A compact weak measurement to observe the spin Hall effect of light.

The spin Hall effect of light (SHEL), a microscopic and transverse splitting of linearly polarized light into circularly polarized components during refraction and reflection, can be measured at subnanometer scales using weak measurements and has emerged as a powerful candidate for precision measurements. However, despite the strong demand for compact and miniaturized sensors and precision metrology, no efforts have downsized the weak measurements. Here I demonstrate that the location of the interface where the SHEL occurs does not impact the results of weak measurements and building on this observation, propose a modified setup called the compact weak measurement to reduce the form factor by replacing one convex lens with a concave one. The concept is theoretically validated and numerically confirmed across various setup parameters and interfaces. The compact weak measurement effectively reduces the required free space distance by twice the focal length and will facilitate the implementation of SHEL-based precision measurements in practical applications.