Devices, methods, and techniques for frequency-dependent optical switching are provided. In one embodiment, a device includes a substrate, a first optical-field confining structure located on the substrate, a second optical-field confining structure located on the substrate, and a composite structure located between the first and second optical-field confining structures. The second optical-field confining structure may be spaced apart from the first optical-field confining structure. The composite structure may include an embedding structure with a surface to receive photons and multiple quantum structures located in the embedding structure.