Inner-cladding-doped optical fiber for high-power radiation balancing (Conference Presentation)

Abstract

Currently heat management is a big hurdle for power-scaling of high-power fiber lasers and amplifiers. Different methods have been developed over the years to mitigate the heat generation in high-power lasers and amplifiers; radiation balancing is a new method that leverages the radiative cooling for heat mitigation. In this study, the effects of different design parameters on the operation of a doped-double-cladding (DC) fiber laser and amplifier for radiation balancing are investigated. The results show that the value of the internal quantum efficiency for an effective heat mitigation by radiation balancing is not required to be very close to unity. Conversely, it is shown that in high-power operation, even small values of background absorption can be detrimental to radiation balancing. It is argued that both the background absorption and the small dopant area of the doped-DC fibers are big hurdles in achieving an effective heat mitigation by radiation balancing in high power operation. In order to address this issue, we suggest to dope the inner cladding of the DC fiber such that at the pump wavelength, the inner cladding cools down by optical refrigeration. Due to the geometry of the fiber, the temperature is uniformly homogenized across the fiber and the effective fiber temperature decreases, allowing Yb-doped DC fiber lasers and amplifiers to operate at Kilo-Watt levels in radiation balanced mode.