Search

A novel colloidal co-casting process was developed to fabricate laser quality, multisegment composite ceramic laser gain materials. The approach was demonstrated for a three segment transparent composite rod 62 mm long by 3 mm diameter consisting of undoped yttrium aluminus garnet (YAG), 0.25% Er:YAG, and 0.5% Er:YAG. The Er concentration profile in the composite has steep, controllable gradients at the segment interfaces, while maintaining constant dopant concentrations within each segment. The composite rod has 84% transmittance at 1645 nm (the lasing wavelength) with a scatter loss of 0.4% cm−1. Laser operation of such a composite Er:YAG ceramic rod was demonstrated for the first time, with nearly equivalent lasing behavior to an Er:YAG single crystal rod.

This paper demonstrates that fine-grained (2–3 μm), transparent Nd:YAG can be achieved at SiO2 doping levels as low as 0.02 wt% by the sinter plus hot isostatic pressing (HIP) approach. Fine grain size is assured by sintering to 98% density, in order to limit grain growth, followed by HIP. Unlike dry-pressed samples, tape-cast samples were free of large, agglomerate-related pores after sintering, and thus high transparency (i.e., >80% transmission at 1064 nm) could be achieved by HIP at

Densification and grain growth in pure YAG, SiO 2 doped YAG and SiO 2 doped Nd:YAG were explored. The activation energy for densification (235 kJ/mol) in pure YAG is lower than that of grain growth (946 kJ/mol) which is unusual in ceramic systems. Consequently, pure YAG sinters to near full density (>99.9%) at 1700 °C with little grain growth (1.2 μm average grain size). The remaining large pores (radius > 2 μm) were determined to be thermodynamically stable because their coordination number with grains was >6. The stability of these pores underscores the importance of powder processing and forming in fabricating transparent YAG. SiO 2 doped YAG sinters to near full density 100 °C lower than pure YAG because SiO 2 enables liquid phase sintering and the removal of large pores. The addition of Nd 2 O 3 further enhances both densification and grain growth at temperatures below 1700 °C. Above 1700 °C higher concentrations of Nd 3+ suppressed grain growth, possibly due to solute drag.

Transparent polycrystalline Nd:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2O3, Y2O3, and Nd2O3 powders. The powders were mixed in methanol and doped with 0.5 wt% tetraethoxysilane (TEOS), dried, and pressed. Pressed samples were sintered from 1700° to 1850°C in vacuum without calcination. Transparent fully dense samples with average grain sizes of ∼50 μm were obtained at 1800°C for all Nd2O3 levels studied (0, 1, 3, and 5 at.%). The sintering temperature was little affected by Nd concentration, but SiO2 doping lowered the sintering temperature by ∼100°C. Abnormal grain growth was frequently observed in samples sintered at 1850°C. The Nd concentration was determined by energy-dispersive spectroscopy to be uniform throughout the samples. The in-line transmittance was >80% in the 350–900 nm range regardless of the Nd concentration. The best 1 at.% Nd:YAG ceramics (2 mm thick) achieved 84% transmittance, which is equivalent to 0.9 at.% Nd:YAG single crystals grown by the Czochralski method.

The development of solid state tunable lasers in the ultraviolet region would have a wide range of applications, including atmospheric remote sensing, atmospheric spectroscopy and pollution monitoring. The first work with Ce : LiCAF was published in 1993, with subsequent reports on favorable results with Ce : LiSAF. While the optical quality of Ce : LiSAF is superior, it suffers from solarization. In contrast, Ce : LiCAF shows minimal solarization and higher efficiencies, even with the typically high-scatter materials available. This presentation will summarize the crystal growth and material characterization of a series of colquiriite crystals with various Sr : Ca ratios. Based on these results, in addition to laser measurements, an optimum composition of Ce : LiSr x Ca 1− x AlF 6 will be determined.

The search for an efficient solid-state laser with tunable emission in the ultraviolet wavelength region has resulted in the growth and development of cerium-doped colquiriite crystals, such as LiCaAlF 6 (LiCAF) and LiSrAlF 6 (LiSAF). Unfortunately, the doping of LiSAF and LiCAF with Ce 3+ introduces different variables into the growth of high optical quality crystals, due to the charge imbalance induced when this trivalent ion substitutes for the divalent site. Charge compensation with Na + tends to produce a more uniformly doped crystal with improved laser properties. Although preliminary research indicated that Ce : LiSAF may be the preferred material of the colquiriite hosts, Ce : LiCAF has also proved to be quite promising.

A diode-pumped room-temperature Ho:Tm:LuLiF/sub 4/ laser achieved an optical efficiency of 9.4% under normal mode operation. Under similar experimental conditions. Ho:Tm:LuLiF/sub 4/ yielded 1.5 times greater optical efficiency than Ho:Tm:YLiF/sub 4/. Absorption spectra and lifetimes as a function of pump energy were measured for evaluation of this laser material.

Intrinsic structural disorder in scandium‐substituted garnets, attributed to mixed occupancy of certain sites in the crystal lattice by different cations, has direct consequences for the optical spectra of rare‐earth activator ions dispersed over multiple sites. In trivalent thulium‐doped yttrium scandium gallium garnet (Tm3+:YSGG), site‐selective laser excitation spectra reveal the presence of Tm3+ ions in regular D2 sites, disturbed regular sites, and in octahedral C3i sites. Absorption spectra obtained at 4 K between 0.26 and 1.85 μm are broader than those observed in more‐ordered crystal hosts and include structure attributed to Tm3+ ions in sites of other than D2 symmetry. A crystal‐field splitting calculation was carried out in which a parametrized Hamiltonian (including Coulombic, spin‐orbit, and crystal‐field terms for Tm3+ ions in D2 symmetry) was diagonalized for all manifolds of the Tm3+ (4f12) configuration. The rms deviation between 52 experimental and calculated Stark levels of Tm3+ in regul...

Stimulated emission was detected in RbCaF(3):Rh(2+) crystals through the observation of power-dependent shortening of the fluorescence lifetime and narrowing of the emission band with a distinct threshold. In addition, single-pass gain was observed to be tunable between about 700 and 720 nm.

Utilizing the results of Cr3+ → Tm3+ transfer efficiency studies, we have demonstrated that yttrium aluminium garnet (YAG) is the preferred host for room-temperature, flashlamp-pumped solid-state lasers operating in the 2.0 µm spectral range. We report data on two different sensitizer-activator combinations in YAG and yttrium scandium gallium garnet (YSGG) laser materials: one is doped with Cr:Tm:Ho and operates on the Ho3+ 5I7 →5I8 transition at 2.097 µm; the other is doped only with Cr:Tm, which lases on the Tm3+ 3F4 →3H6 transition at 2.014 µm. We have achieved a slope efficiency of 5.1% with the Cr:Tm:Ho:YAG laser, which is the highest slope efficiency yet reported for a room-temperature, flashlamp-pumped, 2 µm solid-state laser. We have measured thresholds as low as 38 J and output energies >1.5 J for that system. We also report the first room-temperature operation of an efficient flashlamp-pumped Cr:Tm:YAG laser at 2.014 µm. Thresholds as low as 43 J, output energies exceeding 2 J, and slope efficiencies as high as 4.5% have been achieved. This is an order of magnitude higher than the efficiency previously reported for a 2.01 µm Cr:Tm:YAG laser operated at cryogenic temperatures. These two efficient 2 µm laser systems (Cr:Tm:Ho:YAG and Cr:Tm:YAG) are discussed in terms of their potential for Q-switched operation.

We have performed a laser evaluation of the Yb 3+ -doped Y 2 O 3 ceramic laser material. The Q-CW output power in excess of 30 W was obtained with the slope efficiency of 47.3%. This output power is, to the best of our knowledge, the highest reported so far for diode-pumped Yb 3+ -doped Y 2 O 3 laser.

We present laser characterization results of a high-power longitudinally diode-pumped Yb3+-doped Y2O3 ceramic laser. Slope efficiency as high as 44.5%, quasi-CW power in excess of 26 W and acousto-optically Q-switched operation are reported.

The Q-CW output power in excess of 30 W and slope efficiency of 47.3% were obtained and are, to the best of our knowledge, the highest reported so far for diode-pumped Yb3+-doped Y 2 O 3 laser.

Comparisons of the spectroscopic, mechanical, thermo-optic, and laser performance properties between single crystal and ceramic oxide gain materials will be presented. Inaccuracies and myths regarding these ceramics will be dispelled by presentation of statistically-significant data.

Recently there has been increasing interest in high quality ceramic laser gain materials, particularly for high-energy lasers, due to the successful application of high-volume advanced ceramics consolidation techniques to transparent oxide gain materials. In this paper, a brief comparison of manufacturing techniques is presented, including an overview of the co-precipitation process and the solid-state reaction process. Merits and risks of each will be presented from a processing viewpoint. Ceramic Nd:YAG in particular shows promise for high power laser design. The program reported here is also compiling a definitive database to compare ceramic and single crystal Nd:YAG materials. Uniform doping levels of up to 9 at% Nd3+ have been reported by Konoshima Chemical Co. in ceramic Nd:YAG, and studied by the US Army Research Laboratory and the US Air Force Research Laboratory. All ceramic Nd:YAG materials studied to date have exhibited similar, if not identical, spectroscopic parameters to those measured for single crystal samples. Thermal properties, laser damage thresholds and refractive indices for a range of temperatures and wavelengths are reported. Diode-pumped free running laser experiment results with highly concentrated (up to 8 at% Nd3+) ceramics and their comparison with our modeling results are presented. High pulse repetition frequency actively (AO) Q-switched laser experiments are in progress. While there are still challenges in the manufacturing of ceramic laser gain materials, and the benefits of the application of ceramic technology to laser material are yet to be fully realized, ceramic Nd:YAG shows promise and could provide new options to the laser design engineer.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report what is believed to be the first demonstration of diode-pumped lasing from highly concentrated (8%) ceramic Nd:YAG. Fluorescence kinetics and laser experiments indicate the material’s potential for high repetition rate Q-switched laser development.

We report what we believe to be the first demonstration of Q-switched, diode-pumped lasing from highly concentrated (8%) ceramic Nd:YAG. Fluorescence kinetics and laser experiments indicate the material's potential for high repetition rate operation.

In this paper, a comparison of ceramic Nd:YAG manufacturing techniques are presented, including an overview of the coprecipitation process and the solid state reaction process. Merits and risks of each from a commercial manufacturing viewpoint are also presented.

Cerium has been doped in both LiCAF and LiSAF. However, each host has some intrinsic problems resulting in scatter and thermal expansion coefficient issues, respectively. In order to optimize the laser host, crystals were grown on various compositions of Ce,Na:LiSr x Ca 1-x AlF 6 . The materials produced were characterized using a variety of methods, including differential thermal analysis, glow-discharge mass spectrometery, electron microprobe, and various microscopic techniques. Samples were fabricated to characterize the absorption and emission properties for each crystal composition. Finally, laser threshold and efficiency were characterized for the various samples. Through an analysis and comparison of these critical aspects, an optimized, commercially-viable crystal can be identified to be incorporated into a tunable, solid-state UV laser system. In the case of the selected crystal system, the crystal growth characteristics of the various crystals are very similar. In the case of the selected crystal system, the crystal growth characteristics of the various crystals are very similar. Absorption and emission values for the strontium-rich compositions are greater than those for the calcium-rich compositions. Lasing was achieved in all of the samples with different output coupler transmissions. The Sr/Ca=35/65 composition showed the highest output powers. Taking into consideration all three aspects of this resaerch, there exists an intermediate composition close to Sr/Ca=35/65, that would be an optimized host as a novel UV laser host.

The development of solid state tunable lasers in the ultraviolet region would have a wide range ofapplications, includingatmospheric remote sensing, atmospheric spectroscopy and pollution monitoring. The first work with Ce:LiCAF waspublished in 1993, with subsequent reports on favorable results with Ce:LiSAF. While the optical quality ofCe:LiSAF issuperior, it suffers from solarization. In contrast, Ce:LiCAF shows minima! solarization and higher efficiencies, even withthe typically high-scatter materials available. This presentation will summarize the crystal growth and materialcharacterization ofa series ofcolquiriite crystals with various Sr/Ca ratios. Based on these results, in addition to lasermeasurements, an optimum composition ofCe:LiSrCa1AlF6 will be determined. 1. INTRODUCTION There are two primary private-sector commercial markets for the cerium-doped colquiriites. The first will be as a new add-on component for research scientists who already have fourth harmonic (266 nm) laser systems in their laboratories. Severallaser companies have introduced diode-pumped 266 nm lasers into the marketplace, and there are over 2000 lasers in the fieldwith the capability ofoperating at 266 nm. The second commercial market that would have an interest in a well-developedCe-doped colquiriite laser material is the environmental monitoring industry. There are many chemical species ofinterest inthe UV that could be accessed ifa highly efficient, broadly tunable, all-solid-state system were available. For this market,laser manufacturers anticipate sales ofcomplete units, which would include the 266 nm pump source and the Ce:colquiriiteadd-on component. Through the appropriate selection of an optimized Ce-doped laser host and laser resonator component forfrequency tuning, the Ce:colquiriite crystals could generate output to probe the absorption ofatmospheric pollutants,contaminants, and aerosol species, such as ozone (280-320 nm). Several other species of interest in the UV include 502, 03,toluene, benzene, N0, ClO, and xylene. This market, albeit somewhat smaller than the market for direct harmonicgeneration at a fixed UV wavelength, is expected to grow rapidly in the next decade if sources and crystals become readilyavailable. Additionally, there are several government-based markets for tunable Ce-doped colquinite solid state lasers.Some ofthe non-classified applications include anti-ship missile defense devices, shipboard threat warning systems, short-range urban communication systems in the solar blind region ofthe ultraviolet, and covert communications systems to beutilized during in-flight fueling by Navy and Air Force pilots. There is also a need for a moderate energy source (lO-lOOmJ,10Hz, 280-320 nm) for standoffdetection ofbiological warfare monitoring and detection. Tryptophan, which is an agenttypically used to carry biological agents in the battlefield, has a broad absorption form 280-310 nm. 290 nm sources wouldbe useful for ground-based line-of-sight monitoring ofchemical pollutants from refineries, power plants, and smokestacks.Previous work with the growth ofthe cerium-doped colquiriites resulted in the selection ofa modified Czochralski furnacefor the growth ofthese crystals. Attempts at improving dopant distribution prompted growth runs using Na, Mg2, and Zn2as co-dopants. The use ofNa as a codopant resulted in crystals with the least amount ofcracking, more uniformity in Ce3doping, and a lower tendency for solarization.Cr:LiSr08CaAlF6was first reported as a potential tunable laser in November 1992.' In this report, it was noted that LiSAFexhibits a weaker crystal field strength, resulting in a larger cross section than Cr:LiCAF. The LiCAF host, however, hasmore favorable mechanical properties. The mixed crystal reportedly had spectroscopic and lasmg properties similar toLiSAF and mechanical properties more typical of LiCAF. In the case of cerium doping of the colquiriites, Ce:LiSA.F grows

The design and performance of a short-pulse (1.5 ns), high-energy (90 mJ/pulse) nonlinear cavity-dumped, frequency-doubled, solid-state intracavity Raman laser is presented. The laser described is utilized as the transmitter in a high-resolution surf-zone marine imaging lidar system.

The introduction of a 532 nm Nd:YAG beam can be used to increase the slope efficiency of an ultraviolet Ce:LiSAF laser pumped at 266 nm by a factor of 1.4 by bleaching the color centers. The addition of a co-dopant, specifically sodium ions at a concentration of 2% in the melt also increases slope efficiency by a factor of 1.2.

A diode side-pumped Cr:LiSAF laser has been demonstrated with a 30 mJ normal mode output energy, and an optical to optical eficiency of 17%. Improved optical quality laser material has been grown with several Cr concentrations. Optimum Cr concentration has been calculated and experimentally confirmed.

The search for an efficient solid state laser with tunable emission in the ultraviolet wavelengthregion has resulted in the growth and development ofcerium doped colquiriite ciystals, such asLiCaAJF6 (LiCAF) and LiSrA1F6 (LiSAF). Results from preliminary research at LawrenceLivermore National Laboratoiy indicate that Ce:LiSAF is the preferred material ofthe colquiriitehosts, since it shows higher gains than Ce:LiCAF. Although the growth ofchromium dopedLiSAF has been developed to produce long boules ofnear-scatter-free material, the doping ofLiSAF with cerium introduces different variables into the growth ofhigh optical quality crystals.The main crystal growth issue for Ce:LiSAF is the charge compensation mandated by thesubstitution ofthe trivalent cerium ion for divalent strontium, which is located in the only sitelarge enough to support the cerium ion. Initial growth runs produced opaque, heavily crackedcrystals with less than 1 0 mm of cleaner, single crystal materiaL The addition of chargecompensating ions into the starting charge and their effect in attaining higher doped and less-stressed material is discussed. The selection ofgrowth parameters needed to produce higher-doped, near-scatter-free Ce:LiSAF will also be described.Keywords: ultraviolet, solid-state laser, tunable, cerium, colquiriite, crystal growth

The ultraviolet laser properties of LiSrAlF 6 doped with trivalent cerium (Ce:LiSAF) and LiCaAlF 6 (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 Ce 3+ 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.

Single crystals of three Nd3+-doped disordered oxides have been grown and characterized as candidates for improved diode-pumped solid state lasers. These hosts include one melilite, SrGdGa3O7 (SGGM), and two gallogermanates, La3Ga5GeO14 (LGG) and its isomorph La3Ga5SiO14 (LGS). Spectroscopic properties such as absorption and emission bandwidth, fluorescent lifetimes, and emission cross-sections are included. Laser properties of the 4F3/2 - 4I11/2 transition at 1.06 microns have been measured.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have investigated diode pumped thulium and holmium YAG lasers. Comparisons of laser performance for several different Tm/Ho concentrations and the results of a prototype Q- switched laser are reported.

The interest in diode pumped solid state lasers in the 2 μm region in recent years has been well documented. The need for compact, highly efficient sources has led to the study of new laser hosts which may improve performance. We have grown and analyzed the spectroscopic properties of two Tm3+-doped silicate oxyapatite hosts and one orthosilicate. These hosts are CaY4(SiO4)3O [CaYSOAP], CaLa4(SiO4)3O [CaLaSOAP], and Y2SiO5 [YSO or YOS]. The spectroscopic properties of these new hosts are compared with those of Tm3+:YAG, and indicate that these hosts may offer improvements to Tm3+:YAG in increasing tunability in the 2 μm region and in improving laser performance for the 2.3 μm transition. Preliminary laser results of a Tm:CaYSOAP laser are also presented.

We have studied the characteristics of Thulium and Holmium/Thulium YAG lasers using high power laser diode pumping. Measurements of laser performance have been combined with spectroscopic measurements and compared to rate equation models for these materials.

This PDF file contains the editorial “Special Section Guest Editorial: Commemorating the 50th Anniversary of the Laser” for OE Vol. 49 Issue 09

Single crystals of Nd(3+):SrGdGa3O7 (SGGM) have been grown and characterized as candidate crystals for improved diode pumped lasers. The width of the 809 nm absorption in this disordered oxide crystal is 8 nm FWHM. The fluorescence lifetime of the 4F3/2 - 4I11/2 transition at 1.06 micron is 245 microsec. Dopant levels of 4 percent Nd have been achieved while maintaining high optical quality material.

We report on the growth and characterization of SrGdGa307, La3Ga5Si014 and La3Ga5GeO14 doped with Nd and Tm as candidate crystals for improved diode pumped lasers.

Trivalent uranium-doped LiYF4, crystals have been grown and evaluated as potential diodepumped lasers. Strong fluorescence in the range of 2.1 - 2.6 μm has been measured with a 170 μs lif e time.

The authors describe room temperature, flash-pumped laser operation of several Cr3+-sensitized, Tm3+-activated garnet crystal hosts. The hosts which have been investigated include YAG, YSGG, and GSGG. Laser action for these systems is based on the 2.0 micrometers, 3F4yields3H6 transition in Tm3+. Slope efficiencies for the 2 micrometers transition exceeded 4% in some of the hosts investigated. Free-running, multimode output energies have exceeded 2 J at 1 Hz repetition rates, while TEM00 output energies of greater than 1 J have also been reported.

We have spectroscopically evaluated crystals of Nd3+:SrGdGa3O7(Nd3+:SGGM) to assess their potential for use as diode pumped solid-state laser materials. The single crystals were grown by the Czochralski method, and the samples were oriented using x-ray diffraction. The host, SrGdGa3O7 is a uniaxial crystal with tetragonal symmetry and is a subset of the melilite series of minerals. The samples studied here were doped with 2 at. % Nd3+ in the melt with respect to the Gd ion. Polarized absorption spectra reveal that the absorption coefficient for light having its E vector perpendicular to the c-axis, Eσ is larger than that for E parallel, Eπ. The absorption coefficient for Eσ at 809 nm is 6.6 cm-1, more than two times larger than that for Eπ at the same wavelength. Similar differences in transition strengths have been measured in the emission spectra. Significant inhomogeneous broadening occurs in Nd:SGGM; the absorption linewidth at 809 nm is 10 nm FWHM. For a diode pumped solid-state laser this represents a significant improvement over the 1-nm FWHM linewidth in Nd: YAG at 810 nm. The fluorescence lifetime for the 4F3/2 → 4I11/2 transition at 1.06 µm is 245 µm in our Nd:SGGM crystals, which is 40% longer than lifetimes measured previously for Nd:SGGM crystals grown by the laser heated pedestal growth method,1 and is comparable to the 230-µm lifetime for Nd:YAG.

We have evaluated the laser performance of flashpumped Cr;Tm -aluminum and scandium garnets and have demonstrated broad tunability from 1.94 μm to 2.09 μm with TEM00 mode output energies exceeding 1 J.

Operation of an efficient room temperature, flashlamp-pumped Cr;Tm:Y3A15O12 (YAG) laser at 2.014 μm is reported with a 43 J threshold, 2 J output energy, and 4.5% slope efficiency. Room temperature, flashlamp-pumped laser action is also demonstrated for the first time in a similar host, Y3Sc2Ga3O12 (YSGG) codoped with Cr and Tm. The observed laser wavelength in Cr;Tm:YSGG is measured as 2.010 μm.

Laser performance results and Cr(3+)-Tm(3+) transfer efficiency studies are used to demonstrate that YAG is the preferred host for the Cr:Tm:Ho laser, and that highest efficiencies are obtained at relatively low Cr(3+) concentrations. A slope efficiency of 5.1 percent was achieved from a flashlamp-pumped room-temperature 2-micron Cr:Tm:Ho:YAG laser.

Nd:LuLF, that is, Nd:LuLiF4, was grown with a Czochralski technique and characterized spectroscopically to include absorption and emission data and lifetime. Evaluation of this laser material for operation on the 4F3/2→4I11/2 and the 4F3/2→4I13/2 transitions was performed. Normal-mode laser performance was achieved on both the π and the σ polarizations for both transitions by use of a simple polarization-selective resonator. Both normal-mode and Q-switched performance was characterized on the 4F3/2→4I11/2 transition.

We have investigated high-peak- and high-average-power operation of diode-pumped, thulium-sensitized, holmium 2.1-microm lasers. Free-running laser powers of 14 W at 29 Hz have been demonstrated with 2.6% electrical efficiency. Q-switched operation produced average powers in excess of 11 W in a burst of short pulses. Preliminary optical parametric oscillator frequency conversion of the holmium laser to 4 microm is also reported.

Continuous-wave laser emission at 1.94 μm is reported in Tm:CaY4(SiO4)3O at room temperature with Ti:sapphire laser pumping at 790 nm. Pump thresholds of 100 mW and slope efficiencies of 32% have been achieved. The 3H6–3H4 pump absorption peak of 6% Tm:CaY4(SiO4)3O is six times stronger than the 3H6–3H4 pump absorption peak of 6% Tm:YAG.

Laser-pumped laser characteristics of a Tm:Ho:Y3Al5O12(YAG) crystal were measured as a function of the wavelength and energy of the alexandrite-laser pump source. Laser thresholds and slope efficiencies were recorded for 765-, 780-, and 785-nm pump wavelengths. Simultaneous laser emission was observed at 2.060, 2.065, 2.097, and 2.101 μm, and the relative intensities of these peaks were measured as a function of absorbed pump energy. Changes in temporal and spectral profiles of the laser emission were observed with variations in absorbed pump energy. When measurements were made with a monolithic crystal cavity instead of an open cavity, laser emission from Ho3+ was observed at 2.097 μm, and an additional laser peak was observed that may be due to transitions of the Tm3+ ions.

We report what is to our knowledge the first room-temperature operation of an efficient flash-lamp-pumped Cr,Tm:YAG laser at 2.014 microm. Thresholds as low as 43 J, output energies exceeding 2 J, and slope efficiencies as high as 4.5% have been achieved using a compact diffuse-reflecting pump cavity. These efficiencies are an order of magnitude higher than those previously reported for a 2.01-microm Cr,Tm:YAG laser operated at cryogenic temperatures.