We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs)array,with a single-mode pulse power of 108 mW at 13 K.The device utilizes a Talbot cavity to achieve phase locking among five ridge l...We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs)array,with a single-mode pulse power of 108 mW at 13 K.The device utilizes a Talbot cavity to achieve phase locking among five ridge lasers with first-order buried distributed feedback(DFB)grating,resulting in nearly five times amplification of the single-mode power.Due to the optimum length of Talbot cavity depends on wavelength,the combination of Talbot cavity with the DFB grating leads to better power amplification than the combination with multimode Fabry-Perot(F-P)cavities.The Talbot cavity facet reflects light back to the ridge array direction and achieves self-imaging in the array,enabling phase-locked operation of ridges.We set the spacing between adjacent elements to be 220μm,much larger than the free-space wavelength,ensuring the operation of the fundamental supermode throughout the laser's dynamic range and obtaining a high-brightness far-field distribution.This scheme provides a new approach for enhancing the single-mode power of THz QCLs.展开更多
We report on the performance improvement of long-wave infrared quantum cascade lasers(LWIR QCLs)by studying and optimizing the anti-reflection(AR)optical facet coating.Compared to the Al2O3 AR coat⁃ing,the Y_(2)O_(3)A...We report on the performance improvement of long-wave infrared quantum cascade lasers(LWIR QCLs)by studying and optimizing the anti-reflection(AR)optical facet coating.Compared to the Al2O3 AR coat⁃ing,the Y_(2)O_(3)AR coating exhibits higher catastrophic optical mirror damage(COMD)level,and the optical facet coatings of both material systems have no beam steering effect.A 3-mm-long,9.5-μm-wide buried-heterostruc⁃ture(BH)LWIR QCL ofλ~8.5μm with Y_(2)O_(3)metallic high-reflection(HR)and AR of~0.2%reflectivity coating demonstrates a maximum pulsed peak power of 2.19 W at 298 K,which is 149%higher than that of the uncoated device.For continuous-wave(CW)operation,by optimizing the reflectivity of the Y_(2)O_(3)AR coating,the maximum output power reaches 0.73 W,which is 91%higher than that of the uncoated device.展开更多
Room temperature operation is an important criterion for high performance of quantum cascade lasers. A strain-compensated quantum cascade laser（λ≈5.5μm） with optimized waveguide structure lasing at room temperatu...Room temperature operation is an important criterion for high performance of quantum cascade lasers. A strain-compensated quantum cascade laser（λ≈5.5μm） with optimized waveguide structure lasing at room temperature is reported. Accurate control of layer thickness and strain-compensated material composition is demonstrated using X-ray diffraction. An output power of at least 45mW per facet is realized for a 20μm-wide and 2mm-long laser at room temperature.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
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
We report on the design and fabrication of λ-7.2μm distributed feedback quantum cascade lasers lot very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90℃. Fo...We report on the design and fabrication of λ-7.2μm distributed feedback quantum cascade lasers lot very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90℃. For a 2-mm-long and 10-μm-wide laser coated with high-reflectivity on the rear facet, more than 170mW of output power is obtained at 20℃ with a threshold power consumption of 2.4 W, corresponding to 30mW with a threshold power consumption of 3.9 W at 90℃. Robust single-mode emission with a side-mode suppression ratio above 25 dB is continuously tunable by the heat sink temperature or injection current.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
<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
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...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
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...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
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
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
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
An InP-based one-dimensional photonic crystal quantum cascade laser is realized. With photo lithography instead of electron beam lithography and using inductively coupled plasma etching, four-period air-semiconductor ...An InP-based one-dimensional photonic crystal quantum cascade laser is realized. With photo lithography instead of electron beam lithography and using inductively coupled plasma etching, four-period air-semiconductor couples are defined as Bragg reflectors at one end of the resonator. The spectral measurement at 80K shows the quasi-continuous-wave operation with the wavelength of 5.36μm for a 22gm-wide and 2mm-long epilayer-up bonded device.展开更多
A high-power and high-effciency GaAs/A1GaAs-based terahertz （THz） quantum cascade laser structure emitting at 3.3 THz is presented. The structure is based on a hybrid bound-to-continuum transition and resonant-phono...A high-power and high-effciency GaAs/A1GaAs-based terahertz （THz） quantum cascade laser structure emitting at 3.3 THz is presented. The structure is based on a hybrid bound-to-continuum transition and resonant-phonon extraction active region combined with a semi-insulating surface-plasmon waveguide. By optimizing material structure and device processing, the peak optical output power of 758mW with a threshold current density of 120 A/cm2 and a wall-plug effciency of 0.92% at 10K and 404mW at 77K are obtained in pulsed operation. The maximum operating temperature is as high as llS K. In the cw mode, a record optical output power of 160roW with a threshold current density of 178A/cm2 and a wall-plug efficiency of 1.32% is achieved at 1OK.展开更多
Improved waveguide designs for 9.0μm GaAs-based quantum cascade laser （QCL） structures are presented. Modal losses and confinement factors are calculated for TM modes with the transfer matrix method （TMM） and eff...Improved waveguide designs for 9.0μm GaAs-based quantum cascade laser （QCL） structures are presented. Modal losses and confinement factors are calculated for TM modes with the transfer matrix method （TMM） and effective index method （EIM）. The thicknesses of the cladding layer and waveguide layer, the ridge-width, and the cavity length are all taken into account. Appropriate thicknesses of epilayers are given with lower threshold gain and more economical material growth time.展开更多
The waveguide design is one of the most important parts in a terahertz quantum cascade laser（QCL）. Si/SiGe QCL waveguides, based on the Drude model and finite-difference time-domain （FDTD） method, are designed by ...The waveguide design is one of the most important parts in a terahertz quantum cascade laser（QCL）. Si/SiGe QCL waveguides, based on the Drude model and finite-difference time-domain （FDTD） method, are designed by the traditional refractive index waveguide structure, the single-sided metal structure, the double-metal clad structure, and a novel metal/metal silicide structure. The metal/metal silicide structure, showing high modal confinement,is convenient in process engineering and is expected to be a viable waveguide solution for Si/SiGe QCLs in the THz range.展开更多
Robust quantum cascade laser(QCL)enduring high temperature continuous-wave(CW)operation is of critical importance for some applications.We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials g...Robust quantum cascade laser(QCL)enduring high temperature continuous-wave(CW)operation is of critical importance for some applications.We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials grown by metal-organic chemical vapor deposition(MOCVD).High interface quality structures designed for light emission at 8.5μm are achieved by optimizing and precise controlling of growth conditions.A CW output power of 1.04 W at 288 K was obtained from a 4 mm-long and 10μm-wide coated laser.Corresponding maximum wall-plug efficiency and threshold current density were 7.1%and 1.18 kA/cm2,respectively.The device can operate in CW mode up to 408 K with an output power of 160 mW.展开更多
基金funded by National Natural Science Foundation of China, grant numbers 62335006, 62274014, 62235016, 61734006, 61835011, 61991430funded by Key Program of the Chinese Academy of Sciences, grant numbers XDB43000000, QYZDJSSW-JSC027Beijing Municipal Science & Technology Commission, grant number Z221100002722018
文摘We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs)array,with a single-mode pulse power of 108 mW at 13 K.The device utilizes a Talbot cavity to achieve phase locking among five ridge lasers with first-order buried distributed feedback(DFB)grating,resulting in nearly five times amplification of the single-mode power.Due to the optimum length of Talbot cavity depends on wavelength,the combination of Talbot cavity with the DFB grating leads to better power amplification than the combination with multimode Fabry-Perot(F-P)cavities.The Talbot cavity facet reflects light back to the ridge array direction and achieves self-imaging in the array,enabling phase-locked operation of ridges.We set the spacing between adjacent elements to be 220μm,much larger than the free-space wavelength,ensuring the operation of the fundamental supermode throughout the laser's dynamic range and obtaining a high-brightness far-field distribution.This scheme provides a new approach for enhancing the single-mode power of THz QCLs.
基金Supported by the National Natural Science Foundation of China(12393830)。
文摘We report on the performance improvement of long-wave infrared quantum cascade lasers(LWIR QCLs)by studying and optimizing the anti-reflection(AR)optical facet coating.Compared to the Al2O3 AR coat⁃ing,the Y_(2)O_(3)AR coating exhibits higher catastrophic optical mirror damage(COMD)level,and the optical facet coatings of both material systems have no beam steering effect.A 3-mm-long,9.5-μm-wide buried-heterostruc⁃ture(BH)LWIR QCL ofλ~8.5μm with Y_(2)O_(3)metallic high-reflection(HR)and AR of~0.2%reflectivity coating demonstrates a maximum pulsed peak power of 2.19 W at 298 K,which is 149%higher than that of the uncoated device.For continuous-wave(CW)operation,by optimizing the reflectivity of the Y_(2)O_(3)AR coating,the maximum output power reaches 0.73 W,which is 91%higher than that of the uncoated device.
文摘Room temperature operation is an important criterion for high performance of quantum cascade lasers. A strain-compensated quantum cascade laser（λ≈5.5μm） with optimized waveguide structure lasing at room temperature is reported. Accurate control of layer thickness and strain-compensated material composition is demonstrated using X-ray diffraction. An output power of at least 45mW per facet is realized for a 20μm-wide and 2mm-long laser at room temperature.
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 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.
基金Supported by the National Basic Research Program of China under Grant No 2013CB632801the National Key Research and Development Program under Grant No 2016YFB0402303+2 种基金the National Natural Science Foundation of China under Grant Nos61435014,61627822,61574136 and 61306058the Key Projects of Chinese Academy of Sciences under Grant No ZDRW-XH-2016-4the Beijing Natural Science Foundation under Grant No 4162060
文摘We report on the design and fabrication of λ-7.2μm distributed feedback quantum cascade lasers lot very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90℃. For a 2-mm-long and 10-μm-wide laser coated with high-reflectivity on the rear facet, more than 170mW of output power is obtained at 20℃ with a threshold power consumption of 2.4 W, corresponding to 30mW with a threshold power consumption of 3.9 W at 90℃. Robust single-mode emission with a side-mode suppression ratio above 25 dB is continuously tunable by the heat sink temperature or injection current.
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.
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 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.
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.
文摘An InP-based one-dimensional photonic crystal quantum cascade laser is realized. With photo lithography instead of electron beam lithography and using inductively coupled plasma etching, four-period air-semiconductor couples are defined as Bragg reflectors at one end of the resonator. The spectral measurement at 80K shows the quasi-continuous-wave operation with the wavelength of 5.36μm for a 22gm-wide and 2mm-long epilayer-up bonded device.
基金Supported by the National Basic Research Program of China under Grant Nos 2014CB339803 and 2013CB632801the National Natural Science Foundation of China under Grant No 61376051
文摘A high-power and high-effciency GaAs/A1GaAs-based terahertz （THz） quantum cascade laser structure emitting at 3.3 THz is presented. The structure is based on a hybrid bound-to-continuum transition and resonant-phonon extraction active region combined with a semi-insulating surface-plasmon waveguide. By optimizing material structure and device processing, the peak optical output power of 758mW with a threshold current density of 120 A/cm2 and a wall-plug effciency of 0.92% at 10K and 404mW at 77K are obtained in pulsed operation. The maximum operating temperature is as high as llS K. In the cw mode, a record optical output power of 160roW with a threshold current density of 178A/cm2 and a wall-plug efficiency of 1.32% is achieved at 1OK.
文摘Improved waveguide designs for 9.0μm GaAs-based quantum cascade laser （QCL） structures are presented. Modal losses and confinement factors are calculated for TM modes with the transfer matrix method （TMM） and effective index method （EIM）. The thicknesses of the cladding layer and waveguide layer, the ridge-width, and the cavity length are all taken into account. Appropriate thicknesses of epilayers are given with lower threshold gain and more economical material growth time.
文摘The waveguide design is one of the most important parts in a terahertz quantum cascade laser（QCL）. Si/SiGe QCL waveguides, based on the Drude model and finite-difference time-domain （FDTD） method, are designed by the traditional refractive index waveguide structure, the single-sided metal structure, the double-metal clad structure, and a novel metal/metal silicide structure. The metal/metal silicide structure, showing high modal confinement,is convenient in process engineering and is expected to be a viable waveguide solution for Si/SiGe QCLs in the THz range.
基金The authors would thank Ping Liang and Ying Hu for their help with device fabrication.This work was supported by the National Key Research and Development Program of China(Grant No.2020YFB0408401)in part by the National Natural Science Foundation of China(Grant Nos.61991430,61774146,61790583,61734006,61835011,61674144,61774150,61805168)+1 种基金in part by Beijing Municipal Science&Technology Commission(Grant No.Z201100004020006)in part by the Key Projects of the Chinese Academy of Sciences(Grant Nos.2018147,YJKYYQ20190002,QYZDJ-SSW-JSC027,XDB43000000,ZDKYYQ20200006).
文摘Robust quantum cascade laser(QCL)enduring high temperature continuous-wave(CW)operation is of critical importance for some applications.We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials grown by metal-organic chemical vapor deposition(MOCVD).High interface quality structures designed for light emission at 8.5μm are achieved by optimizing and precise controlling of growth conditions.A CW output power of 1.04 W at 288 K was obtained from a 4 mm-long and 10μm-wide coated laser.Corresponding maximum wall-plug efficiency and threshold current density were 7.1%and 1.18 kA/cm2,respectively.The device can operate in CW mode up to 408 K with an output power of 160 mW.
