## 4 Experimental Results and Discussion
### Output Characteristics of Q-Switched Laser Based on PSM-SA
When the pumping power approaches around 340 mW, the fiber laser system operates at its most stable state, consistently producing Q-switched pulses. The corresponding spectrum is shown in Figure 5b. However, as the pumping power further escalates and reaches approximately 390 mW, a special transformation occurs, as seen in Figure 5a. The increase in power corresponds to a rise in temperature, which, in turn, exerts an influence on the PS polymer chain. This thermal effect triggers shear vibrations that affect the relative positions and structures of the molecules within the PSM-SA. Consequently, the molecular polarity and electric dipole moment decrease, resulting in a reduced refractive index. As the pumping power continues to rise beyond this critical point, the Q-switched behavior begins to diminish. Under the sampler power, the amplitude of the spectral waveform has begun to decrease and deviate from the Q-switched state, the spectrum has redshifted, and the shape has begun to become irregular. This distinctive behavior is observed when the laser system goes beyond the ultimate limit of the Q-switched state, which is intrinsically linked to characteristics of the 430 nm PSMs and their interaction with the laser system. This observation provides a profound insight into the intricate dynamics within our experimental setup, illuminating the delicate balance between pumping power, temperature, and the material properties of the PSM-SA. Interestingly, a stable Q-switched pulse can be obtained again when the pumping power is decreased. This compelling phenomenon underscores the unique attributes of the PSMs employed in our research, specifically their substantial volume  
Figure 5: (**a**) Output pulse sequence in time domain and (**b**) Output spectrum in stable Q-switched state; (**c**) Waveform comparison and (**d**) spectral comparison between PSM-SA sample and PS sample. and expansive specific surface area. These characteristics endow them with remarkable resilience to thermal stress and enable the restoration of their stable Q-switched behavior. These observations demonstrate the influence of pumping power and heat on the Q-switched dynamics of the laser system based on PSM-SA and the resilience and recovery capabilities of the PSM used in the experiment. PSM-SA was compared with samples containing only PS film on the gold mirror inserted into the ring cavity, in which the PS-only samples did not show any Q-switched behavior, and the nonlinear properties of PS did not seem to be activated, as shown in Figure 5c,d. The spectral characteristics were distinct, with the PS-only sample's spectral profile closely resembling that of the CIR output spectrum. This comparison highlights the fact that incorporating a microsphere structure into the design of photonic crystals can significantly enhance the intrinsic nonlinear characteristics of the material, potentially leading to the generation of nonlinear effects. Despite PS not displaying Q-switched signals, the introduction of PSM successfully enabled the Q-switched laser operation. Figure 6 unveils a comprehensive depiction of the output characteristics, providing a nuanced insight into the dynamic evolution of the Q-switched pulse waveform as previously illustrated in Figure 5a. First and foremost, the average output power of the fiber laser demonstrates an intriguingly linear increase in correspondence with the ascending pump power. At its zenith, the system achieves an impressive output power of 1.17 mW, mirroring the ascending waveform height illustrated in Figure 6a. This linear correlation is a testament to the system's capacity to efficiently harness and convert pump power into useful laser output. As the pump power intensifies, the duration of pulse energy accumulation within the PSM notably diminishes. This reduction in pulse duration translates into an elevation in the repetition frequency, denoted as \(f\). When the pump power reaches its maximum value, the frequency increases to 42.1 kHz, as depicted in Figure 6b.