Laser-based defect characterization and removal process for manufacturing fused silica optic with high ultraviolet laser damage threshold

Residual processing defects during the contact processing processes greatly reduce the anti-ultraviolet(UV)laser damage performance of fused silica optics,which significantly limited development of high-energy laser systems.In this study,we demonstrate the manufacturing of fused silica optics with a high damage threshold using a CO_(2)laser process chain.Based on theoretical and experimental studies,the proposed uniform layer-by-layer laser ablation technique can be used to characterize the subsurface mechanical damage in three-dimensional full aperture.Longitudinal ablation resolutions ranging from nanometers to micrometers can be realized;the minimum longitudinal resolution is<5 nm.This technique can also be used as a crack-free grinding tool to completely remove subsurface mechanical damage,and as a cleaning tool to effectively clean surface/subsurface contamination.Through effective control of defects in the entire chain,the laser-induced damage thresholds of samples fabricated by the CO_(2)laser process chain were 41%(0%probability)and 65.7%(100%probability)higher than those of samples fabricated using the conventional process chain.This laser-based defect characterization and removal process provides a new tool to guide optimization of the conventional finishing process and represents a new direction for fabrication of highly damage-resistant fused silica optics for high-energy laser applications.

High-sensitivity modulation of electromagnetically induced transparency analog in a THz asymmetric metasurface integrating perovskite and graphene

Active control of the electromagnetically induced transparency(EIT)analog is desirable in photonics development.Here,we theoretically and experimentally proposed a novel terahertz(THz)asymmetric metasurface structure that can possess high-sensitivity modulation under extremely low power density by integrating perovskite or graphene.Using the novel metasurface structure with the perovskite coating,the maximum amplitude modulation depth(AMD)of this perovskite-based device reached 490.53%at a low power density of 12.8037 mW/cm^(2).In addition,after the novel THz metasurface structure was combined with graphene,this graphene-based device also achieved high AMD with the maximum AMD being 180.56%at 16.312 mW/cm^(2),and its transmission amplitude could be electrically driven at a low bias voltage.The physical origin of this modulation was explained using a two-oscillator EIT model.This work provides a promising platform for developing high-sensitivity THz sensors,light modulators,and switches.

Physics-based virtual coherence scanning interferometer for surface measurement

Virtual instruments provide task-specific uncertainty evaluation in surface and dimensional metrology.We demonstrate the first virtual coherence scanning interferometer that can accurately predict the results from measurements of surfaces with complex topography using a specific real instrument.The virtual instrument is powered by physical models derived from first principles,including surface-scattering models,three-dimensional imaging theory,and error-generation models.By incorporating the influences of various error sources directly into the interferogram before reconstructing the surface,the virtual instrument works in the same manner as a real instrument.To enhance the fidelity of the virtual measurement,the experimentally determined three-dimensional transfer function of a specific instrument configuration is used to characterise the virtual instrument.Finally,we demonstrate the experimental validation of the virtual instrument,followed by virtual measurements and error predictions for several typical surfaces that are within the validity regime of the physical models.