Showing papers on "Slope efficiency published in 2002"
TL;DR: In this paper, the optical properties of the monoclinic crystal of the ytterbium transition have been characterized and the optical anisotropy of the material has been characterized.
Abstract: We present our recent achievements in the growing and optical characterization of $\mathrm{KYb}({\mathrm{WO}}_{4}{)}_{2}$ (hereafter KYbW) crystals and demonstrate laser operation in this stoichiometric material. Single crystals of KYbW with optimal crystalline quality have been grown by the top-seeded-solution growth slow-cooling method. The optical anisotropy of this monoclinic crystal has been characterized, locating the tensor of the optical indicatrix and measuring the dispersion of the principal values of the refractive indices as well as the thermo-optic coefficients. Sellmeier equations have been constructed valid in the visible and near-IR spectral range. Raman scattering has been used to determine the phonon energies of KYbW and a simple physical model is applied for classification of the lattice vibration modes. Spectroscopic studies (absorption and emission measurements at room and low temperature) have been carried out in the spectral region near $1 \ensuremath{\mu}\mathrm{m}$ characteristic for the ytterbium transition. Energy positions of the Stark sublevels of the ground and the excited state manifolds have been determined and the vibronic substructure has been identified. The intrinsic lifetime of the upper laser level has been measured taking care to suppress the effect of reabsorption and the intrinsic quantum efficiency has been estimated. Lasing has been demonstrated near 1074 nm with $41%$ slope efficiency at room temperature using a 0.5 mm thin plate of KYbW. This laser material holds great promise for diode pumped high-power lasers, thin disk and waveguide designs as well as for ultrashort (ps/fs) pulse laser systems.
200 citations
TL;DR: In this article, a diode pumped Nd:GdVO4 ground-state laser at 912 nm with a maximum cw output power of nearly 2.1 W at 16.7 W pump power was presented.
168 citations
TL;DR: In this paper, a new solid-state laser based on Yb3+-doped highly transparent nanocrystalline yttria (Y2O3) ceramics was developed.
Abstract: A new solid-state laser based on Yb3+-doped highly transparent nanocrystalline yttria (Y2O3) ceramics was developed. At room temperature and under a pump power of 2.63 W from a single InGaAs laser diode at ≈ 0.94 µm, a continuous-wave laser output of 0.47 W at 1.077 µm wavelength was obtained corresponding to a slope efficiency of about 32%. Some main spectroscopic properties of Yb3+:Y2O3 ceramics were also investigated.
119 citations
TL;DR: A continuous-wave, room-temperature Cr(2+) ZnS laser that is compact and tunable over 700 nm that is intrinsically polarized and sensitization of the output radiation by a few milliwatts of the visible and near-infrared radiation.
Abstract: We report the development of a continuous-wave, room-temperature Cr2+:ZnS laser that is compact and tunable over 700 nm. The laser is pumped by a diode-pumped Er-fiber laser and generates 0.7 W of linearly polarized radiation at 2.35 µm, at up to 40% slope efficiency. Cr2+:ZnS directly diode-pumped at 1.6 µm yields polarized radiation that is tunable over 400 nm at up to 25 mW of output power. A comparison of Cr2+:ZnS with Cr:ZnSe (70 mW, 350 nm) in a similar setup is given. As opposed to Cr:ZnSe, the Cr:ZnS laser is intrinsically polarized. Finally, we observe sensitization of the output radiation by a few milliwatts of the visible (470–500-nm) and near-infrared (740–770-nm) radiation.
114 citations
Journal Article•
TL;DR: In this paper, a simple design rule for diode-laser pumped quasi-three-level laser by using the M/sup 2/factor was presented, and the validity of this model was demonstrated by diodepumped Yb:YAG laser experiments.
Abstract: We present a simple design rule for diode-laser pumped quasi-three-level lasers by using the M/sup 2/ factor. The validity of this model was demonstrated by diode-pumped Yb:YAG laser experiments. The maximum output power of 1.33 W and optical slope efficiency of 63% were obtained in a 400-/spl mu/m Yb:YAG chip miniature laser. Using a 200-/spl mu/m Yb:YAG chip, a 70% optical slope efficiency was reached. In a coupled-cavity configuration, with a quartz birefringent tuning filter, 8.2 THz (29 nm) of tuning was obtained at room temperature. By changing to a calcite birefringent filter, single-axial-mode oscillation with an output power of 500 mW was observed.
100 citations
TL;DR: In this paper, laser emission at 2.8 μm in Er3+:CaF2 crystals is analyzed for different excitation pump wavelengths: 800, 968 and 1545 nm.
98 citations
TL;DR: In this paper, the authors performed a detailed analysis of the population mechanisms and the characteristics of the output from Er/sup 3+/-singly-doped and Pr/sup3+/-codoped ZBLAN fiber lasers operating at 3 /spl mu/m, for various Er/Sup 3+// concentrations and pump powers.
Abstract: Based on recently published spectroscopic measurements of the relevant energy-transfer parameters, we performed a detailed analysis of the population mechanisms and the characteristics of the output from Er/sup 3+/-singly-doped and Er/sup 3+/, Pr/sup 3+/-codoped ZBLAN fiber lasers operating at 3 /spl mu/m, for various Er/sup 3+/ concentrations and pump powers. Whereas both approaches resulted in similar laser performance at Er/sup 3+/ concentrations <4 mol.% and pump powers <10 W absorbed, it is theoretically shown here that the Er/sup 3+/-singly-doped system will be advantageous for higher Er/sup 3+/ concentrations and pump powers. In this case, energy recycling by energy-transfer upconversion from the lower to the upper laser level can increase the slope efficiency to values greater than the Stokes efficiency, as is associated with a number of Er/sup 3+/-doped crystal lasers. Output powers at 3 /spl mu/m on the order of 10 W are predicted.
90 citations
TL;DR: The 885-nm Ti:Sapphire pumping into the emitting level 4F3/2 of Nd:YAG produces a highly efficient (0.68 slope efficiency in absorbed power) 946-nm laser emission; a strong reduction of heat generation could also be also obtained.
Abstract: The 885-nm Ti:Sapphire pumping into the emitting level 4F3/2 of Nd:YAG produces a highly efficient (0.68 slope efficiency in absorbed power) 946-nm laser emission; a strong reduction of heat generation could be also obtained.
78 citations
TL;DR: In this article, the first time laser operation with the monoclinic stoichiometric crystal KYb(WO4)2 (hereafter KYbW) has been demonstrated.
Abstract: We demonstrate for the first time laser operation with the monoclinic stoichiometric crystal KYb(WO4)2 (hereafter KYbW). Lasing on the 2
F
5/2
?2
F
7/2
transition of Yb3+ at room temperature has been achieved near 1074 nm with >41% slope efficiency (>26% maximum conversion efficiency) using a 0.5-mm-thick plate of KYbW. This new laser material holds great promise for diode-pumped high-power lasers, thin-disk and waveguide designs as well as for ultrashort (ps/fs) pulse laser systems.
77 citations
TL;DR: In this article, the authors experimentally found that in a random laser based on Nd0.5 La 0.5 Al 3 (BO 3 ) 4 scattering ceramic, the threshold pumping density decreases and the output slope efficiency increases with the increase of the diameter of the pumped spot.
76 citations
TL;DR: In this article, a thin plate of Cr:ZnS was used as a saturable absorber for passive Q-switched operation of Yb,Tm:KY(WO4)2 and Tm:KW(WOW) diode pumped at 805 nm, achieving a maximum average output power of 116 mW emitted at 1.9 μm.
Abstract: Passively Q-switched operation of Yb,Tm:KY(WO4)2 and Tm:KY(WO4)2 lasers diode pumped at 805 nm has been investigated. A thin plate of Cr:ZnS was used as a saturable absorber for passive Q switching. A maximum average output power of 116 mW emitted at 1.9 μm in comparison to 160 mW for the free-running regime at the same pumping level has been obtained with a slope efficiency of 26% with respect to the incident pump power. Using a Tm:KYW sample with broadband antireflection coatings and dichroic laser resonator mirror, the first Stokes component of Raman self-frequency conversion was observed at 2365 nm.
TL;DR: Stimulated and spontaneous Brillouin scattering effects are investigated in the HF, and it is shown that the high lasing threshold is due mainly to reduction of the effective gain coefficient caused by structural nonuniformity along the fiber length.
Abstract: We demonstrate for what is believed to be the first time a Brillouin laser based on a holey fiber (HF). Using a simple Fabry-Perot resonator scheme containing a 73.5m long highly nonlinear HF with an effective area of 2.85µm2, we obtain a threshold of 125mW and a slope efficiency of ~70%. Stimulated and spontaneous Brillouin scattering effects are investigated in the HF, and we show that the high lasing threshold is due mainly to reduction of the effective gain coefficient caused by structural nonuniformity along the fiber length.
TL;DR: In this article, a new laser medium for diode pumped solid state laser applications operating around 1.9 to 2.0 μm has been investigated and the main laser characteristics are presented.
Abstract: A new laser medium – Yb,Tm:KY(WO4)2 – for diode pumped solid state laser applications operating around 1.9 to 2.0 μm has been investigated and the main laser characteristics are presented. Diode pumping at 981 nm and around 805 nm was realised. For 981-nm pumping, the excitation occurs into Yb3+ ions followed by an energy transfer to Tm3+ions. A slope efficiency of 19% was realised. For pumping around 805 nm, the excitation occurs directly into the Tm3+ ions. Here a maximum slope efficiency of 52%, an optical efficiency of 40%, and output powers of more than 1 W were realised. Using a birefringent quartz plate as an intracavity tuning element, the tunability of the Yb,Tm:KY(WO4)2 laser in the spectral range of 1.85–2.0 μm has been demonstrated. The possibility of laser operation in a microchip cavity configuration for this material has also been shown.
TL;DR: In this article, a diode-pumped, intracavity-doubled Nd:YVO4 laser, generating as much as 760 mW of power at 671 nm, which was used to efficiently pump a Cr:LiSAF laser, was described.
Abstract: A diode-pumped, intracavity-doubled Nd:YVO4 laser, generating as much as 760 mW of power at 671 nm, which was used to efficiently pump a Cr:LiSAF laser, is described. A slope efficiency of ≈39% with maximum continuous-wave output power of >180 mW was achieved with this system. Experiments in tunability and generation of ultrashort pulses are also reported.
TL;DR: In this article, a Nd:YVO4 laser, end-pumped by a fiber-coupled diode-laser array, generates 7.3 W of output power at 1342 nm, the highest so far reported for this host crystal.
Abstract: A Nd:YVO4 laser, end-pumped by a fiber-coupled diode-laser array, generates 7.3 W of output power at 1342 nm, the highest so far reported for this host crystal. The slope efficiency is 40% and the output-beam divergence is close to the diffraction limit. An important point in attaining such results is the choice of crystals with low Nd concentration.
TL;DR: In this paper, a mid-infrared broadly tunable around 2.5 μm room-temperature continuous-wave diode-pumped Cr:ZnSe laser is reported.
Abstract: A midinfrared broadly tunable around 2.5 μm room-temperature continuous-wave diode-pumped Cr:ZnSe laser is reported. The laser is tunable over 350 nm and delivers up to 70 mW of the output radiation at 460 mW of the absorbed pump power and 17.5% slope efficiency. We observe the analog of the optical switching process, where the laser output is strongly modulated by only a few milliwatts of the visible radiation.
TL;DR: In this paper, an Er:Yb codoped phosphate glass microchip laser has been studied under pumping with a Ti:sapphire laser ranging from 945 to 990 nm.
TL;DR: In this article, the authors reported the first continuous-wave tunable over ∼280 nm around 2.3 μm room-temperature operation of a chemical vapor transport-grown and diffusion-doped Cr2+:ZnS laser, pumped by a Co:MgF2 laser at 1.67 μm and generating over 100 mW of output power at 16% slope efficiency.
Abstract: We report the first continuous-wave tunable over ∼280 nm around 2.3 μm room-temperature operation of a chemical vapor transport-grown and diffusion-doped Cr2+:ZnS laser, pumped by a Co:MgF2 laser at 1.67 μm and generating over 100 mW of output power at 16% slope efficiency. The self-consistent results of the laser and spectroscopic analysis demonstrate a large potential of this crystal as an active medium for diode-pumped tunable mid-infrared sources.
TL;DR: In this article, the authors report on a recent development of diluted nitride laser diodes operating at the wavelengths around 1.3 /spl mu/m, with a threshold current density as low as 563 A/cm/sup 2, slope efficiency of 0.2 W/A per facet, light power up to 40mW continuous wave, and characteristic temperature of 97-133 K.
Abstract: In this letter, we report on a recent development of diluted nitride laser diodes operating at the wavelengths around 1.3 /spl mu/m. The lasers grown by molecular beam epitaxy and processed into 20-/spl mu/m-wide ridge waveguide structures, mounted episides up on subcarriers, exhibit a threshold current density as low as 563 A/cm/sup 2/, slope efficiency of 0.2 W/A per facet, light power up to 40-mW continuous-wave, and characteristic temperature of 97-133 K.
TL;DR: Efficient diode pumping at wavelengths of 1.9 and 2.0microm of a Cr(2+): ZnSe laser with an output power of 105 mW and a slope efficiency of 35% with respect to the absorbed pump power is presented.
Abstract: Efficient diode pumping at wavelengths of 1.9 and 2.0 µm of a Cr2+:ZnSe laser with an output power of 105 mW and a slope efficiency of 35% with respect to the absorbed pump power is presented. In addition, Cr2+:CdMnTe has been laser diode pumped as well as operated in the continuous-wave regime, to the best of our knowledge for the first time.
TL;DR: In this article, a distributed Bragg reflector (DBR) waveguide laser array using an Ag film ion exchange technique was demonstrated, achieving an output power of 11 mW at 1540 nm for a coupled pump power of 145 mW.
Abstract: We demonstrate a distributed Bragg reflector (DBR) waveguide laser array by using an Ag film ion-exchange technique. We achieve an output power of 11 mW at 1540 nm for a coupled pump power of 145 mW, with a threshold of 60 mW and slope efficiency of 13%. The thin film ion exchange produces the highest index change possible at the surface, due to the ion exchange technique. Hence a wide array of wavelengths can be implemented in a single chip. We demonstrate a lasing wavelength range of 2.1 nm (1548.6 to 1550.7 nm) in an array with a single grating. Since the index change due to our process is large, we can fine tune the wavelengths of the array to fall on International Telecommunication Union (ITU) grid wavelengths by annealing. We demonstrate fine tuning of the wavelength for a channel from 1540.2 to 1540 nm, ITU specified wavelength, by annealing.
TL;DR: In this paper, the optical and laser properties of Cr2+-doped cadmium chalcogenides (CdTe) were investigated and the authors reported the first demonstration of pulsed-laser operation with a free-running spectrum centered at 2,535 nm.
Abstract: We are engaged in a systematic study of the optical and laser properties of Cr2+-doped cadmium chalcogenides. Previously, we demonstrated quasi-continuous wave lasing from Cr2+-doped Cd0.55Mn0.45Te with slope efficiencies as high as 64% and a laser tuning range from 2,170-3,010 nm. In this paper, we report the first demonstration of lasing from Cr:CdTe at room temperature. Pulsed-laser operation was obtained with a free-running spectrum centered at 2,535 nm. The slope efficiency of the laser was low (∼1%) because of large parasitic losses at the laser wavelength. The spectroscopic properties of Cr:CdTe are favorable for laser applications because of a large emission cross section (∼2.5 × 10-18 cm2) and a high emission-quantum yield (∼88%). In addition, CdTe can easily incorporate Cr ions either through melt growth or diffusion doping. Along with our results on Cr2+:CdTe, we report on the optical properties of several other Cr2+-doped II-VI semiconductors (ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, Cd0.9Zn0.1Te, Cd0.65Mg0.35Te, Cd0.85Mn0.15Te, and Cd0.55Mn0.45Te) and compare them for applications as solid-state laser materials.
TL;DR: In this paper, low-temperature absorption and fluorescence spectra of the Yb 3+ ions were measured in phosphate glass with compositions of (60-65)P 2 O 5 -(4-8)B 2 O 3 -(5-10)Al 2 O3 -(10-15)K 2 O-(5−10)BaO-(0-2)La 2O 3 -0−2)Nb 2 O5 -4−8)
Abstract: Low-temperature absorption and fluorescence spectra of the Yb 3+ ions were measured in phosphate glass with compositions of (60–65)P 2 O 5 –(4–8)B 2 O 3 –(5–10)Al 2 O 3 –(10–15)K 2 O–(5–10)BaO–(0–2)La 2 O 3 –(0–2)Nb 2 O 5 –(4–8)Yb 2 O 3 (mol%). Temperature dependence of lifetime of Yb 3+ : 2 F 5/2 level was investigated. Laser performance of sample pumped by 940 nm laser diode at low temperature were presented. At 8 K, laser oscillation of diode pumped Yb 3+ : phosphate glass yielded a slope efficiency of 4% and a maximum power of 2 mW, the peak laser wavelength is 1001 nm.
TL;DR: In this article, the authors developed a waveguide laser source in a neodymium-doped chalcogenide (Ga:La:S) glass, where the channel waveguide structures were directly written via above band gap illumination provided by a focused UV-laser beam with fluencies 1.5-150 J/cm2.
Abstract: We report the development of a waveguide laser source in a neodymium-doped chalcogenide (Ga:La:S) glass. Channel waveguide structures were directly written via above band gap (=244 nm) illumination provided by a focused UV-laser beam with fluencies 1.5–150 J/cm2. Effects of photoinduced material modification in the form of surface compaction and photodensification were evident. Characterization revealed a low threshold waveguide laser with emission at 1075 nm and slope efficiency of 17%. The active device was spatially single mode and exhibited laser operation with 8.6 mW peak power and attenuation <0.5 dB cm–1.
TL;DR: Continuous-wave passive mode locking of a diode-pumped Nd:KGd(WO(4)(4))(2) laser is demonstrated and the use of a saturable Bragg reflector as the mode-locking element permits the generation of 6.3-ps pulses.
Abstract: Continuous-wave passive mode locking of a diode-pumped Nd:KGdWO42 laser is demonstrated. The use of a saturable Bragg reflector as the mode-locking element permits the generation of 6.3-ps pulses, assuming a sech2 pulse shape. An output power of 1 W was obtained, which corresponds to a slope efficiency of 34.5%.
TL;DR: In this paper, the authors developed 405 nm high-power laser diodes suitable for use in Blu-ray Disk systems, the next generation of large-capacity optical recording systems.
Abstract: The authors have developed 405 nm high-power laser diodes suitable for use in Blu-ray Disk systems, the next generation of large-capacity optical recording systems. Epitaxial lateral overgrowth was refined considering the spatial distribution of dislocation density in the lateral growth region to achieve satisfactory lifetimes. Improvements in the threshold/operating current, slope efficiency and characteristic temperature are discussed, in particular with respect to the effect of the location of an AlGaN electron-blocking layer.
TL;DR: In this paper, the authors presented a spectroscopic analysis and laser characterization of uniform channel waveguides in neodymium-doped gallium lanthanum sulphide (Nd/sup 3+/-Ga:La:S) chalcogenide glass.
Abstract: We present a spectroscopic analysis and laser characterization of optically written waveguides in neodymium-doped gallium lanthanum sulphide (Nd/sup 3+/-Ga:La:S) chalcogenide glass. Uniform channel waveguides were fabricated in Nd/sup 3+/-Ga:La:S by exposure to radiation from a focused UV-laser beam (/spl lambda/=244 nm), producing a refractive index change /spl utri/n/spl ap/+10/sup -3/. The observed laser performance and fluorescence decay were in good agreement with values calculated from a spectroscopic analysis of 85 /spl mu/s for the /sup 4/F/sub 3/2/ lifetime and 5.9/spl times/10/sup -20/ cm/sup 2/ for the emission cross section at 1075 nm. Low threshold laser operation with emission at 1075 nm and a slope efficiency of 17% is demonstrated. The active device is spatially single mode and exhibits up to 8.6 mW of output power and propagation losses of <0.5 dBcm/sup -1/. Waveguide fabrication, photoinduced effects, and optical characterization in terms of spectroscopy, laser performance, and device attenuation are discussed.
TL;DR: In this paper, a plane wave model has been developed to describe the dynamic behavior of end-pumped CW quasi-three-level laser oscillators, and the authors derived algebraic equations and analytic expressions from a set of coupled rate equations.
Abstract: A plane wave model has been developed to describe the dynamic behavior of end-pumped CW quasi-three-level lasers. We have derived algebraic equations and analytic expressions from a set of coupled rate equations. The analytic expression predicts that characteristics of a laser are affected not only by the Boltzmann occupation factor of the pump states, but also by that of the laser states. To illustrate the utility of the model, an end-pumped Yb:YAG laser oscillator was investigated and optimized. We have examined the threshold value of the pump beam, pump beam depletion in the gain medium, optimal crystal length, and laser output power for a given pump power. Finally, we have shown the pump and laser intensities and the population of each manifold as a function of crystal length.
TL;DR: In this paper, a detailed approach has been developed, whereby the individual performances of the emitters comprising a laser bar are assessed separately as part of a larger coupled system, where degradation of the emitter performances is only observed when the local packaging-induced strain is above a certain critical value.
Abstract: A new detailed approach has been developed, whereby the individual performances of the emitters comprising a laser bar are assessed separately as part of a larger coupled system. The results reveal the existence of a strain threshold, wherefore degradation of the emitter performances is only observed when the local packaging-induced strain is above a certain critical value. This degradation which occurs after aging, is manifested in an increase in the "apparent" threshold current and a decrease in the "apparent" slope efficiency of the individual emitters. This degradation is also revealed by the presence of facet defects as previously reported. These results suggest that measurement and control of packaging-induced strain will allow significant improvement in the degradation behavior of high-power AlGaAs laser bars.
TL;DR: In this article, the authors reported efficient laser operation at 1.5-1.6 /spl mu/m in an Er,Yb:YCOB laser with a slope efficiency of 20%.
Abstract: We report efficient laser operation at 1.5-1.6 /spl mu/m in an Er,Yb:YCOB laser. The maximum output power of 110 mW was achieved in a hemispherical cavity with a slope efficiency of 20%. We also report 100 mW of output in a flat-flat cavity configuration, and the first report of operation of this type of laser crystal in a true microchip arrangement with >10-mW output.