Optimal pump intensity for quantum-enhanced stimulated Raman scattering microscopy

We investigate the optimal pump intensity in quantum-enhanced stimulated Raman scattering (SRS) microscopy using an asymmetric beamsplitter. Specifically, we derive the intensity that maximizes the signal-to-noise ratio (SNR) under the condition where the total optical intensity of the pump and Stokes pulses is constrained to prevent photodamage, and under the condition without such constraints. In the absence of power constraints, the highest SNR is achieved by simply maximizing the pump intensity without using squeezed light. Under power constraints, the optimal pump intensity in classical SRS is known to be one-third of the photodamage threshold. We reveal that, in the quantum-enhanced regime, the optimal pump intensity is lower than the classical optimum, and as the squeezing level increases, this deviation from the classical optimum grows more pronounced. Our analysis provides valuable guidelines for achieving high-sensitivity SRS imaging with quantum enhancement.