Optical Path Difference Modulation Method Based on the Kerr Effect

Optical path difference is commonly used to adjust the signal of coherent light. Current optical systems typically adjust the transmission distance of the beam or the refractive index of the medium to change the optical path. However, the former approach often involves complex operations, risks of mechanical damage, and difficulties in adjustment, while the latter has a limited adjustment range. This letter proposes a Kerr-fiber-based optical path difference adjustment system. In this system, the Kerr liquid inside the fiber induces a change in birefringence due to the electric field's polarization effect, enabling rapid optical path adjustment. The system adjusts the effective refractive index by applying an external voltage: a 10-V voltage induces a one-cycle change in interference fringes, and increasing the voltage to 50 V results in a 0.1 change in the refractive index, with a minimum adjustment precision of 0.01. Experimental results demonstrate a millisecond-level response rate for the overall system. Comparative tests show that this method is similar to classic adjustment methods but offers simplified operation. In addition, the system exhibits enhanced stability in scenarios requiring rapid and precise adjustments.