Passive radiative cooling, a promising strategy for energy savings and sustainability, enables cooling of the ambient temperature by synchronously reflecting sunlight and dissipating heat to the ultracold outer space through the atmospheric transparency window. While designed photonic structures have shown intriguing passive radiative cooling performance, the implementation of such photonic radiators remains challenging due to complex nanoscale lithography/synthesis and rigidity. Here, we experimentally demonstrate a simple and versatile approach of fabricating flexible polydimethylsiloxane radiator thin films with built-in three-dimensional microvoid (inverse-opal-like) arrays for highly efficient daytime radiative cooling. The microvoid-embedded polymer radiator film with tailored spectral responses shows an optimized total reflectivity of ∼93.4% in the sunlight region and a strong infrared emissivity of ∼94.6% within the atmospheric window, respectively. Through such remarkable solar reflection and infrared thermal radiation, the structural polymer radiator achieves subambient cooling of ∼9.8 °C during the night and ∼5.8 °C under direct sunlight in a nonvacuum setup. The three-dimensionally embedded microvoid arrays in our engineered photonic polymer films efficiently backscatter the incident solar radiation and simultaneously enhance the absorption/emissivity in mid-infrared wavelengths, leading to continuous subambient all-day cooling. Our findings provide an effective pathway toward a low-cost, high-performance flexible photonic radiative cooler for passive daytime cooling.

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The comparison of output powers between self-Raman Nd:YVO4 lasers and Nd:YVO4/KGW Raman lasers operating at lime and orange wavelengths is presented. We exploit the LBO crystal with cutting angle θ = 90° and φ = 8° for the lime wavelengths, and then we change the angle to θ = 90° and φ = 3.9° for the orange wavelengths. In self-Raman Nd:YVO4 lasers, experimental results reveal that thermal loading can impact on the output performances, especially at the high pump power. However, by using a KGW crystal as Raman medium can remarkably share the thermal loading from gain medium. Besides, the designed coating for high reflectively at the Stokes field on the surface of KGW also improved the beam quality and reduced the lasing threshold. For self-Raman Nd:YVO4 lasers, we have achieved the output powers of 6.54 W and 5.12 W at 559 nm and 588 nm, respectively. For Nd:YVO4/KGW Raman lasers, the output powers at 559 nm and 589 nm have been increased to 9.1 W and 7.54 W, respectively. All lasers operate at a quasi-CW regime with the repetition rate 50 Hz and the duty cycle 50%.

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We demonstrate a hybrid Si photodetector structure by employing an additional layer of fluorescent carbon quantum dot (CQDs) nanoparticles constructed on the surface of Si photodetector. The experimental studies reveal that the optimized hybrid device can efficiently enhance short-wavelength range responsibility between 300 nm to 600 nm without inducing any deteriorated photodetection performance beyond the short-wavelength region, and thereby achieve broadband sensitivity across UV-Vis-NIR spectra region. The measured photoresponsivity of the optimized device can achieve 0.088 A/W (@500 nm), which was 25% higher than that of a commerical blank PIN Si photodetector.