Development of passive ultrafast fiber lasers at telecom wavelengths using indium nitride as saturable absorber

Abstract

This thesis focuses on the research of new technologies for fabrication of passive ultrafast mode-locked fiber lasers, operating at telecom wavelengths (C-band, 1.53-1.57 μm). For this purpose novel saturable absorbers based on indium nitride (InN) are proposed, which have been deposited using molecular beam epitaxy. This material presents unique properties such as direct band gap energy, high thermal and chemical stability, and high radiation hardness.

In this thesis, the InN based structures have been completely characterized, being particularly detailed the optical characterization of both the linear and nonlinear behavior. The developed devices have demonstrated high nonlinear optical effects, with modulation depth over 30%. Moreover, they have proved to support over 100 mJ/cm2, with no sign of apparent optical damage, converting them in promising devices for high energy applications.

Also, the design and fabrication of laser resonators have been carried out. For this purpose, optical fiber has been used as active medium, besides the InN-based saturable absorbers for achievement of the mode-locking. The developed lasers deliver ultrashort pulses (200-250 fs) with high peak power (over 40 kW). Furthermore, all the lasers using InN based saturable absorbers have exhibited properties such as polarization independence or self-starting operation.

For all the experiments that have been performed along this work, InN can be situated as a promising material for application in the design of ultrafast lasers with emission at telecom wavelengths.