4.3 THz quantum-well photodetectors with high detection sensitivity

We demonstrate a high performance GaAs/AlGaAs-based quantum-well photodetector(QWP)device with a peak response frequency of 4.3 THz.The negative differential resistance(NDR)phenomenon is found in the dark currentvoltage(I-V)curve in the current sweeping measurement mode,from which the breakdown voltage is determined.The photocurrent spectra and blackbody current responsivities at different voltages are measured.Based on the experimental data,the peak responsivity of 0.3 A/W(at 0.15 V,8 K)is derived,and the detection sensitivity is higher than 10^(11)Jones,which is in the similar level as that of the commercialized liquid-helium-cooled silicon bolometers.We attribute the high detection performance of the device to the small ohmic contact resistance of-2Ωand the big breakdown bias.

Characteristics,Types,and Prospects of Geological Sweet Sections in Giant Continental Shale Oil Provinces in China

“Sweet sections”in giant shale oil provinces are preferential fields that primarily support China to increase the reserves and production of continental shale oil.Based on the study of the geological conditions of shale oil in the continental basins in China,it was found that the shale stratum in major oil generation windows generally has higher degrees of oil and gas accumulation,and mostly contains oil.Hydrocarbon generation and reservoir capacities are the two key parameters for evaluating and optimizing favorable shale oil provinces.The evaluation index(volume of shale stratum multiplied by total organic carbon(TOC)multiplied by total porosity)for the giant continental shale oil provinces is also proposed.It is optimized that the Upper Triassic Chang 7 Member in the southcentral Ordos Basin,Lower Cretaceous Qing 1 Member in the Gulong-Changling Sag in the Songliao Basin,Middle-Lower Permian in the Junggar Basin,Da’anzhai Member of the Ziliujing Formation of Lower Jurassic in the central and northern Sichuan Basin,and Paleogene oil-rich sag in the Bohai Bay Basin are the five giant continental shale oil provinces.The word“geological sweet sections”in continental shale oil provinces of China refers to favorable shale intervals which are relatively rich in oil,with superior physical properties,and more easily modified and developed commercially under applicable economic and technological conditions.After evaluation,there are mainly two types of“geological sweet sections”of giant continental shale oil developed onshore in China.One type of“geological sweet sections”is generally mudstone with optimal physical properties or a thin tight reservoir,to which the shale oil migrates a short distance.They are medium-to-high-mature zones with a thin sandy shale stratum in the Chang 7 Member in the Ordos Basin,mixed shale stratum in the mediummature Lucaogou Formation in the Jimsar Sag,and multi-layered mixed Paleogene shale stratum in the Bohai Bay Basin.The other type of“geological sweet sections”is generally shale oil residing in various shale reservoir spaces.This type was developed in the Qing 1 Member in the Gulong Sag and Da’anzhai Member in the north-central Sichuan Basin.Free shale oil mainly occurs in shale,sandycarbonate lamina,micro-lamella structure,and micro-fractures.Layers with lamina,lamination,and micro-fractures are generally shale oil“geological sweet sections.”Starting from field tests and the construction of the“geological sweet sections”in giant continental shale oil provinces,the shale oil industry has been rapidly developing and will become an important supplement to domestic oil production in China.

Metasurfaces for manipulating terahertz waves

Terahertz(THz)science and technology have attracted significant attention based on their unique applications in non-destructive imaging,communications,spectroscopic detection,and sensing.However,traditional THz devices must be sufficiently thick to realise the desired wave-manipulating functions,which has hindered the development of THz integrated systems and applications.Metasurfaces,which are two-dimensional metamaterials consisting of predesigned meta-atoms,can accurately tailor the amplitudes,phases,and polarisations of electromagnetic waves at subwavelength resolutions,meaning they can provide a flexible platform for designing ultra-compact and high-performance THz components.This review focuses on recent advancements in metasurfaces for the wavefront manipulation of THz waves,including the planar metalens,holograms,arbitrary polarisation control,special beam generation,and active metasurface devices.Such ultra-compact devices with unique functionality make metasurface devices very attractive for applications such as imaging,encryption,information modulation,and THz communications.This progress report aims to highlight some novel approaches for designing ultra-compact THz devices and broaden the applications of metasurfaces in THz science.

Omicron variants breakthrough infection elicited higher specific memory immunity than third dose booster in healthy vaccinees

Homologous booster,heterologous booster,and Omicron variants breakthrough infection(OBI)could improve the humoral immunity against Omicron variants.Questions concerning about memory B cells(MBCs)and T cells immunity against Omicron variants,features of long-term immunity,after booster and OBI,needs to be explored.Here,comparative analysis demonstrate antibody and T cell immunity against ancestral strain,Delta and Omicron variants in Omicron breakthrough infected patients(OBIPs)are comparable to that in Ad5-nCoV boosted healthy volunteers(HVs),higher than that in inactivated vaccine(InV)boosted HVs.However,memory B cells(MBCs)immunity against Omicron variants was highest in OBIPs,followed by Ad5-nCoV boosted and InV boosted HVs.OBIPs and Ad5-nCoV boosted HVs have higher classical MBCs and activated MBCs,and lower naïve MBCs and atypical MBCs relative to both vaccine boosted HVs.Collectively,these data indicate Omicron breakthrough infection elicit higher MBCs and T cells against SARS-CoV-2 especially Omicron variants relative to homologous InV booster and heterologous Ad5-nCoV booster.

Configurable microcavity-enhanced graphene photothermoelectric terahertz detectors

Terahertz(THz)detectors with high sensitivity,fast response speed,room temperature operation,and self-powered feature are the key component for many THz applications.Microcavity resonators can effectively improve the sensitivity of THz detectors.However,it is difficult to precisely evaluate the microcavity resonator induced such improvement in experiment.Here,we realize a configurable microcavity–antenna-integrated graphene photothermoelectric(PTE)THz detector.Through the microcavity–antenna hybrid structure,THz radiations are localized and enhanced at one end of the graphene channel,and the temperature difference along the channel is greatly increased,resulting in the strong enhancement of PTE response.At the resonant frequency,the device has a high responsivity(976 V/W),low noise equivalent power(2.87 pW∕Hz1∕2),and fast response speed(300 ns)at room temperature and in zero-bias operation mode.The microcavity-induced peak enhancement factor of 13.14 is accurately extracted.The microcavity–antenna introduced enhancement is further confirmed by using a two-temperature heat transfer model.The strategy of using a configurable microcavity is useful for further optimizing THz detectors by introducing the critical coupling mechanism.