Abstract:Infrared thermal imaging， which measures the surface temperature by detecting infrared radiation （IR） spontaneously emitted by the object itself， is widely used in important fields such as military， civil aviation， security monitoring， and industrial manufacturing. However， due to the diffraction limit， the spatial resolution of IR thermal imaging is usually above the micron scale and cannot be used to image nanoscale objects. In recent years， we have developed a passive-type infrared near-field （NF） microscopy. It detects the NF radiation exists on the sample surface and therefore achieves high spatial resolution well-below the diffraction limit. In this paper， we introduce the construction and detailed mechanism of this novel microscope and recently achieved research progress， i.e.， sensitive detection of NF radiation and super-high resolution infrared temperature mapping of working devices.

Abstract:The development of type II superlattice dual-band long-/long-wavelength infrared focal plane photodetector is reported. Through the design of energy band structure and molecular beam epitaxial technology， dual-band long-/long-wavelength superlattice epitaxial material with good surface quality has been obtained. The 320×256 dual-band long-/long-wavelength InAs/GaSb superlattice focal plane photodetector with pixel center distance of 30 μm was prepared by breaking through the key technologies of low dark current passivation and low damage dry etching. The detector chip is interconnected with a dual color readout circuit， packaged in a Dewar package， and coupled to a refrigerator to form a detector assembly. The dual-band 50% cut-off wavelengths of the photodetector are 7.7 μm （band 1） and 10.0 μm （band 2）， respectively. The average peak detectivity of band 1 reached 8.21×10¹⁰ cm·W^-1·Hz^1/2， and NETD achieved 28.8 mK. The average peak detectivity of band 2 reached 6.15×10¹⁰ cm·W^-1·Hz^1/2， and the NETD was 37.8 mK. Clear imaging of both colors has been achieved， demonstrating the realization of long-/long-wavelength dual-band photodetection.

Abstract:The accurate acquisition of optical constants of SnTe nanofilm is of great significance for the design of high-performance optoelectronic devices and their potential applications in the field of optoelectronics. However， there are still few reports about the methods to obtain the optical constants of the nanofilm. SnTe nanofilm was prepared on quartz substrate by magnetron sputtering with a SnTe single target. Under the conditions of with no heating of the substrate and annealing treatment， using the appropriate process parameters， a crystalline and compositionally controlled face-centered cubic SnTe nanofilm has been obtained. The thickness， composition， refractive index， extinction coefficient and other optical constants of SnTe nanofilm were studied by using spectral ellipsometry （SE）. Different fitting model structures were established. SnTe material data lists in SE database and the Tauc-Laurents model were used for fitting analysis respectively. The results show that the SnTe nanofilm with such thickness has a higher refractive index in the visible band and a wider spectral absorption from visible to near infrared.

Abstract:This paper presents the recent progress in the research of high operating temperature （HOT） mid-wavelength infrared （MWIR） HgCdTe focal plane arrays （FPAs） at Kunming Institute of Physics. By optimizing the structural parameters of mid-wavelength infrared HgCdTe detectors， a 640×512@15 μm mid-wavelength infrared focal plane array （FPA） was fabricated based on high-quality in situ indium-doped HgCdTe film grown by liquid phase epitaxy （LPE） using arsenic-ion-implanted p-on-n planar junction device technology. The spectral response， device dark current， noise equivalent temperature difference （NETD）， operability， and the distribution of defective pixels of the prepared p-on-n chip arrays at various operating temperatures were tested using a variable temperature Dewar. The test results demonstrate that the detector has the ability to operate at temperatures above 180 K.

Abstract:Infrared thermal detectors are of significant importance in both military and civilian fields. Traditional infrared thermal detectors usually have broadband absorption characteristics， although which brings the detectors featuring broadband responses， it also increases the noise due to the presence of additional radiative thermal conductance， thus limiting the detection performance. Recently， it has been demonstrated that thermal detectors assisted by artificially engineered structures would have performance beyond traditional broadband thermal detectors， since such elaborately designed media can not only reduce the thermal conductance of the detectors by spectrally suppressing the undesirable thermal emission， but also decrease the thermal capacitance due to their subwavelength features， and thus improving the performance of the thermal detectors. In this review， we first give a brief overview of the fundamental concepts of infrared detectors， including bolometric， thermoelectric and pyroelectric detectors， and then summarize the recent developments of spectrally selective infrared thermal detectors based on artificially engineered nanostructures.

Abstract:In practical applications， effective manipulation of polaritons brings great prospect for nanophotonic devices， subwavelength imaging， anomalous refraction and other fields of interest. But the modulation flexibility of polaritons in conventional dielectric materials is relatively low and cannot meet the broad needs of reality， and it becomes a challenging problem. However， phonon polaritons， as a new type of quasiparticle with strong photon-phonon coupling， have stronger light-binding ability， longer lifetime and lower loss than other polaritons， and can play a crucial role in the field of subwavelength-scale infrared light modulation. In recent years， with the research and reports on two-dimensional van der Waals crystals， dielectric materials capable of hosting hyperbolic phonon polaritons have come into the public eye， and with the support of ultra-high resolution nano-imaging technology， many novel near-field infrared optical phenomena have been explored by various manipulation methods， which greatly enriches the knowledge of polarization excitations. This review starts with the mechanism of hyperbolic phonon polaritons， introducing the concept of phonon polaritons， the dispersion relation and the hyperbolic media （h-BN and α-MoO₃） that have recently received much attention. Subsequently， the different propagation properties of hyperbolic phonon polaritons in the above mentioned media and the analysis of near-field imaging under various dimensional modulations， such as changing the surrounding dielectric environment of van der Waals crystals， resonant cavities， in-plane modulation of metallic antennas， etc.， are summarized. Finally， we give an outlook on the study of phonon polaritons. The diverse modulation tools show the rich applications of phonon polaritons， which provide avenues for infrared nanophotonic devices such as nano-imaging， integrated optical circuits， and nano-lenses， and may also lead to more emerging fields in the future.

Abstract:Optoelectronic chips are important for complex information conversion in the age of artificial intelligence. The highest efficiency of electron-photon conversion is achieved through strongly coupled electron-photon states， particularly using the degree of freedom of electron spin has unique advantages. Collective excitations of spin can form magnons， which have unique merits such as long lifetimes and immunity to Joule heating. These advantages can be combined through the strong coupling between magnons and high-speed photons to form “cavity-magnon polariton （CMP）.” Recent progresses have focused on constructing high cooperative CMP， controlling radiation and transmission of CMP， understanding the perfect absorption mechanism of CMP， and developing electrical tuning and logical operation functions of on-chip CMP prototype devices. These studies on the coherent coupling dynamics of CMP are expected to promote the development of low-loss optoelectronic devices and the cutting-edge information processing technology.

Abstract:The function of rapid thermal annealing on zinc-diffused In_0.53Ga_0.47As/InP PIN detector was systemically studied. By using electrochemical capacitance-voltage and secondary ion mass spectroscopy techniques， Zn and net acceptor concentration profiles were investigated， indicating that the annealing process would affect the dopant concentration but not affect the diffusion depth. In_0.53Ga_0.47As/InP PIN detectors under different annealing conditions were fabricated， the results showed that the detector without annealing process outperformed in terms of lower device capacitance and higher activation energy from 260 to 300K. By analyzing the mechanism of dark current， the unannealed sample exhibited lower Shockley-Read-Hall generation-recombination and diffusion currents， explaining the higher peak detectivity at room temperature. Therefore， for the purpose of fabricating high-performance planar InGaAs detectors with low-doped absorption layer， annealing process is inadvisable.

Abstract:Scanning near-field optical microscopy in the infrared and terahertz ranges has attracted much interest in studying objects far below the diffraction limit， particularly in the detection of optical properties of structures on the nanoscale. To further understand the tip-sample interaction， analytical and numerical description of the near fields from the probe is essential. Here， we established and analytically solved a more realistic analytical model based on the real probe shape. Based on the combination of the analytical model and numerical simulation to develop the source dipole model （SDM），a comparison with the new method to full-wave simulation （FWS） results was performed. In simulations combined with the theoretical model， the detection information is obtained directly， and the computational efficiency is improved. Based on simulation results， the antenna effect， tip apex radius influence， and the influence of charge amount are explained. This paper provides a new perspective to further understand the tip-sample junction in optical nanoscopy.

Abstract:In this paper， Se microrods were synthesized using a physical vapor deposition method， and a metal-semiconductor-metal （MSM） photodetector was fabricated by using silver paste as the electrode. This photodetector exhibits a fast response time （T_r = 41 ms， T_d = 46 ms）， excellent responsivity （18.32 mA/W）， and detectivity （1.65×10⁸ Jones） at 3 V bias and under 450 nm light illumination. Spectral measurements demonstrate that the device has a broadband detection range from visible to near infrared range （450~1 550 nm）. Additionally， the device can also perform self-powered detection without bias. This research will further improve the application and development of Se in broadband photodetection.

Abstract:We reported a broadband photodetector with a spectral range of 365-965 nm， based on a SnS₂/InSe vertical heterojunction. In this device， InSe serves as the optical absorption layer， effectively extending the spectral range， while SnS₂ functions as the transmission layer， forming a heterojunction with InSe to facilitate separation of electron-hole pairs and enhance the responsivity. The photodetector exhibits a responsivity of 813 A/W under 365 nm. Moreover， it still maintained a high responsivity of 371 A/W， an external quantum efficiency of 1.3 × 10⁵%， a specific detectivity of 3.17 × 10¹² Jones， and a response time of 27 ms under 965 nm illumination. The above investigation provides a new approach for broadband photodetectors with high responsivity.

Abstract:Vertical van der Waals heterostructures stacked by low-dimensional InAs materials and other two-dimensional layered materials have been widely applied in emerging fields such as nanoelectronics， optoelectronics， and quantum information. To comprehend their extraordinary device performance， it is crucial to explore the charge transfer mechanism across the junction interface. First-principles calculations play an indispensable role in revealing the intrinsic relationship between interfacial charge transfer characteristics and electrical， optical， and magnetic principle physical properties as well as device performance variations in various energetically stable InAs-based van der Waals heterojunctions. Recent theoretical research on interfacial charge transfer characteristics in InAs-based van der Waals heterostructures， as well as their potential for functional applications are combed， summarized， and discussed. Several avenues are proposed for the potent development of first-principles calculations in terms of theoretical methodology and calculation accuracy， providing a basis for quantitative research that can be leveraged to propel fundamental scientific studies and applied device designs of InAs-based van der Waals heterojunctions.

Abstract:Coherent anti-Stokes Raman scattering （CARS） microscopy showed great potential for rapid pathological analysis， pharmacokinetics and other fields. However， the non-resonant background （NRB） signals generated during imaging will affect the detection of CARS signals. By tuning the wavelength， the signal can be generated at the coexistence of resonance and NRB， or at the place where there is only NRB. The influence of NRB can be eliminated to a certain extent by cancelling the two signals. In this paper， a wavelength tunable erbium-doped fiber laser system based on divided pulse amplifier and crystal frequency doubling was built. It was proposed to control the pump power of two-stage amplifiers to achieve wavelength tuning. Finally， 110.8 mW and 136 fs pulses were output at 779.1-784.5 nm， 777.5-786.1 nm and 784.5-790.5 nm. The laser and ytterbium-doped laser system can be used for CARS imaging through passive synchronization.

Abstract:The research on the surface emissivity directionality is a hot and difficult issue in the international thermal infrared quantitative remote sensing area. The existing emissivity directional models for sandy area in thermal infrared bands have some disadvantages， such as too many prior parameters， low accuracy and poor applicability. Therefore， with the aid of long-time series （2018-2020） multi-angle observations from geostationary-orbit MSG/SEVIRI and polar-orbit AQUA/MODIS， after data pre-processing related to inter-sensor calibration， atmospheric correction， spatial and temporal matching， we retrieved the directional emissivity under different viewing zenith angles （VZAs） between 0~65°over five pseudo-invariant calibration sites based on the thermal infrared radiation transfer equation， including Algeria3_1km， Algeria5_1km， Libya1_1km， Mauritania1_1km and Mauritania2_1km. Subsequently， a model for retrieving the kilometer-scale directional emissivity was established， and its uncertainty was evaluated. The result shows that the surface emissivity decreases with the increase in VZA， and the directional effect decreases with the increase in the MODIS band central wavelength； Algeria5_1km has the smallest directional effect， and Mauritania1_1km has the strongest effect， the uncertainty of the directional emissivity model in each region increases with VZA， and is better than 3%.

Abstract:Due to the long distance and complex background， it is hard for the infrared detecting and tracking system to find and locate the dim-small targets in time. The proposed method， ACE-STDN， aims to tackle this difficult task and improve the detection accuracy. First of all， an adaptive contrast enhancement subnetwork preprocesses the input infrared image， which is conducive for the low-contrast dim targets. Next， a detection subnetwork with a hybrid backbone takes advantage of both convolution and self-attention mechanisms. Besides， the regression loss is designed based on 2D Gaussian distribution representation instead of Intersection over Union measurement. To verify the effectiveness and efficiency of our method， we conduct extensive experiments on two public infrared small target datasets. The experimental results show that the model trained by our method has a significant improvement in detection accuracy compared with other traditional and data-based algorithms， with the average precision reaching 93.76%. In addition， ACE-STDN achieves outstanding detection performance in a multiclass object dataset and a general small object dataset， verifying the effectiveness and robustness.