Diode-pumped Laser Operation Research Articles

Diode-Pumped Tunable Continuous Wave Laser Operation In Yb: NaY(WO4)2 Crystal

Diode-Pumped Tunable Continuous Wave Laser Operation In Yb: NaY(WO4)2 Crystal

Luminescence properties of Pr3+ doped Bi4Ge3O12 crystal fibers grown by the micro-pulling down technique

The luminescence properties of 0.5%Pr-doped BGO crystals grown by using the micro-pulling down technique were carefully investigated. Room temperature absorption spectra were registered and analyzed within the framework of the Judd-Ofelt formalism and the best fit to the data is obtained by using a modified treatment allowing for the admixture of intensity enabling wave-functions. The results indicate 3P0 and 1D2 radiative lifetimes of about 5.7 μs and 79 μs, in perfect agreement with the time-constants derived from the measured fluorescence decays at room and liquid-nitrogen temperatures. Registration of time-resolved emission and excitation spectra and calibration of the 3P0 emission spectrum in cross section unit clearly indicate that Pr-doped BGO could be the first isotropic crystalline material leading to efficient diode-pumped laser operation at room temperature with laser performances, at least in the deep-red spectral region, comparable to that found with the most important anisotropic Pr-doped fluoride and oxide crystals.

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.

Spectroscopy and diode-pumped laser operation of transparent Tm:Lu3Al5O12 ceramics produced by solid-state sintering.

A transparent Tm:Lu3Al5O12 ceramic is fabricated by solid-state reactive sintering at 1830 °C for 30 h using commercial α-Al2O3 and Lu2O3/Tm2O3 powders and sintering aids - MgO and TEOS. The ceramic belongs to the cubic system and exhibits a close-packed structure (mean grain size: 21 µm). The in-line transmission at ∼1 µm is 82.6%, close to the theoretical limit. The spectroscopic properties of the ceramic are studied in detail. The maximum stimulated-emission cross-section is 2.37×10-21 cm2 at 1749nm and the radiative lifetime of the 3F4 state is about 10 ms. The modified Judd-Ofelt theory accounting for configuration interaction is applied to determine the transition probabilities of Tm3+, yielding the intensity parameters Ω2 = 2.507, Ω4 = 1.236, Ω6 = 1.340 [10-20 cm2] and α = 0.196×10-4 cm. The effect of excited configurations on lower-lying interconnected states with the same J quantum number is discussed. First laser operation is achieved under diode-pumping at 792 nm. A 4 at.% Tm:Lu3Al5O12 ceramic laser generated 3.12 W at 2022-2035nm with a slope efficiency of 60.2%. The ceramic is promising for multi-watt lasers at >2 µm.

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.

Growth, spectroscopy and diode-pumped laser operation of acentric Yb:KGd(PO3)4 crystal

Growth, spectroscopy and diode-pumped laser operation of acentric Yb:KGd(PO₃)₄ crystal

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.

Spectroscopy and diode-pumped laser operation of Pr:LaMgAl11O19 crystal

We report on the growth, spectroscopic properties and visible laser operation of Pr3+-doped LaMgAl11O19 (LMA) crystal. The absorption and emission spectra were recorded in visible wavelength range and the decay time of 3P0 manifold was measured to be about 34.5 μs at room temperature. Using an InGaN laser diode as pump source, continuous-wave laser operation of Pr:LMA crystal have also been demonstrated in red at about 645 nm and deep red at about 725 nm, which provide new linearly polarized sources for various potential applications.

Growth, spectral properties, and diode-pumped laser operation of a Nd3+-doped LaMgAl11O19 crystal.

A Nd3+-doped LaMgAl11O19 (Nd:LMA) crystal was grown by the Czochralski method. Room temperature polarized absorption spectra, fluorescence spectra, and fluorescence lifetime of the Nd:LMA crystal were measured and analyzed. The Judd-Ofelt parameters Ω2,4,6 were calculated to be 1.21×10-20, 3.63×10-20, and 2.35×10-20 cm2, respectively. The absorption and emission cross sections were calculated. Using a 790-nm diode laser as pump source, continuous-wave laser operation of an a-cut Nd:LMA crystal has been demonstrated with a maximum output power of 1.71W and slope efficiency of 40.4% for a 1055nm laser. Low-gain laser operation at 1082nm is also realized with a maximum output power of 1.46W and slope efficiency of 34.5%.

Spectroscopy and microchip laser operation of Tm, Ho:KYW crystals with different Ho concentrations

The spectroscopic properties of Tm, Ho:KYW crystals with different Ho concentrations were investigated. The diode-pumped microchip laser operation of Tm (5 at.%), Ho (0.5 at.%):KYW and Tm (5 at.%), Ho (1 at.%):KYW was demonstrated. The highest, to our knowledge, output power of 480 mW with slope efficiency of 31% for CW Tm (5 at.%), Ho (0.5 at.%):KYW microchip laser was obtained.

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 $0.48~\mu \text{s}$ .

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.

Diode-pumped laser operation of Pr3+:Ba(Y0.8Lu0.2)2F8 in the visible region.

We report on, to the best of our knowledge, the first growth, spectroscopy, and laser operation of monocrystalline Ba(Y0.8Lu0.2)2F8 doped with 1.25at.% of Pr3+ ions (Pr:BYLF). We studied the spectroscopic properties of this material, particularly in comparison with its isomorph Pr3+: BaY2F8 (Pr:BYF). Under diode-pumped excitation, we achieved continuous-wave laser operation in the orange, red, and deep red regions in the three possible crystal orientations. We obtained considerably improved laser performances and remarkably low passive losses, in comparison with Pr:BYF crystals and other fluorides, indicating that Pr:BYLF is an excellent host material in the visible region.

Growth, spectroscopy and lasing of the Yb-doped monoclinic Gd2SiO5 in the prospect of hydrogen laser cooling with Lyman-α radiation

We have grown good optical quality 10% Yb-doped Gd2SiO5 monocrystal by the Czochralski technique. The Yb segregation coefficient was measured to be 0.747. In agreement with the monoclinic symmetry of the host, the Yb fluorescence extrema were found to deviate from the Nm and Ng principal axes and a fourth spectroscopic parameter representing the rotation of the fluorescence distribution was introduced for a full description. Diode pumped laser operation at Brewster incidence was demonstrated to be significantly more efficient if the lasing propagation corresponds to the maximum fluorescence inside the crystal. We obtained a laser emission tunable between 1079 and 1100 nm, showing that our crystal is the best choice for the application to the production of QCW Lyman-α radiation by resonant four-wave-mixing in mercury vapor.

Diode-Pumped 1178-nm High-Power Yb-Doped Fiber Laser Operating at 125 C

We demonstrate a high-power Yb-doped fiber laser operating at 1178 nm based on commercial silica double-cladding fiber and laser diode (LD) pumping regime at 976 nm. It is experimentally proved that heating the active fiber is an efficient way to suppress amplified spontaneous emission (ASE) and to increase the parasitic lasing threshold in long-wavelength Yb-doped fiber lasers. By adopting output coupling fiber Bragg grating (OC FBG) with high reflectivity and heating the Yb-doped fiber to 125 $^{\circ}\text{C}$ , a record output power of 31 W is obtained, and the corresponding slope efficiency is $\sim$ 44% with respect to the pump power. To the best of our knowledge, it is the highest output power of Yb-doped fiber lasers, which adopt commercial double-cladding active fiber and operate in the range beyond 1160 nm. Furthermore, it is first experimentally proved that the parasitic lasing threshold is related to the power of the backward ASE and the length of the active fiber.

Peculiarities of Forming Single-Frequency Generation in a Monopulse YAG:Nd-Laser with Transverse Diode Pumping and Injection of Narrow-Band Radiation

The features of forming output radiation in a powerful monopulse single-frequency side diode-pumped laser operating in external narrow-band signal seeding mode were investigated. The monopulse single-frequency laser was fabricated of a YAG:Nd active element excited by three laser diode matrices. A compact continuous-wave YAG:Nd-laser with longitudinal diode pumping served as the seeding laser. It was shown experimentally that the transition of the monopulse laser from multimode to single-frequency lasing with a spectral line width of about 54 MHz (0.2 pm) occurs at seeding-laser radiation power P th ≈ 0.14 mW (radiation intensity of 1.8·10–2 W/cm2). Increasing the seeding-laser power over P th does not lead to a noticeable change of the output characteristics of the monopulse laser for a given pump level (above the threshold). If the pump power varies from 1.5 to 3.0 kW, the P th value is not changed but the energy of the output pulses of single-frequency monopulse generation increases to 40 MJ. The low level of the external narrow-band seeding signal allows us to consider the single-frequency low-power semiconductor laser as a promising source of the seeding signal.