Single-frequency glass waveguide lasers S. Taccheo* ab , G. Della Valle b and D. Milanese c a University of Swansea, Singleton Park, SA28PP, Swansea, UK b Politecnico di Milano, Dipartimento di Fisica, Piazza L. da Vinci 32, 20133 Milano, Italy c Politecnico di Torino, Viale Duca degli Abruzzi 24, 10100, Italy ABSTRACT We report results on a single-end pumped waveguide laser for sensing applications Output power in excess of 20 mW with 17% slope efficiency in robust single-frequency operation at 1533.5 nm is demonstrated. The overall laser cavity laser was 60-mm long but the active medium, an Er:Yb-doped phosphate glass, was only 9-mm long. The waveguide was fabricated by two-step Ag-Na ion-exchange technique. The overall cavity length including butt-coupled fiber- Bragg-grating mirrors was <60 mm. We also reports on recent work to reach 100-mW single-frequency output power. To extend the operation wavelength to 2-micron wavelength region we also developed new tellurite glasses. Preliminary results on glass investigation are also reported. Keywords: Single-frequency lasers, waveguide lasers, ion-exchange, tellurite glasses, 1. INTRODUCTION Several applications ranging from free space optical communications [1], laser radar and satellite based remote sensing [2], distribute fiber-optic sensors [3], and frequency domain reflectometry [4], demands high-power, compactness, insensitivity to environmental disturbance and high temporal coherence. In particular airborne based remote sensing will benefit from high insensitivity to environmental disturbance and satellite based remote sensing from flexible laser management. Standard solutions such are represented by bulk and fiber lasers. However the first one while is able to provide high output powers in view of large mode volume, actually suffers from several limitations in terms of compactness and robustness of the cavity. In addition bulk lasers may bring additional problems when airborne or satellite installed due to free-space output. Ob the other side guided lasers, such as fiber and waveguide lasers, can be placed everywhere, even close to satellite power unit and the output, coupled to a fiber optic, easily delivered to the anywhere needed. Short fiber lasers [5] have recently demonstrated the potential to satisfy all the requirements thanks to proper choice of glass host and provide a monolithic cavity structure. Power level of the order of 1W in single frequency operation at 1.5 µm has been already reported [6]. However waveguide laser, who allows rigid substrate on which all laser components can be made, are expected to provide even better performance in terms of robustness and insensitivity to technical noise. Despite this clear advantage waveguide laser were little investigated and only limited output power in the order of few mW was demonstrated until recently. The limit origins from the difficulty in fabricating high quality active waveguides in heavily-doped glasses and in optimizing doping concentration for efficient pumping over short lengths. In fact a highly-doped material is required to meet the demand of high-power together with a compact laser cavity (around few cm long) allowing single longitudinal mode operation. This requirement makes glass-on-silicon technology unsuitable because erbium concentration is limited by quenching effects in silica [7]. On the contrary phosphate glass offers a far better solubility with respect to silica and also makes codoping with Yb ions more beneficial for pumping due to higher phonon energies in the phosphate resulting in a more efficient energy transfer from Yb to Er. We note here that the use of codopant such as Yb is a key solution to enhance high pump absorption over short lengths. *s.taccheo@swansea.ac.uk; phone +44 01792 602465; Invited Paper Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing IV, edited by Upendra N. Singh, Gelsomina Pappalardo, Proc. of SPIE Vol. 7111, 711103 · © 2008 SPIE · CCC code: 0277-786X/08/$18 · doi: 10.1117/12.800408 Proc. of SPIE Vol. 7111 711103-1 2008 SPIE Digital Library -- Subscriber Archive Copy