Discovery of Several New Families of Saturable Absorbers for Ultrashort Pulsed Laser Systems

Syed Asad Hussain

doi:10.1038/s41598-019-56460-5

Abstract

Saturable Absorber (SA) is a key element of any passive mode-locked laser system to provide ultrashort laser system. So far various materials have been proposed that could be used for this purpose. However, the field is still looking for new ways to make the fabrication process easier and cost-effective. Another challenge in testing mode-locked laser systems using various SA samples is the lack of knowledge in preparing these by laser physicists given this is outside their remit of expertise. In this study, we have proposed a novel method to produce these SAs from plastic materials and glycol. Our new method relies upon increase in thickness up to a value where the modulation depth is enough to give stable ultrashort pulses. Although we have shown this method for four materials; similar approach could be applied to any material. This will open the door of unlimited families of SAs that could be easily prepared and applied without any prior knowledge in material sciences.

Highlights

Lasers are frequently used in various commercial and scientific instruments notably surgery, spectroscopy, telecommunication, microscopy to name few[1,2,3,4,5,6]
In this paper, we have presented a method to obtain inexpensive materials to be used as Saturable Absorber (SA) inside a laser to provide mode-locked ultrashort pulses
Provided the material has absorption at the laser wavelength, the thickness of the material should increase until its modulation depth is as per the requirement of the laser

Summary

Introduction

Lasers are frequently used in various commercial and scientific instruments notably surgery, spectroscopy, telecommunication, microscopy to name few[1,2,3,4,5,6]. Whereas for a constant sample thickness, non-linear absorption decreases as we increase the power This is due to the fact that in this case we are providing more photons to the sample that has finite number of electrons[10]. Hönninger et al provides us a good guideline on this[12] According to their guidelines, the product of saturation energy of laser gain material (EL) and absorption (EA), and modulation depth (ΔR) should be lower than energy inside the cavity (Ep), i.e. Ep > ELEAΔR. The product of saturation energy of laser gain material (EL) and absorption (EA), and modulation depth (ΔR) should be lower than energy inside the cavity (Ep), i.e. Ep > ELEAΔR By satisfying this criteria, the laser will give mode locked pulses, otherwise Q-switched pulses will be achieved, please see Fig. 8 in ref. The SA must withstand high peak powers of the laser cavity

Methods

Results

Conclusion