We have studied the quantum-noise properties of a small slow-inversion laser experimentally and theoretically. As a function of pump rate, the average output intensity shows a sharp threshold, but the intensity fluctuations do not. Under quite generic conditions the intensity fluctuations of a sufficiently small slowinversion laser show highly super-Poissonian statistics ͑even two times above threshold͒, due to the very weak damping of the spontaneous-emission-driven relaxation oscillation.

We have measured the photon number probability distribution of a laser in which the inversion is not slaved to the field. For the experiments, we have used a Nd(3+):YVO(4) laser which has a sufficiently slow inversion to allow measurement of the photon fluctuations at a time scale much shorter than that of the relaxation oscillations. The photon distribution function becomes highly nonstandard (i.e., non-Poissonian) in such a laser; this is consistent with available theoretical work. We point out the relevance of our results for the case of the semiconductor microlaser.

We investigated laser-induced deposition processes on BK7 substrates under the influence of pulsed Q-switched Nd:YAG laser radiation, starting from small toluene partial pressures in a background vacuum environment. The composition and structure of the deposit was analyzed using microscopic methods like Nomarski DIC, dark-field and white-light interference microscopy, TEM, EDX and XPS. We found a distinct threshold for deposition built-up dependant on the partial pressure of toluene (0.2 J/cm 2 at 0.1 mbar, 0.8 J/cm 2 at 0.01 mbar toluene). The deposits strictly followed the spherical geometry of the laser spot. No deposit accumulated on MgF 2 AR coated BK7 samples even at high toluene partial pressures. The onset of deposit was accompanied by periodic surface ripples formation. EDX and XPS analysis showed a carbon-like layer which strongly absorbed the 1 µm laser radiation. The typical number of shots applied was 50 000. In addition, long term lifetime tests of more than 5 Mio. shots per site were run.

Observation of transverse modes in a microchip laser with combined gain-and indexguiding van Druten, N.J.; Oemrawsingh, S.S.R.; Lien, Y.; Serrat, C.; van Exter, M.P.; Woerdman, J.P. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. The transverse-mode profiles for a plano-concave Nd:YVO 4 microchip laser near threshold are examined, both experimentally and theoretically, and in both the near and the far field. We study in particular the transition from dominant quadratic index guiding to dominant gain guiding. The modal profiles change dramatically in this transition, and the agreement between experiment and the theoretical model is excellent.