A model is developed for an end-pumped quasi-three-level laser with population in the lower laser level at equilibrium such as for transitions to the manifolds4I 9/2 in Nd3+,4I 15/2 in Er3+,5I 8 in Ho3+and3H 6 in Tm3+. It is shown that the effect of residual lower laser level population on laser operation can be treated as a saturable loss. Room temperature operation on the4F 3/2 -4I 9/2 transition in Nd:YAG under CW dye laser pumping has been demonstrated with a threshold as low as 11.5 mW incident power and a slope efficiency of 7 percent with 0.3 percent output coupling. Performance is limited by the low output coupling and diffraction loss.

Modeling and CW operation of a quasi-three-level 946 nm Nd: YAG laser

The measurement of branching ratios, cross sections and radiative lifetimes for rare earth ions in solids is considered The methods are applied to Tm and Ho in YLF as a test case De-activation rates for electric dipole and magnetic dipole emission are calculated for many of the lower lying manifolds in Tm:YLF and Ho:YLF in the context of the Judd-Ofelt theory to determine radiative lifetimes Measured values for the branching ratios as well as the absorption and emission cross sections are also presented for many of the excited state manifolds From these measurements, a methodology is developed to extract measured values for the radiative lifetimes These results are compared with the Judd-Ofelt theory as a guide for consistency and for determining the accuracy of the Judd-Ofelt theory in predicting branching ratios and radiative lifetimes The parameters generated by the methods covered here have potential applications for more accurate modeling of Tm:Ho laser systems

Branching ratios, cross sections, and radiative lifetimes of rare earth ions in solids: Application to Tm3+ and Ho3+ ions in LiYF4

Radiation trapping causes significant lengthening of the measured fluorescence lifetime in optically thin solid-state laser gain media, which leads to underestimates of the stimulated emission cross section by as much as 30%. A measurement technique is demonstrated that greatly reduces radiation trapping in Yb:YAG, a prototypical quasi-three-level laser medium. The radiative lifetime of the (2)F(5/2) manifold was measured to be 0.951 ms at 300 K, which is more than 10% lower than any previous measurement. This more-accurate radiative lifetime gives a 1.03-microm peak effective stimulated emission cross section of 2.3 x 10(-20) cm(2). Our measurement technique is expected to be most relevant for three-level and quasi-three-level laser media.

Effect of radiation trapping on fluorescence lifetime and emission cross section measurements in solid-state laser media.

Spectroscopic measurements and analysis of diode laser-pumped operation of Tm,Ho:YAG at 2.1 mu m at room temperature have been performed. The peak effective stimulated emission cross section is measured to be 9*10/sup -21/ cm/sup 2/ at 2.091 mu m and the upper state lifetime is 8.5 ms. Under diode laser pumping, thresholds of 4.4 mW of absorbed power and slope efficiency of 19% have been demonstrated. Calculations of threshold power are performed based on the spectroscopic measurements. An energy transfer upconversion process is identified which leads to a sublinear rise in upper-state population with pump power. >

Spectroscopy and diode laser-pumped operation of Tm,Ho:YAG

Laser oscillation in Nd:MgO:LiNbO3 has been demonstrated. Thresholds as low as 3.6 mW and slope efficiencies up to 39% were achieved in a resonantly pumped miniature device. The electro-optical and nonlinear-optical properties of the host were also used to make active internal Q-switched and self-frequency-doubled lasers. Photorefractive damage is shown to be greatly suppressed compared with that for non-MgO-doped material. Absorption spectra, fluorescence spectra, and lifetime measurements are also reported.

/pdf/nd-mgo-linbo-3-spectroscopy-and-laser-devices-1oce9wcfgj.pdf

Nd:MgO:LiNbO 3 spectroscopy and laser devices

In this paper we discuss the quantum efficiency of the metastable4 F_{3/2} state in Nd:YAG. We show that the vibronic interaction disrupts the equality between absorption and emission cross section ("reciprocity") upon which spectroscopic quantum efficiency measurements are based. Even if the electron-lattice coupling is weak, a phonon whose energy matches the energy difference between two electronic states can have a significant effect. Our spectroscopic measurements clearly show nonreciprocity and establish the importance of vibronics in Nd:YAG. The data are consistent with a high quantum efficiency.

Vibronic interactions in Nd:YAG resulting in nonreciprocity of absorption and stimulated emission cross sections

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Vibronic interactions in Nd:YAG resulting in nonreciprocity of absorption and stimulated emission cross sections