High-power,high-speed quantum cascade lasers(QCLs)with stable emission in the mid-infrared regime are of great importance for applications in metrology,telecommunication,and fundamental tests of physics.Owing to the i...High-power,high-speed quantum cascade lasers(QCLs)with stable emission in the mid-infrared regime are of great importance for applications in metrology,telecommunication,and fundamental tests of physics.Owing to the intersubband transition,the unique ultrafast gain recovery time of the QCL with picosecond dynamics is expected to overcome the modulation limit of classical semiconductor lasers and bring a revolution for the next generation of ultrahigh-speed optical communication.Therefore,harmonic injection locking,offering the possibility to fast modulate and greatly stabilize the laser emission beyond the rate limited by cavity length,is inherently adapted to QCLs.In this work,we demonstrate for the first time the harmonic injection locking of a mid-infrared QCL with an output power over 1Win continuous-wave operation at 288 K.Compared with an unlocked laser,the intermode spacing fluctuation of an injection-locked QCL can be considerably reduced by a factor above 1×10^(3),which permits the realization of an ultrastable mid-infrared semiconductor laser with high phase coherence and frequency purity.Despite temperature change,this fluctuation can be still stabilized to hertz level by a microwave modulation up to∼18 GHz.These results open up the prospect of the applications of midinfrared QCL technology for frequency comb engineering,metrology,and the next-generation ultrahigh-speed telecommunication.It may also stimulate new schemes for exploring ultrafast mid-infrared pulse generation in QCLs.展开更多
The LWIR and longer wavelength regions are of particular interest for new developments and new approaches to realizing long-wavelength infrared(LWIR)photodetectors with high detectivity and high responsivity.These pho...The LWIR and longer wavelength regions are of particular interest for new developments and new approaches to realizing long-wavelength infrared(LWIR)photodetectors with high detectivity and high responsivity.These photodetectors are highly desirable for applications such as infrared earth science and astronomy,remote sensing,optical communication,and thermal and medical imaging.Here,we report the design,growth,and characterization of a high-gain band-structure-engineered LWIR heterojunction phototransistor based on type-Ⅱ superlattices.The 1/e cut-off wavelength of the device is 8.0 pm.At 77 K,unity optical gain occurs at a 90 mV applied bias with a dark current density of 3.2×10^(-7)A/cm^(2).The optical gain of the device at 77 K saturates at a value of 276 at an applied bias of 220 mV.This saturation corresponds to a responsivity of 1284 A/W and a specific detectivity of 2.34×10^(13)cm Hz^(1/2)/W at a peak detection wavelength of~6.8 pm.The type-Ⅱ superlattice-based high-gain LWIR device shows the possibility of designing the high-performance gain-based LWIR photodetectors by implementing the band structure engineering approach.展开更多
文摘High-power,high-speed quantum cascade lasers(QCLs)with stable emission in the mid-infrared regime are of great importance for applications in metrology,telecommunication,and fundamental tests of physics.Owing to the intersubband transition,the unique ultrafast gain recovery time of the QCL with picosecond dynamics is expected to overcome the modulation limit of classical semiconductor lasers and bring a revolution for the next generation of ultrahigh-speed optical communication.Therefore,harmonic injection locking,offering the possibility to fast modulate and greatly stabilize the laser emission beyond the rate limited by cavity length,is inherently adapted to QCLs.In this work,we demonstrate for the first time the harmonic injection locking of a mid-infrared QCL with an output power over 1Win continuous-wave operation at 288 K.Compared with an unlocked laser,the intermode spacing fluctuation of an injection-locked QCL can be considerably reduced by a factor above 1×10^(3),which permits the realization of an ultrastable mid-infrared semiconductor laser with high phase coherence and frequency purity.Despite temperature change,this fluctuation can be still stabilized to hertz level by a microwave modulation up to∼18 GHz.These results open up the prospect of the applications of midinfrared QCL technology for frequency comb engineering,metrology,and the next-generation ultrahigh-speed telecommunication.It may also stimulate new schemes for exploring ultrafast mid-infrared pulse generation in QCLs.
基金supported by the Defense Advanced Research Projects Agency(DARPA)under agreement number FA8650-18-1-7810。
文摘The LWIR and longer wavelength regions are of particular interest for new developments and new approaches to realizing long-wavelength infrared(LWIR)photodetectors with high detectivity and high responsivity.These photodetectors are highly desirable for applications such as infrared earth science and astronomy,remote sensing,optical communication,and thermal and medical imaging.Here,we report the design,growth,and characterization of a high-gain band-structure-engineered LWIR heterojunction phototransistor based on type-Ⅱ superlattices.The 1/e cut-off wavelength of the device is 8.0 pm.At 77 K,unity optical gain occurs at a 90 mV applied bias with a dark current density of 3.2×10^(-7)A/cm^(2).The optical gain of the device at 77 K saturates at a value of 276 at an applied bias of 220 mV.This saturation corresponds to a responsivity of 1284 A/W and a specific detectivity of 2.34×10^(13)cm Hz^(1/2)/W at a peak detection wavelength of~6.8 pm.The type-Ⅱ superlattice-based high-gain LWIR device shows the possibility of designing the high-performance gain-based LWIR photodetectors by implementing the band structure engineering approach.
