Optical bistability of azo dye-doped PMMA polymer

•The optical bistability of DR1-doped PMMA polymer is investigated.•The experimental set up is Mach–Zehnder interferometer.•Two dominant mechanisms: Cis–Trans isomerization and local thermal effect.•Comparing the gain of OB based on applying internal and external feedbacks.

In this paper, the optical bistability (OB) in three DR1-doped PMMA polymer samples with different thicknesses is experimentally investigated. The measurements are performed in the presence and absence of external feedback in a Mach–Zehnder interferometer nonlinear-ring-cavity. A CW Nd:YAG laser (λ = 532 nm) with 300 mW power is used to interact with the thin polymer films. The results show a hysteresis loop due to optical bistability, indicating that increase of feedback (by 20%) results in OB-index increase. So, increasing the external feedback improved the OB-gain. Cis–Trans isomerization and local thermal effect are responsible for OB-hysteresis loop observation.