A comparative study is made of the laser crystals 50 at. % Er:YAG and 50 at. % Er:YSGG. Both lasers are constructed in the bounce geometry with quasi continuous wave (QCW) diode pumping. In Er:YAG, pulse energies of up to ~31mJ, slope efficiency of 12.6% and a red-shift in laser wavelength are observed with a final and dominant wavelength of 2.936μm. In Er:YSGG, higher performance is achieved with pulse energies of ~55mJ, slope efficiency of 20.5% and a single transition wavelength of 2.797μm observed. The study indicates that diode pumped Er:YSGG is a superior laser source at 3μm than Er:YAG and it has greater energy storage potential for Q-switched operation.

We report the investigation of an Alexandrite laser end-pumped by a fibre-coupled red diode laser module. Power, efficiency, spatial, spectral, and wavelength tuning performance are studied as a function of pump and laser cavity parameters. It is the first demonstration, to our knowledge, of greater than 1W power and also highest laser slope efficiency (44.2%) in a diodepumped Alexandrite laser with diffraction-limited TEM 00 mode operation. Spatial quality was excellent with beam propagation parameter M 2 ~ 1.05. Wavelength tuning from 737 -796nm was demonstrated using an intracavity birefringent tuning filter. Using a novel double pass endpumping scheme to get efficient absorption of both polarisation states of the scrambled fibredelivered diode pump, a total output coupled power of 1.66 W is produced in TEM 00 mode with 40% slope efficiency.

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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.

In the present paper, we report on a comprehensive spectroscopic study of yttrium scandium gallium garnet, YSGG, highly-doped (38 at.%) with Er 3+ ions. Main focus of this work is the determination of stimulated-emission cross-sections spectra for ~1.5 μm ( 4 I 13/2 → 4 I 15/2 ) and ~3 μm ( 4 I 11/2 → 4 I 13/2 ) transitions of Er 3+ ions, for the first time, to the best of our knowledge. Absorption cross-sections spectra are also determined. This information is crucial for development of novel near-IR and mid-IR erbium lasers. To determine radiative lifetimes of the excited states of Er 3+ ions, we involve Judd-Ofelt theory modified for systems with an intermediate configuration interaction. Up-conversion is also studied for this crystal. Finally, laser operation with Er:YSGG crystal at ~3 μm is achieved.We confirm that the manuscript is the authors' original work; it has not been published and it has not been submitted simultaneously elsewhere. We also confirm that all authors have checked the manuscript and have agreed to the submission.Dear Editor, Thank you for considering our manuscript for publication in Journal of Luminescence and for permitting us this opportunity to respond to the reviewers' comments. We welcome the comments from the reviewers and have complied with all of the comments.A detailed list of the corrections follows. Reviewer #1The authors have answered satisfactorily all my requirements. There is only one more thing I have not noticed up to now and I really have to check: 1. Page 3: The authors do not specify explicitly whether the contributions of the magnetic dipole to the experimental oscillator strengths were subtracted before fitting the data with the Judd-Ofelt model. If they were subtracted, please specify this fact in the paper. If this is not the case, the calculations should be corrected. Yes, we have subtracted MD contributions to the experimental oscillator strengths prior to the JuddOfelt modeling. Now this is specified in the text (page 3): Prior to the fitting of experimental oscillator strengths with the J-O model, MD contributions were subtracted from the fexp values.Judd-Ofelt analysis and stimulated-emission cross-sections for highly doped (38 at.%) Er:YSGG laser crystal Abstract Stimulated-emission cross-section spectra are determined for the ~1.5 μm and 3 μm transitions of Er 3+ ions in YSGG crystal. For the 4 I 11/2 → 4 I 13/2 channel, the maximum stimulated-emission cross-section σ SE is 0.43×10 -20 cm 2 at 2797.1 nm. For the 4 I 13/2 → 4 I 15/2 channel, σ SE = 1.20×10 -20 cm 2 at 1532.8 nm. Due to the reabsorption loss, laser operation is expected at 1644 nm. Radiative lifetimes of all excited states of the Er 3+ ion from 4 I 13/2 to 2 H 9/2 and probabilities of radiative transitions from these states are determined using the Judd-Ofelt theory. Radiative lifetimes of the 4 I 13/2 and 4 I 11/2 excited states for Er 3+ ions in YSGG are 7.73 ms and 9.75 ms, respectively. Non-radiative decay is analyzed for lower excited-states of Er 3+ ions in YSGG.Keywords: erbium ions...