Experimental investigation and numerical simulation of the spatio-temporal dynamics of nanosecond pulses in Q-switched Nd:YAG lasers

• Published in: Applied physics. B, Lasers and optics Vol. 76; no. 8; pp. 833 - 838
• Main Authors: ANSTETT, G, NITTMANN, M, BORSUTZKY, A, WALLENSTEIN, R
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.07.2003
• Subjects: Beam characteristics: profile, intensity, and power; spatial pattern formation; Computer simulation; Doped-insulator lasers and other solid state lasers; Dynamic tests; Dynamics; Evolution; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Laser cavities; Laser optical systems: design and operation; Lasers; Mathematical models; Optics; Physics; Resonators; Beam profiles; YAG laser; Digital simulation; Time evolution; Optical pumping; Photoflash lamp; Experimental study; Pulsed lasers; Solid state lasers; Q switched laser; Pulse shape; ns range; Neodymium lasers
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-003-1189-4

This paper reports on an experimental investigation and numerical simulation of the spatio-temporal dynamics of the pulse formation in flashlamp-pumped Q-switched Nd:YAG lasers. The temporal evolution of the spatial intensity distribution is measured with a fast two-dimensional CCD camera. The measurements are performed for two lasers with different cavity configurations. A laser with an optically stable resonator and an internal mode aperture generated pulses with a spatial intensity distribution which is Gaussian at all times during the 10-ns-long pulse. During the pulse evolution the value of the beam-quality factor Mremains below 1.3. In a laser with a positive-branch unstable resonator the laser pulse also starts with a Gaussian intensity distribution, but becomes rapidly non-Gaussian. The corresponding Mvalues increase from about 1 at the beginning of the formation of the pulse to more than 12 in the tail of the pulse. The measurements are compared with the results of a numerical simulation which takes the laser amplification, the properties of the laser cavity, and the diffraction of the beam in the laser cavity into account. The spatio-temporal dynamics of the pulse formation predicted by the numerical model are in good agreement with the experimental results.