM value of 0.0091 wt.% Nd3+-doped PbClF crystal at 1064 nm reached up to 30 nm with the peak emission cross-section of 1.05×10-19 cm2. All the results indicated that Nd-doped PbClF crystal should be a promising tunable and ultrafast laser material. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

High-quality Dy:PbWO 4 crystal has been successfully grown by the Bridgman method. Fluorescence properties of the grown crystal at the yellow-light region were discussed. The absorption cross-section of Dy3+ ions at 454 nm was calculated to be 0.142 × 10−20 cm2, which corresponded to the transition from 6H 15/2 to 4I 15/2 level. Based on Judd-Ofelt theory, the J-O intensity parameters Ω t and the emission cross-section were calculated. The fluorescence lifetime of 4F 9/2 level was measured to be 193 μs. • Dy: PbWO 4 crystal was grown successfully by the Bridgman method. • Judd-Ofelt theory was used to analyze the spectral properties of Dy: PbWO 4 for the first time. • Dy: PbWO 4 crystal is a potential laser medium for yellow laser operation. [ABSTRACT FROM AUTHOR]

Abstract: 20 at.% Yb:YAG single crystals have been grown by the CZ method and gamma-ray irradiation induced color centers and valence change of Fe3+ and Y b3+ ions in Yb:YAG have been studied. One significant 255 nm absorption band was observed in as-grown crystals and was attributed to Fe3+ ions. Two additional absorption (AA) bands located at 255 nm and 345 nm, respectively, were produced after gamma irradiation. The changes in the AA spectra after gamma irradiation and air annealing are mainly related to the charge exchange of the Fe3+, Fe2+, oxygen vacancies and F-type color centers. Analysis shows that the broad AA band is associated with Fe2+ ions and F-type color centers. The transition Y b3+→Y b2+ takes place as an effect of recharging of one of the Y b3+ ions from a pair in the process of gamma irradiation. [Copyright &y& Elsevier]

Abstract: For the first time, a quaternary doping system of Er3+, Yb3+, Ce3+, Na+: CaF2 single crystal was demonstrated to have high fluorescence yield in the 1.5μm region. Through a simplified model, the branching ratio of the Er3+ 4I11/2→4I13/2 transition was estimated to be improved more than 40 times by the deactivating effect of Ce3+ in the quaternary-doped CaF2 crystal with dopants of 0.2-at% Er3+ and 2.0-at% Ce3+. Owing to the broad emission bandwidth and large emission cross-section, the quaternary-doped CaF2 system shows the great potential to achieve the high laser performance in the 1.5μm region. [Copyright &y& Elsevier]

Abstract: Gd2SiO5 (GSO) single crystal codoped with Yb3+ and Er3+ (Abbr. as Er:Yb:GSO) was successfully grown by the Czochralski (CZ) method for the first time and the spectral characteristics were investigated. The absorption and fluorescence spectra were measured. The emission lifetime of the 4I13/2–Er-level was measured to be 5.84ms and the emission cross-section at 1529nm was calculated to be 1.03×10−20 cm2. The results indicate that Er:Yb:GSO is a potential laser material at ∼1.55μm wavelength region. [Copyright &y& Elsevier]

Abstract: The effects of Na+ doping level on the thermal conductivities, absorption and emission spectra, and fluorescence lifetimes of Yb3+,Na+:CaF2 crystals were systematically studied. Sites structure, covalent force, and crystal field strength of Yb3+:CaF2 crystals were markedly varied by codoping Na+ as charge compensator. The 2.0at% Yb3+ and 3.0at% Na+-codoped CaF2 crystal was demonstrated to operate in diode-pumped passively mode-locking scheme. Transform-limited 1ps laser pulses were obtained, showing the crystal capable of producing ultra-short laser pulses. [Copyright &y& Elsevier]

Antiphase dynamics has been observed experimentally for the laser modes operation in a laser-diode-pumped Q-switched microchip Yb:YAG laser with GaAs as a saturable absorber in the presence of spatial hole-burning. The Q-switched pulses sequences of two modes at different pump power have been obtained. The experimental results have shown that the pulses sequences displayed classic antiphase dynamics. [Copyright &y& Elsevier]

• Diode-pumped CW Pr,Mg:SRA lasers at 643 nm, 724 nm and 622 nm are demonstrated. • The highest output power of the diode-pumped Pr,Mg:SRA laser is 675 mW. • Passively Q-switched Pr,Mg:SRA lasers are also demonstrated, for the first time. • The shortest pulse width is 105.6 ns for the 622 nm laser, while 211.7 ns for the 643 nm laser. We report on compact blue-diode-pumped Pr,Mg:SrAl 12 O 19 (SRA) lasers in continuous-wave and passively Q-switched regimes. For continuous-wave mode, three lasers have been achieved with maximum output powers of 675 mW, 566 mW and 312 mW at wavelengths of 643 nm, 724 nm and 622 nm, respectively. The maximum slope efficiencies with respect to absorbed power for the three lasers are 18.7%, 16.6% and 11.1%. Using a uniaxial Co2+-doped strontium, lanthanum and magnesium aluminate (Co:ASL) crystal as saturable absorber with remarkable absorptions at 643 nm and 622 nm, we have achieved passively Q-switched Pr,Mg:SRA lasers at the two emissions with maximum output powers of 175 mW and 118 mW, respectively, for the first time to our knowledge. The shortest pulse widths for the two lasers are 211.7 ns and 105.6 ns. Correspondingly, we estimated that pulse energies and peak power are 2.13 μJ and 10.1 W for the 643 nm laser as well as 0.98 μJ and 9.27 W for the 622 nm laser. This work reveals that Pr,Mg:SRA as one of the few reported Pr3+-doped oxides could be potential in generating compact and efficient lasers in visible spectral range. [ABSTRACT FROM AUTHOR]

Nd:SrAl 11 O 19 (Nd:SRA) crystal has been grown by the Czochralski method. Polarized absorption spectra, polarized fluorescence spectra and fluorescence lifetime were investigated. For σ-polarization, the peak absorption cross section at 798 nm is 2.08 × 10−20 cm2 with full width at half maximum (FWHM) of 10.2 nm and the peak emission cross section is 3.36 × 10−20 cm2 at 1048.5 nm with FWHM of 4.80 nm. The Judd-Ofelt parameters Ω 2,4,6 were obtained to be 0.51 × 10−20 cm2, 2.08 × 10−20 cm2, and 2.12 × 10−20 cm2, respectively. Continuous-wave laser operation of the a-cut and c-cut Nd:SRA sample has been demonstrated. The maximum output power of 8.33 W was achieved from c-cut sample at an absorbed power of 27.73 W, corresponding to a slope efficiency of 31.3%. • Nd:SrAl 12 O 19 crystal has been gown by the Czochralski method. • Spectral parameters of Nd:SrAl 12 O 19 crystal were obtained. • Continuous-wave laser was demonstrated from Nd:SrAl 12 O 19 crystal. [ABSTRACT FROM AUTHOR]

In this paper, we have demonstrated a continuous-wave (CW) dual-wavelength Yb:LuYAG laser which works at 1029.41 and 1047.16 nm simultaneously. The laser operation state of dual-wavelength can be adjusted continuously by change the angle of the cavity mirror. And passively Q-switched operation of the crystal Yb:LuYAG was proceeded at the wavelength of 1028.99 nm using the MoS 2 saturable absorber. The pulse duration and maximum repetition rate were 293 ns and 251.27 kHz, respectively. [ABSTRACT FROM AUTHOR]

• A Pr:YLF-based single-frequency orange laser at 607 nm has been first demonstrated. • A Pr:YLF-based single-frequency orange laser at 604 nm has been first demonstrated. • The single-frequency orange lasers have potential application in biomedicine. We report on blue diode-pumped single-frequency Pr:YLF lasers in orange spectral region, for the first time to the best of our knowledge. For a single-frequency σ-polarized 607 nm laser, a maximum output power up to 175 mW is achieved with a slope efficiency of about 16.6%. Linewidth of the 607 nm single-frequency laser is measured to be about 6 MHz. Single-frequency operation has also been obtained at π-polarized 604 nm laser with a maximum output power up to 91 mW and a slope efficiency of about 8.9%. The corresponding linewidth of the 604 nm laser is about 22 MHz. The two single-frequency orange lasers exhibit wavelength tuning ranges of about 0.15 nm and 0.35 nm, respectively. This work has proposed the simplest way for single-frequency laser generation in orange spectral region, which could be obtained by complicated and low-efficiency sum-frequency mixing of Nd3+ lasers. This work paves a practical way for various orange-related applications. [ABSTRACT FROM AUTHOR]

High quality 7 at%Er:Y 2 O 3 crystal was successfully grown by Fz method. Judd-Ofelt theory was applied to analyze spectroscopic properties at 2.7 μm. The larger value of Ω 2 shows low local environment symmetry exists in Er:Y 2 O 3 crystal, and the large Ω 4 /Ω 6 indicates better spectral quality. The larger absorption cross-section and FWHM are beneficial to efficient absorption of pump source. The fluorescence spectra and lifetimes of Er:Y 2 O 3 crystal were measured and studied at 2.7 μm. The emission cross-sections at 2723 nm was calculated to be 1.41 × 10−20cm2. Compared with other Er3+ doped crystals, the large spectral quality factors Q and low fluorescence lifetime ratio illustrate that Er:Y 2 O 3 crystal has excellent laser properties at 2.7 μm. In addition, the low inversion ratio also indicates great potential of Er:Y 2 O 3 crystal for laser generation at 2.7 μm. • A high quality 7%Er:Y 2 O 3 laser crystal was successfully grown by Fz method. • Judd-ofelt (J-O) parameterization scheme was applied to analyze the spectroscopic properties of 7%Er:Y 2 O 3 laser crystal at 2.7 μm. • The large spectral quality factors Q with low fluorescence lifetime ratio illustrates that Er:Y 2 O 3 crystal has excellent laser properties at 2.7 µm. • The low inversion ratio indicates great potential of Er:Y 2 O 3 crystal for laser generation at 2.7 μm. [ABSTRACT FROM AUTHOR]

The high optical quality Er:Lu 2 O 3 and Er,Pr:Lu 2 O 3 crystals were grown by Floating zone method. The spectral properties of Er:Lu 2 O 3 and Er,Pr:Lu 2 O 3 crystals were investigated. After co-doping small concentration of Pr3+, the depopulated influence of Pr3+ to the NIR emission was much stronger than the MIR emission. The near-infrared and up-conversion fluorescence were significantly quenched. Moreover, the fluorescence lifetime of 4I 13/2 abviously decreases from 4.02 ms to 1.71 ms in 7% Er, 0.05% Pr: Lu 2 O 3 crystal, and the lifetime ratio is 1.63 with large fluorescence lifetime of 4I 11/2 which is desirable lifetime ratio in these crystals. Thus, the spectral performance was significantly improved by co-doping 0.05 at.% of Pr3+. The high laser performance at 2.7 μm of 7% Er, 0.05% Pr: Lu 2 O 3 crystal is expectable. • The high optical quality Er:Lu 2 O 3 and Er,Pr:Lu 2 O 3 crystals were firstly grown by Floating zone method. • The spectral properties of Er:Lu 2 O 3 and Er,Pr:Lu 2 O 3 crystals were firstly investigated. • After co-doping low concentration of Pr3+, the near-infrared, ESA and up-conversion fluorescence were significantly quenched. • The spectral performance of Er:Lu 2 O 3 crystal was significantly improved at 2.7 μm by co-doping 0.05 at.% of Pr3+. [ABSTRACT FROM AUTHOR]

• The performance of diode-pumped (Nd3+-doped) Ca 0.7 La 0.3 Al 12 O 19 (Nd:CLA) lasers was studied for the first time. • By inserting a Cr4+:YAG absorber, we successfully achieved a passively Q-switched laser. • Comparation between a- and c-cut disordered Nd:CLA lasers were made. A new neodymium-doped (Nd3+-doped) Ca 0.7 La 0.3 Al 12 O 19 (Nd:CLA) disordered crystal was successfully grown by the Czochralski method. The performance of diode-pumped Nd:CLA (a-cut and c-cut) lasers was demonstrated for the first time. For the c-cut crystal continuous-wave (CW) operation, we obtained the highest output power of 2.08 W at the wavelength of 1053.2 nm, and the slope efficiency was 23% versus the incident pump power. By inserting a Cr4+:YAG absorber, we successfully achieved a passively Q-switched laser, and the shortest pulse width was 18.36 ns with a peak power of 364.6 W. Compared with a-cut crystal, c-cut crystal has superior laser characteristics. [ABSTRACT FROM AUTHOR]