Simulating the neural synapses of the brain is a key step to realize the next generation computer, that is, the brain-like neuromorphic computing system. To mimic the plasticity of neural synapses using photons and develop all-optical artificial synaptic devices, we carried out an experimental study on the chalcogenide amorphous semiconductor artificial synaptic device based on controllable light-induced inhibition. The control of the material chemical composition and pumping optical power on the artificial neural synapse was studied, and the plasticity of the artificial neural synapse was described. The results show that As-S planar waveguides with different impurities have different light-induced inhibition processes, and different pumping optical powers correspond to different suppression depths. Based on these characteristics, the artificial neural synapse exhibits short-term plasticity (STP), long-term plasticity (LTP), and paired-pulse depression (PPD), demonstrating that it has good plasticity.