Solution-processed two-dimensional material for generation of pulse fiber laser near 2 Μm spectral region / Nur Atikah Azali

Nur Atikah , Azali (2023) Solution-processed two-dimensional material for generation of pulse fiber laser near 2 Μm spectral region / Nur Atikah Azali. Masters thesis, Universiti Malaya.

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Abstract

The passively mode-locking is more desirable than passively Q-switching due to the ultrafast pulse that can reach until picoseconds or femtoseconds. The ultrafast fiber laser received high interest in wide applications such as welding, communication system, material processing, photonics and medical. The increasing in demands has caused huge development of saturable absorber (SA) using various type of materials. However, each of the SA has some limitation in terms of fabrication and operation that caused barrier to produce better mode-locked pulse. This thesis proposed an alternative SA from mono-elemental group for generation of the mode-locked pulsed by using thulium-doped fiber (TDF) and thulium/holmium-doped fiber (THDF) as gain medium. The main objective of the proposed method is to introduce new SA that has simpler fabrication method, low cost, and can produce better laser performance in terms of high output power and narrow pulse width. There are two materials from mono-elemental group named as bismuthene and antimonene were proposed as new SA, which were synthesized using liquid phase exfoliation (LPE) process. The mode-locked pulse was generated by depositing the SA on top of the arc-shaped fiber and incorporated it in the laser cavity. The pulses were generated by means of the strong nonlinear interaction between the material and the evanescent field of the wave propagating in the arc-shaped fiber. To test the effectiveness of the proposed method, bismuthene and antimonene/arc-shaped fiber as SA were utilized in the THDF and TDF laser cavity. The generation of mode-locking in THDF was conducted using bismuthene, which was prepared with four different concentrations, such as 3 mg/ml, 7 mg/ml, 10 mg/ml, and 20 mg/ml. The aim is to study the effect of concentrations on the generation of mode-locking. Next, the best laser performance of bismuthene was further used to compare with the laser performance induced by other materials such as gallium telluride (GaTe), antimonene, and bulk bismuth. Besides that, the mode-locking generation in TDF using antimonene has also been studied. The output pulse induced by antimonene was compared with hafnium diselenide (HfSe2). The comparison of new SA with other material was conducted to observe the laser performances when utilized in the ring cavity configuration. Mode-locked pulse in THDF and TDF laser were successfully achieved in this work. The bismuthene with different concentrations has produced central wavelength ranging from 1908 nm to 1932 nm. The 10 mg/ml bismuthene/arc-shaped fiber shows the best laser performance compared to the other concentrations. It also has better output power, pulse energy and peak power as compared to other group of materials. Antimonene/arc-shaped fiber also gives good laser performance in the TDF laser. Overall, the bismuthene, antimonene, HfSe2 and GaTe had shown good mode-locking results, thus suggesting new alternative for SA, which is useful for development of technology.

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