Polymer composite cladding for selective frequency filtration: An experimental and modeling study

Abstract

Laser selective frequency filtering is currently performed using expensive, heavy, and bulky (millimeters in thickness) ceramic composite claddings around the laser rod, which limits the miniaturization and transportability of the laser. The cladding absorbs undesired spontaneous emissions and reflects the desired wavelength of the "pump" diode. As an improved alternative for the cladding on, say, a diode-pumped solid-state Nd:YAG laser rod, we investigate a spray-coated polymer composite cladding (micrometers in thickness). The polymer composite cladding is easier to process and lighter and has a much smaller volume vs. traditional ceramic composite claddings. The approach is demonstrated on spray-coated glass slides, where cubic samaria (Sm₂O₃) particles are used as the filler in the polymer composite cladding. The rationale for using samaria as the filler in the composite is its absorption near the laser spontaneous emission wavelength (i.e., 1064 nm) and high reflectivity at the incident pump wavelength (i.e., 808 nm). The addition of a second polymer composite layer loaded with alumina particles enables reduction of the samaria composite layer thickness. The Kubelka-Munk model is shown to successfully predict the experimentally measured optical performance of single and bilayer claddings, making it a reliable design tool for multilayer claddings.