Nd:YAG陶瓷与单晶4F3/2–4I13/2跃迁的弱谱线多波长激光性能对比

报道了基于半导体激光端面抽运Nd:YAG的⁴F_3/2–⁴I_13/2 跃迁的弱谱线多波长激光输出. 实验对比了透明陶瓷与单晶材料的激光输出特性, 表明透明陶瓷和单晶材料荧光谱强度的略微差异, 导致了多波长输出时相同两个波长之间的激光强度比在两种材料中的差异. 基于两种耦合输出镜片, 激光阈值都在2 W左右. 在13.5 W的抽运功率下, 基于Nd:YAG透明陶瓷获得了输出功率4.05 W、强度比1 :2的1338与1356 nm双波长激光和输出功率3.65 W、强度比13 : 1的1356与1414 nm 双波长激光, 斜率效率分别达33.9% 和31.9%.     

The optical properties and laser characteristics of Cr and Nd co-doped Y3Al5O12 ceramics

We have fabricated Cr³⁺ and Nd³⁺ co-doped YAG (Cr;Nd:YAG) ceramics, and investigated their optical properties and laser characteristics. The Cr;Nd:YAG has two broad absorption bands at around 440 nm (⁴A₂→⁴T₁) and 600 nm (⁴A₂→⁴T₂) respectively, caused by Cr³⁺ ions. In the case of pumping at 440 nm, the maximum effective lifetime of the Cr;Nd:YAG was 737 μs with a 0.1 at% Cr³⁺ and 1.0 at% Nd³⁺ co-doped YAG sample. Cr³⁺ ions take a role of an effective sensitizer to convert the UV light of flashlamp. For single-shot laser operation, a 10.4 J output energy at 1064 nm was obtained with 0.1 at% Cr³⁺ and 1.0 at% Nd³⁺ co-doped YAG ceramic rod with a laser efficiency of 4.9%. The laser efficiency was found to be more than twice that of a 1.0 at % Nd³⁺:YAG ceramic rod.     

ANALYSIS OF LASING PERFORMANCES OF Yb3+-DOPED YAG, FAP, KYW CRYSTALS

The Yb³⁺ laser emitting at a 1.03μm wavelength has been evoking strong interest recently due to its advantages of long fluorescence lifetime, broad absorption band and the fact that it never shows concentration quenching. On the other hand, as a laser of three-level system it has, in general, a relatively high threshold power, which makes it important to seek some suitable host crystals to reduce this. Here, we present a comparison of the lasing performances of Yb³⁺-doped YAG [Y₃Al₅O₁₂], FAP [Ca₅(PO₄)₃F] and KYW [KY(WO₄)₂] crystals, including threshold power and slope efficiency, with those of the Nd:YAG laser based on the threshold formula of three-and four-level systems deduced by the authors. The results show that the Yb³⁺ laser can output a power larger than the Nd:YAG laser does in the case of comparably higher pumping power, if the length of the lasing rod and the concentration of the active ions satisfy some conditions. The theoretical results are also close to the experimental results reported.     

110 W ceramic Nd<Superscript>3+</Superscript> : Y<Subscript>3</Subscript>Al<Subscript>5</Subscript>O<Subscript>12</Subscript> laser

A high-power, continuous-wave 0.6% Nd³⁺-doped ceramic Y₃Al₅O₁₂ (Nd:YAG) laser has been developed. 110 W laser output at 1064 nm was obtained, with a slope efficiency of about 41%. The M² factor was found to be around 6. The laser performance of the ceramic laser material was found to compare favorably with that obtained with single crystal Nd:YAG. PACS 42.55.-f; 42.55.Xi; 42.70.Hj     

Optical characteristics of Cr and Nd codoped Y3Al5O12 ceramics

The optical characteristics of Cr³⁺ and Nd³⁺ codoped Y₃Al₅O₁₂ (YAG) ceramics are measured. These measurements are done using two pumping sources, a 808 nm laser diode (LD) and a Xe short-arc lamp, to simulate solar radiation. The specimens used are 0.1%Cr³⁺/1.0%Nd³⁺ and 3.0%Cr³⁺/1.0%Nd³⁺ (atomic%) codoped YAG ceramics. A Nd:YAG crystal doped with 1.0%Nd³⁺ is used as a reference. The saturation intensities of the Cr/Nd:YAG ceramics pumped by the LD are the same as that of the Nd:YAG crystal, while they are higher when they are pumped by the Xe lamp. The saturation intensities are for the 0.1% Cr-doped ceramic and for the 3.0%Cr-doped ceramic. The small signal gains of the 0.1%Cr-doped and 3.0%Cr-doped ceramics are measured and found to be 1.8 times and 7.0 times higher than that of Nd:YAG for the same intensity of solar pumping, respectively. The quantum efficiency of energy transfer from Cr³⁺ to Nd³⁺ is estimated to be 0.88±0.09 for the 0.1%Cr-doped ceramic and 0.67±0.08 for the 3.0%Cr-doped ceramic.     

Luminescence of La and Sc impurity centers in YAlO3 single-crystalline films

The luminescence of La_Y³⁺ and Sc_Y³⁺ and Sc_Al³⁺ centers created by lanthanum and scandium ions at Y³⁺ and Al³⁺ cation sites of YAlO₃ perovskite lattice was investigated. The features of emission of excitons localized at the mentioned centers in YAlO₃:La and YAlO₃:Sc single-crystalline films were analyzed by means of time-resolved emission spectroscopy and luminescence decay kinetics measurements under excitation by synchrotron radiation at 9 and 300 K.     

Characteristics of Nd：GdVO4 Laser with Different Nd-Doping Concentrations

We report the properties of a compact diode-pumped continuous-wave Nd：GdV04 laser with a linear cavity and different Nd-doped laser crystals. In a 0.2at.% Nd-doped Nd：GdVO4 laser, 1.54 W output laser power is achieved at 912nm wavelength with a slope efficiency of 24.8% at an absorbed pump power of 9.4W. With 0.3at.% Nd-doping concentration, we can obtain the either single-wavelength emission at 1064nm or 912nm or the dual-wavelength emission at 1064nm and 912nm by controlling the incident pump power. From an incident pump power of 11.6 W, the 1064nm emission between ^4Fa/2 and ^4I11/2 is suppressed completely by the 912nm emission between ^4Fa/2 and ^4I9/2. We obtain 670 mW output of the 912nm single-wavelength laser emission with a slope efficiency of 5.5% by taking an incident pump power of 18.4 W. Using a Nd：GdV04 laser with 0.4at.% Nd-doping concentration, we obtain either the single-wavelength emission at 1064nm or the dual-wavelength emission at both 1064nm and 912nm by increasing the incident pump power. We observe a strong competition process in the dualavelength laser.     

Intermittent oscillation of 1064 nm and 1342 nm obtained in?a?diode-pumped doubly passively Q-switched Nd:YVO4 laser

The intermittent oscillation of 1064 nm and 1342 nm was demonstrated in a diode-pumped doubly passively Q-switched Nd:YVO₄/Cr⁴⁺:YAG/V³⁺:YAG laser for the first time to our best knowledge. By exploiting a three-mirror configuration and choosing appropriate reflectivity values for the two wavelengths on the output couplers, the dual-wavelength pulsed operation was obtained. The maximum dual-wavelength average output power was 428 mW, corresponding to an optical-to-optical conversion efficiency of 8.5%. The corresponding physical explanations for the intermittent oscillation as well as the related phenomena are also given in this paper.     

Dual-wavelength Nd:YAP laser at 930 and 1341 nm and sum-frequency mixing for an emission at 549 nm

A dual-wavelength continuous-wave (CW) diode end-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser that generates simultaneous laser action at the wavelengths 930 and 1341 nm is demonstrated. A total output power of 778 mW for the dual-wavelength was achieved at the incident pump power of 17.8 W. Furthermore, intracavity sum-frequency mixing at 930 and 1341 nm was then realized in a LBO crystal to reach the yellow-green range. We obtained a total CW output power of 103 mW at 549 nm.     

Temperature-dependent lasing and spectroscopy of Yb:Y2O3 and Yb:Sc2O3

Spectroscopic and laser properties of Yb³⁺ in ceramic Y₂O₃ have been studied at room and cryogenic temperatures. Laser performance is very substantially improved by cooling to liquid nitrogen temperature, primarily due to the great reduction in ground state absorption that permits laser operation on the much stronger 1030-nm emission line rather than the 1077-nm line. The 976-nm “zero line” is observed to become much weaker as the temperature is reduced. Several models for this behavior are considered, but none adequately explains this surprising result. Spectroscopy of Yb:Sc₂O₃ indicates that it is likely to be an even better cryogenic gain material, given samples of comparable optical quality.     

Dual-Wavelength and Passively Q-Switched Nd :GdVO4 Lasers Operated at 1.34 μm Under 880 nm Diode Pumping

We report continuous-wave (CW) and passively Q-switched Nd :GdVO₄ lasers on ⁴F_3/2 → ⁴I_13/2 transition directly pumped by an 880 nm diode laser. A widely investigated Nd :GdVO₄ laser at about 1341 nm is operated with a maximum output power of 5.23 W and a slope efficiency of about 30.6%. Using an etalon for wavelength selection, we realize laser emission at about 1344 nm, for the first time to our knowledge, in a Nd :GdVO₄ laser, with a maximum output power of 4.19 W and a slope efficiency of 20.1%. Moreover, we achieve simultaneous dual-wavelength lasing at 1341 and 1344 nm with a maximum output power of 2.27 W and a slope efficiency of 13.5%, respectively. Using V³⁺ :YAG as a saturable absorber, stable Q switching is obtained at about 1341 nm with a maximum average output power of 1.15 W. The pulse width is 52.8 ns at a repetition rate of 279.8 kHz.

     

Simultaneous dual-wavelength CW laser operation at 1064 and 930 nm in Nd<Superscript>3+</Superscript>:YAlO<Subscript>3</Subscript>

A dual-wavelength continuous-wave (CW) diode end-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser that generates simultaneous laser action at the wavelengths 1064 and 930 nm is demonstrated. A total output power of 2.15 W (1.57 W at 1064 nm and 0.58 W at 930 nm) for the dual-wavelength was achieved at the incident pump power of 17.8 W with optical conversion efficiency of 12.1%. The M ² values for 930 and 1064 nm lights were found to be around 1.21 and 1.32, respectively.     

Passively Q-switched self-frequency doubling Nd:Ca4GdO(BO3)3 laser with Cr:YAG saturable absorber

Nd³⁺ : Ca₄GdO(BO₃)₃, known as Nd : GdCOB, is a new self-frequency doubling laser crystal. Using Cr⁴⁺ : YAG as passive Q-switch, we have realized the Q-switched laser running at 0.53 μm with an Nd : GdCOB crystal. Meanwhile, the pulse width, the single pulse energy and the repetition rate under different small-signal transmission of Cr⁴⁺ : YAG and different pump conditions are measured and the numerical solutions of the coupling wave rate equations agree with the experimental results.     

Sm共掺对Sr4Al14O25:M (M=Mn4+, Cr3+）荧光粉发光性能的影响

用固相反应法合成了Sr₄Al₁₄O₂₅:M和Sr₄Al₁₄O₂₅:(M+Sm³⁺)(M=Mn⁴⁺, Cr³⁺)荧光粉, 研究了其发光性能．Sm的共掺并没有改变Sr₄Al₁₄O₂₅:Cr³⁺激发带和发射带的位置, 但是显著提高了材料的发光性能;Sm共掺Sr₄Al₁₄O₂₅:Mn⁴⁺反而降低了发光强度． 对于Cr³⁺, Sm³⁺共掺的Sr₄Al₁₄O₂₅荧光粉, 呈现了从Sm³⁺到Cr³⁺ 的辐射形式的能量传递过程,说明了Sm的共掺对于Sr₄Al₁₄O₂₅:Cr³⁺荧光粉的发光强度提高的原因．     

Spectroscopic characteristics of Tm3+ in Tm and Tm,Nd, Yb:Sc2O3 ceramic

The spectroscopic investigation of Tm³⁺ or (Nd, Yb, Tm)-doped Sc₂O₃ transparent ceramics, as laser-active media for visible and IR emission, was performed. The spectra are dominated by Tm³⁺ ions in sites of C₂ symmetry and an energy level scheme and other spectral parameters were determined. The strong concentration quenching of ³H₄ level emission in Tm:Sc₂O₃ at 300 K is discussed by considering the resonant cross-relaxation (³H₄→³F₄)?(³H₆→³F₄) process and multipolar interactions of various orders. The main energy-transfer processes leading to the blue upconversion emission from the ¹G₄ Tm³⁺ level in (Tm, Nd, Yb):Sc₂O₃ ceramic, under pulsed pumping at 808.3 nm were evidenced.     

Crystal field analysis of Er in Sc2O3 transparent ceramics

A crystal field investigation of Er³⁺-doped Sc₂O₃ transparent ceramics is presented.The established energy level diagram is analyzed with crystal-field Hamiltonian of C₂ symmetry including J-mixing effect. Very satisfactory correlations were obtained between 53 calculated and experimental Stark energy levels, with an rms of 7.7 cm⁻¹. These results are compared with those reported for other rare earth ions in the same host and with Er³⁺ ions in other sesquioxides. The concordance between the crystal-field strength parameters indicates the consistence of our analysis. Furthermore, based on the extended electrostatic point charge model, a theoretical trend is proposed for rare earth ions in Sc₂O₃ in comparison with Y₂O₃. Based on this trend, very satisfactory results are obtained for Yb³⁺ ion in Sc₂O₃.     

Simultaneous dual-wavelength emission at 0.90 and 1.06 µm in Nd-doped laser crystals

Continuous-wave (CW) simultaneous laser emission on the 0.9-μm ⁴ F _3/2 → ⁴ I _9/2 transition and the ⁴ F _3/2 → ⁴ I _11/2 transition at 1.06 μm is obtained in Nd-based laser crystals of thin-disk geometry and using a multi-pass pumping scheme. A Nd:Y₃Al₅O₁₂ (Nd:YAG) thin disk emitted simultaneous laser radiation at 946 and 1064 nm with 5.1 W output power, and Nd:YVO₄ and Nd:GdVO₄ thin-disk lasers with more than 3 W output power at 0.91 and 1.06 μm were realized. The ratio between the output power at one of the wavelengths and the total output power could be varied by the laser resonator design. An intracavity frequency-doubled Nd:YVO₄ thin-disk laser with alternate green at 532 nm and “deep-blue” at 457 nm generation of high average output powers is demonstrated.     

Rotating-disk diode-pumped continuous-wave Nd:YAG laser

Continuous-Wave (CW) diode-laser-pumped experiments using rotating Nd: YAG disk(s) have been performed in the input-power range of 1–6 W and rotation-speed range of 0–25 Hz. With a single Nd: YAG disk in the laser cavity, about 1.56 W of output power at 1.06 µm due to the Nd³⁺ (⁴ F _3/2–⁴ I _11/2) transition at an absorbed input power of 4.2 W has been observed, leading to an optical-to-optical conversion efficiency of over 37% and slope efficiency of 52% using 7.5% transmission output coupler. The laser output power has been observed to decrease by either increasing the number of Nd:YAG disks in the cavity or increasing the rotation speed of the disk(s).     

Characteristics of a passively Q-switched Nd:NaY(WO4)2 laser with Cr:YAG saturable absorber

By using xenon flash lamp as pump source and Cr⁴⁺:YAG as passive Q-switcher, we have performed the Q-switched laser operation at 1.06 μm with an Nd³⁺:NaY(WO₄)₂ (known as Nd:NYW) crystal. Meanwhile, the pulse width, the single pulse energy and the repetition rate under different small-signal transmissions of Cr⁴⁺:YAG and different reflectivities of output reflector are measured, and the numerical solutions of the coupling wave rate equations agree with the experimental results.     

Y3Al5O12 ceramic absorbers for the suppression of parasitic oscillation in high-power Nd:YAG lasers

The objective of this study was to identify a material suitable to absorb radiation at the wavelength of neodymium-doped Yttrium Aluminum Garnet (Y₃Al₅O₁₂:YAG), 1064 nm. M-(M= Sm³⁺, Co²⁺, Co³⁺, Cr³⁺, and Cr⁴⁺) doped highly transparent YAG ceramics were fabricated, and their absorption spectra were measured. Unlike Co²⁺ and Cr³⁺-doped ceramic samples, Co³⁺ and Cr⁴⁺ and Sm³⁺-doped:YAG ceramics were found to have significant absorption at 1064 nm. However, the Sm³⁺-doped YAG clearly emerged as the best candidate because it is also transparent at 808 nm, the pumping wavelength laser diode (LD), and also at most absorption bands used for flash-lamp pumping.