Dichroic laser mirrors with mixture layers and sandwich-like-structure interfaces

• 作 者: TingtingZeng MeipingZhu YingjieChai JingpingLi JiandaShao
• 机 构: LaboratoryofThinFilmOptics,KeyLaboratoryofMaterialsforHighPowerLaser,ShanghaiInstituteofOpticsandFin
• 出 处: PhotonicsResearch
• 发表日期: 2021年9期

The requirements for dichroic laser mirrors continue to increase with the development of laser technology. The challenge of a dichroic laser mirror coating is to simultaneously obtain spectral performance with significantly different reflection or transmission properties as well as a high laser-induced damage threshold (LIDT) at two different wavelengths. Traditional dichroic laser mirrors composed of alternating high- and low-refractive-index pure materials often has difficulty achieving excellent spectral performance and high LIDTs at two wavelengths simultaneously. We propose to use a new design with mixture layers and sandwich-like-structure interfaces to meet the challenging requirements. An ${\mathrm{Al}}_2{\mathrm{O}}_3-{\mathrm{HfO}}_2$ mixture-based dichroic laser mirror, which can be used as a harmonic separator in a fusion-class laser or a pump/signal beam separator in a petawatt-class Ti-sapphire laser system, is experimentally demonstrated using e-beam deposition. The mixture-based dichroic mirror coating shows good spectral performance, fine mechanical property, low absorption, and high LIDT. For the $s$-polarized 7.7 ns pulses at a wavelength of 532 nm and the $p$-polarized 12 ns pulses at a wavelength of 1064 nm, the LIDTs are almost doubled. The excellent performance of this new design strategy with mixture layers and sandwich-like-structure interfaces suggests its wide applicability in high-performance laser coating.