Improved Pulsed Laser Operation with Engineered Nanomaterials

The power efficiency of a diode-pumped solid state laser was improved by encasing the Nd:YAG lasing medium with gold nanorod-doped epoxy. Gold nanorods were synthesized with a specific aspect ratio tuned to absorb at the Nd:YAG lasing wavelength of 1064 nm. The surfactant-stabilized nanorods in aqueous solution were then treated with a sequential, two-step functionalization in order to improve nanorod solubility in organic solvents. This process required treating the gold nanorods with a thiol-containing polyethylene glycol (PEG) polymer followed by replacing the PEG-SH polymer with a multidentate thiol containing block copolymer synthesized using RAFT synthesis. With a multidentate polymer, the nanorods were soluble in traditional epoxies that could be used to coat the outside of Nd:YAG rods. By absorbing excess lateral 1064 nm emission, the gold nanorod coating attenuates amplified spontaneous emission (ASE), a parasitic, incoherent process that limits power produced by Q-switch laser designs. Laser power increased by nearly 2-fold with addition of the 1064 nm absorbing gold nanorod coating. Gold nanorod epoxy coatings stand out as attractive materials for attenuating ASE by avoiding the fabrication difficulties of samarium oxide ceramics and the photostability limitations of organic dyes.