A photonics-based high-order subharmonic mixer, which enables a low-frequency LO source to be used for high-frequency RF signal frequency downconversion, is presented. It is based on an optically injected semiconductor laser, which is oscillated in the period-one state, sandwiched between two optical phase modulators. It has the advantages of a simple and compact structure, wide bandwidth, absence of electrical components, reconfigurable subharmonic mixing operation, stable output IF signal performance, high signal-to-noise ratio, infinite LO-to-RF port isolation, and high LO-to-IF port isolation. Furthermore, it is suitable for use in remote antenna applications. We set up a proof-of-concept experiment that demonstrates a reconfigurable second-, fourth-, sixth-, and eighth-order subharmonic mixing operation for different input RF signal frequencies and powers. The experimental results also demonstrate that the proposed structure exhibits a stable output IF signal performance, which overcomes the IF signal phase stability problem in the reported high-order subharmonic mixers.