The design and performance of a laser diode pumped ruby laser is reported. The laser consists of a 5 mm long 0.05% doped ruby crystal placed within a hemispherical laser resonator. A single mode gallium nitride laser diode, operating at 405 nm provided up to 320 mW of pump power. Beam shaping optics were used to circularize the pump beam and a 150 mm focal length lens produced a ~20 μm waist in the crystal. The laser produced up to 44 mW of output power with a slope efficiency of 17%.
We report on the results from several of our alkali laser systems. We show highly efficient performance from an
alexandrite-pumped rubidium laser. Using a laser diode stack as a pump source, we demonstrate up to 145 W of
average power from a CW system. We present a design for a transversely pumped demonstration system that will show
all of the required laser physics for a high power system.
We report on the results of our diode pumped alkali laser experiments. Using volume bragg gratings, we have produced
a 1.28 kW diode stack with a 0.35 nm bandwidth and ~70% of the power contained in the peak. We use two of these stacks to pump a 23 mm rubidium cell. We achieve 29 W of average output power at a 14% duty factor.
The concept of power-scalable, high beam-quality diode pumped alkali lasers was introduced in 2003 [Krupke, US
Patent No. 6,643,311; Opt. Letters, 28, 2336 (2003)]. Since then several laboratory DPAL devices have been reported
on, confirming many of the spectroscopic, kinetic, and laser characteristics projected from literature data. This talk will
present an overview of the DPAL concept, summarize key relevant properties of the cesium, rubidium, and potassium
alkali vapor gain media so-far examined, outline power scaling considerations, and highlight results of published DPAL
laboratory experiments.
Diode pumped alkali lasers have developed rapidly since their first demonstration. These lasers offer a path to convert highly efficient, but relatively low brightness, laser diodes into a single high power, high brightness beam. General Atomics has been engaged in the development of DPALs with scalable architectures. We have examined different species and pump characteristics. We show that high absorption can be achieved even when the pump source bandwidth is several times the absorption bandwidth. In addition, we present experimental results for both potassium and rubidium systems pumped with a 0.2 nm bandwidth alexandrite laser. These data show slope efficiencies of 67% and 72% respectively.
General Atomics has been engaged in the development of diode pumped alkali vapor lasers. We have been examining
the design space looking for designs that are both efficient and easily scalable to high powers. Computationally, we
have looked at the effect of pump bandwidth on laser performance. We have also looked at different lasing species. We
have used an alexandrite laser to study the relative merits of different designs. We report on the results of our
experimental and computational studies.
The new class of diode-pumped alkali vapor lasers (DPALs) offers high efficiency cw laser radiation at near-infrared wavelengths: cesium 895 nm, rubidium 795 nm, and potassium 770 nm. The working physical principles of DPALs will be presented. Initial 795 nm Rb and 895 nm Cs laser experiments performed using a titanium sapphire laser as a surrogate pump source demonstrated DPAL slope power conversion efficiencies in the 50-70% range, in excellent agreement with device models utilizing only literature spectroscopic and kinetic data. Using these benchmarked models for Rb and Cs, optimized DPALs with optical-optical efficiencies >60%, and electrical efficiencies of 25-30% are projected. DPAL device architectures for near-diffraction-limited power scaling into the high kilowatt power regime from a single aperture will be described. DPAL wavelengths of operation offer ideal matches to silicon and gallium arsenide based photovoltaic power conversion cells for efficient power beaming.
DPAL, a new class of diode pumped alkali vapor lasers, offers the prospect for high efficiency cw laser radiation at near-infrared wavelengths: cesium 895 nm, rubidium 795 nm, and potassium 770 nm. The physics of DPAL lasers are outlined, and the results of laboratory demonstrations using a titanium sapphire surrogate pump are summarized, along with benchmarked device models. DPAL electrical efficiencies of 25-30% are projected and near-diffraction-limited DPAL device power scaling into the multi-kilowatt regime from a single aperture is also projected.
The features of modern, high-power semiconductor diode laser arrays as sources for pumping high power solid state lasers are reviewed. The status and prospects for high power, high- beam quality Nd:YAG and Yb:YAG DPSSLs are examined. Developing concepts for novel high power DPSSLs are also outlined.
The features of modern, high-power semiconductor diode laser arrays as sources for pumping high power solid state lasers are reviewed. The status and prospects for high power, high- beam quality Nd:YAG and Yb:YAG DPSSLs are examined. Developing concepts for novel high power DPSSLs are also outlined.
The features of modern, high-power semiconductor diode laser arrays as sources for pumping high power solid state lasers are reviewed. The status and prospects for high power, high- beam quality Nd:YAG and Yb:YAG DPSSLs are examined. Developing concepts for novel high power DPSSLs are also outlined.
The features of modern, high-power semiconductor diode laser arrays as sources for pumping high power solid states lasers are reviewed. The status and prospects for high power, high- beam quality Nd:YAG and Yb:YAG DPSSLs are examined. Developing concepts for novel high power DPSSLs are also outlined.
The features of modern, high-power semiconductor diode laser arrays as sources for pumping high power solid state lasers are reviewed. The status and prospects for high power, high- beam quality Nd:YAG and Yb:YAG DPSSLs are examined. Developing concepts for novel high power DPSSLs are also outlined.
In this work we studied the optical spectra of dysprosium and ytterbium doped double chloride MePb2Cl5:RE3+ (Me equals K, Rb), and double fluoride LiYF4:RE3+ (RE3+ equals Dy, Yb) crystals. RE3+ doped double chloride and double fluoride crystals have been grown, by using Bridgeman technique. Optical spectra were studied, intensity parameters are determined using Judd-Ofelt method and radiative probabilities and branching ratio were calculated. Yb3+ -Dy3+ energy transfer processes in KPb2Cl5:Dy3+,Yb3+ and LiYF4:Dy3+,Yb3+ were considered.
KEYWORDS: Solid state lasers, Ions, Disk lasers, Solid state electronics, Temperature metrology, Laser applications, Fusion energy, Solid state physics, Physics, Laser crystals
In this paper we describe the concept, and the basic scaling relationships of solid state heat capacity lasers. Intermediate between single shot and average power systems, the heat capacity concept scales solid state lasers to MW levels of burst power.
The status of diode-pumped, transverse-gas-flow cooled, Yb- S-FAP slab lasers is reviewed. Recently acquired experimental performance data are combined with a cost/performance IFE driver design code to define a cost- effective development path for IFE DPSSL drivers. Specific design parameters are described for the Mercury 100J/10 Hz, 1 kW system (first in the development scenario).
A new class of room-temperature, diode-pumped solid state lasers, that are broadly tunable in the mid-IR spectral region, has been conceptualized and demonstrated. These lasers are based on intra-ion transitions of divalent transition metals placed in substitutional cation sites of tetrahedral symmetry in large bandgap chalcogenide semiconductor crystals. These combinations of laser-ions and host crystals are seen to provide favorable radiative and non-radiative transition processes for the realization of the desired laser performance characteristics. Spectroscopic data for candidate schemes are reviewed and divalent chromium doped zinc chalcogenides are identified as potentially superior laser candidates. Preparation of laser quality Cr2+:ZnSe crystals is described and experimental results to date for a diode-pumped laser are given. Remaining laser development issues are discussed briefly.
We discuss the optical and laser properties of two new tunable laser crystals, Ce:LiSAF and Cr:ZnSe. These crystals are unique in that they provide a practical alternative to optical parametric oscillators as a means of generating tunable radiation in the near ultraviolet and mid-infrared regions (their tuning ranges are at least 285 - 315 nm and 2.2 - 2.8 microns, respectively). While these crystals are relatively untested in field deployment, they are promising and likely to be useful in the near future.
Nonlinear optical frequency converters (harmonic generators and optical parametric oscillators) are reviewed with an emphasis on high-average power performance and limitations. NLO materials issues and NLO device designs are discussed in reference to several emerging scientific, military and industrial-commercial applications requiring approximately equals 100 watt average power level in the visible and infrared spectral regions. Research efforts required to enable practical approximately equals 100 watt class NLO based laser systems are identified.
Although solid-state lasers have been the primary means by which the physics of inertial confinement fusion (ICF) have been investigated, it was previously thought that solid-state laser technology could not offer adequate efficiencies for an inertial fusion energy (IFE) power plant. Orth and co-workers have recently designed a conceptual IFE power plant, however, with a high efficiency diode-pumped solid-state laser (DPSSL) driver that utilized several recent innovations in laser technology. It was concluded that DPSSLs could offer adequate performance for IFE with reasonable assumptions. This system was based on a novel diode pumped Yb-doped Sr5(PO4)3F(Yb:S-FAP) amplifier. Because this is a relatively new gain medium, a project was established to experimentally validate the diode-pumping and extraction dynamics of this system at the smallest reasonable scale. This paper reports on the initial experimental results of this study. We found the pumping dynamics and extraction cross-sections of Yb:S-FAP crystals to be similar to those previously inferred by purely spectroscopic techniques. The saturation fluence for pumping was measured to be 2.2 J/cm2 using three different methods based on either the spatial, temporal, or energy transmission properties of a Yb:S-FAP rod. The small signal gain implies an emission cross section of 6.0 multiplied by 10-20 cm2 that falls within error bars of the previously reported value of 7.3 multiplied by 10-20 cm2, obtained from spectroscopic techniques. Up to 1.7 J/cm3 of stored energy density was achieved in a 6 multiplied by 6 multiplied by 44 mm3 Yb:S-FAP amplifier rod. In a free running configuration diode-pumped slope efficiencies up to 43% were observed with output energies up to approximately 0.5 J per 1 ms pulse from a 3 multiplied by 3 multiplied by 30 mm3 rod. When the rod was mounted in a copper block for cooling, 13 W of average power was produced with power supply limited operation at 70 Hz with 500 microsecond pulses.
We have explored the major technical and conceptual issues relating to the suitability of a diode-pumped solid state laser as a driver for an inertial fusion energy power plant. While solid state lasers have long served as the workhorse of inertial confinement fusion physics studies, the deployment of a driver possessing adequate efficiency, reliability, and repetition rate for inertial fusion energy requires the implementation of several technical innovations discussed in this article.
The ultraviolet laser properties of LiSrAlF6 doped with trivalent cerium (Ce:LiSAF) and LiCaAlF6 (Ce:LiCAF) are reported. The polarized absorption, emission and excited state absorption cross sections for both Ce:LiSAF and Ce:LiCAF were determined for the 266 nm pump and 290 nm laser emission wavelengths. The single exponential emission lifetime was measured to be 28 +/- 2 and 25 +/- 2 ns for Ce:LiSAF and Ce:LiCAF, respectively. The gain was found to be highest when the probe was polarized parallel to the optic axis of the crystal due to the anisotropic nature of the excited state absorption. The excited state absorption is ascribed to a transition from the 5d orbital of Ce3+ to the conduction band of the host. Laser slope efficiencies of up to 29% and 21% were measured for Ce:LiSAF and Ce:LiCAF when the 266 nm pulsed pump beam was polarized parallel to the optic or c- axis. These are the highest laser slope efficiencies yet observed for any known solid-state ultraviolet laser material. When the pump beam was polarized perpendicular to the optic axis of the crystals, the gain and laser efficiencies dropped by up to an order of magnitude. The magnitude of pump-induced solarization was found to be highly variable for different crystals, and to have insignificant impact on the laser performance when favorable crystals were utilized.
The Cr:LiSAF (Cr-doped LiSrAlF6) laser material is currently being studied and employed in many types of laser systems, such as flashlamp-pumped oscillators and amplifiers, femtosecond regenerative amplifiers, diode-pumped minilasers, alexandrite laser- pumped systems, and Ar-ion laser-pumped self-mode-locked oscillators. While researchers certainly require a basic knowledge of the parameters that characterize the Cr:LiSAF material operating under 'normal' conditions (e.g., the emission cross section, storage time, dn/dT, etc.), they now also need to better understand the natural limits encountered by the material in optimized or novel laser systems. In particular, three areas will be addressed including, firstly, the pump-induced Auger upconversion mechanism, which entails the annihilation of pairs of Cr3+-excited states. Secondly, the thermomechanical properties of Cr:LiSAF will be reported and compared to other materials. Lastly, the results of assessing the durability of Cr:LiSAF at various temperatures, and for water/ethylene glycol solutions, will be addressed and compared to values characterizing common crystals and glasses.
The recent emergence of high performance semiconductor laser diodes and diode arrays emitting at wavelengths between 630 and 2300 nm has enabled the demonstration of several novel diode-pumped solid state laser materials. Narrowly, laser diode arrays may be viewed as simple replacements for conventional flash or arc lamp pumps in solid state lasers. The examples discussed in this paper illustrate that laser diode array pumps are considerably more versatile, enabling novel high performance lasers that are technically not feasible using conventional flashlamps. Additionally, several relatively new nonlinear optical materials, possessing high nonlinearities and excellent phase-matching properties, offer good prospects for the development of efficient, compact, wavelength-diverse all-solid-state laser sources.
A ground state depleted (GSD)1,2 laser has been demonstrated in the form of a Q-switched oscillator operating at 912 nm. Using Nd3+ as the active ion and Y2SiO5 as the host material, the laser transition is from the lowest lying stark level of the Nd3+4F3/2 level to a stark level 355 cm-1 above the lowest lying one in the 4I9/2 manifold. The necessity of depleting the ground 4I9/2 manifold is evident for this level scheme as transparency requires a 10% inversion. To achieve the high excitation levels required for the efficient operation of this laser, bleach wave pumping using an alexandrite laser at 745 nm has been employed. The existence of a large absorption feature at 810 nm also allows for the possibility of A1GaAs laser diode pumping. Using KNbO3, noncritical phase matching is possible at 140°C using d32 and has been demonstrated. The results of Q-switched laser performance and harmonic generation in KNbO3 will be presented. Orthosilicate is a monoclinic biaxial crystal. An oriented spectroscopic evaluation consisting of a Judd-Ofelt analysis of oriented absorption spectra and the measurements of oriented emission spectra has been completed and will be presented. Results of modeling using these spectroscopically determined parameters will be compared with the actual laser performance. The performance of this laser at 911 nm which allows accessing Cs atomic resonance filters through harmonic doubling will also be discussed. Orthosilicate can be grown in large boules of excellent optical quality using a Czochralski technique. Because of the relatively small 912 nm emission cross section of 2-3 x 10-20cm2 (orientation dependent) fluences of 10-20 J/cm2 must be circulated in the laser cavity for the efficient extraction of stored energy. This necessitates very aggressive laser damage thresholds. Results from the Reptile laser damage facility at Lawrence Livermore National Laboratory (LLNL) will be presented showing Y2SiO5 bulk and AR sol-gel coated surface damage thresholds of greater than 40 J/cm2 for 10 nsec, 10 Hz, 1.06 μ pulses.
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