High-efficiency waveguide optical amplifiers and lasers via FS-laser induced local modification of the glass composition

Abstract

FS-laser irradiation at high repetition pulse rate enables producing high-performance passive waveguides in different glasses through the local modification of the glass composition. In this paper, we show that this mechanism can similarly be used to produce high-performance waveguide amplifiers and lasers. Furthermore, we show the feasibility of producing active waveguides with different optical gains in the same phosphate glass sample by changing the laser writing parameters. The lanthanides present in the glass composition (Er, Yb, and La, the refractive index carrying element) experience similar local concentration changes upon fs-laser writing, enabling to determine the concentration of La and thus the refractive index contrast of the guiding region by measuring its absorption at 1534 nm. The produced waveguide lasers show slope efficiencies (respect to the absorbed pump power) above 38%, which could reach up to 42% by further optimization of the waveguide laser cavity configuration. The active waveguides produced are thermally stable for temperatures up to at least 450 °C.