A device includes an optical gain medium through which optical radiation is amplified. The device includes first and second reflectors disposed around the gain medium. One of the reflectors includes an emission region though which optical output is emitted and a metallic structure that has an array of features that couple the radiation to at least one surface plasmon mode of the structure, thereby enhancing the device's output. The device may be a laser, e.g., a diode laser. The emission region may have a width of, for example, between 10 and 100 nanometers, and this emission region may be in the shape of a rectangular slit. The optical radiation in the gain medium may be advantageously polarized perpendicularly to an axis along which a longer dimension of the emission region is oriented. The device is useful for data recording, e.g., thermally assisted data recording.