Boosting plasmon–exciton coupling in gold gratings for C-band pulsed lasers

Surface plasmon resonance (SPR) is attractive for applications in solar cells, photodetectors, and lasers due to its properties of localized electric field enhancement, subwavelength confinement, and overcoming the diffraction limit. GaAs-based heterostructures are well-known for their high electron mobility and excellent light absorption properties, making them widely used in optoelectronic devices. However, they are generally limited to wavelengths below 1.3 μm, which restricts their effectiveness in the C-band. This limitation can be addressed using a noble metal subwavelength grating structure, which allows for effective adjustment of the absorption band by varying the grating periods. In addition, SPR effectively increases the generation of electron-hole pairs in GaAs and promotes light-matter interactions, leading to more efficient light absorption. This study leverages the plasma effect of the grating to extend the absorption band into the C-band, enabling efficient light absorption beyond the inherent limitations of GaAs. The gold grating enhances photocarrier generation at the Au/GaAs interface at 1550 nm wavelength, increasing light absorption by 17% and achieving a modulation depth(MD) of 6.9%. Gratings with an 1100 nm period exhibit excellent saturable absorption in a 1550 nm laser system, resulting in a stable <i>Q</i>-switched laser output with the C-band.