A multimode interference(MMI)structure is designed to simplify the fabrication of quantum cascade laser(QCL)phase-locked arrays.The MMI geometry is optimized with a sufficient output channel distance to accommodate co...A multimode interference(MMI)structure is designed to simplify the fabrication of quantum cascade laser(QCL)phase-locked arrays.The MMI geometry is optimized with a sufficient output channel distance to accommodate conventional photolithography and wet etching process by which power amplifier array is fabricated without using the complicated two-step etching-regrowth or dry etching technique.The far-field pattern with periodically modulated peaks reveals that the beams from the arrays are phase-locked.Furthermore,the frequency tuning performance of the MMI-based phase-locked arrays is studied using the Littrow-configuration external cavity structure.A wavelength tuning range of more than 60 cm^(−1) is demonstrated,which will eventually realize the high power,frequency tunable,large-scale phase-locked arrays,and their application in spectroscopy.展开更多
We demonstrate a broad gain,continuous-wave(CW)operation InP-based quantum cascade laser(QCL)emitting at 11.8μm with a modified dual-upper-state(DAU)and diagonal transition active region design.A 3 mm cavity length,1...We demonstrate a broad gain,continuous-wave(CW)operation InP-based quantum cascade laser(QCL)emitting at 11.8μm with a modified dual-upper-state(DAU)and diagonal transition active region design.A 3 mm cavity length,16.5μm average ridge wide QCL with high-reflection(HR)coatings demonstrates a maximum peak power of 1.07 W at 283 K and CW output power of 60 m W at 293 K.The device also shows a broad and dual-frequency lasing spectrum in pulsed mode and a maximum average power of 258.6 mW at 283 K.Moreover,the full width at half maximum(FWHM)of the electroluminescent spectrum measured at subthreshold current is 2.37μm,which indicates a broad gain spectrum of the materials.The tuning range of 1.38μm is obtained by a grating-coupled external cavity(EC)Littrow configuration,which is beneficial for gas detection.展开更多
A beam steering effect of high-power quantum cascade(QC) lasers emitting at 4.6 μm was investigated. The continuous wave(CW) output power of an uncoated, 6-mm-long, 7.5-μm-wide buried-heterostructure QC laser at 25...A beam steering effect of high-power quantum cascade(QC) lasers emitting at 4.6 μm was investigated. The continuous wave(CW) output power of an uncoated, 6-mm-long, 7.5-μm-wide buried-heterostructure QC laser at 25℃ was as high as 854.2 m W. The maximum beam steering angle was offset by ±14.2° from the facet normal(0°) in pulsed mode. The phenomenon was judged explicitly by combining the diffraction limit theory and Fourier transform of the spectra. It was also verified by finite element method software simulation and the calculation of two-dimensional(2 D)effective-index model. The observed steering is consistent with a theory for coherence between the two lowest order lateral modes. Therefore, we have established an intrinsic linkage between the spectral instabilities and the beam steering by using the Fourier transform of the spectra, and further presented an extremely valid method to judge the beam steering. The content of this method includes both three equidistant peak positions in the Fourier transform of the spectra and the beam quality located between once the diffraction limit(DL) and twice the DL.展开更多
In this study, a series of monodispersed poly（L-lactide）（PLLA） were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight（Mn） o...In this study, a series of monodispersed poly（L-lactide）（PLLA） were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight（Mn） on the crystallization and melting behaviors of PLLA were investigated by differential scanning calorimetry（DSC） and wide-angle X-ray diffraction（WAXD）. The total crystallization rate of PLLA was Mn-dependent, which reached the maximum value for PLLA with Mn of 18.6 kg/mol. In addition, when Mn of PLLA was 18.6 kg/mol, the melting enthalpy（ΔHm） showed a maximum value（87.1 J/g）, which was the highest reported value till now. The critical temperature for change of crystal formation from ？-form to ？-form crystals increased in the isothermal crystallization process with Mn increasing. In the reheating procedure, high-Mn PLLA demonstrated a small exothermal peak prior to the dominant melting peak, corresponding to crystal transition from ？- to ？-form, but low-Mn PLLA didn＇t show the peak of crystal transition. These different crystallization and melting behaviors were attributed to the different chain mobility of PLLA with different Mn.展开更多
The normal fabrication process for electronic and optoelectronic devices can bring in significant modifications on two-dimensional(2D)semiconductors’intrinsic properties.To address this issue,some dry methods have be...The normal fabrication process for electronic and optoelectronic devices can bring in significant modifications on two-dimensional(2D)semiconductors’intrinsic properties.To address this issue,some dry methods have been developed,such as“transfer contact”method and“shadow mask technology”.However,the method that can combine the advantages of low cost,non-destruction,and high reliability at sub-micrometer scale is rarely reported.Here,we demonstrate a fabrication technique using ultrafine quartz fibers as shadow masks.In this technique,sub-micrometer scale devices can be“all dry”fabricated facilely,and the intrinsic properties of 2D semiconductors are preserved.Meanwhile,the masking effect can be evaluated in situ based on the light interference between the quartz fiber and the substrate to increase the fabrication reliability.展开更多
Dynamic states in mutual-coupled mid-infrared quantum cascade lasers(QCLs) were numerically investigated in the parameter space of injection strength and detuning frequency based on the Lang-Kobayashi equations model....Dynamic states in mutual-coupled mid-infrared quantum cascade lasers(QCLs) were numerically investigated in the parameter space of injection strength and detuning frequency based on the Lang-Kobayashi equations model. Three types of period-one states were found, with different periods of injection time delay τ_(inj), 2τ_(inj), and reciprocal of the detuning frequency. Besides, square-wave, quasi-period, pulse-burst and chaotic oscillations were also observed. It is concluded that external-cavity periodic dynamics and optical modes beating are the mainly periodic dynamics. The interaction of the two periodic dynamics and the high-frequency dynamics stimulated by strong injection induces the dynamic states evolution.This work helps to understand the dynamic behaviors in QCLs and shows a new way to mid-infrared wide-band chaotic laser.展开更多
Power scaling in a broad area quantum cascade laser(QCL) tends to deteriorate beam quality with the emission of a multiple-lobe far-field pattern. In this paper, we demonstrate a coupled ridge waveguide QCL array cons...Power scaling in a broad area quantum cascade laser(QCL) tends to deteriorate beam quality with the emission of a multiple-lobe far-field pattern. In this paper, we demonstrate a coupled ridge waveguide QCL array consisting of five elements with chirped geometry. In-phase mode operation is secured by managing supermode loss with properly designed geometries of ridges. A single-lobe lateral far-field with a near diffraction limited beam pattern was obtained in the whole current dynamic range. The devices were fabricated with the wet and dry etching method. The regrowth technique of the In P:Fe insulation layer and In P:Si waveguide layer was employed.Such a structure has the potential to optimize the beam quality of the recently reported high-power broad-area QCL with a reduced cascade number.展开更多
We report an index-coupled distributed feedback quantum cascade laser by employing an equivalent phase shift(EPS) of quarter-wave integrated with a distributed Bragg reflector(DBR) at λ~5.03 μm. The EPS is fabricate...We report an index-coupled distributed feedback quantum cascade laser by employing an equivalent phase shift(EPS) of quarter-wave integrated with a distributed Bragg reflector(DBR) at λ~5.03 μm. The EPS is fabricated through extending one sampling period by 50% in the center of a sampled Bragg grating. The key EPS and DBR pattern are fabricated by conventional holographic exposure combined with the optical photolithography technology, which leads to improved flexibility, repeatability, and cost-effectiveness. Stable single-mode emission can be obtained by changing the injection current or heat sink temperature even under the condition of large driving pulse width.展开更多
To investigate the role of co-stimulatory and co-inhibitory molecules on immune tolerance in immune thrombocytopenia(ITP),this study mapped the immune cell heterogeneity in the bone marrow of ITP at the single-cell le...To investigate the role of co-stimulatory and co-inhibitory molecules on immune tolerance in immune thrombocytopenia(ITP),this study mapped the immune cell heterogeneity in the bone marrow of ITP at the single-cell level using Cytometry by Time of Flight(CyTOF).Thirtysix patients with ITP and nine healthy volunteers were enrolled in the study.As soluble immunomodulatory molecules,more sCD25 and sGalectin-9 were detected in ITP patients.On the cell surface,co-stimulatory molecules like ICOS and HVEM were observed to be upregulated in mainly central memory and effector T cells.In contrast,co-inhibitory molecules such as CTLA-4 were significantly reduced in Th1 and Th17 cell subsets.Taking a platelet count of 30×10^(9)L^(−1)as the cutoff value,ITP patients with high and low platelet counts showed different T cell immune profiles.Antigen-presenting cells such as monocytes and B cells may regulate the activation of T cells through CTLA-4/CD86 and HVEM/BTLA interactions,respectively,and participate in the pathogenesis of ITP.In conclusion,the proteomic and soluble molecular profiles brought insight into the interaction and modulation of immune cells in the bone marrow of ITP.They may offer novel targets to develop personalized immunotherapies.展开更多
Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications,especially for optical coherence tomography systems.Although near-infrared br...Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications,especially for optical coherence tomography systems.Although near-infrared broadband light emitters have found increasingly wide utilization in these imaging applications,the requirement to simultaneously achieve both a high spectral bandwidth and output power is still challenging for such devices.Owing to the relatively weak amplified spontaneous emission,as a consequence of the very short non-radiative carrier lifetime of the inter-subband transitions in quantum cascade structures,it is even more challenging to obtain desirable mid-infrared broadband light emitters.There have been great efforts in the past 20 years to pursue high-efficiency broadband optical gain and very low reflectivity in waveguide structures,which are two key factors determining the performance of broadband light emitters.Here we describe the realization of a high continuous wave light power of 420 mW and broadband width of 4130 nm with near-infrared broadband light emitters and the first mid-infrared broadband light emitters operating under continuous wave mode at room temperature by employing a modulation p-doped InGaAs/GaAs quantum dot active region with a‘J’-shape ridge waveguide structure and a quantum cascade active region with a dual-end analogous monolithic integrated tapered waveguide structure,respectively.This work is of great importance to improve the performance of existing near-infrared optical coherence tomography systems and describes a major advance toward reliable and costeffective mid-infrared imaging and sensing systems,which do not presently exist due to the lack of appropriate low-coherence mid-infrared semiconductor broadband light sources.展开更多
A multi-wavelength sampled Bragg grating(SBG) quantum cascade laser array operating between 7.32 and7.85 μm is reported. The sampling grating structure, which can be analyzed as a conventional grating multiplied by a...A multi-wavelength sampled Bragg grating(SBG) quantum cascade laser array operating between 7.32 and7.85 μm is reported. The sampling grating structure, which can be analyzed as a conventional grating multiplied by a sampling function, is fabricated by holographic exposure combined with optical photolithography. The sampling grating period was varied from 8 to 32 μm, and different sampling order(-1 st,-2 nd, and-3 rd order)modes were achieved. We propose that higher-order modes with optimized duty cycles can be used to take full advantage of the gain curve and improve the wavelength coverage of the SBG array, which will be beneficial to many applications.展开更多
基金supported by the National Basic Research Program of China(Grant Nos.2018YFA0209103 and 2018YFB2200504)the National Natural Science Foundation of China(Grant Nos.61991430,61774146,61790583,61674144,61774150,and 61805168)+1 种基金the Beijing Municipal Science&Technology Commission,China(Grant No.Z201100004020006)the Key Projects of the Chinese Academy of Sciences(Grant Nos.2018147,YJKYYQ20190002,QYZDJ-SSW-JSC027,and XDB43000000).
文摘A multimode interference(MMI)structure is designed to simplify the fabrication of quantum cascade laser(QCL)phase-locked arrays.The MMI geometry is optimized with a sufficient output channel distance to accommodate conventional photolithography and wet etching process by which power amplifier array is fabricated without using the complicated two-step etching-regrowth or dry etching technique.The far-field pattern with periodically modulated peaks reveals that the beams from the arrays are phase-locked.Furthermore,the frequency tuning performance of the MMI-based phase-locked arrays is studied using the Littrow-configuration external cavity structure.A wavelength tuning range of more than 60 cm^(−1) is demonstrated,which will eventually realize the high power,frequency tunable,large-scale phase-locked arrays,and their application in spectroscopy.
基金Project supported by the National Basic Research Program of China(Grant No.2018YFA0209103)the National Natural Science Foundation of China(Grant Nos.61991430,61774146,61790583,61734006,61835011,61674144,61774150,and 61805168)+1 种基金Beijing Municipal Science&Technology Commission,China(Grant No.Z201100004020006)the Key Projects of the Chinese Academy of Sciences(Grant Nos.2018147,YJKYYQ20190002,QYZDJ-SSWJSC027,XDB43000000,and ZDKYYQ20200006)。
文摘We demonstrate a broad gain,continuous-wave(CW)operation InP-based quantum cascade laser(QCL)emitting at 11.8μm with a modified dual-upper-state(DAU)and diagonal transition active region design.A 3 mm cavity length,16.5μm average ridge wide QCL with high-reflection(HR)coatings demonstrates a maximum peak power of 1.07 W at 283 K and CW output power of 60 m W at 293 K.The device also shows a broad and dual-frequency lasing spectrum in pulsed mode and a maximum average power of 258.6 mW at 283 K.Moreover,the full width at half maximum(FWHM)of the electroluminescent spectrum measured at subthreshold current is 2.37μm,which indicates a broad gain spectrum of the materials.The tuning range of 1.38μm is obtained by a grating-coupled external cavity(EC)Littrow configuration,which is beneficial for gas detection.
基金Project supported by the National Basic Research Program of China(Grant Nos.2018YFA0209103 and 2018YFB2200504)the National Natural Science Foundation of China(Grant Nos.61991430,61774146,61790583,61674144,and 61774150)the Key Projects of the Chinese Academy of Sciences(Grant Nos.2018147,YJKYYQ20190002,QYZDJ-SSW-JSC027,and XDB43000000).
文摘A beam steering effect of high-power quantum cascade(QC) lasers emitting at 4.6 μm was investigated. The continuous wave(CW) output power of an uncoated, 6-mm-long, 7.5-μm-wide buried-heterostructure QC laser at 25℃ was as high as 854.2 m W. The maximum beam steering angle was offset by ±14.2° from the facet normal(0°) in pulsed mode. The phenomenon was judged explicitly by combining the diffraction limit theory and Fourier transform of the spectra. It was also verified by finite element method software simulation and the calculation of two-dimensional(2 D)effective-index model. The observed steering is consistent with a theory for coherence between the two lowest order lateral modes. Therefore, we have established an intrinsic linkage between the spectral instabilities and the beam steering by using the Fourier transform of the spectra, and further presented an extremely valid method to judge the beam steering. The content of this method includes both three equidistant peak positions in the Fourier transform of the spectra and the beam quality located between once the diffraction limit(DL) and twice the DL.
基金financially supported by the National Natural Science Foundation of China(Nos.5130317651373169+3 种基金5103300351473166 and 51403089)Innovative Research Group(No.51321062)The National High-tech R&D Program of China(863 program)(No.2011AA02A202)
文摘In this study, a series of monodispersed poly（L-lactide）（PLLA） were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight（Mn） on the crystallization and melting behaviors of PLLA were investigated by differential scanning calorimetry（DSC） and wide-angle X-ray diffraction（WAXD）. The total crystallization rate of PLLA was Mn-dependent, which reached the maximum value for PLLA with Mn of 18.6 kg/mol. In addition, when Mn of PLLA was 18.6 kg/mol, the melting enthalpy（ΔHm） showed a maximum value（87.1 J/g）, which was the highest reported value till now. The critical temperature for change of crystal formation from ？-form to ？-form crystals increased in the isothermal crystallization process with Mn increasing. In the reheating procedure, high-Mn PLLA demonstrated a small exothermal peak prior to the dominant melting peak, corresponding to crystal transition from ？- to ？-form, but low-Mn PLLA didn＇t show the peak of crystal transition. These different crystallization and melting behaviors were attributed to the different chain mobility of PLLA with different Mn.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.61734006,61835011 and 61991430)the National Basic Research Program of China(Nos.2018YFA0209100 and 2020YFB0408400).The authors would like to thank Ping Liang and Ying Hu from the Institute of Semiconductors Chinese Academy of Sciences for their help in device processing.
文摘The normal fabrication process for electronic and optoelectronic devices can bring in significant modifications on two-dimensional(2D)semiconductors’intrinsic properties.To address this issue,some dry methods have been developed,such as“transfer contact”method and“shadow mask technology”.However,the method that can combine the advantages of low cost,non-destruction,and high reliability at sub-micrometer scale is rarely reported.Here,we demonstrate a fabrication technique using ultrafine quartz fibers as shadow masks.In this technique,sub-micrometer scale devices can be“all dry”fabricated facilely,and the intrinsic properties of 2D semiconductors are preserved.Meanwhile,the masking effect can be evaluated in situ based on the light interference between the quartz fiber and the substrate to increase the fabrication reliability.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2019YFB1803500)the National Natural Science Foundation of China (Grant No. 61805168)+4 种基金the Natural Science Foundation of Shanxi Province, China (Grant Nos. 201801D221183 and 20210302123185)International Cooperation of Key Research and Development Program of Shanxi Province (Grant No. 201903D421012)Research Project Supported by Shanxi Scholarship Council of China (Grant No. 2021-032)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi (Grant No. 2019L0133)Fund for Shanxi “1331 Project” Key Innovative Research Team。
文摘Dynamic states in mutual-coupled mid-infrared quantum cascade lasers(QCLs) were numerically investigated in the parameter space of injection strength and detuning frequency based on the Lang-Kobayashi equations model. Three types of period-one states were found, with different periods of injection time delay τ_(inj), 2τ_(inj), and reciprocal of the detuning frequency. Besides, square-wave, quasi-period, pulse-burst and chaotic oscillations were also observed. It is concluded that external-cavity periodic dynamics and optical modes beating are the mainly periodic dynamics. The interaction of the two periodic dynamics and the high-frequency dynamics stimulated by strong injection induces the dynamic states evolution.This work helps to understand the dynamic behaviors in QCLs and shows a new way to mid-infrared wide-band chaotic laser.
基金National Natural Science Foundation of China(NSFC)(61435014,61574136,61627822,61774146,61790583)Chinese Academy of Sciences Key Project(CAS Key Project)(QYZDJ-SSW-JSC027,ZDRW-XH-2016-4)Natural Science Foundation of Beijing Municipality(4172060)
文摘Power scaling in a broad area quantum cascade laser(QCL) tends to deteriorate beam quality with the emission of a multiple-lobe far-field pattern. In this paper, we demonstrate a coupled ridge waveguide QCL array consisting of five elements with chirped geometry. In-phase mode operation is secured by managing supermode loss with properly designed geometries of ridges. A single-lobe lateral far-field with a near diffraction limited beam pattern was obtained in the whole current dynamic range. The devices were fabricated with the wet and dry etching method. The regrowth technique of the In P:Fe insulation layer and In P:Si waveguide layer was employed.Such a structure has the potential to optimize the beam quality of the recently reported high-power broad-area QCL with a reduced cascade number.
基金National Basic Research Program of China(2013CB632800)National Key Research and Development Program(2016YFB0402303)+2 种基金National Natural Science Foundation of China(NSFC)(61404131,61435014,61674144,61574136,61627822)Chinese Academy of Sciences Key Project(CAS Key Project)(QYZDJ-SSWJSC027,ZDRW-XH-2016-4)Natural Science Foundation of Beijing Municipality(4162060,4172060)
文摘We report an index-coupled distributed feedback quantum cascade laser by employing an equivalent phase shift(EPS) of quarter-wave integrated with a distributed Bragg reflector(DBR) at λ~5.03 μm. The EPS is fabricated through extending one sampling period by 50% in the center of a sampled Bragg grating. The key EPS and DBR pattern are fabricated by conventional holographic exposure combined with the optical photolithography technology, which leads to improved flexibility, repeatability, and cost-effectiveness. Stable single-mode emission can be obtained by changing the injection current or heat sink temperature even under the condition of large driving pulse width.
基金supported by the National Natural Science Foundation of China(82230004,81970113,82300149)the National Key Research and Development Program of China(2021YFC2500304)+1 种基金Capital Health Research and Development of Special(2022-1-4082)Peking University Medicine Fund for world's leading discipline or discipline cluster development(71003Y3035).
文摘To investigate the role of co-stimulatory and co-inhibitory molecules on immune tolerance in immune thrombocytopenia(ITP),this study mapped the immune cell heterogeneity in the bone marrow of ITP at the single-cell level using Cytometry by Time of Flight(CyTOF).Thirtysix patients with ITP and nine healthy volunteers were enrolled in the study.As soluble immunomodulatory molecules,more sCD25 and sGalectin-9 were detected in ITP patients.On the cell surface,co-stimulatory molecules like ICOS and HVEM were observed to be upregulated in mainly central memory and effector T cells.In contrast,co-inhibitory molecules such as CTLA-4 were significantly reduced in Th1 and Th17 cell subsets.Taking a platelet count of 30×10^(9)L^(−1)as the cutoff value,ITP patients with high and low platelet counts showed different T cell immune profiles.Antigen-presenting cells such as monocytes and B cells may regulate the activation of T cells through CTLA-4/CD86 and HVEM/BTLA interactions,respectively,and participate in the pathogenesis of ITP.In conclusion,the proteomic and soluble molecular profiles brought insight into the interaction and modulation of immune cells in the bone marrow of ITP.They may offer novel targets to develop personalized immunotherapies.
基金the financial support from the Natural Science Foundation of China(61575215)the National Research Projects of China(2013CB632800)the Thousand Youth Talents Plan and the Key Research and Development Plan of Ministry of Science and Technology(2016YFB0402303)。
文摘Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications,especially for optical coherence tomography systems.Although near-infrared broadband light emitters have found increasingly wide utilization in these imaging applications,the requirement to simultaneously achieve both a high spectral bandwidth and output power is still challenging for such devices.Owing to the relatively weak amplified spontaneous emission,as a consequence of the very short non-radiative carrier lifetime of the inter-subband transitions in quantum cascade structures,it is even more challenging to obtain desirable mid-infrared broadband light emitters.There have been great efforts in the past 20 years to pursue high-efficiency broadband optical gain and very low reflectivity in waveguide structures,which are two key factors determining the performance of broadband light emitters.Here we describe the realization of a high continuous wave light power of 420 mW and broadband width of 4130 nm with near-infrared broadband light emitters and the first mid-infrared broadband light emitters operating under continuous wave mode at room temperature by employing a modulation p-doped InGaAs/GaAs quantum dot active region with a‘J’-shape ridge waveguide structure and a quantum cascade active region with a dual-end analogous monolithic integrated tapered waveguide structure,respectively.This work is of great importance to improve the performance of existing near-infrared optical coherence tomography systems and describes a major advance toward reliable and costeffective mid-infrared imaging and sensing systems,which do not presently exist due to the lack of appropriate low-coherence mid-infrared semiconductor broadband light sources.
基金National Key Research and Development Program(2017YFB0405300,2016YFB0402303)National Natural Science Foundation of China(NSFC)(61734006,61774150,61435014,61627822,61574136)
文摘A multi-wavelength sampled Bragg grating(SBG) quantum cascade laser array operating between 7.32 and7.85 μm is reported. The sampling grating structure, which can be analyzed as a conventional grating multiplied by a sampling function, is fabricated by holographic exposure combined with optical photolithography. The sampling grating period was varied from 8 to 32 μm, and different sampling order(-1 st,-2 nd, and-3 rd order)modes were achieved. We propose that higher-order modes with optimized duty cycles can be used to take full advantage of the gain curve and improve the wavelength coverage of the SBG array, which will be beneficial to many applications.
