Abstract
Metasurfaces, consisting of artificially created meta-atoms arranged in a single layer on a subwavelength scale, exhibit the capability to manipulate both the amplitude and phase of the light field, generating significant interest within the photonics community. Through the applications of advanced experimental techniques such as nanofabrication and characterization, meta-devices have been created and assessed for various applications including nonlinear signal modulation, photoelectric detection, optical imaging, and sensing. Our studies have delved into second-order nonlinear effects like second harmonic generation (SHG) and photocurrent generation using metasurfaces. The modulation of second harmonic generation is examined by employing nonlinear scattering theory, particularly when twist angles vary between the artificial meta-atoms and single crystalline molybdenum disulfide (MoS2), leading to a sine-like pattern with enhanced SHG signals. This is subsequently validated using a nonlinear characterization setup equipped with a femtosecond laser. Moreover, we study photocurrent generation on gold nanoholes as another form of second-order nonlinear effect. The experimentally obtained photocurrents match theoretical predictions and are a result of exciting surface plasmon polaritons, showcasing varied profiles based on incident polarizations. Lastly, metasurfaces with plasmon-induced transparency (PIT) effects are designed and their potential is showcased in surface-enhanced infrared absorption spectroscopy (SEIRA) for molecular detection and sensing, facilitated by the synthesis of complex frequency waves (CFWs).
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