Development of sol-gel saturable absorber for integrated Q-switched lasers

The diversity of integrated photonic sensors such as LIDARs increased in part thanks to integrated laser sources development. Glass integrated lasers fit well sensing demand because of their high durability and great integration potential. We propose here a new kind of saturable absorber (SA) for glass integrated Q-switched lasers, based on a solgel matrix. This is intended to improve durability and output power of existing lasers, whose SA is often based on plastic materials. While sol-gel is already used for optical limiting devices, its use as a host for SA has not been investigated so far. Due to its interesting properties such as durability, high laser induced damage threshold (LIDT) and coating convenience, it should also be a good candidate to realize a reliable SA matrix. We mixed a hybrid organic-inorganic sol with toluene and (bis(4_dimethylaminodithiobenzil) nickel – BDN I, a SA dye molecule. Drops of this mix have been coated and annealed to obtain a SA sol-gel thick layer. We modeled BDN I with a four energy-level system and measured its absorption over optical input power at the wavelength of 1064nm in order to extract its physical parameters: absorption cross sections and relaxation time. This SA showed good performances with 30% modulation depth. This sol-gel has also been spin coated on ion-exchanged glass integrated waveguide. The characteristics of this waveguide SA have been measured and the evanescent light interaction between the waveguide and the saturable absorber layer has been modeled. This study will allow further integrated Q-switched lasers design.