ABSTRACT
An eye-safe 1567 nm continuous-wave laser with a maximum output power of 50 mW and a slope efficiency of 21.1% was demonstrated in an Er:Yb:Ba3Gd(PO4)3 crystal. By using a Co2+:MgAl2O4 crystal with an initial transmission of 95% as a saturable absorber, a stable passively Q-switched pulsed laser was also realized in the crystal. The effects of the output coupler transmission and cavity length on pulsed performance were investigated. At an absorbed pump power of 350 mW, a 1541 nm Er:Yb:Ba3Gd(PO4)3 pulsed laser with a repetition frequency of 0.86 kHz, duration of 38 ns, energy of 21.2 µJ, and peak output power of 0.56 kW was obtained.
ABSTRACT
Passively Q-switched Er:Yb:LuAl3(BO3)4 pulse microlasers were investigated at a low repetition frequency of 10-200 Hz. End-pumped by a 975.6 nm quasi-continuous-wave laser diode with pump pulse width of 0.5 ms and period of 10 ms, a stable 1522 nm pulse microlaser with single pulse energy of 48.3 µJ, duration of 1.9 ns, repetition frequency of 100 Hz, peak output power of 25.4 kW and beam quality factor less than 1.2 was realized at a pump beam waist diameter of 260 µm. This eye-safe passively Q-switched pulse microlaser with high peak output power and narrow duration can be used in the portable laser rangefinder.
ABSTRACT
It has remained a big challenge to grow large crystals of compounds at very anisotropic crystal growth rates. GdPO4 is such an example, which usually grows into a needle-like shape. This work solved this problem by using Li+ ions, predicted by first-principles calculations, to adjust the crystal morphology of GdPO4. Based on the calculated surface energies and the polar properties of the surfaces, we identified two crystal planes, i.e. (-102) and (-111), which can be used to adjust the morphology of the GdPO4 crystal by using extrinsic cations in the flux system. With a predicted Li containing flux system, Li2O-MoO3-B2O3, a large crystal with a record size, 10.0 × 9.0 × 18.2 mm3, was grown by using the top-seeded solution growth (TSSG) method. Based on the grown large crystal and the polarized Raman measurements, four new Raman bands missing in early studies and other bands were unambiguously assigned. By introducing a new formula, the phonon-phonon interactions were shown to be weak in the temperature range from 83 to 803 K. Our study indicates that the crystal of GdPO4 can be used as a promising laser host material working under relatively high temperature conditions.
ABSTRACT
Monodisperse Tb-doped NaCeF4 nanocrystals were synthesized via a hydrothermal method. The morphology, and room temperature and temperature dependent luminescent properties were investigated. Excited at 254 nm, the emissions of Ce3+ at 270-370 nm and those of Tb3+ at 475-700 nm can be observed. The strongest visible emission was observed in NaCeF4:20 at% Tb with a quantum yield of 49%. The efficiency of energy transfer from Ce3+ to Tb3+ increases with the Tb3+ doping concentration and reaches 95% for NaCeF4:30 at% Tb. The ratio of Tb3+ emission to Ce3+ emission is sensitive to temperature, and the relative sensitivity was calculated to be 1.0% °C-1 at 60 °C. The mechanisms for this thermal dependence were analyzed in terms of non-radiative relaxation and energy migration.
ABSTRACT
A single longitudinal-mode passively Q-switched 1537 nm pulse microchip laser was realized in an Er:Yb:Lu2Si2O7 crystal. The effects of the pump beam diameter and output mirror transmission on pulse characteristics of the Er:Yb:Lu2Si2O7 microchip laser were investigated, when a Co2+:MgAl2O4 saturable absorber with an initial transmission of 95% was used. At an absorbed pump power of 3.4 W, a 1537 nm single-longitudinal-mode pulse laser with energy of 25.8 µJ, repetition frequency of 0.89 kHz, duration of 4.3 ns, and peak output power of 6.0 kW was obtained, when the pump beam diameter and output mirror transmission were 420 µm and 3.0%, respectively. The beam quality factor of output laser with TEM00 mode was less than 1.3.
ABSTRACT
It is still a technical challenge to obtain a 1.55 µm passively $Q$Q-switched ${{\rm Er}^{3 + }}/{{\rm Yb}^{3 + }}$Er3+/Yb3+ pulse laser with high energy and high repetition frequency, especially when it is end-pumped by a continuous-wave 0.98 µm diode laser. Benefitting from its long fluorescence lifetime of the $^4{{\rm I}_{13/2}}$4I13/2 upper laser level and high thermal conductivity, ${\rm Er}:{\rm Yb}:{{\rm Lu}_2}{{\rm Si}_2}{{\rm O}_7}$Er:Yb:Lu2Si2O7 crystal may be an excellent gain medium for realizing a high energy and high repetition frequency 1.55 µm pulse laser. At a continuous-wave absorbed pump power of 6.1 W, a 1537 nm pulse laser with energy of 45.5 µJ, repetition frequency of 1.32 kHz, and duration of 25 ns was first, to the best of our knowledge, realized in an ${\rm Er}:{\rm Yb}:{{\rm Lu}_2}{{\rm Si}_2}{{\rm O}_7}$Er:Yb:Lu2Si2O7 crystal.
ABSTRACT
The polarized spectra associated with 1.55 µm lasing in an Er:Yb:Ca3NbGa3Si2O14 crystal were investigated at room temperature. The crystal had a large absorption cross section of 3.60 × 10-20 cm2 at 978 nm, long fluorescence lifetime of 5.81 ms for the 4I13/2 multiplet of Er3+, and broad emission band at 1.55 µm with full width at half-maximum of 60 nm. End-pumped by a 975 nm diode laser, a 1555 nm continuous-wave microlaser with a maximum output power of 0.4 W and a slope efficiency of 10.6% was demonstrated in a c-cut, 2.5-mm-thick crystal. Combining with natures of the long fluorescence lifetime and the broad emission band, the Er:Yb:Ca3NbGa3Si2O14 crystal with a good thermal performance may be a promising gain medium for high-energy pulse and broadly tunable lasers around 1.55 µm.
ABSTRACT
A single-longitudinal-mode 1521 nm pulse microchip laser Q-switched by a Co2+:MgAl2O4 saturable absorber was demonstrated in an Er:Yb:YAl3(BO3)4 crystal. The influence of the waist radius of pump beam at 976 nm on the laser performance was investigated. At an incident pump power of 6.54 W and pump beam waist radius of 60 µm, a 1521.4 nm single-longitudinal-mode pulse laser with average output power of 434 mW, energy of 16.5 µJ, repetition frequency of 26.3 kHz and width of 2.9 ns was obtained. The result shows that caused by the mode selection of the saturable absorber and large cavity losses, a single-longitudinal-mode 1.55 µm pulse microchip laser can also be realized in the Er:Yb:YAl3(BO3)4 crystal.
ABSTRACT
An Er:Yb:Lu2Si2O7 microchip laser was constructed by placing a 1.2 mm thick, Y-cut Er:Yb:Lu2Si2O7 microchip between two 1.2 mm thick sapphire crystals, in which input and output mirrors were directly deposited onto one face of each crystal. End-pumped by a continuous-wave 975.4 nm diode laser, a 1564 nm multi-longitudinal-mode laser with a maximum output power of 940 mW and slope efficiency of 20% was realized at an absorbed pump power of 5.5 W when the transmission of output mirror was 2.2%. When the transmission of the output mirror was increased to 6%, a 1537 nm single-longitudinal-mode laser with a maximum output power of 440 mW and slope efficiency of 12% was realized at an absorbed pump power of 4.3 W. The results indicate that the Er:Yb:Lu2Si2O7 crystal is a promising microchip gain medium to realize a single-longitudinal-mode laser.
ABSTRACT
A composite crystal consisting of a 1.5-mm-thick Er:Yb:YAl3(BO3)4 crystal between two 1.2-mm-thick sapphire crystals was fabricated by the thermal diffusion bonding technique. Compared with a lone Er:Yb:YAl3(BO3)4 crystal measured under the identical experimental conditions, higher laser performances were demonstrated in the sapphire/Er:Yb:YAl3(BO3)4/sapphire composite crystal due to the reduction of the thermal effects. End-pumped by a 976 nm laser diode in a hemispherical cavity, a 1.55 µm continuous-wave laser with a maximum output power of 1.75 W and a slope efficiency of 36% was obtained in the composite crystal when the incident pump power was 6.54 W. Passively Q-switched by a Co2+:MgAl2O4 crystal, a 1.52 µm pulse laser with energy of 10 µJ and repetition frequency of 105 kHz was also realized in the composite crystal. Pulse width was 315 ns. The results show that the sapphire/Er:Yb:YAl3(BO3)4/sapphire composite crystal is an excellent active element for 1.55 µm laser.
ABSTRACT
Efficient 1.57 µm continuous-wave laser was demonstrated in an X-cut, 2.0 mm-thick Er3+:Yb3+:LaMgB5O10 crystal with sapphire cooling end-pumped by a 976 nm laser diode. In a plano-concave cavity, a laser with a maximum output power of 0.61 W and a slope efficiency of 23% was realized at an absorbed pump power of 4.0 W. A continuous-wave 1566 nm micro-laser with a maximum output power of 0.47 W and a slope efficiency of 16% was also obtained. The lasers were totally linear polarization parallel to the crystalline Z axis. The results show that the Er3+:Yb3+:LaMgB5O10 crystal with high thermal conductivity may be a good gain medium for laser around 1.55 µm.
ABSTRACT
Efficient continuous-wave diode-pumped laser operation of Czochralski grown Er:Yb:Lu2Si2O7 crystal is reported. Polarized absorption and emission spectra, fluorescence lifetimes, and energy transfer efficiency from Yb3+ to Er3+ were determined. A maximal output power of 522 mW was achieved at 1620 nm with slope efficiency of 15.8% and absorbed pump threshold of 470 mW. Among the Er3+ and Yb3+ co-doped materials with long fluorescence lifetimes of the upper level 4I13/2, which are candidates for gain media of pulsed laser around 1.55 µm with high energy, comprehensive performance of the Er:Yb:Lu2Si2O7 crystal is the best till now.
ABSTRACT
A scheme to measure temperature distribution inside a gain medium of a diode-pumped solid-state laser is proposed based on the fluorescence intensity ratio technique. By recording the temperature-dependent upconversion fluorescence related to the H11/22âI15/24 and S3/24âI15/24 transitions of Er3+, the real-time temperature distribution inside an Er3+:Yb3+:LuAl3(BO3)4 crystal end-pumped by a 976 nm diode laser can be measured while a 1.55 µm laser is operating. Influences of pump power, output power, and output mirror transmissivity on the temperature distribution inside the gain medium are investigated. This scheme can conveniently and accurately measure the temperature distribution along the laser path in a rare-earth-doped gain medium in real time.
ABSTRACT
A composite crystal consisting of a 0.4-mm-thick (1.1 at.%)Er:(25 at.%)Yb:YAl3(BO3)4 crystal and a pure 1.0-mm-thick YAl3(BO3)4 crystal was successfully fabricated by the thermal diffusion bonding method. When the pure YAl3(BO3)4 crystal was used as an effective heat sink, thermal effects in the Er:Yb:YAl3(BO3)4/YAl3(BO3)4 composite crystal can be reduced, and the maximum output power of 1.55 µm laser was increased from 350 mW in a lone 0.4-mm-thick Er:Yb:YAl3(BO3)4 crystal to 780 mW in the composite crystal under identical experimental conditions. The results show that using such a diffusion-bonded Er:Yb:YAl3(BO3)4/YAl3(BO3)4 composite crystal as a gain medium can effectively enhance the performance of a 1.55 µm laser.
ABSTRACT
A sandwich-type sapphire/Er3+:Yb3+:LuAl3(BO3)4/sapphire micro-laser was fabricated by tightly pressing two sapphire crystals and a Er3+:Yb3+:LuAl3(BO3)4 microchip together, and directly depositing cavity mirrors onto the outside surfaces of the sapphire crystals. Pumped by a continuous-wave 976 nm diode laser, a 1543 nm laser with maximum output power of 1.17 W and slope efficiency of 33% with respect to incident pump power was realized in the sandwich-type micro-laser, whereas a laser with maximum output power of 0.46 W and slope efficiency of 17% was obtained in a monolithic Er3+:Yb3+:LuAl3(BO3)4 micro-laser. Furthermore, efficient 1521 nm continuous-wave and passively Q-switched pulse lasers were also demonstrated in the sandwich-type micro-laser.
ABSTRACT
Yb3+:Bi4Si3O12 single crystal with Yb3+ concentration of 5.7 at.% has been grown successfully by the Czochralski method. The energy level positions of Yb3+ in Bi4Si3O12 crystal were determined based on the absorption and fluorescence spectra. The peak absorption cross-section is 0.98 × 10−20 cm2 at 976 nm and the peak emission cross-section is 0.57 × 10−20 cm2 at 1035 nm. The fluorescence lifetime of the excited multiplet is 1.26 ms. Diode-pumped continuous-wave laser operation around 1038 nm has been demonstrated in the Yb3+:Bi4Si3O12 crystal with a slope efficiency of 27% and maximum output power of 240 mW.
ABSTRACT
Er3+ doped YbAl3(BO3)4 crystal with large absorption coefficient of 184 cm(-1) at pump wavelength of 976 nm is a promising microchip gain medium of 1.5-1.6 µm laser. End-pumped by a 976 nm diode laser, 1.5-1.6 µm continuous-wave laser with maximum output power of 220 mW and slope efficiency of 8.1% was obtained at incident pump power of 4.54 W in a c-cut 200-µm-thick Er:YbAl3(BO3)4 microchip. When a Co2+:Mg0.4Al2.4O4 crystal was used as the saturable absorber, 1521 nm passively Q-switched pulse laser with about 0.19 µJ energy, 265 ns duration, and 96 kHz repetition rate was realized.
ABSTRACT
Aluminate garnet phosphors Ca2GdZr2(AlO4)3:Ce(3+) (CGZA:Ce(3+)) for solid-state white lighting sources are reported. The crystal structure and Mulliken bonding population of the CGZA:Ce(3+) have been analyzed. The larger 5d ((2)D) barycenter shift εc and smaller phenomenological parameter 10Dq of Ce(3+) in CGZA are related to the larger covalent character of Ce-O. The tuning spectral properties of the Ce(3+)-doped CGZA-based isostructural phosphors are presented. The splitting of cubic crystal field energy level (2)Eg in Ca2REZr2(AlO4)3:Ce(3+) (CREZA:Ce(3+)) (RE = Lu, Y, and Gd) increases as the radius of RE(3+) increases, and the splitting of (2)Eg may dominate the difference of spectroscopic red-shift D(A) in CREZA:Ce(3+). The splitting of the (2)Eg in CaGd2ZrSc(AlO4)3:Ce(3+) (CGZSA:Ce(3+)) phosphors increases seemly due to the decreasing of the covalent character of Ce-O. Thermal quenching properties of Ce(3+)-doped CGZA-based isostructural phosphors are also presented and analyzed. For CREZA:Ce(3+) phosphors, the increasing of the radius of RE(3+) results in an enhancement of thermal quenching. The quenching of CGZSA:Ce(3+) is obviously stronger mainly due to the smaller energy difference between the lowest 5d excited state and 4f ground state.
ABSTRACT
End-pumped by a 970 nm diode laser, 1534 nm pulse laser with about 16 µJ energy, 48 ns duration, and 21 kHz repetition rate was obtained at absorbed pump power of 11.8 W in a Z-cut 1.08-mm-thick Er(3+):Yb(3+):Sr(3)Lu(2)(BO(3))(4) crystal passively Q-switched by a Co(2+):Mg(0.4)Al(2.4)O(4) crystal. The effects of absorbed pump power and resonator cavity length on output performances of the pulse laser were investigated. Compared with that of the Er(3+):Yb(3+):LuAl(3)(BO(3))(4) laser in a similar experimental condition, higher pulse energy realized in the Er(3+):Yb(3+):Sr(3)Lu(2)(BO(3))(4) crystal may be originated from its smaller stimulated-emission cross section at 1534 nm and longer fluorescence lifetime of the (4)I(13/2) upper laser level of Er(3+) ions.
ABSTRACT
1520 and 1560 nm acousto-optic Q-switched pulse lasers with high peak power and narrow width were respectively realized in Er:Yb:RAl(3)(BO(3))(4) (R = Y and Lu) crystals end-pumped by a 970 nm diode laser. For Er:Yb:LuAl(3)(BO(3))(4) crystal, 1520 nm laser with 350 µJ energy, 32 ns width and 10.9 kW peak power, and 1560 nm laser with 520 µJ energy, 67 ns width and 7.8 kW peak power were respectively obtained at pulse repetition frequency of 1 kHz. For Er:Yb:YAl(3)(BO(3))(4) crystal, 1520 nm laser with 210 µJ energy, 45 ns width and 4.7 kW peak power, and 1560 nm laser with 380 µJ energy, 102 ns width and 3.7 kW peak power were respectively obtained at pulse repetition frequency of 1 kHz. Pulse performances of 1520 and 1560 nm lasers were compared and the narrower pulse width of 1520 nm laser was ascribed to the higher stimulated emission cross-section.
