Tunable Diode-pumped-lna Laser

Diode-pumped crystals provided recently new compact laser devices. We report the first end pumping of a La Ndl-xMgAEl,Ol,(LNA) crystal using a 200mW diode array (Spectra Diode Lab). We also rgport the first results obtained with a ImW diode (SONY). This C.W. laser can be tuned from 1.048~ to 1.086pm. Without selective elements in the cavity, the laser emits around 1.054pm with a threshold of 24mW and a slope efficiency of 4.4% (outputmirrorof transmission T = 1%) when pumped by the diode array. With the selective elements, the threshold increases to lOOmW and we obtain a power of 4mW for a pump power of 200mW. Diode-pumped solid laser materials provide highly efficient as well as compact and relatively low cost laser devices leading to a wide range of potential applications [I]: End pumping of Nd:YAG cystals can deliver over lOOmW of continuous power at 1 . 0 6 ~ when pumped with diode arrays ['I, the overall wall-plug efficiency being as large as 8%[']. There is now a rapidly increasing number of neodymium doped material which has been shown to lase under diode excitation such as LiNbO,["] or silica fibers ["I. Bere we report the diode pumping of La Nd -xMg&lq, (LNA) [ 5 ' 6 ] which is a crystal with laser characteristics similar to N ~ ? Y A ~ or Nd:YAP r7] although with differentcrystal1inesymmetry.We also report the ability to tune the LNA laser output within the range 1.048pm-1.086pm. An important difference between LNA and YAG is the Nd concentration, which can be higher in LNA than in YAG without quenching of the fluorescence [5]. This could be an advantage for future high power 1asers.LNA was recently found to be a slightly tunqble infra-red laser with an efficiency comparable to YAG when excited by Ar of Kr It oscillates at wavelengths significantly different from YAG, with a main peak around 1.054pm and twootherweaker peaks around 1.065pm and 1.082pm. The laser band around 1.065pm had not been observed earlier. It corresponds to a weak fluorescence band actually observed in r5] and L9]. The LNA crystal ia s cylinder, 5mm in diameter and 5mm in length, grown in LET1 (Grenoble). The -rod axis coincides with the crystalline c-axis. One of the two polished parallel faces is high reflectivity coated for the laser radiation and high transmission coated for the pump radiation. The other is antireflection coated for X=1.06@m. It is excited longitudinally by a C.W. diode focused on one end of the crystal. The set-up is shown in figure 1. The diode emits at 800nm, wavelength within the absorption band of LNA[5'9] The light emitted by the diode is collimated by corrected lenses of large aperture (Melles Griot 06 GLC 002). Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987784