Diode-pumped Continuous-wave Laser Research Articles

Diode-pumped continuous-wave laser of a self-frequency-doubling Yb:La2CaB10O19 crystal.

We report the first, to the best of our knowledge, laser operation of acentric Yb3+-doped La2CaB10O19 (Yb:LCB) crystal since its discovery in 1998. The polarized absorption and emission cross-section spectra of Yb:LCB were calculated at room temperature. Using a fiber-coupled 976 nm laser diode (LD) as the pump source, we realized effective dual-wavelength laser generation at around 1030 and 1040 nm. The highest slope efficiency of 50.1% was obtained in the Y-cut Yb:LCB crystal. In addition, via resonant cavity design on a phase-matching crystal, a compact self-frequency-doubling (SFD) green laser at 521 nm was also realized in a single Yb:LCB crystal with an output power of 152 mW. These results promote Yb:LCB as a competitive multifunctional laser crystal, especially for highly integrated microchip laser devices ranging from the visible to the near-infrared regime.

Structural disordered orthophosphate crystal Nd3+:YBa3(PO4)3 with cubic symmetry

A novel laser crystal Nd3+-doped yttrium barium phosphate (Nd:YBa3(PO4)3, hereafter Nd:YBP) with disordered crystal structure was reported. Single crystal growth, thermal, spectral and laser performances were investigated. The thermal conductivity at room temperature was found to be 1.35 W·m−1·K−1 and shown an increased tendency with increased temperature. The spontaneous transition probabilities, radiation lifetime and other parameters were evaluated by using the Judd-Ofelt (J-O) theory. The maximum absorption and emission cross sections for Nd:YBP crystal were obtained to be ∼ 2.32 × 10−20 cm2 (@ 804 nm) and 6.72 × 10−20 cm2 (@ 1056 nm), respectively. The measured fluorescence lifetime for Nd:YBP crystal was equal to 351 μs. Furthermore, diode-pumped continuous-wave laser operation was firstly realized near 1060 nm. The slope efficiency was found to be approximately 22% and the maximum output power for Nd:YBP crystal was 256 mW. Results reveal that the disordered crystal Nd:YBP might be further optimized for uses in laser field.

Nd-doped structurally disordered YSr3(PO4)3 single crystal: Growth and laser performances

Disordered-structure crystals have drawn increasing attention as promising ultrashort laser material hosts owing to their broad linewidth. Herein, a novel disordered Nd:YSr3(PO4)3 (Nd:YSP) crystal with good quality was successfully grown via the Czochralski pulling technique. The absorption and fluorescence spectra of the Nd:YSP single crystal were recorded at ambient temperature. The maximum absorption cross section for Nd:YSP single crystal is found to be approximately 3.89 × 10−20 cm2. The stimulated emission cross section for Nd:YSP crystal at ∼1060 nm was determined to be 7.64 × 10−20 cm2 with the full width half maximum value of 22 nm. The fluorescence lifetime of the Nd3+ ions in the Nd:YSP crystal is fitted to be 288 μs. Diode-pumped continuous-wave laser operation is firstly realized at approximately 1060 nm. The maximum output power value from the Nd:YSP crystal is 714 mW, corresponding to a slope efficiency of ∼12.8%. The results indicate that the Nd:YSP crystal with a disordered structure may be a promising disordered laser host.

Laser operation of cleaved single-crystal plates and films of Tm:KY(MoO4)2.

We report on the crystal growth, spectroscopy and first laser operation of a novel double molybdate compound - Tm:KY(MoO4)2. This orthorhombic (sp. gr. Pbna) crystal exhibits strong anisotropy of the spectroscopic properties due to its layered structure. The maximum stimulated emission cross-section for the 3F4 → 3H6 transition is 2.70×10-20 cm2 at 1856nm with a bandwidth of >110 nm (for E || b). The lifetime of the 3F4 state is 2.29 ms. Crystalline films and plates (thickness down to 70 µm) of high optical quality are obtained by mechanical cleavage along the (100) plane. Continuous-wave diode-pumped laser operation is achieved in such thin films and plates yielding a maximum output power of 0.88 W at ∼1.9 µm with a slope efficiency of 65.8% and a linearly polarized laser output. Vibronic lasing is demonstrated at ∼2.06 µm. Tm:KY(MoO4)2 is promising for microchip and thin-disk lasers.

Spectroscopy and diode-pumped continuous-wave laser operation of Tm:Y2O3 transparent ceramic at cryogenic temperatures

We present the spectroscopic and laser characteristics of a 3 at.% Tm:Y2O3 transparent ceramic at cryogenic temperatures. An absorption cross section of 4.7 × 10−21 cm2 with a bandwidth of 0.7 nm centered at 793.3 nm and an emission cross section of 29.0 × 10−21 cm2 centered at 1930.9 nm were estimated at 80 K. Continuous-wave laser operation was achieved using broadband and VBG stabilized laser diodes emitting around 793 nm as pump sources. With the VBG pump diode, a maximum output power of 6.4 W was achieved at 80 K corresponding to a slope efficiency of 52.0% with respect to absorbed power.

Synthesis, characterization, and nonlinear optical properties of some new series ofS-(5-aryl-1,3,4-oxadiazol-2-yl) 2-chloroethanethioate derivatives

In the present investigation, some novel S-(5-aryl-1,3,4-oxadiazol-2-yl)2-chloroethanethioate (3a-3e) derivatives were synthesized and their impact on optical properties was studied. They have also been characterized by elemental analysis and various spectroscopic methods including FTIR, $^{1}$H NMR, $^{13}$C NMR, and UV-Vis techniques. The nonlinear refractive indexes of 3a-3e were also measured in dichloromethane via Z-scan method using a continuous wave diode-pumped laser at 532 nm wavelength. The nonlinear refractive coefficient of compounds was obtained from ${10}^{11}\, \, {m}^{{2}}{/W}$ order. Regarding the appropriate nonlinearity of these compounds, they could be considered good candidates for biooptical and photonic applications. All the synthesized compounds (3a-3e) have also been evaluated for their antimicrobial and antifungal activities. The bioactive assay showed that the synthetic compounds displayed variable inhibition zones against tested bacterium Escherichia coli and fungus Aspergillus fumigatus in comparison to enrofloxacin and amphotericin as reference drugs, which are normally used for treating such infections.

Diode-pumped solid-state laser platform for compact and long-lasting strontium-based optical clocks.

Optical clocks based on strontium (Sr) atoms and ions are currently used to provide precise standards for measuring time. These devices require several narrow-band visible laser sources at specific wavelengths to operate. We report on the diode-pumped continuous-wave laser operation at 674, 688, 689, 698, and 707nm of a single crystal of Pr3+:LiGdF4 (Pr:GLF). To the best of our knowledge, Pr:GLF is the only active medium suitable for solid-state laser operation at all the wavelengths of interest for Sr-based clocks in the deep-red region. We also investigated the spectral tunability of this source, achieving an uninterrupted tuning range of 17nm, between 697 and 714nm.

A optimized diode-pumped continuous-wave laser with novel Nd:GdLaNbO4 mixed crystal

A diode-pumped continuous-wave (CW) laser with a novel Nd:GdLaNbO4 mixed crystal at 1065 nm was demonstrated. The influence of various parameters on CW output performance was investigated theoretically and experimentally, including the transmission of output mirror, the resonance length and the focusing radius of pump light. When the resonator length was 40 mm and the focusing radius of pump light was 256 μm, the maximum output power of 3.06 W was obtained with optimum output mirror transmission of 20% at absorbed pump power of 12.24 W. The corresponding slope efficiency was 29.1%.

Study of linear and nonlinear optical properties of nickel immobilized on acid-activated montmorillonite and copper ferrite nanocomposites

In this paper, the third-order nonlinear optical properties of nickel immobilized on acid-activated montmorillonite (MMT@Ni) and copper ferrite (CuFe2O4@Ni) nanocomposites were investigated. The mentioned nanomaterials were synthesized and then characterized using FT-IR, SEM, EDX, XRD, VSM, and TEM analyses. The nonlinear absorption and refractive coefficients of these nickel nanocomposites were measured by Z-scan technique through a continuous wave diode-pumped laser at 532 nm wavelength. The values of nonlinear absorption and refractive indexes of samples were obtained in order of 10−4m/w and 10−10m2/w, respectively. In addition, the sign of nonlinear refractive index for MMT@Ni and CuFe2O4@Ni was shown to be positive and negative, respectively. It seems that the difference in activities of nanocomposites was relevance to their structural frameworks. Nickel immobilized on acid-activated montmorillonite has layered structure and this provides the possibility to focus the laser beams, and so self-focusing phenomenon was happened. Whereas, nickel immobilized on copper ferrite has inverse spinel structure and this provides the possibility to diverge the laser beams, and so self-defocusing phenomenon was taken place. The results also showed that the values of nonlinearity for solution of CuFe2O4@Ni and MMT@Ni nanoparticles were respectively increased and decreased by rising of the input intensity. In addition, we found that the support of nickel nanoparticles could change the sign of nonlinear optical behavior.

Efficient 1620 nm continuous-wave laser operation of Czochralski grown Er:Yb:Lu2Si2O7 crystal.

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.

Diode-pumped laser performance of Tm:Sc2SiO5 crystal at 1971 nm**Project supported by the Shanghai Municipal Engineering Research Center for Sapphire Crystals, China (Grant No. 14DZ2252500), the Fund of Key Laboratory of Optoelectronic Materials Chemistry and Physics, Chinese Academy of Sciences (Grant No. 2008DP17301), the Fundamental Research Funds for the Central Universities, the National Natural Science Foundation of China and the China

The 4-at.% Tm:Sc2SiO5 (Tm:SSO) crystal is successfully obtained by the Czochralski method. The optical properties and thermal conductivity of the crystal are investigated. The broad continuous wave (CW) laser output of (100)-cut Tm:SSO with the dimensions of 3 mm× 3 mm× 3 mm under laser diode (LD)-pumping is realized. The full width at half maximum (FWHM) of the laser emitting reaches up to 21 nm. The laser threshold of Tm:SSO is measured to be 0.43 W. Efficient diode-pumped CW laser performance of Tm:SSO is demonstrated with a slope efficiency of 25.9% and maximum output power of 934 mW.

Passively Q-Switched Tm:CaYAlO4 Laser Using a MoS2 Saturable Absorber

We report here for the first time on the diode-pumped continuous-wave laser operation of an a-cut Tm:CaYAlO4 (CYAO) crystal in a two-mirror laser configuration at about 1850 nm, which is the shortest laser wavelength ever achieved with this material, with a maximum output power of 0.88 W. Using a MoS2 saturable absorber deposited directly onto the surface of the output coupler, the Tm:CYAO laser is then operated in the Q-switched mode with a maximum output power of 0.49 W and the narrowest pulse width of $0.48~\mu \text{s}$ .

Crystal growth, spectral properties and continuous wave laser operation of new mixed Nd:GdYNbO4 laser crystal

A new mixed laser crystal Nd:Gd0.69Y0.3NbO4 (Nd:GYNO) with high quality was grown successfully by Czochralski method. Its structure parameters are obtained by the X-ray Rietveld refinement method. The effective segregation coefficient of Nd3+ ions is 0.61 in GYNO host. The maximum absorption cross section at 809 nm and peak emission cross section at 1065.6 nm of Nd:GYNO crystal are 11.6 × 10−20 and 20.5 × 10−20 cm2, respectively. The fluorescence lifetime of 4F3/2 manifold for Nd3+ in Nd:GYNO crystal is fitted to be 156 μs. Diode-pumped continuous-wave laser operations at 1.06 μm with Nd:GYNO crystals cut perpendicular to crystallographic a, b, and c axes (denoted as a-, b- c-cut, respectively) were demonstrated. A maximum output power of 0.98 W was obtained with c-cut crystal, corresponding to an optical-to-optical conversion efficiency of 31.3% and a slope efficiency of 30.4%. All these results imply that the Nd:GYNO crystal has great potential application in low and even moderate lasers.

Nd:LYAG and Nd:LGAG Mixed Crystals: Potential Candidates for 1.83 μm Laser Source

We report here, for the first time, diode-pumped continuous-wave laser operation of Nd:LuYAG (LYAG) and Nd:LuGdAG (LGAG) mixed crystals around 1.83 μ m. Cooling the laser samples down to about 6 °C, output powers of about 0.56 and 0.46 W with slope efficiencies of about 5.5% and 5.6% can be achieved, respectively, for the two crystals. These ${\rm{Nd}}^{3+ }{- \rm{doped}}$ garnet mixed crystals, like single crystal Nd:YAG, are believed to be the potential for laser generation at the important 1.83- μ m near-infrared wavelength domain.

Polarized spectroscopic properties and continuous-wave laser operation of Yb:Gd2SiO5 crystal

Yb3+:Gd2SiO5 single crystal with Yb3+ concentration of 6.33 at.% was grown by the Czochralski method. Polarized absorption and fluorescence spectra were measured at room temperature. Intrinsic fluorescence lifetime of the 2F5/2 multiplet was measured to be 0.87 ms when the powder of Yb3+:Gd2SiO5 crystal with low Yb3+ concentration of 0.5 at.% immersed in refractive index-matching fluid was adopted to weaken the influence of radiation trapping and concentration dependent fluorescence quenching. Furthermore, diode-pumped continuous-wave laser around 1090 nm with a slope efficiency of 52% and maximum output power of 1.2 W was demonstrated in the crystal.

Efficient and Compact Diode-Pumped Nd:YAG Lasers at 1073 and 1078 nm

We report on the efficient diode-pumped continuous-wave laser operation of a Nd:YAG crystal at several wavelengths by using a simple and compact two-mirror laser cavity and an undoped YAG thin plate acting as a Fabry-Perot (F-P) etalon. We thus obtain a high-power single-wavelength laser operation at about 1073 nm with a maximum output power of 5.58 W and a laser slope efficiency of about 36.6%, with respect to absorbed pump power, which is believed to be the highest output power ever obtained with Nd:YAG at 1073 nm. We also achieve dual-wavelength laser operation at 1064 and 1078 nm, with a maximum output power of 1.57 W, and triwavelength laser operation at 1061, 1064, and 1078 nm, with a maximum output power of 2.16 W. This is the first demonstration, to the best of our knowledge, of a diode-pumped Nd:YAG laser at 1078 nm.

Diode-Pumped CW Laser Operation of a c-cut Nd:YAlO <sub>3</sub> Crystal on Low-Gain Emission Lines Around 1.1 <inline-formula> <tex-math notation="LaTeX">$\mu\textrm{m}$</tex-math></inline-formula>

We report on the diode-pumped continuous-wave laser operation of a c-cut Nd:YAlO 3 (YAP) laser crystal at various low gain emission wavelengths around 1.1 μm by using a simple and compact linear cavity and a glass etalon. Inserting and tilting the etalon in a particular position, single-wavelength operation at 1099 nm is achieved first, at low pump power, with a maximum output power value of 0.15 W. Then, increasing the pump power leads to dual-wavelength operation at 1079 and 1099 nm with a maximum output power value of 2.28 W and a laser slope efficiency value of about 20%. Further tilting the etalon, dual- and single-wavelength laser operations could be achieved, for the first time to our knowledge, at 1090 and 1106 nm. Single-wavelength laser operations at 1106 and 1090 nm are obtained with maximum output power values of 0.25 and 1.44 W, respectively, and simultaneous dual-wavelength lasing could be obtained with a maximum output power value of 1.89 W and a laser slope efficiency value of nearly 18%.

Spectroscopic properties and continuous-wave laser operation of Yb:Bi₄ Si₃ O₁₂ crystal.

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.

Crystal growth of CW diode-pumped (Er3+,Yb3+):GdAl3(BO3)4 laser material

Phase relationships in the Er:YbxGd1−xAl3(BO3)4–K2Mo3O10–B2O3–(Gd,Er,Yb)2O3 (x=0–0.2, Er-1at%) system were studied in the temperature range from 1150 to 900°С. Multicomponent melts of 55mol%K2Mo3O10–45mol% B2O3 (I) and 55mol% K2Mo3O10–40mol% B2O3–5mol% (Gd,Er,Yb)2O3 (II) were suggested as reasonable fluxes for high-temperature solution growth of (Yb3+,Er3+):GdAl3(BO3)4 single crystals. Yb0.15Gd0.85Al3(BO3)4 solubility in the complex flux of II composition has been found as varying from 17 to 9.5mol% with decreasing temperature in the interval of 1000–800°C. As a result, (Er,Yb):GdAB single crystals with high optical quality and sizes up to 20×10×10mm were grown on dipped “point” seeds. Absorption and stimulated emission spectra, emission lifetimes, and efficiencies of energy transfer from Yb3+ to Er3+ ions were determined. Highly efficient continuous-wave diode-pumped laser operation of (Er,Yb):GdAl3(BO3)4 crystal was realized.

Highly efficient continuous-wave diode-pumped Er, Yb:GdAl_3(BO_3)_4 laser

We report the highly efficient continuous-wave diode-pumped laser operation of Er, Yb:GdAl3(BO3)4 crystal. Absorption and stimulated emission spectra, emission lifetimes, and efficiencies of energy transfer from Yb3+ to Er3+ ions were determined. A maximal output power of 780 mW was obtained at 1531 nm at absorbed pump power of 4 W with slope efficiency of 26%.