Dilute nitride absorbers in passive devices for mode locking of solid-state lasers

We report on the growth, material and nonlinear optical properties of GaInNAs quantum wells (QWs) used in semiconductor saturable absorber mirrors (SESAMs) for passive mode locking of solid-state lasers in the telecommunication wavelength range from 1.3 to 1.55 μm. The antiresonant SESAMs were grown by molecular beam epitaxy with a nitrogen concentration of 1.6% and 2.6%, respectively. They were subject to rapid thermal annealing to fine-tune the absorption wavelength by blueshifting the photoluminescence wavelength. The appearance of QW intermixing upon thermal annealing was studied by X-ray rocking curve measurements. The thermal annealing procedure was proved not to alter the GaInNAs SESAM by QW intermixing for temperatures up to 800 °C. Optical characterization was applied to investigate the nonlinear SESAM properties. Degenerate pump-probe experiments revealed similar recovery times for both SESAMs in the tens of picoseconds range. We demonstrated stable self-starting passive cw mode locking with sub-10 ps pulses at 1314 and 1534 nm.