Effect of the residual doping on the performance of InN epilayers as saturable absorbers for ultrafast lasers at 155µm

• Published in: Optical materials express Vol. 9; no. 7; p. 2785
• Main Authors: Monroy, L., Jiménez-Rodríguez, M., Ruterana, P., Monroy, E., González-Herráez, M., Naranjo, F. B.
• Format: Journal Article
• Language: English
• Published: Washington Optical Society of America 01-07-2019; OSA pub
• Subjects: Absorbers; Buffer layers; Doping; Engineering Sciences; Fiber lasers; Substrates; Ultrafast lasers
• ISSN: 2159-3930; 2159-3930
• DOI: 10.1364/OME.9.002785

We report on the improvement of performance of InN-based saturable absorbers in fiber lasers operating at 1.55 µm by reducing the residual doping, due to the lower Burstein-Moss effect. The improved tuning of the band-to-band transition with respect to the operation wavelength leads to an enhancement of nonlinear optical effects, resulting in 30 % of modulation depth. We introduce the development of an ultrafast mode-locked fiber laser using an improved InN-based saturable absorber that incorporates a buffer layer between the active layer and the substrate. The laser delivers output pulses with a temporal width of ∼220 fs, a repetition rate of 5.25 MHz, and high-pulse energy of 5.8 nJ.