Infrared Thermal Emission Mediated By Photonic Structures Combined With Phase Change Materials

Thermal emission is a widespread physical phenomenon during which "light" is generated by "heat".Among the full spectrum of thermal emission,infrared(IR)thermal emission is widely present in the natural environment and plays an important role in radiative heat management,thermal imaging,remote sensing detection,and other fields.In the past ten years,with the continuous deepening of research in the field of micro-nano photonics and the rapid development of micro-nano fabrication methods,various novel optical structures,from optical thin films,gratings to photonic crystals and metasurfaces,have been applied to the design of thermal emission devices based on micro-nano photonics.Current thermal emission manipulation devices are mostly static devices,that is,the thermal emission characteristics of the devices are adjusted through the design of micro-nano photonics structures and determined once the fabrication is completed.To introduce dynamic tunability,phase change materials(PCMs)are widely used in dynamically reconfigurable electronic and photonic devices due to the huge changes in electrical and optical properties,which are brought about by the phase transition under external excitation.However,since the change of the optical parameters during the phase transition is completely dependent on the material properties,it usually cannot directly meet the target requirements of thermal emission control in terms of range and trend.Therefore,it is necessary to make full use of the optical parameter changes of the PCM in the phase transition process through the appropriate micro-nano photonics structure design so that the spectral control range of the thermal emission control device can be expanded.To broaden the application of thermal emission control devices in IR information-related scenarios,controlling the spatial characteristics of thermal emission has become an urgent need.Based on the above requirements,this thesis relies on two PCMs,namely volatile VO2 and non-volatile Ge2Sb2Te5(GST)to achieve dynamic reconfigurable regulation of radiation spectra and regulation of spatial distribution characteristics.Volatile and non-volatile thermal emission devices are analyzed and demonstrated from the perspective of theory and experiment.In terms of the dynamic control of thermal emission based on the volatile PCM VO2,this thesis proposes a device with dynamically adjustable emissivity and space control capabilities.By integrating VO2 with a planar optical resonator,the influence of the change in optical characteristics caused by the phase change of VO2 on the absorption and radiation characteristics of the device is enhanced,and the dynamic switching of the average emissivity from 0.19 to 0.91 is realized in the 8-14 ?m atmospheric transmission window;With the hysteresis effect of the VO2 phase transition process,this thesis demonstrates the use of thermal and optical stimulus to achieve spectral emissivity switching and at least 9 levels of spectral emissivity intermediate states;Through the introduction of laser direct writing technique,the spatial control thermal emission is demonstrated,which exhibits great potential in applications such as IR target simulatingIn terms of the dynamic control of thermal emission based on the non-volatile PCM GST,a reconfigurable thermal emitter with a large dynamic range of spectral emissivity control is demonstrated.Besides the IR emissivity,the visible scattering property is also independently tunable.By introducing GST into the optical resonator,the optical parameter changes brought about by the phase transition of a 25-nm-thick GST is enhanced.The peak spectral emissivity in the 8-14 ?m atmospheric transmission window is switched between 0.10 and 0.70.By applying direct writing technique to write phase-change metasurface by laser,this thesis realizes the multi-level control of spectral emissivity(at least 8 levels).Furthermore,sub-micron-sized bumps are controllably fabricated by focused nanosecond laser pulses without affecting the IR thermal emission characteristics,which demonstrates the application of the device as a visible-IR dual-band anti-counterfeiting labelIn this thesis,dynamically reconfiogurable and spatial control of thermal emission are realized by designing and fabricating micro-nano photonic devices that combine PCMs,photonic structures,and laser direct writing technique.Both volatile and non-volatile controls of thermal emission are realized.Meanwhile,the coordinated control of surface morphology and phase transition of PCMs by focused laser pulses realizes independent control of visible-IR band scattering-radiation characteristics.Results above deepens the understanding of the PCMs-integrated photonic structure in the fields of micro-nano photonics and exhibited broad application prospects in applications related to energy,information,and security.