External modulation of a CW fiber laser via thermocavitation microbubbles: A novel approach for short pulse generation

Abstract

This research introduces a novel method for generating short pulses using microbubbles produced by thermocavitation, a process initiated in both absorbent and non-absorbent solutions. The innovation uses a multimode optical fiber, onto which silver and copper nanoparticles are photodeposited, enabling precise control over the pulse generation process. By immersing the fiber tip in ethanol or a Hibiscus flower extract in ethanol, tunable pulses are generated with frequencies ranging from 0.4 to 3.3 kHz in ethanol and 0.64–2.8 kHz in the Hibiscus solution, with pulse durations of 15–81 μs and 22–41 μs, respectively. The emitted pulse wavelength remains consistently at 443 nm, demonstrating the system's ability to produce short, precise pulses across different media. Additional experiments were carried out using methylene blue as the working solution. A maximum frequency of 1.51 kHz was achieved through interaction with a continuous-wave laser at a wavelength of 658 nm. Subsequently, ethanol was used as the medium, achieving a maximum frequency of 1.43 kHz with a laser operating at a wavelength of 976 nm. The innovation of this device is attributed to its tunability and versatility in using various media to control pulse characteristics. This flexibility, combined with a relatively simple and cost-effective fabrication process, positions the system as a promising solution for applications in quantum telecommunications, ophthalmic surgery, ultrasound imaging, metrology, and sensor technology. Its ability to generate controlled, high-frequency pulses from thermocavitation microbubbles marks a significant advancement in pulse generation technology.