Yb3+：Pr3+：ZBLAN光纤中4f5d上转换激发的理论研究

利用粒子数速率方程和相关的辐射跃迁理论,计算了Yb³⁺:Pr³⁺:ZBLAN光纤中Pr³⁺离子4f5d能级两步上转换激发的动力学过程.得到不同Pr³⁺掺杂浓度下,激发光的光谱强度和粒子数密度的纵向分布和有效光纤长度随激发光的光谱强度的变化关系.另外,还得到了4f5d荧光强度与入射光强、光纤长度和Pr³⁺掺杂浓度的关系,给出了激发效率与激发光的光谱强度和Pr³⁺掺杂浓度的关系.     

Theory of Pr:ZBLAN ultraviolet upconversion fiber master oscillator power amplifier

A theoretical study for ultraviolet upconversion fiber master oscillator power amplifier (MOPA) based on the transition from the 4f5d state to the ³H₄ ground state in Pr³⁺:ZBLAN fiber is performed by using steady population rate equations and propagation equations. The variation of the output power with the fiber length of master oscillator and MOPA and the launched pump powers, the dependence of the slope efficiency on the fiber length of master oscillator and MOPA, and the optimum fiber length of MOPA as a function of the launched pump powers, are calculated. Both the output power and the slope efficiency of MOPA are 2-3 times those of the simplex oscillator. It is found that the UV upconversion fiber MOPA system can effectively improve the output power and the slope efficiency of laser.     

YAG:Pr3+的真空紫外光谱分析及其4f5d能级的研究

用共沉淀法制备出不同掺杂浓度的钇铝石榴石(Y3Al5O12,YAG):Pr3+粉末.在不同温度下用同步辐射的真空紫外光(VUV)作为激发光源测量了其发射和激发光谱.对YAG:Pr3+被VUV激发后的发光过程进行了分析,并估算了YAG:Pr3+的声子能量、黄昆因子S及Stokes位移.当用170nm光激发样品时,可能存在自陷激子和通过自陷激子能量传递引发的3P0发射,这种跃迁途径不同于用240nm和289nm两个波长激发后的跃迁途径;对Pr3+在YAG中的4f5d能级进行了研究,从而对其4f5d组态有了一个较清晰的认识.     

Analysis of the effect of numerical aperture on Pr:ZBLAN upconversion fiber lasers

Theoretical analyses show that the use of high-numerical-aperture (NA) fibers can significantly increase the conversion efficiency of a blue Pr(3+) -doped fluoride fiber upconversion laser and reduce the pump-power threshold. A record high efficiency of ~14% and a low 1017-nm threshold of ~30 mW were achieved experimentally with a fiber with a NA of ~0.39.     

掺Er3+氟化物光纤振荡器中红外超短脉冲的产生

基于非线性薛定谔方程建立了氟化物(ZrF₄-BaF₂-LaF₃-AlF₃-NaF, ZBLAN)光纤振荡器中产生中红外超短脉冲的理论模型, 在此基础上研究了中红外超短脉冲在氟化物光纤振荡器中形成的物理机理, 数值模拟了氟化物光纤振荡器中中红外超短脉冲的演化过程. 分析了腔内净色散和小信号增益系数对振荡器中锁模脉冲产生的影响, 并给出了参数设置范围. 研究发现: 当掺Er³⁺氟化物光纤长度, 小信号增益系数, 不饱和损耗为一定值时, 腔内净色散在一定范围内才会出现稳定的锁模脉冲, 且随着腔内净色散增加脉冲宽度变宽, 光谱变窄, 峰值功率降低; 当掺Er³⁺氟化物光纤长度及不饱和损耗一定, 腔内净色散量为合理值, 小信号增益系数在合理的范围时可以得到稳定的锁模脉冲, 且随着小信号增益系数的增加脉冲宽度变宽, 光谱变宽, 峰值功率增加.     

YAG:Pr3+的真空紫外光谱分析及其4f5d能级的研究

用共沉淀法制备出不同掺杂浓度的钇铝石榴石(Y₃Al₅O_{12，YAG)：Pr³⁺粉末.在不同温度下用同步辐射的真空紫外光(VUV)作为激发光 源测量了其发射和激发光谱.对YAG：Pr³⁺被VUV激发后的发光过程进行了分析， 并估算了YAG：Pr³⁺的声子能量、黄昆因子S及Stokes位移.当用170nm光激发样 品时，可能存在自陷激子和通过自陷激子能量传递引发的³P0发射 ，这种跃迁途径不同于用240nm和289nm两个波长激发后的跃迁途径；对Pr³⁺在Y AG中的4f5d能级进行了研究，从而对其4f5d组态有了一个较清晰的认识. 关键词： 3+')" href="#">YAG：Pr³⁺ 同步辐射 4f5d能级 VUV}     

Pr(0.5):ZBLAN的双频激发上转换发光的研究

报道了Pr(0.5):ZBLAN玻璃在双频双光束光源激发下的激发态上转换现象.发现上转换发射谱的荧光与常规荧光发射谱的荧光一致，还发现双频激发下的上转换激发谱有3个明显的谱峰，它们依此对应于788.5nm 1G4→3P2,850.5nm 1G4→1I6和805.0nm 3H6→1D2的激发态吸收跃迁，而大的850.5nm上转换激发谱峰是由大的1G4(Pr3+ )→1I6(Pr3+)跃迁的振子强度f=23.04×10-6所致.这说明起源于1G4能级的激发态吸收上转换尤其1G4(Pr3+)→1I6(Pr3+)     

Power scaling of Tm3+ doped ZBLAN blue upconversion fiber lasers: modeling and experiments

Power scaling of Tm³⁺ doped ZBLAN blue upconversion fiber lasers was investigated by a simple model. Based on our experimental results on blue fiber lasers, we discuss the effects of photodegradation and photocuring, fiber length, the reflectivity of the coupler mirror and fiber core diameter on further enhancement of blue fiber laser, respectively. The optimal parameters (including fiber length, fiber core diameter and the reflectivity of the coupler mirror) for the operation of high power (>1 W) blue fiber laser were presented through simple numerical simulations, which are valuable for the future design of high power blue upconversion fiber laser. PACS 42.55.Wd; 42.60. Lh     

The study of two-color excitation upconversion of Pr(0.5)Yb(3):ZBLAN

The excited state absorption upconversion of Pr(0.5)Yb(3):ZBLAN glass material, under two-color excitation of the 960 nm semiconductor laser and the Xe lamp light simultaneously, is reported in this article. It was found that the upconversion emission spectra of 480.1, 519.0, 601.9 and 631.8 nm coincide with the common emission spectra. Meanwhile, the upconversion-excitation spectrum has three obvious peaks under two-color excitation, and they respectively correspond to the 856.0 nm upconversion excitation transition [¹G₄(Pr³⁺)→¹I₆(Pr³⁺) and ¹G₄(Pr³⁺)→³P₁(Pr³⁺)], the 789.0 nm upconversion excitation transition ¹G₄(Pr³⁺)→³P₂(Pr³⁺), and the 803.7 nm upconversion excitation transition ³H₆(Pr³⁺)→¹D₂(Pr³⁺). The upconversion excitation transition ¹G₄(Pr³⁺)→¹I₆(Pr³⁺) is strong because its oscillator strength f = 23.040×10⁻⁶ is large, which results in a large peak appearing in the upconversion excitation spectrum. That is just the new interesting two-color excitation upconversion luminescence phenomenon of Pr(0.5)Yb(3):ZBLAN induced by one laser and one continuous normal light simultaneously.     

Energy upconversion and spectroscopic studies of ZBLAN:Er3+

A detailed spectroscopic investigation of ZBLAN:Er3+ sample was performed. Infrared to green, red to blue and blue to ultraviolet energy upconversion studies in this material were also performed. When the material was pumped with a 637 nm dye laser upconversion signals at 402 nm, whose efficiency is ~0.04%, were detected. Intensity parameters, transition probabilities, lifetimes and quantum efficiencies are also obtained.     

Efficient 521 nm all-fiber laser: splicing Pr(3+)-doped ZBLAN fiber to end-coated silica fiber

We demonstrated a green all-fiber laser by splicing both ends of a Pr(3+)-doped ZBLAN fiber to silica fibers, whose ends were coated with a dielectric thin film. The output power and the slope efficiency were 322 mW and 53%, respectively, and the coupled pump power of the two blue GaN pump lasers in the silica fiber core was 652 mW. We estimated that the damage threshold of the spliced structure was at least 21 MW/cm2. This splicing technique should be applicable for other wavelengths and glass fibers having low melting temperatures.     

Vacuum ultraviolet 5d14f9-4f10 emission of Ho3+ ions in alkaline-earth fluorides

Time-resolved emission and excitation spectra as well as emission decay kinetics of CaF₂, SrF₂, BaF₂ doped with HoF₃ were investigated. Intensive emission bands near 168 nm, having long decay time, are caused by the spin-forbidden transitions from the 5d¹4f⁹ high-spin states to the ground ⁵I₈ states of Ho³⁺ ions. Weak spin allowed 5d¹4f⁹(low-spin)-4f¹⁰ emission band at 158 nm was observed only in CaF₂–Ho crystals. Spin allowed and spin-forbidden excitation bands were observed near 166 and 155 nm, respectively, in all studied crystals. Fast component of spin-forbidden emissions due to multiphonon relaxation to low-lying 4f¹⁰ Ho³⁺ level also was observed for all crystals.     

温度对于掺杂在SrAl12O19中Pr3+4f5d发射的影响

测量了在真空紫外光激发下,SrAl12O19∶Pr3 在不同温度(308~483 K)时的发射光谱,同时观测到了电偶极禁戒的4f2→4f2和电偶极允许的4f5d→4f2跃迁。随温度升高,4f5d→4f2与1S0发射的相对强度逐渐增强。运用Pr3 4f2组态最高的能级—1S0能级和4f5d组态最低能级间的热平衡模型成功解释了SrAl12O19∶Pr3 发射光谱随温度变化的现象。     

Ultraviolet upconversion in Pr3+:Y2SiO5 crystal by Ar+ laser (488 nm) excitation

Ultraviolet upconversion fluorescence band (260–350 nm) has been observed from Pr³⁺:Y₂SiO₅ pumped by Ar⁺ ion laser (488 nm). Power dependence of the fluorescence emitted from 4f5d, ³P₀ and ¹D₂ were measured. The upconversion mechanism was analyzed using the rate equations with a simplified three level model. It appears that excited state absorption (ESA) is the dominant upconversion process for lower Pr³⁺ concentration and energy transfer upconversion (ETU) is dominant for higher Pr³⁺ concentration.     

基于铒镱共掺光纤光栅光学上转换的实验研究

通过载氢和紫外光曝光在铒镱共掺光纤上制作了光纤光栅,当波长为976.4nm的半导体连续激光泵浦该光栅时,在只有4mW的抽运功率水平下,便可以观察到显著的上转换蓝绿光辐射,随泵浦功率的增加,辐射强度也在增加。通过单色仪和光电倍增管记录到了绿光、蓝光、紫光和紫外等多波长的上转换辐射光。利用显微镜数码相片证实在同种铒镱共掺光纤中没有上转换现象。     

Blue light-emitting-diode-pumped point temperature sensor based on a fluorescence intensity ratio in Pr3+: ZBLAN glass

A fluorescence intensity ratio technique has been applied to Pr³⁺: ZBLAN glass, realising a point temperature sensor. We present data for a blue light emitting diode-pumped prototype which provides accurate and self-referenced measurements.     

Mid-infrared upconversion spectroscopy based on a Yb:fiber femtosecond laser

We present a system for molecular spectroscopy using a broadband mid-infrared laser with near-infrared detection. Difference frequency generation of a Yb:fiber femtosecond laser produced a mid-infrared (MIR) source tunable from 2100–3700 cm⁻¹ (2.7–4.7 μm) with average power up to 40 mW. The MIR spectrum was upconverted to near-infrared wavelengths for broadband detection using a two-dimensional dispersion imaging technique. Absorption measurements were performed over bandwidths of 240 cm⁻¹ (7.2 THz) with 0.048 cm⁻¹ (1.4 GHz) resolution, and absolute frequency scale uncertainty was better than 0.005 cm⁻¹ (150 MHz). The minimum detectable absorption coefficient per spectral element was determined to be 4.4×10⁻⁷ cm⁻¹ from measurements in low pressure CH₄, leading to a projected detection limit of 2 parts-per-billion of methane in pure nitrogen. In a natural atmospheric sample, the methane detection limit was found to be 30 parts-per-billion. The spectral range, resolution, and frequency accuracy of this system show promise for determination of trace concentrations in gas mixtures containing both narrow and broad overlapping spectral features, and we demonstrate this in measurements of air and solvent samples.     

Seven-photon ultraviolet upconversion emission of Er3+ induced by 1,540-nm laser excitation

The multi-photon ultraviolet upconversion emission properties and synergistic effect are investigated in BaSr₂Y₆O₁₂:Er³⁺ phosphor. The deep-ultraviolet emissions centered at 274, 297 and 324-nm are observed under the 1,540-nm excitation, which results from a seven-, six- and six-photon upconversion process, respectively. A synergistic effect is found, which shows that the red emission intensity under 351- and 1,540-nm dual excitation is 4.7 % time stronger than the sum of red emission intensities under the 351 and 1,540-nm single excitation. This phenomenon is attributed to the ⁴I_13/2 and ⁴I_11/2 levels of Er³⁺ from non-radiative transition process under the 351-nm excitation are excited again to ⁴F_9/2 level by absorbing 1,540-nm photon in the 351- and 1,540-nm dual-excitation process.