3-μm cw laser operations in erbium-doped YSGG, GGG, and YAG

Dinerman, B. J.; Moulton, Peter F.

doi:10.1364/ol.19.001143

Cited by 195 publications

(69 citation statements)

References 7 publications

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“…30% for other diode-pumped garnets, 2,11 and 15% for diode-pumped f luorides. different from those of the normal processes, we calculate an optimum output power for a 20% erbium concentration.…”

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confidence: 98%

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Investigation of diode-pumped 28-μm laser performance in Er:BaY_2F_8

Pollnau

Lüthy

Weber³

et al. 1996

Opt. Lett.

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Laser operation at 2.8 mm in BaY 2 F 8 with erbium concentrations of 7.5% and 20% is investigated under laser-diode pumping at 967 nm. Output powers as high as 250 mW and slope efficiencies as high as 24% are obtained. 3) have been reported. The upper laser level of the erbium 3-mm transition has a shorter lifetime than the lower laser level. The interionic upconversion process that depletes the lower laser level and feeds the upper laser level is a significant process in the establishment of cw inversion. 4,5 This has been demonstrated by cw laser emission for pumping of the lower laser level. The increase of the lower-state upconversion and its saturation above a 30% erbium concentration as well as the increase of the upperstate upconversion above a 30% erbium concentration suggest an optimum dopant concentration near 30%. Concentration-dependent laser experiments determined this concept for YSGG, 11 but in LiYF 4 the optimum concentration was found to be considerably lower. 3BaY 2 F 8 is a promising candidate for efficient 2.8-mm laser performance. Owing to a small phonon energy of 415 cm 21 the ratio of upper-state to lower-state lifetime is very favorable. 10Diode-pumped laser performance has been demonstrated 12 with slope eff iciencies as high as 19% and an output power of approximately 100 mW. However, the erbium concentration has as yet not been optimized for maximum slope eff iciency, which, in view of the results cited above, is important for efficient laser operation.In this Letter the 2.8-mm laser performance of Er 31 :BaY 2 F 8 with dopant concentrations of 7.5% and 20% is investigated. Our convention for the erbium concentration is atomic percent at the yttrium site. The 7.5% sample was grown at Hughes Research Laboratories, and the 20% sample was grown at the Massachusetts Institute of Technology. The crystal end faces are f lat polished, but the ref lection of He-Ne laser light indicates that the surfaces are not parallel to each other. The samples are uncoated, because diff iculties have occurred in the past with industrial antiref lection coatings at 2.8 mm.The experimental arrangement reported in Ref. 11 is shown in Fig. 1 and is applied to the laser experiments with BaY 2 F 8 . Two IBM laser diodes specif ied at powers of 1 W, each with an emission zone of 1 mm 3 50 mm and operating at 967 nm, are collimated and polarization combined. They provide a cw 0146-9592/96/010048-03$6.00/0

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confidence: 98%

“…Continuous-wave output powers as high as 500 mW in Er 31 :YSGG (Ref. 2) and above 1 W in Er 31 : LiYF 4 (Ref.…”

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confidence: 99%

Investigation of diode-pumped 28-μm laser performance in Er:BaY_2F_8

Pollnau

Lüthy

Weber³

et al. 1996

Opt. Lett.

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“…Self-termination of free-running, flashlamp-pumped Er,Cr:YSGG Whilst Yttrium Aluminium Garnet (YAG) is commonly used as a host for   3 m erbium lasers, Yttrium Scandium Gallium Garnet (YSGG) is a potentially superior candidate for Q-switching [12] because of its longer upper laser level lifetime (1.3 ms in YSGG compared to 0.12 ms in YAG [13]) This longer upper laser-level lifetime also makes the YSGG based lasers more suited to "slow" methods of Q-switching. With the YSGG host, the primary laser wavelength is  = 2.794 m, and when flashlamp-pumped, the erbium ions are co-doped with chromium to increase pump energy absorption, giving Er,Cr:YSGG [14].…”

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confidence: 99%

“…The output pulse in fact consists of a pulse-train of ~20 pulses, each of ~400 ns duration, separated by 10 s. This is indicative of self-termination of laser action, caused by the fact that, for   3 m erbium, the lower laser level is longer-lived than the upper laser level (for example, 3.4 ms compared to 1.3 ms in Er,Cr:YSGG [13]). Experimental pulse trace of the free-running, flashlamp-pumped Er,Cr:YSGG laser, as detected with a Molectron P3-01 pyroelectric detector.…”

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Optical chopper Q-switching for flashlamp-pumped Er,Cr:YSGG lasers

et al. 2015

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We present a novel way of Q-switching a flashlamp-pumped,  2.8 m Er,Cr:YSGG laser, wherein a rotating polygon is used as an optical chopper. Single pulse energies of ~3.8 mJ were achieved with pulsewidths of ~305 ns. The scheme benefits from the simplicity of design, and, compared with other Q-switching methods, a reduction in losses and laser damage problems from intracavity components. We also investigate the optimisation of the laser output through purging of the laser with nitrogen, and find a 29% increase in peak output energy.

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Police Use of Force

Gallo

2009

Wiley Encyclopedia of Forensic Science

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Traditionally, the hallmarks of policing involve officers responding to criminal and noncriminal calls for police service, detecting and preventing criminal activity, investigating past crimes, and enforcing laws. To carry out these activities, the police have institutional authority to use force. Such authority, power, or legal right comes from rules of law, which recognize that the police must sometimes use coercive action against law‐violating citizens to accomplish legal objectives. Whenever the police invoke their legal right to use force against citizens, courts in the United States generally apply three major legal decisions that clarify standards surrounding the appropriateness of police use of force: West v. Atkins, Graham v. Connor , and Tennessee v. Garner . Under the umbrella of West v. Atkins , the police must act under color of law to be liable for use‐of‐force actions against citizens that amount to violations of police authority. Police must make objectively reasonable use‐of‐force choices under the Graham rules, which include a balancing test, subjective, objective, hindsight, and totality of circumstances tests. If the police decide to use deadly force against law‐violators, then the Garner rules highlight three conditions in which deadly force may be reasonable: deadly force is necessary, suspects are dangerous, and police are able to warn suspects. Expert testimony by other experienced law enforcement officials is often required to determine and express an opinion on whether the officers acted reasonably in a particular case. In other accusatory system jurisdictions as in civil law jurisdictions, the use of force by the police is regulated primarily by legislative acts, rules, and custom. The use of expert witnesses has somewhat less importance in those jurisdictions.

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3-μm cw laser operations in erbium-doped YSGG, GGG, and YAG

Cited by 195 publications

References 7 publications

Investigation of diode-pumped 28-μm laser performance in Er:BaY_2F_8

Investigation of diode-pumped 28-μm laser performance in Er:BaY_2F_8

Optical chopper Q-switching for flashlamp-pumped Er,Cr:YSGG lasers

Police Use of Force

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