Illinois ECE graduate students' work chosen as APL Editor's Pick

12/2/2021

Joseph Park, Illinois ECE

Schematic diagrams of (a) an ASF cooling process, (b) RBL operation, and (c) DWE operation in Yb<sup>3+</sup>-doped materials. 
Schematic diagrams of (a) an ASF cooling process, (b) RBL operation, and (c) DWE operation in Yb3+-doped materials. 

Illinois ECE graduate students Nanjie Yu and Kavita V Desai collaborated on a research piece that was recently published in Applied Physics Letters and was chosen to be the Editor’s Pick. Established in 1962, Applied Physics Letters is one of the premier journals focused on the applications of physics. 

Nanjie Yu
Nanjie Yu

While conventional wisdom indicates that the wavelength of a pump should be shorter than that of the laser, in their work Nanjie and Kavita show this is not strictly true. They utilized a dual-wavelength pumping scheme in a Yb-doped fiber laser, with one pumping wavelength longer and the other shorter than that of the laser. They provide experimental evidence that the long-wavelength pump can directly contribute to stimulated emission, during which phonons are extracted from the active medium and leading to cooling. Through such a process, the effective quantum defect and lasing threshold are significantly decreased. By carefully selecting the power and temporal settings of the two pumps, near-zero quantum defect heating was possible. This principle is applicable to other solid-state laser systems, offering a novel solution to respective thermal problems.

Kavita V Desai
Kavita V Desai

Currently, thermal problems such as transverse mode instability serve as the limiting factor for further power scaling of high-power laser systems. The graduate students’ work offers a novel solution to the thermal problems in solid-state systems and may potentially lead to a new type of excitation-balanced laser operating in a quasi-continuous wave or pulsed regime.

Yu is from Peter D Dragic’s research group and Desai is from James Gary Eden’s research group.