Single-mode generation in the random fiber laser with an embedded microcavity

A random fiber laser with an embedded external microresonator is shown to be capable of narrow-band generation with a stable single spectral line. Generation takes place right above the lasing threshold at a wavelength of about 1.55 µm with a characteristic spectral width of less than 10 MHz. Generation wavelength remains stable for thousands of seconds, though it is sensitive to external acoustic noises or vibrations. With power increase, narrow-band generation becomes multimode with a spectrum consisting of numerous narrow lines. Here, the microcavity imposes the mode generation with the mode spacing that corresponds to the microresonator's free spectral range.