Recently, many researches in laser light development have been focused on developing Q-switched fiber lasers because of its many advantages. They have many potential applications in areas such as remote sensing, material processing, range search, laser reflectometry, telecommunications, and medical. Q-switching can be realized by active or passive methods. The active method uses a modulator to produce Q-switching pulses, while the passive technique is obtained by inserting a saturable absorber (SA) device in the laser cavity resonator. Therefore, passive techniques are generally cost-effective and more useful than active method, which requires additional electronic switching.
Passive method is also more compact and flexible in their use compared to active method. To date, several types of SA have been intensively reported to produce Q-switching pulses, including semiconductor SA mirrors (SESAMs), carbon nanotubes (CNTs) and 2D nano materials such as graphene and transition metal di-chalcogenides (TMDs).
In this study, A passively Q-switched erbium-doped fibre laser was demonstrated by using tris-(8-hydroxyquinoline)aluminium (Alq3) organic material as a passive saturable absorber (SA). The SA was fabricated by a drop casting technique at room temperature and incorporated into a laser cavity by inserting it between two optical fibre ferrules. The Q-switched fibre laser operates at a centre wavelength of 1559 nm with a full-width half maximum of 1 nm. The generated pulse train is stable and has a pulse width decreased from 6.65 to 1.2 µs and the pulse repetition rate increased from 31.65 to 144.5 kHz as the pump power increased from 20 to 122 mW. The maximum pulse energy obtained is 63.89 nJ.
This work indicates that the Alq3 as SA has a great potential to be utilised for pulsed laser generation. To the best of the authors’ knowledge, this is the first time an organic material is utilised as a SA device for generating a stable Q-switched laser pulse.
Author: Moh Yasin
