We demonstrate Ga Sb-based interband cascade lasers(ICLs) emitting around 3.65 μm, which exhibit a room-temperature continuous-wave(CW) output power above 100 m W. Cavity-length analysis showed that the laser structu...We demonstrate Ga Sb-based interband cascade lasers(ICLs) emitting around 3.65 μm, which exhibit a room-temperature continuous-wave(CW) output power above 100 m W. Cavity-length analysis showed that the laser structure has a low internal loss of 3 cm^(-1) while maintaining a total internal quantum efficiency greater than one. After 6400 h CW operation at 25°C,the threshold current of the laser increased by 3%, and the output power decreased by 7%, indicating good reliability of the device.展开更多
InAs-based interband cascade lasers(ICLs) with InAs plasmon waveguides or InAs/AlSb superlattice(SL) waveguides were demonstrated at emission wavelengths below 4.1 μm. The threshold current densities of the lasers wi...InAs-based interband cascade lasers(ICLs) with InAs plasmon waveguides or InAs/AlSb superlattice(SL) waveguides were demonstrated at emission wavelengths below 4.1 μm. The threshold current densities of the lasers with SL waveguides were 37 A/cm^2 at 77 K in continuous wave mode. The operation temperature of these lasers reached room temperature in pulsed mode. Compared with the thick InAs n++ plasmon cladding layer, the InAs/AlSb superlattice cladding layers have greater advantages for ICLs with wavelengths less than 4 μm even in InAs based ICLs because in the short-wavelength region they have a higher confinement factor than InAs plasmon waveguides.展开更多
We report on a long wavelength interband cascade photodetector with type Ⅱ InAs/GaSb superlattice absorber.The device is a three-stage interband cascade structure.At 77 K,the 50%cutoff wavelength of the detector is 8...We report on a long wavelength interband cascade photodetector with type Ⅱ InAs/GaSb superlattice absorber.The device is a three-stage interband cascade structure.At 77 K,the 50%cutoff wavelength of the detector is 8.48μm and the peak photoresponse wavelength is 7.78μm.The peak responsivity is 0.93 A/W and the detectivity D*is 1.12×10^(11)cm·Hz0.5/W for 7.78μm at-0.20 V.The detector can operate up to about 260 K.At 260 K,the 50%cutoff wavelength is 11.52μm,the peak responsivity is 0.78 A/W and the D*is 5.02×10^(8)cm·Hz0.5/W for the peak wavelength of 10.39μm at-2.75 V.The dark current of the device is dominated by the diffusion current under both a small bias voltage of-0.2 V and a large one of-2.75 V for the temperature range of 120 to 260 K.展开更多
Sharing the advantages of high optical power,high efficiency and design flexibility in a compact size,quantum cascade lasers(QCLs)are excellent mid-to-far infrared laser sources for gas sensing,infrared spectroscopic,...Sharing the advantages of high optical power,high efficiency and design flexibility in a compact size,quantum cascade lasers(QCLs)are excellent mid-to-far infrared laser sources for gas sensing,infrared spectroscopic,medical diagnosis,and defense applications.Metalorganic chemical vapor deposition(MOCVD)is an important technology for growing high quality semiconductor materials,and has achieved great success in the semiconductor industry due to its advantages of high efficiency,short maintenance cycles,and high stability and repeatability.The utilization of MOCVD for the growth of QCL materials holds a significant meaning for promoting the large batch production and industrial application of QCL devices.This review summarizes the recent progress of QCLs grown by MOCVD.Material quality and the structure design together determine the device performance.Research progress on the performance improvement of MOCVD-grown QCLs based on the optimization of material quality and active region structure are mainly reviewed.展开更多
We report a type-Ⅱ GaSb-based interband cascade laser operating a continuous wave at room temperature. The cascade region of interband cascade laser was designed using the ‘W' configuration of the active quantum...We report a type-Ⅱ GaSb-based interband cascade laser operating a continuous wave at room temperature. The cascade region of interband cascade laser was designed using the ‘W' configuration of the active quantum wells and the ‘Carrier Rebalancing' method in the electron injector. The devices were processed into narrow ridges and mounted epitaxial side down on a copper heat sink. The 25-μm-wide, 3-mm-long ridge without coated facets generated 41.4 mW of continuous wave output power at T = 15℃. And a low threshold current density of 267 A/cm^2 is achieved. The emission wavelength of the ICL is 3452.3 nm at 0.5 A.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
We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength.The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector.Th...We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength.The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector.The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper.And the quantum well cascade laser with 100-μm-wide,2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature.The characteristic temperature T_(0) is estimated at above 60 K.展开更多
In this paper, we report a single-mode Fabry-Pérot long wave infrared quantum cascade lasers based on the double phonon resonance active region design. For room temperature CW operation, the wafer with 35 stages ...In this paper, we report a single-mode Fabry-Pérot long wave infrared quantum cascade lasers based on the double phonon resonance active region design. For room temperature CW operation, the wafer with 35 stages was processed into buried heterostructure lasers. For a 4 mm long and 13 μm wide laser with high-reflectivity (HR) coating on the rear facet, continuous wave output power of 43 mW at 288 K and 5 mW at 303 K is obtained with threshold current densities of 2.17 and 2.7 kA/cm2. The lasing wavelength is around 10.5 μm. Single mode emission was observed for this particular device over the whole investigated current and temperature range.展开更多
For non-invasive measurement of blood glucose levels, a measurement system based on mid-infrared, attenuated-total-reflection spectroscopy equipped with hollow optical fibers, a trapezoidal multi-reflection prism, and...For non-invasive measurement of blood glucose levels, a measurement system based on mid-infrared, attenuated-total-reflection spectroscopy equipped with hollow optical fibers, a trapezoidal multi-reflection prism, and two fixed-wavelength quantum cascade lasers emitting different wavelengths is proposed. From the absorption spectra of lip mucosa measured by Fourier-transform infrared spectrometry, two wavelengths, 1152 cm-1 for absorption by glucose and 1186 cm-1 for the background, were chosen. To reduce measurement errors, the power distribution on the prism surface was investigated, and it was found that some high-intensity spots appear on the prism surface due to the coherency of the laser beam. This inhomogeneous power distribution causes measurement errors for slight movements of the lip mucosa. To homogenize the intensity distribution on the prism, a lens to excite higher modes in the fiber was introduced, and the incident angle was changed to suppress interference due to back-reflected light. These improvements increased the measurement stability, and in-vivo experiments demonstrated that the measured optical absorption correlates well with blood glucose levels.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
<div style="text-align:justify;"> In this paper, we report a single-mode Fabry-Pérot long wave infrared quantum cascade lasers based on the double phonon resonance active region design. For room t...<div style="text-align:justify;"> In this paper, we report a single-mode Fabry-Pérot long wave infrared quantum cascade lasers based on the double phonon resonance active region design. For room temperature CW operation, the wafer with 35 stages was processed into buried heterostructure lasers. For a 4 mm long and 13 μm wide laser with high-reflectivity (HR) coating on the rear facet, continuous wave output power of 43 mW at 288 K and 5 mW at 303 K is obtained with threshold current densities of 2.17 and 2.7 kA/cm2. The lasing wavelength is around 10.5 μm. Single mode emission was observed for this particular device over the whole investigated current and temperature range. </div>展开更多
A strain-compensated InP-based quantum cascade laser(QCL) structure emitting at 4.6 μm is demonstrated,based on a two-phonon resonant design and grown by solid-source molecular beam epitaxy(MBE).By optimizing the gro...A strain-compensated InP-based quantum cascade laser(QCL) structure emitting at 4.6 μm is demonstrated,based on a two-phonon resonant design and grown by solid-source molecular beam epitaxy(MBE).By optimizing the growth parameters,a very high quality heterostructure with the lowest threshold current densities ever reported for QCLs was fabricated.Threshold current densities as low as 0.47 kA/cm^2 in pulsed operation and 0.56 kA/cm^2 in continuous-wave(cw) operation at 293 K were achieved for this state-of-the-art QCL.A minimum power consumption of 3.65 W was measured for the QCL,uncooled,with a high-reflectivity(HR) coating on its rear facet.展开更多
Terahertz quantum cascade lasers(THz QCLs) emitted at 4.4 THz are fabricated and characterized. An equivalent circuit model is established based on the five-level rate equations to describe their characteristics. In o...Terahertz quantum cascade lasers(THz QCLs) emitted at 4.4 THz are fabricated and characterized. An equivalent circuit model is established based on the five-level rate equations to describe their characteristics. In order to illustrate the capability of the model, the steady and dynamic performances of the fabricated THz QCLs are simulated by the model.Compared to the sophisticated numerical methods, the presented model has advantages of fast calculation and good compatibility with circuit simulation for system-level designs and optimizations. The validity of the model is verified by the experimental and numerical results.展开更多
For mode selection in a quantum cascade laser(QCL),we demonstrate an anti-symmetric sampled grating(ASG).The wavelength of the-1-th mode of this laser has been blue-shifted more than 75 nm(~10 cm^(-1))compared with th...For mode selection in a quantum cascade laser(QCL),we demonstrate an anti-symmetric sampled grating(ASG).The wavelength of the-1-th mode of this laser has been blue-shifted more than 75 nm(~10 cm^(-1))compared with that of an ordinary sampled grating laser with an emission wavelength of approximately 8.6μm,when the periodicities within both the base grating and the sample grating are kept constant.Under this condition,an improvement in the continuous tuning capability of the QCL array is ensured.The ASG structure is fabricated in holographic exposure and optical photolithography,thereby enhancing its flexibility,repeatability,and cost-effectiveness.The wavelength modulation capability of the two channels of the grating is insensitive to the variations in channel size,assuming that the overall waveguide width remains constant.The output wavelength can be tailored freely within a certain range by adjusting the width of the ridge and the material of the cladding layer.展开更多
Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This st...Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.展开更多
基金This work was supported by the National Key Research and Development Project(No.2018YFB2200500)the National Natural Science Foundation of China(Nos.61790583 and 61774150)。
文摘We demonstrate Ga Sb-based interband cascade lasers(ICLs) emitting around 3.65 μm, which exhibit a room-temperature continuous-wave(CW) output power above 100 m W. Cavity-length analysis showed that the laser structure has a low internal loss of 3 cm^(-1) while maintaining a total internal quantum efficiency greater than one. After 6400 h CW operation at 25°C,the threshold current of the laser increased by 3%, and the output power decreased by 7%, indicating good reliability of the device.
基金Project supported by the National Natural Science Foundation of China(Nos.61790583,61774150,61774151)the National Basic Research Program of China(No.2014CB643903)
文摘InAs-based interband cascade lasers(ICLs) with InAs plasmon waveguides or InAs/AlSb superlattice(SL) waveguides were demonstrated at emission wavelengths below 4.1 μm. The threshold current densities of the lasers with SL waveguides were 37 A/cm^2 at 77 K in continuous wave mode. The operation temperature of these lasers reached room temperature in pulsed mode. Compared with the thick InAs n++ plasmon cladding layer, the InAs/AlSb superlattice cladding layers have greater advantages for ICLs with wavelengths less than 4 μm even in InAs based ICLs because in the short-wavelength region they have a higher confinement factor than InAs plasmon waveguides.
基金supported in part by China’s NSF Program 61874103
文摘We report on a long wavelength interband cascade photodetector with type Ⅱ InAs/GaSb superlattice absorber.The device is a three-stage interband cascade structure.At 77 K,the 50%cutoff wavelength of the detector is 8.48μm and the peak photoresponse wavelength is 7.78μm.The peak responsivity is 0.93 A/W and the detectivity D*is 1.12×10^(11)cm·Hz0.5/W for 7.78μm at-0.20 V.The detector can operate up to about 260 K.At 260 K,the 50%cutoff wavelength is 11.52μm,the peak responsivity is 0.78 A/W and the D*is 5.02×10^(8)cm·Hz0.5/W for the peak wavelength of 10.39μm at-2.75 V.The dark current of the device is dominated by the diffusion current under both a small bias voltage of-0.2 V and a large one of-2.75 V for the temperature range of 120 to 260 K.
基金supported by National Key Research and Development Program of China (Grant No.2021YFB3201900)National Natural Science Foundation of China (Grant Nos.61991430,62235016)+1 种基金Youth Innovation Promotion Association of CAS (Grant Nos.2022112,Y2022046)Key projects of the Chinese Academy of Sciences (Grant No.XDB43000000)。
文摘Sharing the advantages of high optical power,high efficiency and design flexibility in a compact size,quantum cascade lasers(QCLs)are excellent mid-to-far infrared laser sources for gas sensing,infrared spectroscopic,medical diagnosis,and defense applications.Metalorganic chemical vapor deposition(MOCVD)is an important technology for growing high quality semiconductor materials,and has achieved great success in the semiconductor industry due to its advantages of high efficiency,short maintenance cycles,and high stability and repeatability.The utilization of MOCVD for the growth of QCL materials holds a significant meaning for promoting the large batch production and industrial application of QCL devices.This review summarizes the recent progress of QCLs grown by MOCVD.Material quality and the structure design together determine the device performance.Research progress on the performance improvement of MOCVD-grown QCLs based on the optimization of material quality and active region structure are mainly reviewed.
基金Project supported by the Major Program of the National Natural Science Foundation of China(Grant No.61790580)the National Natural Science Foundation of China(Grant No.61435012)the National Basic Research Program of China(Grant No.2014CB643903)
文摘We report a type-Ⅱ GaSb-based interband cascade laser operating a continuous wave at room temperature. The cascade region of interband cascade laser was designed using the ‘W' configuration of the active quantum wells and the ‘Carrier Rebalancing' method in the electron injector. The devices were processed into narrow ridges and mounted epitaxial side down on a copper heat sink. The 25-μm-wide, 3-mm-long ridge without coated facets generated 41.4 mW of continuous wave output power at T = 15℃. And a low threshold current density of 267 A/cm^2 is achieved. The emission wavelength of the ICL is 3452.3 nm at 0.5 A.
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Project supported by the Major Program of the National Natural Science Foundation of China(Grant No.61790581)the Key Area Research and Development Program of Guangdong Province,China(Grant No.2020B0303020001).
文摘We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength.The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector.The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper.And the quantum well cascade laser with 100-μm-wide,2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature.The characteristic temperature T_(0) is estimated at above 60 K.
文摘In this paper, we report a single-mode Fabry-Pérot long wave infrared quantum cascade lasers based on the double phonon resonance active region design. For room temperature CW operation, the wafer with 35 stages was processed into buried heterostructure lasers. For a 4 mm long and 13 μm wide laser with high-reflectivity (HR) coating on the rear facet, continuous wave output power of 43 mW at 288 K and 5 mW at 303 K is obtained with threshold current densities of 2.17 and 2.7 kA/cm2. The lasing wavelength is around 10.5 μm. Single mode emission was observed for this particular device over the whole investigated current and temperature range.
文摘For non-invasive measurement of blood glucose levels, a measurement system based on mid-infrared, attenuated-total-reflection spectroscopy equipped with hollow optical fibers, a trapezoidal multi-reflection prism, and two fixed-wavelength quantum cascade lasers emitting different wavelengths is proposed. From the absorption spectra of lip mucosa measured by Fourier-transform infrared spectrometry, two wavelengths, 1152 cm-1 for absorption by glucose and 1186 cm-1 for the background, were chosen. To reduce measurement errors, the power distribution on the prism surface was investigated, and it was found that some high-intensity spots appear on the prism surface due to the coherency of the laser beam. This inhomogeneous power distribution causes measurement errors for slight movements of the lip mucosa. To homogenize the intensity distribution on the prism, a lens to excite higher modes in the fiber was introduced, and the incident angle was changed to suppress interference due to back-reflected light. These improvements increased the measurement stability, and in-vivo experiments demonstrated that the measured optical absorption correlates well with blood glucose levels.
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.
文摘<div style="text-align:justify;"> In this paper, we report a single-mode Fabry-Pérot long wave infrared quantum cascade lasers based on the double phonon resonance active region design. For room temperature CW operation, the wafer with 35 stages was processed into buried heterostructure lasers. For a 4 mm long and 13 μm wide laser with high-reflectivity (HR) coating on the rear facet, continuous wave output power of 43 mW at 288 K and 5 mW at 303 K is obtained with threshold current densities of 2.17 and 2.7 kA/cm2. The lasing wavelength is around 10.5 μm. Single mode emission was observed for this particular device over the whole investigated current and temperature range. </div>
基金supported by the National Basic Research Program of China(Grant Nos.2013CB632801 and 2013CB632803)the National Natural Science Foundation of China(Grant Nos.61306058,61274094,and 61435014)the Beijing Natural Science Foundation(Grant No.4144086)
文摘A strain-compensated InP-based quantum cascade laser(QCL) structure emitting at 4.6 μm is demonstrated,based on a two-phonon resonant design and grown by solid-source molecular beam epitaxy(MBE).By optimizing the growth parameters,a very high quality heterostructure with the lowest threshold current densities ever reported for QCLs was fabricated.Threshold current densities as low as 0.47 kA/cm^2 in pulsed operation and 0.56 kA/cm^2 in continuous-wave(cw) operation at 293 K were achieved for this state-of-the-art QCL.A minimum power consumption of 3.65 W was measured for the QCL,uncooled,with a high-reflectivity(HR) coating on its rear facet.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB339803)the National High Technology Research and Development Program of China(Grant No.2011AA010205)+5 种基金the National Natural Science Foundation of China(Grant Nos.61131006,61321492,and 61404149)the Major National Development Project of Scientific Instrument and Equipment,China(Grant No.2011YQ150021)the National Science and Technology Major Project,China(Grant No.2011ZX02707)the Major Project,China(Grant No.YYYJ-1123-1)the International Collaboration and Innovation Program on High Mobility Materials Engineering of the Chinese Academy of Sciencesthe Shanghai Municipal Commission of Science and Technology,China(Grant Nos.14530711300)
文摘Terahertz quantum cascade lasers(THz QCLs) emitted at 4.4 THz are fabricated and characterized. An equivalent circuit model is established based on the five-level rate equations to describe their characteristics. In order to illustrate the capability of the model, the steady and dynamic performances of the fabricated THz QCLs are simulated by the model.Compared to the sophisticated numerical methods, the presented model has advantages of fast calculation and good compatibility with circuit simulation for system-level designs and optimizations. The validity of the model is verified by the experimental and numerical results.
基金Project supported by the National Basic Research Program of China (Grant No. 2021YFB3201900)in part by the National Natural Science Foundation of China (Grant Nos. 61991430, 61774146, 61790583,61627822, and 61774150)in part by the Key Projects of the Chinese Academy of Sciences (Grant Nos. 2018147, YJKYYQ20190002, QYZDJ-SSW-JSC027,XDB43000000)
文摘For mode selection in a quantum cascade laser(QCL),we demonstrate an anti-symmetric sampled grating(ASG).The wavelength of the-1-th mode of this laser has been blue-shifted more than 75 nm(~10 cm^(-1))compared with that of an ordinary sampled grating laser with an emission wavelength of approximately 8.6μm,when the periodicities within both the base grating and the sample grating are kept constant.Under this condition,an improvement in the continuous tuning capability of the QCL array is ensured.The ASG structure is fabricated in holographic exposure and optical photolithography,thereby enhancing its flexibility,repeatability,and cost-effectiveness.The wavelength modulation capability of the two channels of the grating is insensitive to the variations in channel size,assuming that the overall waveguide width remains constant.The output wavelength can be tailored freely within a certain range by adjusting the width of the ridge and the material of the cladding layer.
文摘Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.
