We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the ...We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).展开更多
We demonstrate 10 Gb/s directly-modulated 1.3 μm InAs quantum-dot （QD） lasers grown on GaAs substrates by molecular beam epitaxy. The active region of the QD lasers consists of five-stacked InAs QD layers. Ridge-wa...We demonstrate 10 Gb/s directly-modulated 1.3 μm InAs quantum-dot （QD） lasers grown on GaAs substrates by molecular beam epitaxy. The active region of the QD lasers consists of five-stacked InAs QD layers. Ridge-waveguide lasers with a ridge width of 4 μm and a cavity length of 600 μm are fabricated with standard lithography and wet etching techniques. It is found that the lasers emit at 1293 nm with a very low threshold current of 5 mA at room temperature. Furthermore, clear eye-opening patterns under 10 Gb/s modulation rate at temperatures of up to 50oC are achieved by the QD lasers. The results presented here have important implications for realizing low-cost, low-power-consumption, and high-speed light sources for next-generation communication systems.展开更多
We report the molecular beam epitaxy growth of 1.3 μm InAs/GaAs quantum-dot （QD） lasers with high characteristic temperature T0. The active region of the lasers consists of five-layer InAs QDs with p-type modulatio...We report the molecular beam epitaxy growth of 1.3 μm InAs/GaAs quantum-dot （QD） lasers with high characteristic temperature T0. The active region of the lasers consists of five-layer InAs QDs with p-type modulation doping. Devices with a stripe width of 4 μm and a cavity length of 1200 μm are fabricated and tested in the pulsed regime under different temperatures. It is found that T0 of the QD lasers is as high as 532 K in the temperature range from 10°C to 60°C. In addition, the aging test for the lasers under continuous wave operation at 100°C for 72 h shows almost no degradation, indicating the high crystal quality of the devices.展开更多
We investigate the thermal stresses for GaAs layers grown on V-groove patterned Si substrates by the finite-element method. The results show that the thermal stress distribution near the interface in a patterned subst...We investigate the thermal stresses for GaAs layers grown on V-groove patterned Si substrates by the finite-element method. The results show that the thermal stress distribution near the interface in a patterned substrate is nonuniform,which is far different from that in a planar substrate. Comparing with the planar substrate, the thermal stress is significantly reduced for the Ga As layer on the patterned substrate. The effects of the width of the V-groove, the thickness, and the width of the SiO_(2) mask on the thermal stress are studied. It is found that the SiO_(2) mask and V-groove play a crucial role in the stress of the Ga As layer on Si substrate. The results indicate that when the width of V-groove is 50 nm, the width and the thickness of the SiO_(2) mask are both 100 nm, the Ga As layer is subjected to the minimum stress. Furthermore,Comparing with the planar substrate, the average stress of the Ga As epitaxial layer in the growth window region of the patterned substrate is reduced by 90%. These findings are useful in the optimal designing of growing high-quality Ga As films on patterned Si substrates.展开更多
The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filt...The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filters is a pretty good alternative to solving this problem.In this paper,a finite element method(FEM)is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations(MDs).Making a comparison of elastic strain energy between the two isolated systems,a reasonable result is obtained.The effect of the cap layer thickness and the base width of QDs on TD bending are studied,and the results show that the bending area ratio of single QD(the bending area divided by the area of the QD base)is evidently affected by the two factors.Moreover,we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs.For the QD with 24-nm base width and 5-nm cap layer thickness,taking the QD density of 10^(11) cm^(-2) into account,the bending area ratio of single-layer QDs(the area of bending TD divided by the area of QD layer)is about 38.71%.With inserting five-layer InAs QDs,the TD density decreases by 91.35%.The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon.展开更多
We present a systematic investigation of calculating quantum dots （QDs） energy levels using finite element method in the frame of eight-band k · p method. Numerical results including piezoelectricity, electron ...We present a systematic investigation of calculating quantum dots （QDs） energy levels using finite element method in the frame of eight-band k · p method. Numerical results including piezoelectricity, electron and hole levels, as well as wave functions are achieved. In the calculation of energy levels, we do observe spurious solutions （SSs） no matter Burt Foreman or symmetrized Hamiltonians are used. Different theories are used to analyse the SSs, we find that the ellipticity theory can give a better explanation for the origin of SSs and symmetrized Hamiltonian is easier to lead to SSs. The energy levels simulated with the two Hamiltonians are compared to each other after eliminating SSs, different Hamiltonians cause a larger difference on electron energy levels than that on hole energy levels and this difference decreases with the increase of QD size.展开更多
We demonstrate InAs/InGaAsP/InP quantum dot(QD)lasers grown by metalorganic chemical vapor deposition.The active region of the lasers consists of five layers of InAs QDs.Ridge waveguide lasers with 6μm width have bee...We demonstrate InAs/InGaAsP/InP quantum dot(QD)lasers grown by metalorganic chemical vapor deposition.The active region of the lasers consists of five layers of InAs QDs.Ridge waveguide lasers with 6μm width have been fabricated by standard optical lithography and wet etching.Under continuous wave operation at room temperature,a low threshold current density of 447 A/cm^(2)per QD layer is achieved for a QD laser with a cavity length of 2 mm.Moreover,the lasing redshifts from 1.61μm to 1.645μm as the cavity length increases from 1.5 mm to 4 mm.A high characteristic temperature of up to 88 K is obtained in the temperature range between 10°C and 40°C.展开更多
We demonstrate a technique of temperature compensation for 1.3μm InAs/GaAs quantum-dot(QD)lasers by facet coating design.The key point of the technique is to make sure that the mirror loss of the lasers decreases as ...We demonstrate a technique of temperature compensation for 1.3μm InAs/GaAs quantum-dot(QD)lasers by facet coating design.The key point of the technique is to make sure that the mirror loss of the lasers decreases as the temperature rises.To realize this,we design a type of facet coating by shifting the central wavelength of the facet coating from 1310nm to 1480nm,whose reflectivity increases as the emission wavelength of the lasers red-shifts.Consequently,the laser with the new facet coating exhibits a characteristic temperature doubled in size and a more stable slope efficiency in the temperature range from 10℃to 70℃,compared with the traditional one with a temperature-independent mirror loss.展开更多
The optical performance of a grating-coupled external Continuous tuning from 1391 nm to 1468 nm is realized at cavity laser based on InAs/InP quantum dots is investigated. an injection current of 1900 mA. With the inj...The optical performance of a grating-coupled external Continuous tuning from 1391 nm to 1468 nm is realized at cavity laser based on InAs/InP quantum dots is investigated. an injection current of 1900 mA. With the injection current increasing to 2300 mA, the tuning is blue shifted to some extent to the range from 1383 nm to 1461 nm. By combining the effect of the injection current with the grating tuning, the total tuning bandwidth of the external cavity quantum-dot laser can reach up to 85 nm. The dependence of the threshold current on the tuning wavelength is also presented.展开更多
We investigate the band structure of a compressively strained In（Ga）As/In0.53Ga0.47As quantum well （QW） on an InP substrate using the eight-band k.p theory. Aiming at the emission wavelength around 2.33 μm, we di...We investigate the band structure of a compressively strained In（Ga）As/In0.53Ga0.47As quantum well （QW） on an InP substrate using the eight-band k.p theory. Aiming at the emission wavelength around 2.33 μm, we discuss the influences of temperature, strain and well width on the band structure and on the emission wavelength of the QW. The wavelength increases with the increase of temperature, strain and well width. Furthermore, we design an InAs /In0.53Ga0.47As QW with a well width of 4.1 nm emitting at 2.33 μm by optimizing the strain and the well width.展开更多
We report the fabrication of intermediate-band solar cells(IBSCs)based on quantum dots(QDs),which consists of a standard P-I-N structure with multilayer stacks of InAs/GaAs QDs in the I-layer.Compared with conventiona...We report the fabrication of intermediate-band solar cells(IBSCs)based on quantum dots(QDs),which consists of a standard P-I-N structure with multilayer stacks of InAs/GaAs QDs in the I-layer.Compared with conventional GaAs single-junction solar cells,the IBSCs based on InAs/GaAs QDs show a broader photo-response spectrum(>1330 nm),a higher short-circle current(about 53%increase)and a stronger radiation hardness.The results have important applications for realizing high efficiency solar cells with stronger radiation hardness.展开更多
Large-signal modulation capability, as an important performance indicator, is directly related to the high-speed optical communication technology involved. We experimentally and theoretically investigate the large-sig...Large-signal modulation capability, as an important performance indicator, is directly related to the high-speed optical communication technology involved. We experimentally and theoretically investigate the large-signal modulation characteristics of the simultaneous ground-state （GS） and the excited-state （ES） lasing in InAs/OaAs quantum dot laser diodes. The large-signal modulation capability of total light intensity in the transition regime from OS lasing to two-state lasing is unchanged as the bias-current increases. However, GS and ES large-signal eye diagrams show obvious variations during the transition. Relaxation oscillations and large-signal eye diagrams for OS, ES, and total light intensities are numerically simulated and analyzed in detail by using a rate-equation model. The -ndings show that a complementary relationship between the light intensities for OS and ES lasing exists in both the transition regime and the two-state lasing regime, leading to a much smaller overshooting power and a shorter settling time for the total light intensity. Therefore, the eye diagrams of GS or ES lasing are diffuse whereas those of total light intensity are constant as the bias-current increases in the transition regime.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61974141)Tianjin Municipal Science and Technology BureauScience and Technology Innovation Bureau of China-Singapore Tianjin Eco-City。
文摘We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2006AA03Z401, One-Hundred Talents Program of Chinese Academy of Sciences, and the National Natural Science Foundation of China under Grant No 60876033.
文摘We demonstrate 10 Gb/s directly-modulated 1.3 μm InAs quantum-dot （QD） lasers grown on GaAs substrates by molecular beam epitaxy. The active region of the QD lasers consists of five-stacked InAs QD layers. Ridge-waveguide lasers with a ridge width of 4 μm and a cavity length of 600 μm are fabricated with standard lithography and wet etching techniques. It is found that the lasers emit at 1293 nm with a very low threshold current of 5 mA at room temperature. Furthermore, clear eye-opening patterns under 10 Gb/s modulation rate at temperatures of up to 50oC are achieved by the QD lasers. The results presented here have important implications for realizing low-cost, low-power-consumption, and high-speed light sources for next-generation communication systems.
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2006AA03Z401, One-Hundred Talents Program of Chinese Academy of Sciences, and the National Natural Science Foundation of China under Grant No 60876033.
文摘We report the molecular beam epitaxy growth of 1.3 μm InAs/GaAs quantum-dot （QD） lasers with high characteristic temperature T0. The active region of the lasers consists of five-layer InAs QDs with p-type modulation doping. Devices with a stripe width of 4 μm and a cavity length of 1200 μm are fabricated and tested in the pulsed regime under different temperatures. It is found that T0 of the QD lasers is as high as 532 K in the temperature range from 10°C to 60°C. In addition, the aging test for the lasers under continuous wave operation at 100°C for 72 h shows almost no degradation, indicating the high crystal quality of the devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61874148,61974141,and 61674020)the Beijing Natural Science Foundation,China(Grant No.4192043)+1 种基金the State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications),China(Grant No.IPOC2018ZT01)the 111 Project of China(Grant No.B07005)。
文摘We investigate the thermal stresses for GaAs layers grown on V-groove patterned Si substrates by the finite-element method. The results show that the thermal stress distribution near the interface in a patterned substrate is nonuniform,which is far different from that in a planar substrate. Comparing with the planar substrate, the thermal stress is significantly reduced for the Ga As layer on the patterned substrate. The effects of the width of the V-groove, the thickness, and the width of the SiO_(2) mask on the thermal stress are studied. It is found that the SiO_(2) mask and V-groove play a crucial role in the stress of the Ga As layer on Si substrate. The results indicate that when the width of V-groove is 50 nm, the width and the thickness of the SiO_(2) mask are both 100 nm, the Ga As layer is subjected to the minimum stress. Furthermore,Comparing with the planar substrate, the average stress of the Ga As epitaxial layer in the growth window region of the patterned substrate is reduced by 90%. These findings are useful in the optimal designing of growing high-quality Ga As films on patterned Si substrates.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61874148,61974141,and 61674020)the Beijing Natural Science Foundation,China(Grant No.4192043)+3 种基金the National Key Research and Development Program of China(Grant No.2018YFB2200104)the Fund from the Beijing Municipal Science&Technology Commission,China(Grant No.Z191100004819012)the Project of the State Key Laboratory of Information Photonics and Optical Communications,Beijing University of Posts and Telecommunications,China(Grant No.IPOC2018ZT01)the 111 Project of China(Grant No.B07005).
文摘The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filters is a pretty good alternative to solving this problem.In this paper,a finite element method(FEM)is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations(MDs).Making a comparison of elastic strain energy between the two isolated systems,a reasonable result is obtained.The effect of the cap layer thickness and the base width of QDs on TD bending are studied,and the results show that the bending area ratio of single QD(the bending area divided by the area of the QD base)is evidently affected by the two factors.Moreover,we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs.For the QD with 24-nm base width and 5-nm cap layer thickness,taking the QD density of 10^(11) cm^(-2) into account,the bending area ratio of single-layer QDs(the area of bending TD divided by the area of QD layer)is about 38.71%.With inserting five-layer InAs QDs,the TD density decreases by 91.35%.The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2006AA03Z401)'One-Hundred Talents Program' of the Chinese Academy of Sciences,and the National Natural Science Foundation of China (Grant No.60876033)
文摘We present a systematic investigation of calculating quantum dots （QDs） energy levels using finite element method in the frame of eight-band k · p method. Numerical results including piezoelectricity, electron and hole levels, as well as wave functions are achieved. In the calculation of energy levels, we do observe spurious solutions （SSs） no matter Burt Foreman or symmetrized Hamiltonians are used. Different theories are used to analyse the SSs, we find that the ellipticity theory can give a better explanation for the origin of SSs and symmetrized Hamiltonian is easier to lead to SSs. The energy levels simulated with the two Hamiltonians are compared to each other after eliminating SSs, different Hamiltonians cause a larger difference on electron energy levels than that on hole energy levels and this difference decreases with the increase of QD size.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61176047,61076050,61204057 and 61204076the National Basic Research Program of China under Grant No 2012CB932701.
文摘We demonstrate InAs/InGaAsP/InP quantum dot(QD)lasers grown by metalorganic chemical vapor deposition.The active region of the lasers consists of five layers of InAs QDs.Ridge waveguide lasers with 6μm width have been fabricated by standard optical lithography and wet etching.Under continuous wave operation at room temperature,a low threshold current density of 447 A/cm^(2)per QD layer is achieved for a QD laser with a cavity length of 2 mm.Moreover,the lasing redshifts from 1.61μm to 1.645μm as the cavity length increases from 1.5 mm to 4 mm.A high characteristic temperature of up to 88 K is obtained in the temperature range between 10°C and 40°C.
基金Supported by the One-Hundred Talents Program of Chinese Academy of Sciences and the National Natural Science Foundation of China under Grant Nos 60876033,61076050 and 61021003.
文摘We demonstrate a technique of temperature compensation for 1.3μm InAs/GaAs quantum-dot(QD)lasers by facet coating design.The key point of the technique is to make sure that the mirror loss of the lasers decreases as the temperature rises.To realize this,we design a type of facet coating by shifting the central wavelength of the facet coating from 1310nm to 1480nm,whose reflectivity increases as the emission wavelength of the lasers red-shifts.Consequently,the laser with the new facet coating exhibits a characteristic temperature doubled in size and a more stable slope efficiency in the temperature range from 10℃to 70℃,compared with the traditional one with a temperature-independent mirror loss.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61274072, 60976057, 61176047, and 60876086)
文摘The optical performance of a grating-coupled external Continuous tuning from 1391 nm to 1468 nm is realized at cavity laser based on InAs/InP quantum dots is investigated. an injection current of 1900 mA. With the injection current increasing to 2300 mA, the tuning is blue shifted to some extent to the range from 1383 nm to 1461 nm. By combining the effect of the injection current with the grating tuning, the total tuning bandwidth of the external cavity quantum-dot laser can reach up to 85 nm. The dependence of the threshold current on the tuning wavelength is also presented.
基金Project supported by the '100 Talents Program' of Chinese Academy of Sciences,China
文摘We investigate the band structure of a compressively strained In（Ga）As/In0.53Ga0.47As quantum well （QW） on an InP substrate using the eight-band k.p theory. Aiming at the emission wavelength around 2.33 μm, we discuss the influences of temperature, strain and well width on the band structure and on the emission wavelength of the QW. The wavelength increases with the increase of temperature, strain and well width. Furthermore, we design an InAs /In0.53Ga0.47As QW with a well width of 4.1 nm emitting at 2.33 μm by optimizing the strain and the well width.
基金Supported by the One-Hundred Talents Program of Chinese Academy of Sciences,and the National Science Foundation of China under Grant Nos 60876033,61076050 and 61021003.
文摘We report the fabrication of intermediate-band solar cells(IBSCs)based on quantum dots(QDs),which consists of a standard P-I-N structure with multilayer stacks of InAs/GaAs QDs in the I-layer.Compared with conventional GaAs single-junction solar cells,the IBSCs based on InAs/GaAs QDs show a broader photo-response spectrum(>1330 nm),a higher short-circle current(about 53%increase)and a stronger radiation hardness.The results have important applications for realizing high efficiency solar cells with stronger radiation hardness.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFB0402302the National Natural Science Foundation of China under Grant No 91433206
文摘Large-signal modulation capability, as an important performance indicator, is directly related to the high-speed optical communication technology involved. We experimentally and theoretically investigate the large-signal modulation characteristics of the simultaneous ground-state （GS） and the excited-state （ES） lasing in InAs/OaAs quantum dot laser diodes. The large-signal modulation capability of total light intensity in the transition regime from OS lasing to two-state lasing is unchanged as the bias-current increases. However, GS and ES large-signal eye diagrams show obvious variations during the transition. Relaxation oscillations and large-signal eye diagrams for OS, ES, and total light intensities are numerically simulated and analyzed in detail by using a rate-equation model. The -ndings show that a complementary relationship between the light intensities for OS and ES lasing exists in both the transition regime and the two-state lasing regime, leading to a much smaller overshooting power and a shorter settling time for the total light intensity. Therefore, the eye diagrams of GS or ES lasing are diffuse whereas those of total light intensity are constant as the bias-current increases in the transition regime.
