Laser action in ion-exchanged waveguides fabricated on Er-Yb-doped phosphate glasses using planar technology

Abstract

Waveguide laser arrays operating at 1.5 micrometers have been fabricated on Er:Yb-doped glass substrates by a two-step silver-sodium ion-exchange process based on thermal diffusion followed by a field-assisted burial step. The fabrication parameters have been optimized to achieve low propagation losses and good mode matching between waveguide channels and standard single-mode output fibers. Each laser cavity is formed by two Bragg gratings butt-coupled to the two ends of the channel waveguide. Fiber-coupled output power in excess of 10 mW is readily available from a single channel, when pumped from both sides by two 980-nm laser diodes providing a maximum power of ~300 mW. Single-longitudinal mode operation with output power of the order of 1 mW has been achieved using narrow reflectivity band (<30 GHz) Bragg gratings with different laser configurations. The laser operating wavelength can be selected across the whole C-band of optical communications (1530-1565 nm) by changing the Bragg grating peak reflectivity wavelength. A relative intensity noise lower than -150 dB/Hz has been measured for frequencies larger than 2 MHz. Stability of single-frequency operation, low intensity noise and flexibility in the choice of the operating wavelength make this laser array particularly attractive for wavelength division multiplexing optical transmissions.