Shanghai Institute of Optics and Fine Mechanics has made progress in synchronously pumped ultrafast Raman fiber lasers

Recently, the research team led by Zhou Jiaqi from the Aerospace Laser Technology and Systems Department of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has made progress in the study of synchronously pumped ultrafast Raman fiber lasers. The related achievements were published in Optics Express under the title "Revealing influence of timing jitter on ultra fast Raman fiber laser synchronously pumped by gain switched diode".

Synchronous pumping technology utilizes ultrafast pulses with high peak power as pumps. Compared to traditional mode-locked Raman fiber lasers with continuous optical pumping, it can effectively overcome the problem of weak Raman gain and obtain high-performance Raman solitons under short cavity conditions. For synchronously pumped Raman fiber lasers, using a gain switching diode (GSD) with adjustable repetition rate as the pump can effectively simplify the synchronization difficulty compared to a mode-locked pump source with fixed repetition rate.

The research team built a GSD synchronously pumped Raman fiber laser (Figure 1), and the experimental results revealed that the inherent strong time jitter characteristics of GSD pump pulses are the fundamental reason for reducing the time-domain stability and frequency-domain coherence of output Raman pulses. A detailed study was conducted on the time-frequency characteristics of output Raman pulses under different pump pulse widths, confirming that stretching the pulse width can effectively reduce the influence of pump time jitter and suppress the relative intensity noise of output Raman pulses (Figure 2). In addition, comparative experiments were conducted using a mode-locked laser instead of GSD pump, and the results further confirmed the key influence of pump pulse time jitter on the frequency domain coherence of output Raman pulses. This study not only deepens the understanding of GSD synchronously pumped Raman fiber lasers, but also paves the way for the generation of high-performance ultrafast Raman pulses.

Figure 1. Schematic diagram of experimental setup for GSD synchronously pumped Raman fiber laser

Figure 2. Relative intensity noise of output Raman pulses under different pumping conditions

Relevant work has been supported by the National Key R&D Program, the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the National Natural Science Foundation of China and other projects.

Source: Opticsky