Showing papers on "Slope efficiency published in 1994"
TL;DR: It is shown that in this regime the laser undergoes a transition from a linear (amplifier) behavior to a nonlinear (oscillatory) behavior at the proposed threshold pump rate, and the photon recycling resulting from the high spontaneous emission coupling efficiency and high absorption may result in lasing without population inversion.
Abstract: We propose that the threshold of a laser is more appropriately described by the pump power (or current) needed to bring the mean cavity photon number to unity, rather than the conventional ``definition'' that it is the pump power at which the optical gain equals the cavity loss. In general the two definitions agree to within a factor of 2, but in a class of microcavity lasers with high spontaneous emission coupling efficiency and high absorption loss, the definitions may differ by several orders of magnitude. We show that in this regime the laser undergoes a transition from a linear (amplifier) behavior to a nonlinear (oscillatory) behavior at our proposed threshold pump rate. The photon recycling resulting from the high spontaneous emission coupling efficiency and high absorption may in this case result in lasing without population inversion, and coherent light is generated via ``loss saturation'' instead of gain saturation. This mechanism for lasing without inversion is very different from lasing without inversion using a radiation trapped state.
218 citations
TL;DR: In this article, a 1.3 /spl mu/m InGaAsP/InGaAsp multiple-quantum-well (MQW) BH Fabry-Perot laser diode was integrated with a MQW tapered thickness waveguide.
Abstract: We propose and demonstrate a novel 1.3 /spl mu/m InGaAsP/InGaAsP multiple-quantum-well (MQW) BH Fabry-Perot laser diode monolithically integrated with a MQW tapered thickness waveguide. A selective area growth (SAG) technique is used to fabricate the tapered thickness waveguide with low absorption loss and to integrate it with the MQW gain region with a high coupling efficiency. We achieve very narrow vertical and lateral far-field FWHM of 11.8/spl deg/ and 8.0/spl deg/, with low threshold current of 19 mA and high slope efficiency of 0.25 mW/mA. >
115 citations
TL;DR: In this paper, spectroscopic properties and laser performance of Czochralski-grown LaSc/sub 3/(BO/sub3/)/sub 4/ (LSB) crystals with high neodymium concentrations up to 2.5/spl middot/10/sup 21/ cm/sup -3/.
Abstract: We report on the spectroscopic properties and laser performance of Czochralski-grown LaSc/sub 3/(BO/sub 3/)/sub 4/ (LSB) crystals with high neodymium concentrations up to 2.5/spl middot/10/sup 21/ cm/sup -3/. The low-concentration quenching of the upper laser level of neodymium and the polarization dependence of the spectra indicate that LaSc/sub 3/(BO/sub 3/)/sub 4/ crystalizes in a huntite-type structure like Nd/sup 3+/:YAl/sub 3/(BO/sub 3/)/sub 4/ (NYAB). With diode laser pumping at 808 nm, a multimode Nd/sup 3+/:LaSc/sub 3/(BO/sub 3/)/sub 4/ (NLSB) laser at 1063 nm is demonstrated. Optical slope efficiency was 64% with respect to absorbed pump power. The possibility of second-harmonic generation in the laser crystal is discussed. >
97 citations
TL;DR: A single-mode Nd(3+)-doped tellurite glass fiber laser operating at 1.061 microm is described, believed to be the first demonstration of a single- mode fiber laser in tellurites glass.
Abstract: A single-mode Nd(3+)-doped tellurite glass fiber laser operating at 1.061 microm is described. We believe this is the first demonstration of a single-mode fiber laser in tellurite glass. A lasing threshold of 27 mW of 818-nm absorbed pump power and a slope efficiency output power versus pump power of 23% emitted from one end were observed in the fiber cavity with 11.9% Fresnel reflection at both ends.
96 citations
TL;DR: In this paper, the design and temperature dependence of a quantum cascade intersubband laser operating pulsed in the midinfrared (λ≂4.3 μm) are reported.
Abstract: The design and temperature dependence of the performance characteristics of a quantum cascade intersubband laser operating pulsed in the midinfrared (λ≂4.3 μm) are reported. The threshold current density varies exponentially with temperature [exp(T/T0)] from ≊6.0 kA/cm2 at 50 K to ≊9.3 kA/cm2 up to the maximum operating temperature (125 K) with a T0∼112 K. This weak temperature dependence, compared to interband lasers operating at similar wavelengths, is due to the intersubband nature of the laser transition, to the physics of optical phonons scattering, and to the negligible intersubband Auger transition rates. The measured peak optical power varies from 32 mW at 10 K to 18 mW at 80 K for a 1.2‐mm cavity length. The measured slope efficiency is 52 mW/A at 80 K which corresponds to an estimated differential quantum efficiency of ≂3.4×10−2 per facet per stage.
92 citations
TL;DR: In this article, the authors report a highly efficient, short, robustly single-frequency and linearly polarised Er3+:Yb3+ codoped fiber laser with fiber-grating Bragg reflectors.
Abstract: The authors report a highly-efficient, short, robustly single-frequency and linearly polarised Er3+:Yb3+ codoped fibre laser with fibre-grating Bragg reflectors. An output power of 19mW for 100mW of 980nm diode pump power and a slope efficiency relative to a launched pump power of 55% is demonstrated. The RIN of the laser was < -157 dB/Hz and the laser linewidth was 300 kHz.
85 citations
TL;DR: Room-temperature, continuous-wave laser action at 2.3 microm corresponding to the (3)H(4)-(3) H(5) transition in Tm(3+)- doped YLF is achieved and continuous tunability of this laser from 2.20 to 2.46 microm is obtained.
Abstract: Room-temperature, continuous-wave laser action at 2.3 μm corresponding to the 3H4−3H5 transition in Tm3+-doped YLF is achieved. Output powers of 200 mW and a slope efficiency of 15% have been obtained for a pump power of 2 W at 0.78 μm. In addition, continuous tunability of this laser from 2.20 to 2.46 μm is obtained.
84 citations
TL;DR: Oscillation in a Tm(3+) and Ho( 3+) codoped silica fiber from the (5)I(7) ?
Abstract: We have observed oscillation in a Tm3+ and Ho3+ codoped silica fiber from the 5I7 → 5I8 transition of Ho3+ in the 2-μm region, by pumping the fiber laser into a Tm3+ absorption between 800 and 830 nm. By a change in the cavity length, the laser was tunable between 2.037 and 2.096 μm. When the laser was pumped with a Ti:sapphire laser at 820 nm, an absorbed threshold power of 214 mW, a slope efficiency of 4.2%, and maximum extracted power of 12.5 mW were measured.
80 citations
TL;DR: In this article, the mid-infrared (λ∼5 μm) luminescence is generated by electron injection into AlInAs/GaInAs coupledquantum wells via a pseudo-quaternary graded gap alloy.
Abstract: Electroluminescence associated with intersubband transition energies greater than the optical phonon energy and at temperatures as high as 300 K is reported. The mid‐infrared (λ∼5 μm) luminescence is generated by electron injection into AlInAs/GaInAs coupled‐quantum wells via an AlInAs/GaInAs pseudoquaternary graded gap alloy. Optical powers up to a few nanowatts and linear in the drive current have been measured. The large Stark shift of the luminescence peak demonstrates the photon‐assisted tunneling nature of the transition. The temperature independence of the luminescence slope efficiency in the 10–100 K range and the linearity of the optical power versus drive current provide strong evidence of population inversion.
77 citations
TL;DR: In this paper, the authors compare the behavior of gain-coupled DFB with index-couple DFB lasers fabricated from identical materials. But the performance of the two types of DFB was not compared.
Abstract: Comprehensive numerical simulations with the transmission-line laser model (TLLM) are used to compare the behavior of gain-coupled DFB lasers with index-coupled DFB lasers fabricated from identical materials. These simulations compare slope efficiency, threshold current, spectra, small-signal modulation bandwidth, maximum-intrinsic modulation bandwidth, large-signal transient response and chirp, relative-intensity-noise (RIN) spectra, and feedback sensitivity for coherence collapse. In most cases gain-coupled lasers with additional index coupling have better performance than index-coupled lasers for a given material. However, high-coupling factor index-coupled lasers do have lower threshold currents, lower RIN levels, and lower sensitivity to external feedback than gain-coupled lasers, although spatial hole burning in these devices can be disadvantageous. >
56 citations
TL;DR: In this paper, a quantum cascade light source based on sequential photon emission in a staircase/coupled quantum well was proposed, whose wavelength can be tailored in an extremely wide region and its line-narrowing above threshold and well resolved longitudinal modes were observed up to 125 K.
Abstract: A unipolar intersub-band semiconductor laser operating above liquid nitrogen temperature at 43 µm wavelength is reported The measured optical power in pulsed operation is 30 mW at 102 K and the slope efficiency 01 W/A Strong line-narrowing above threshold and well resolved longitudinal modes are observed up to 125 K This new light source, called the quantum cascade laser, is based on sequential photon emission in a staircase/coupled quantum well AlInAs/GaInAs structure grown by MBE and its wavelength can be tailored in an extremely wide region
TL;DR: In this paper, a 19 mu m Tm-doped silica fiber laser was used to achieve a maximum output power of 21 mW at a launched pump power of 127 mW.
Abstract: A 19 mu m Tm-doped silica fibre laser pumped at 157 mu m is described The pump source is an Er-doped fibre laser pumped by a 098 mu m Ti:sapphire laser The threshold pump power is 95 mW and the slope efficiency is as high as 71% A maximum output power of 21 mW was obtained at a launched pump power of 127 mW The oscillation wavelength can be tuned from 184 to 190 mu m by changing the length of the Tm-doped fibre >
TL;DR: In this article, the emission wavelength of a unidirectional ring erbium-doped fiber laser (EDFL) with no filters has been characterized, and a measurement of the emission and the absorption EDF cross sections together with a theoretical model based on the solution of the rate equations for the ring laser has been provided.
Abstract: The emission wavelength of a unidirectional ring erbium-doped fiber laser (EDFL) with no filters has been characterized A measurement of the emission and the absorption erbium-doped fiber cross sections together with a theoretical model based on the solution of the rate equations for the ring laser shows that the laser emission wavelength depends on the cold-cavity losses or on the active fiber length and dopant concentration The threshold pump power, the output power, and the slope efficiency of the EDFL have been measured and theoretically evaluated versus cold-cavity loss and active fiber length A simple relation among loss, active fiber length, and dopant concentration that permits the design of the cavity with the maximum slope efficiency has been found
TL;DR: A Y-junction channel waveguide laser, operating at room temperature, in Nd-diffused Ti:LiNbO(3), with feedback provided only by the polished end faces of the device is reported on.
Abstract: We report on a Y-junction channel waveguide laser, operating at room temperature, in Nd-diffused Ti:LiNbO3. Pumping was performed with a cw Ti:Al2O3 laser operating at 816 nm. With feedback provided only by the polished end faces of the device, a cw lasing threshold of ~39-mW launched pump power was obtained, with a slope efficiency of ~35%. Using 95% reflectivity mirrors at the waveguide ends, we reduced the lasing threshold to ~4 mW, with a slope efficiency of ~2.6%. Tuning of the lasing signal over a range of 2.3 nm around a center wavelength of 1092.7 nm was demonstrated, with a monolithically integrated phase modulator.
TL;DR: In this paper, a nonlinear mirror is made by a lithium triborate frequency doubling crystal and a dichroic mirror that partially transmits the fundamental frequency and totally reflects the second harmonic.
Abstract: We report on passive mode‐locking of a cw diode‐pumped Nd:YAG laser using the nonlinear mirror technique. The nonlinear mirror is made by a lithium triborate frequency doubling crystal and a dichroic mirror that partially transmits the fundamental frequency and totally reflects the second harmonic. The laser produces nearly transform‐limited pulses of 10 ps duration and 700 mW average power, with a slope efficiency of 28%. The mode‐locking is self‐starting under optimized conditions. Long term stability requires accurate control of the crystal temperature.
TL;DR: In this article, the authors reported upconversion lasing at 810 nm in thulium doped fluorozirconate fiber pumped by an Nd:YAG laser at 1064 nm, with an output power greater than 1.2 W and slope efficiency of 37%.
Abstract: The Letter reports upconversion lasing at 810 nm in thulium doped fluorozirconate fibre pumped by an Nd:YAG laser at 1064 nm, with an output power greater than 1.2 W and slope efficiency of 37%. Tunability over the range 803–816 nm is demonstrated. This is the highest power and most efficient upconversion laser reported to date in any gain medium.
TL;DR: A Nd:YLF laser that operates at 1053 nm without optical intracavity elements for the suppression of the stronger 1047-nm transition is reported on.
Abstract: We report on a Nd:YLF laser that operates at 1053 nm without optical intracavity elements for the suppression of the stronger 1047-nm transition. The Nd:YLF crystal is end pumped by a fiber optically coupled 10-W diode-laser bar. The different thermal-lensing focal lengths of the two main lasing wavelengths in a plane-parallel resonator were used to achieve the selection by tilting the end mirror slightly from its optimum position for maximum output power. With 9.8-W cw diode-laser-pumping power the 1053-nm Nd:YLF laser produces a maximum output power of 1.9 W in cw operation and nearly 1 W of average power at a Q-switch repetition rate of 15 kHz. The highest slope efficiency of 47% achieved in cw operation.
TL;DR: In this paper, a 1064 nm upconversion pumped thulium doped fluoride fiber laser operating on the 3F4 -3H4 transition around 1.47 µm is presented.
Abstract: Results are presented on a 1064 nm upconversion pumped thulium doped fluoride fibre laser operating on the 3F4 – 3H4 transition around 1.47 µm. A minimum threshold of 8.7mW (3.6mW absorbed), and a maximum slope efficiency of 58% (80% photon conversion efficiency), with respect to launched pump power has been observed. In addition a maximum gain efficiency of 0.22 dB/mW has been demonstrated.
TL;DR: In this article, the epitaxial regrowth required in most distributed feedback devices is eliminated by using lateral evanescent coupling of the field to gratings etched along the sides of the ridge.
Abstract: Results are presented on laterally-coupled distributed feedback (LC-DFB) ridge laser diodes. The epitaxial regrowth required in most distributed feedback devices is eliminated by using lateral evanescent coupling of the field to gratings etched along the sides of the ridge. A pulsed singlemode output power of 36 mW per facet was achieved at 937.5 nm with a sidemode suppression ratio (SMSR) of 30 dB for a 1.5 mm cavity length. A pulsed threshold of 11 mA, slope efficiency of 0.46 mW/mA per facet, and temperature sensitivity of 0.63 AA/ degrees C were measured for a 250 mu m cavity length LC-DFB.
TL;DR: An empirical expression for the effective thermal focusing power in terms of the pump power, beam diameter, crystal length, and absorption coefficient is determined and may be used to estimate average power limitations in designing AgGaSe(2) optical parametric oscillators.
Abstract: We performed an experimental investigation of thermal lensing in silver gallium selenide (AgGaSe(2)) optical parametric oscillator crystals pumped by a 2-µm laser at ambient temperature. We determined an empirical expression for the effective thermal focusing power in terms of the pump power, beam diameter, crystal length, and absorption coefficient. This relation may be used to estimate average power limitations in designing AgGaSe(2) optical parametric oscillators. We also demonstrated an 18% slope efficiency from a 2-µm pumped AgGaSe(2) optical parametric oscillator operated at 77 K, at which temperature thermal lensing is substantially reduced because of an increase in the thermal conductivity and a decrease in the thermal index gradient dn/dT. Cryogenic cooling may provide an additional option for scaling up the average power capability of a 2-µm pumped AgGaSe(2) optical parametric oscillator.
TL;DR: In this article, the lasing threshold and slope efficiency were optimized in an 8-spl mu/m-wide planar waveguide, in which the waveguide was fabricated on a silicon substrate by flame hydrolysis deposition and reactive ion etching.
Abstract: Fabrication and lasing characteristics of Nd-doped P/sub 2/O/sub 5/-SiO/sub 2/ core planar waveguide lasers are described. CW oscillation at a wavelength of 1052.5 nm was successfully demonstrated in 0.2 wt%-Nd-doped silica-based planar waveguides fabricated on a silicon substrate by flame hydrolysis deposition and reactive ion etching. The lasing threshold and slope efficiency were optimized in an 8-/spl mu/m-wide waveguide, in which a lasing threshold pump power of 26 mW and a slope efficiency of 2.0% were obtained for 805-nm pumping. The measured lasing characteristics agreed with theoretical characteristics calculated by employing finite-element waveguide analysis, indicating that the waveguide structure was well controlled by the developed waveguide fabrication technique. The possible lasing characteristics of the waveguide lasers are discussed based on this agreement. The attenuation and emission properties of the waveguides are also described. >
13 Oct 1994
TL;DR: In this paper, the effect induced by using different basic catalysts, such as N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 3- aminopropyltriethoxyselane, has been studied.
Abstract: Organic dye molecules have been widely used in solution as amplifying media in tunable lasers. The possibility of trapping these molecules in a solid state matrix may lead to a new field of application outside the laboratory. Many types of matrices can be used. We present results with new hybrid organic/inorganic xerogels prepared by hydrolysis-condensation of the methyl- or vinyl-triethoxysilane precursor under acid-catalyzed hydrolysis and basic-catalyzed condensation. Organic methyl or vinyl groups attached to the silica network provide a favorable environment to dye fluorescence. We have studied the effect induced by using different basic catalysts: N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 3- aminopropyltriethoxysilane are found to lead to the best matrix characteristics. Perylenes and pyrromethenes were chosen because of their thermal- and photo-stability. After gelation, 10 mm thick samples, polished to a surface roughness of about 4 nm, are placed in a plano- concave cavity as gain media and pumped by a frequency doubled nanosecond Q:switched Nd:YAG laser. Efficiency is the greatest with a pyrromethene 597 doped sample: more than 6 mJ output energy for a 10 mJ pump energy (2 J/cm 2 fluence) leading to a slope efficiency of 63%. The lifetime of the laser emission when the same point of the sample is sequentially used is also an important characteristic. Best results are obtained with perylene red dye: for a pump energy of 0.7 mJ at 1 Hz repetition rate, the output energy is still 50% of the initial value (0.1 mJ) after 80,000 shots. For a pyrromethene 597 doped MTEOS sample, it appears that the measured lifetimes are independent of the operating frequency in the 0.2 - 20 Hz range, indicating a reasonable heat conductivity for this type of matrix. We have also studied tunability by adding a grating or prism to the cavity: a typical tunability of over 50 nm or more is obtained with many of these dyes. Finally we report laser activity obtained with rhodamine B doped xerogels in which the dye molecules were covalently bonded to the silica network in order to stabilize the organic molecule structure.
TL;DR: In this paper, a reproducible and efficient Nd-doped LiNbO3 waveguide laser fabricated by thermal diffusion of Nd into commercially available MgO was presented.
Abstract: The authors present a reproducible and efficient Nd-doped LiNbO3 waveguide laser fabricated by thermal diffusion of Nd into commercially available MgO:LiNbO3 doped with 5 mol % MgO, followed by formation of singlemode annealed proton-exchanged waveguides. A Fabry-Perot cavity was provided by the polished waveguide ends alone. In the resulting waveguide laser, any output power up to 25mW (limited by the available pump power) at 1084nm was obtained with an emission linewidth of 0.26nm, and a slope efficiency as high as 50% was achieved with no photorefractive damage.
TL;DR: In this paper, a high-power room-temperature AlGaAs graded index separately confined heterostructure (GRINSCH) laser is reported for the first time, which is gain-guided and consists of 12 stripes, each 5 /spl mu/m in width with a centerline separation of 9 /spl µ/m. The epitaxial layer was grown with significantly lower levels of oxygen compared to those grown using standard metalorganic sources.
Abstract: A high-power room-temperature AlGaAs graded index separately confined heterostructure (GRINSCH) laser emitting in the visible spectral regime (/spl sime/715 nm) is reported for the first time. The device is gain-guided and consists of 12 stripes, each 5 /spl mu/m in width with a centerline separation of 9 /spl mu/m. This high-power visible laser has been successfully fabricated using a GaAlAs active layer. The epitaxial layer was grown with significantly lower levels of oxygen compared to those grown using standard metalorganic sources. Threshold currents of 310 mA at 10/spl deg/C were routinely measured on uncoated devices. The uncoated device had a catastrophic optical damage limit of 540 mW and has a slope efficiency as high as 0.48. No degradation in device performance was observed during a 50-hour 150-mW burn-in. >
TL;DR: It is shown that the proper use of a self-imaging confocal cavity can be a simple way to optimize the efficiency of optical pumping of solid-state lasers.
Abstract: We show that the proper use of a self-imaging confocal cavity can be a simple way to optimize the efficiency of optical pumping of solid-state lasers. In this type of resonator the transverse mode self-adjusts to fit the pumped volume optimally. Self-optimization of the mode size of a laser-diode pump Nd:YAG laser (54% slope efficiency) is demonstrated, and an intrinsic efficiency of 68% is measured.
TL;DR: In this paper, a lasing wavelength of 480.5 nm for a II-VI laser diode (LD) has been realized, and the threshold current of this blue LD is 470 mA.
Abstract: A lasing wavelength of 480.5 nm for a II-VI laser diode (LD) has been realised. The threshold current of this blue LD is 470 mA. The threshold current of the II-VI LD, whose lasing wavelength is 495 nm, is ~ 100 mA. The light output power of the 495 nm LD is 600 mW and the slope efficiency is 0.63 W/A. These values are the best so far reported in a II-VI LD.
TL;DR: In this paper, the performance of a Tm:YVO/sub 4/ laser has been optimized by varying the thickness of the laser crystal and the reflectivity of the output coupler.
Abstract: The performance of a Tm:YVO/sub 4/ laser has been optimized by varying the thickness of the laser crystal and the reflectivity of the output coupler. This has led to the measurement of a slope efficiency of 48% for the laser output. Formulas describing the saturation of the pump and the upper laser level in the presence of up-conversion loss have been developed. Fitting of the experimental data to the saturation curves calculated using these formulas has yielded an up-conversion rate constant from /sup 3/F/sub 4/ to /sup 3/H/sub 5/ of 2/spl middot/10/sup -18/ cm/sup 3/ s/sup -1/. >
08 May 1994
TL;DR: In this article, a diode-laser-pumped cw Nd:YAG laser operating at a power level of 150 W was presented, achieving an optical slope efficiency of 32% and an optical to optical efficiency of 29%.
Abstract: We report on a diode-laser-pumped cw Nd: YAG laser operating at a power level of 150 W. By using a transverse pump geometry, the radiation of 54 diode lasers with an output power of 10 W each is coupled into a Nd:YAG rod. In multimode operation, an optical slope efficiency of 32% and an optical to optical efficiency of 29% are obtained. In TEM00 operation, an output power of more than 30 W is realized with an optical to optical efficiency of 10%.
TL;DR: A reliable room-temperature-operated, pulsed LiF:(3)(+) color-center laser with a two-mirror cavity has been constructed and has shown a long-lifetime operation and remarkable amplitude stability by pumping with a dye laser.
Abstract: A reliable room-temperature-operated, pulsed LiF:F3+ color-center laser with a two-mirror cavity has been constructed. This laser is useful as a tunable, green, coherent light source. The laser has shown a long-lifetime operation and remarkable amplitude stability by pumping with a dye laser. The laser light has a peak at 543 nm. The slope efficiency is approximately 2%, and the pump threshold is approximately 75 mW.
Patent•
09 Mar 1994TL;DR: In this article, a side-pumped laser cavity design with high optical to optical conversion efficiency and a high slope efficiency is presented. But the design of the cavity is not described.
Abstract: A novel diode bar, side-pumped laser cavity design having high optical to optical conversion efficiency and a high slope efficiency is provided. A slab geometry with a single, high angle of incidence internal reflection permits gain to be accessed near the pump face of a laser material which absorbs strongly at the pump wavelength.