Tianze Zhao

Nanoparticle aggregate structures allow for efficient photon capture, and thus exhibit excellent optical absorption properties. In this study, a model of randomly distributed nanochain aggregates on silicon substrates is developed and analyzed. The Gaussian, uniform, and Cauchy spatial distribution functions are used to characterize the aggregate forms of the nanochains and their morphologies are realistically reconstructed. The relationships between the structural parameters (thickness and filling factor), equivalent physical parameters (density, heat capacity, and thermal conductivity), and visible absorptivity of the structures are established and analyzed. All the above-mentioned parameters exhibit extreme values, which maximize the visible-range absorption; these values are determined by the material properties and nanochain aggregate structure. Finally, Al nanochain aggregate samples are fabricated on Si substrates by reducing the kinetic energy of the metal vapor during deposition. The spectral reflection characteristics of the samples are studied experimentally. The Spearman correlation coefficients for the calculated spectral absorption curves and those measured experimentally are higher than 0.82, thus confirming that the model is accurate. The relative errors between the calculated visible-range absorptivities and the measured data are less than 0.3%, further confirming the accuracy of the model.

An infrared scene projector (IRSP) that can operate at an ambient temperature lower than 190 K is developed for the hardware-in-the-loop (HIL) simulation of space-borne IR detection systems. The IRSP is composed of a visible scene generator (VSG), a visible to IR converter, and an IR projection system optimized for cryogenic environments. The core component of the IRSP is a light-driven blackbody micro cavity array (BMCA). The BMCA is a photothermal conversion device. It can transform visible light images into IR images. The BMCA can operate properly in an ultralow temperature environment, and the temperature of the BMCA is the same as the ambient temperature. This property allows the BMCA to generate IR scenes with a pure low temperature background, which is crucial for the ground testing of space-borne IR detection systems. The performance of the IRSP was tested in a vacuum cold chamber. In the cryogenic environment with an ambient temperature of 187.75K, the observed highest temperature of the generated IR scene was 426.15 K, the lowest temperature was 187.75 K, the dynamic range of the IR scene was 38.69 db, and the frame rate of the IR scene reached 76 Hz. The average visible to IR conversion efficiency of BMCA was about 10.6%∼3.1% under different ambient temperatures. The radiation spectrum of the IRSP is close to the standard blackbody radiation spectrum both in the MWIR band and the LWIR band. The IRSP has been applied in a HIL simulation test of a space-borne IR detection system.