High-density Orbital Angular Momentum mode analyzer based on the mode converters combining with the modified Mach-Zehnder interferometer

Here, we have proposed a high-density orbital angular momentum (OAM) analyzer consisting of two OAM mode converters and a modified Mach-Zehnder interferometer (MZI) that is composed of the standardized MZI and a pair of Dove Prisms, which can effectively avoid the inherent overlap of two adjacent OAM modes in the OAM mode converter. In this scheme, the multiplexing OAM beam is incident into the modified MZI, which can sort and separate the even and odd OAM modes into different ports respectively. Two successive OAM mode converters can efficiently measure the sorted even and odd OAM modes in the port A and the port B of the modified MZI, respectively. By this method, the topological charge interval between two neighboring OAM beams would be at least greater than or equal to 2 at both MZI output ports, and then the distance of two adjacent light spots converted from the output OAM modes will be greater than the width of the light spot. Therefore, the proposed scheme can exactly avoid the overlapping effect and solve the problem about the limited discrimination resolution, from which the analysis of the high-density OAM modes can be realized.