The Maxwell's work has taught us the electric field, magnetic field, and optical field are entangled together. Unlike the electromagnetic coupling that has been deeply and widely explored, the interconversion between light and magnetization remains to be carefully elucidated. Different light induced magnetization theory has been developed, while their applications and verifications in real materials are still underway. We use nonlinear optical response theory to calculate the photoinduced magnetization in ferroelectric bilayers, whose band gaps can be effectively controlled under gate voltage with a wide tuning range (from a few tens meV to a few eV). Orbital contributions to magnetizations are revealed to be equilvalent or even overpassing the spin contributions. Interestingly, we propose that the theoretically discovered "hidden spin polarization" can be observed under such mechanism, which is very subtle and remains experimental observations. Our work has just appeared online in Advanced Optical Materials at https://onlinelibrary.wiley.com/doi/10.1002/adom.202200428.