Spin waves interact with both microwaves and light. Being electromagnetic waves, light and microwaves show similar behaviour. For example, they diffract around edges of objects and can interfere constructively or destructively.
A similar interferometer can be made for microwaves; just replace all optical components with microwave counterparts. The branch of optics (physics of light) encapsulating wave phenomena such as interference is called classical optics. Classical optics also explains wave phenomena like reflection, refraction, diffraction and polarisation. Most of these physical phenomena can be studied in an undergraduate or graduate course with experiments. Moreover, the analogy between optics and microwave physics can be exploited to create new experiments to improve our comprehension of wave physics and electromagnetics.
According to quantum mechanics, one can also observe non-classical behaviour of light in certain experiments. A famous example is the grainy or particle-like nature of light. These aspects of light, which are not explained by wave physics, are studied in the branch of optics known as quantum optics. Thanks to the availability of very sensitive light detectors, it is not too difficult to design quantum optical experiments. Although more challenging in practice, similar quantum experiments can be created for microwaves.
Since spin waves can interact with both microwaves and light, they can potentially be used to convert microwaves into light and vice versa. This process is called frequency conversion. Microwave frequencies are in gigahertz (billions of oscillations per second) whereas light frequencies are in terahertz (trillions of oscillations per second).
Frequency conversion with spin waves holds great promise from a technological point of view. Microwave systems are efficient in computing whereas optical systems are optimal for sending information over long distances. Hence, conversion between these frequency regimes can help create more effective, well-connected computing systems.