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
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
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
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
In this work,we demonstrated high-power quantum cascade laser(QCL)arrays lasing at λ~5μm by employing an optimized coupled-ridge waveguide(CRW)structure.Five-element QCL arrays were simulated and fabricated through ...In this work,we demonstrated high-power quantum cascade laser(QCL)arrays lasing at λ~5μm by employing an optimized coupled-ridge waveguide(CRW)structure.Five-element QCL arrays were simulated and fabricated through a two-step etching method to extend the CRW structure to a mid-wave infrared regime.A lateral far-field with the main peak near a diffraction-limited intensity curve of about 10°was observed by properly designing a geometric shape of the ridges and interspaces.By introducing a buried 2nd-order distributed feedback(DFB)grating,substrate emission with a radiation power above 1 W at 25℃ is achieved.Single longitudinal mode operation is obtained by changing the temperature of the heatsink with a good linear wavelength tuning coefficient of -0.2 cm^(-1)/K.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 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
The pulse generation from active mode-locking terahertz quantum cascade laser is studied by Maxwell-Bloch equations.It is shown that longer dephasing time will lead to multiple pulses generation from the laser.The dep...The pulse generation from active mode-locking terahertz quantum cascade laser is studied by Maxwell-Bloch equations.It is shown that longer dephasing time will lead to multiple pulses generation from the laser.The dependence of output field on modulation length and radio-frequency parameters is obtained.In order to achieve short pulse generation,the DC bias should close to threshold value and modulation length should be shorter than 0.256 mm.The output pulse is unstable and the envelope shows many oscillations in the presence of spatial hole burning,resulting destabilization of mode-locking.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
An external cavity quantum cascade laser(QCL)array with a wide tuning range and high output power is presented.The coherent QCL array combined with a diffraction grating and gold mirror is tuned in the Littrow configu...An external cavity quantum cascade laser(QCL)array with a wide tuning range and high output power is presented.The coherent QCL array combined with a diffraction grating and gold mirror is tuned in the Littrow configuration.Taking advantage of the single-lobed fundamental supermode far-field pattern,the tuning capability of 30.6 cm^(-1)is achieved with a fixed injected current of 3.5 A at room temperature.Single-mode emission can be observed in the entire process.The maximum single-mode output power of the external cavity setup is as high as 25 mW and is essential in real applications.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
We report on the design and fabrication of a dual-wavelength switchable quantum cascade laser(QCL)by optimizing thedesign of a homogeneous active region and combining superposed distributed feedback gratings.Coaxial,s...We report on the design and fabrication of a dual-wavelength switchable quantum cascade laser(QCL)by optimizing thedesign of a homogeneous active region and combining superposed distributed feedback gratings.Coaxial,single-modeemissions at two different wavelengths were achieved only through adjusting the bias voltage.Room temperature continuous-wave operation with output powers of above 30 mW and 75 mW was realized for single-mode emission at 7.61μmand 7.06μm,respectively.The simplified fabrication process and easy wavelength control of our designed dual-wavelengthQCL make it very attractive for developing miniature multi-species gas sensing systems.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 paper,we presented single mode terahertz quantum cascade lasers(THz QCLs)with sampled lateral grating emitting approximately 3.4 THz.Due to strong mode selection,the implementation of sampled lateral grating o...In this paper,we presented single mode terahertz quantum cascade lasers(THz QCLs)with sampled lateral grating emitting approximately 3.4 THz.Due to strong mode selection,the implementation of sampled lateral grating on THz QCL ridges can result in stable single longitudinal mode emission with a side-mode suppression ratio larger than 20 dB.The measured peak power of the grating laser is improved by about 11.8%compared to the power of devices with uniform distributed feedback gratings.Furthermore,the far-field pattern of the presented device is uninfluenced by grating structures.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
We demonstrate experimentally that mid-infrared quantum cascade lasers(QCLs)operating under external optical feedback exhibit extreme pulses.These events can be triggered by adding small amplitude periodic modulation,...We demonstrate experimentally that mid-infrared quantum cascade lasers(QCLs)operating under external optical feedback exhibit extreme pulses.These events can be triggered by adding small amplitude periodic modulation,with the highest success rate for the case of a pulse-up excitation.These findings broaden the potential applications for QCLs,which have already been proven to be a semiconductor laser of interest for spectroscopic applications and countermeasure systems.The ability to trigger extreme events paves the way for optical neuron-like systems where information propagates as a result of high intensity bursts.展开更多
The quantum cascade laser(QCL),a potential laser source for mid-infrared applications,has all of the advantages of a semiconductor laser,such as small volume and light weight,and is driven by electric power.However,th...The quantum cascade laser(QCL),a potential laser source for mid-infrared applications,has all of the advantages of a semiconductor laser,such as small volume and light weight,and is driven by electric power.However,the optical power of a single QCL is limited by serious self-heating efects.Therefore,beam combination technology is essential to achieve higher laser powers.In this letter,we demonstrate a simple beam combination scheme using two QCLs to extend the output peak power of the lasers to 2.3 W.A high beam combination efciency of 89% and beam quality factor of less than 5 are also achieved.展开更多
This paper describes a promising route for the exploration and development of 3.0 THz sensing and imaging with FET-based power detectors in a standard 65 nm CMOS process.Based on the plasma-wave theory proposed by Dya...This paper describes a promising route for the exploration and development of 3.0 THz sensing and imaging with FET-based power detectors in a standard 65 nm CMOS process.Based on the plasma-wave theory proposed by Dyakonov and Shur,we designed high-responsivity and low-noise multiple detectors for monitoring a pulse-mode 3.0 THz quantum cascade laser(QCL).Furthermore,we present a fully integrated high-speed 32×32-pixel 3.0 THz CMOS image sensor(CIS).The full CIS measures 2.81×5.39 mm^(2) and achieves a 423 V/W responsivity(Rv)and a 5.3 nW integral noise equivalent power(NEP)at room temperature.In experiments,we demonstrate a testing speed reaching 319 fps under continuous-wave(CW)illumina-tion of a 3.0 THz QCL.The results indicate that our terahertz CIS has excellent potential in cost-effective and commercial THz imaging and material detection.展开更多
Resonators and the way they couple to external radiation rely on very different concepts if one considers devices belonging to the photonic and electronic worlds.The terahertz frequency range,however,provides intrigui...Resonators and the way they couple to external radiation rely on very different concepts if one considers devices belonging to the photonic and electronic worlds.The terahertz frequency range,however,provides intriguing possibilities for the development of hybrid technologies that merge ideas from both fields in novel functional designs.In this paper,we show that high-quality,subwavelength,whispering-gallery lasers can be combined to form a linear dipole antenna,which creates a very efficient,lowthreshold laser emission in a collimated beam pattern.For this purpose,we employ a terahertz quantum-cascade active region patterned into two 19-μm-radius microdisks coupled by a suspended metallic bridge,which simultaneously acts as an inductive antenna and produces the dipole symmetry of the lasing mode.Continuous-wave vertical emission is demonstrated at approximately 3.5 THz in a very regular,low-divergence(±10°)beam,with a high slope efficiency of at least 160 mWA^(−1) and a mere 6 mA of threshold current,which is ensured by the ultra-small resonator size(VRES/λ^(3)≈10^(−2)).The extremely low power consumption and the superior beam brightness make this concept very promising for the development of miniaturized and portable THz sources to be used in the field for imaging and sensing applications as well as for exploring novel optomechanical intracavity effects.展开更多
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.
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.
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.
基金supported by National Basic Research Program of China(Grant Nos.2018YFA0209103,2018YFB2200504)in part by 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 No.2018147,Grant No.YJKYYQ20190002,Grant No.QYZDJ-SSW-JSC027,Grant No.XDB43000000,Grant No.ZDKYYQ20200006).
文摘In this work,we demonstrated high-power quantum cascade laser(QCL)arrays lasing at λ~5μm by employing an optimized coupled-ridge waveguide(CRW)structure.Five-element QCL arrays were simulated and fabricated through a two-step etching method to extend the CRW structure to a mid-wave infrared regime.A lateral far-field with the main peak near a diffraction-limited intensity curve of about 10°was observed by properly designing a geometric shape of the ridges and interspaces.By introducing a buried 2nd-order distributed feedback(DFB)grating,substrate emission with a radiation power above 1 W at 25℃ is achieved.Single longitudinal mode operation is obtained by changing the temperature of the heatsink with a good linear wavelength tuning coefficient of -0.2 cm^(-1)/K.
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 Key Research and Development Program of China(Grant No.2017YFF0106302)the National Natural Science Foundation of China(Grant Nos.61975225 and 61927813)Shanghai International Cooperation Project,China(Grant No.18590780100).
文摘The pulse generation from active mode-locking terahertz quantum cascade laser is studied by Maxwell-Bloch equations.It is shown that longer dephasing time will lead to multiple pulses generation from the laser.The dependence of output field on modulation length and radio-frequency parameters is obtained.In order to achieve short pulse generation,the DC bias should close to threshold value and modulation length should be shorter than 0.256 mm.The output pulse is unstable and the envelope shows many oscillations in the presence of spatial hole burning,resulting destabilization of mode-locking.
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Supported by the National Basic Research Program of China under Grant No 2013CB632801the National Key Research and Development Program of China under Grant No 2016YFB0402303+2 种基金the National Natural Science Foundation of China under Grant Nos 61435014,61627822,61574136,61306058 and 61404131the Key Projects of Chinese Academy of Sciences under Grant No ZDRW-XH-2016-4the Beijing Natural Science Foundation under Grant No 4162060
文摘An external cavity quantum cascade laser(QCL)array with a wide tuning range and high output power is presented.The coherent QCL array combined with a diffraction grating and gold mirror is tuned in the Littrow configuration.Taking advantage of the single-lobed fundamental supermode far-field pattern,the tuning capability of 30.6 cm^(-1)is achieved with a fixed injected current of 3.5 A at room temperature.Single-mode emission can be observed in the entire process.The maximum single-mode output power of the external cavity setup is as high as 25 mW and is essential in real applications.
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 Natural Science Foundation of China(Nos.61874110,61734006,61991430,61835011,and 62174158)Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021107)Key Program of the Chinese Academy of Sciences(No.XDB43000000).
文摘We report on the design and fabrication of a dual-wavelength switchable quantum cascade laser(QCL)by optimizing thedesign of a homogeneous active region and combining superposed distributed feedback gratings.Coaxial,single-modeemissions at two different wavelengths were achieved only through adjusting the bias voltage.Room temperature continuous-wave operation with output powers of above 30 mW and 75 mW was realized for single-mode emission at 7.61μmand 7.06μm,respectively.The simplified fabrication process and easy wavelength control of our designed dual-wavelengthQCL make it very attractive for developing miniature multi-species gas sensing systems.
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This work was supported by the National Key R&D Program of China(No.2018YFB1801502)the National Natural Science Foundation of China(Grant Nos.61927813,61975225,and 61704181)+1 种基金the Natural Science Foundation of Shanghai(No.17ZR1448300)Shanghai International Cooperation Project(No.18590780100).
文摘In this paper,we presented single mode terahertz quantum cascade lasers(THz QCLs)with sampled lateral grating emitting approximately 3.4 THz.Due to strong mode selection,the implementation of sampled lateral grating on THz QCL ridges can result in stable single longitudinal mode emission with a side-mode suppression ratio larger than 20 dB.The measured peak power of the grating laser is improved by about 11.8%compared to the power of devices with uniform distributed feedback gratings.Furthermore,the far-field pattern of the presented device is uninfluenced by grating structures.
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Thiswork was supported by the French Defense Agency (DGA), theFrench ANR program (ANR-17-ASMA-0006)the EuropeanOffice of Aerospace Research and Development (FA9550-18-1-7001)+1 种基金the Office of Naval Research (N00014-16-1-2094)the National Science Foundation (DMR-1611598).
文摘We demonstrate experimentally that mid-infrared quantum cascade lasers(QCLs)operating under external optical feedback exhibit extreme pulses.These events can be triggered by adding small amplitude periodic modulation,with the highest success rate for the case of a pulse-up excitation.These findings broaden the potential applications for QCLs,which have already been proven to be a semiconductor laser of interest for spectroscopic applications and countermeasure systems.The ability to trigger extreme events paves the way for optical neuron-like systems where information propagates as a result of high intensity bursts.
基金supported by the National Natural Science Foundation of China(Nos.61076064 and 61176046)the International Science Technology Cooperation Program of China(No.2013DFR00730)the Hundred Talents Program of Chinese Academy of Sciences for their fnancial support
文摘The quantum cascade laser(QCL),a potential laser source for mid-infrared applications,has all of the advantages of a semiconductor laser,such as small volume and light weight,and is driven by electric power.However,the optical power of a single QCL is limited by serious self-heating efects.Therefore,beam combination technology is essential to achieve higher laser powers.In this letter,we demonstrate a simple beam combination scheme using two QCLs to extend the output peak power of the lasers to 2.3 W.A high beam combination efciency of 89% and beam quality factor of less than 5 are also achieved.
基金Project supported by the National Natural Science Foundation of China under Grant Nos.61874107,62075211.
文摘This paper describes a promising route for the exploration and development of 3.0 THz sensing and imaging with FET-based power detectors in a standard 65 nm CMOS process.Based on the plasma-wave theory proposed by Dyakonov and Shur,we designed high-responsivity and low-noise multiple detectors for monitoring a pulse-mode 3.0 THz quantum cascade laser(QCL).Furthermore,we present a fully integrated high-speed 32×32-pixel 3.0 THz CMOS image sensor(CIS).The full CIS measures 2.81×5.39 mm^(2) and achieves a 423 V/W responsivity(Rv)and a 5.3 nW integral noise equivalent power(NEP)at room temperature.In experiments,we demonstrate a testing speed reaching 319 fps under continuous-wave(CW)illumina-tion of a 3.0 THz QCL.The results indicate that our terahertz CIS has excellent potential in cost-effective and commercial THz imaging and material detection.
文摘Resonators and the way they couple to external radiation rely on very different concepts if one considers devices belonging to the photonic and electronic worlds.The terahertz frequency range,however,provides intriguing possibilities for the development of hybrid technologies that merge ideas from both fields in novel functional designs.In this paper,we show that high-quality,subwavelength,whispering-gallery lasers can be combined to form a linear dipole antenna,which creates a very efficient,lowthreshold laser emission in a collimated beam pattern.For this purpose,we employ a terahertz quantum-cascade active region patterned into two 19-μm-radius microdisks coupled by a suspended metallic bridge,which simultaneously acts as an inductive antenna and produces the dipole symmetry of the lasing mode.Continuous-wave vertical emission is demonstrated at approximately 3.5 THz in a very regular,low-divergence(±10°)beam,with a high slope efficiency of at least 160 mWA^(−1) and a mere 6 mA of threshold current,which is ensured by the ultra-small resonator size(VRES/λ^(3)≈10^(−2)).The extremely low power consumption and the superior beam brightness make this concept very promising for the development of miniaturized and portable THz sources to be used in the field for imaging and sensing applications as well as for exploring novel optomechanical intracavity effects.
