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 10 K 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 a 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.