Optical External and Intrinsic Fiber Cooler for GaN Microwave Amplifier

In this STTR program, Photonic Systems Inc. and Prof. Jacob Khurgin at Johns Hopkins University propose novel optical external and internal fiber cooling approaches to efficiently cool the high power GaN microwave amplifier. The external cooler is a single end, square-shape, Yb:ZLAN fiber with high reflection (HR) coated surface which can attach to the amplifier surface and create a cold spot at the vicinity of the drain area where the amplifier hot spot is located. The internal Raman cooling approach, consisting of a photonic crystal resonant structure and pump-collect fiber pair, suppresses the hot optical phonon directly by using Raman scattering in GaN with resonance enhanced anti-Stokes and mitigated Stokes processes.