Tunable multimode lasing in a fiber ring

We experimentally study a fiber loop laser with an integrated Erbium doped fiber (EDF). The output optical spectrum is measured as a function of the EDF temperature. We find that below a critical temperature of about 10K the measured optical spectrum exhibits a sequence of narrow and unequally-spaced peaks. Externally injected light and filtering are employed for tuning the peaks' wavelengths. Operation of the device as an optical memory having storage time of about 20 ms is demonstrated. The multimode lasing tunability can be exploited for novel applications in the fields of sensing, communication, and quantum data storage.