Moisture measurement is of great needs in semiconductor industry, combustion diagnosis, meteorology, and atmospheric studies. We present an optical hygrometer based on cavity ring-down spectroscopy （CRDS）. By using ...Moisture measurement is of great needs in semiconductor industry, combustion diagnosis, meteorology, and atmospheric studies. We present an optical hygrometer based on cavity ring-down spectroscopy （CRDS）. By using different absorption lines of H20 in the 1.56 and 1.36 gm regions, we are able to determine the relative concentration （mole fraction） of water vapor from a few percent down to the 10-12 level. The quantitative accuracy is examined by comparing the CRDS hygrometer with a commercial chilled-mirror dew-point meter. The high sensitivity of the CRDS instrument allows a water detection limit of 8 pptv.展开更多
In long-cavity edge-emitting diode lasers,longitudinal spatial hole burning(LSHB),two-photon ab⁃sorption(TPA)and free carrier absorption(FCA)are among the key factors that affect the linear increase in out⁃put power a...In long-cavity edge-emitting diode lasers,longitudinal spatial hole burning(LSHB),two-photon ab⁃sorption(TPA)and free carrier absorption(FCA)are among the key factors that affect the linear increase in out⁃put power at high injection currents.In this paper,a simplified numerical analysis model is proposed for 1.06μm long-cavity diode lasers by combining TPA and FCA losses with one-dimensional(1D)rate equations.The ef⁃fects of LSHB,TPA and FCA on the output characteristics are systematically analyzed,and it is proposed that ad⁃justing the front facet reflectivity and the position of the quantum well(QW)in the waveguide layer can improve the front facet output power.展开更多
We report comparatively on fabrication of two-section ridge-waveguide tapered 3 quantum well (QW) InGaAsP/InP (1300 nm) and 5 QW AlGaInAs/InP (1550 nm) diode lasers. Gas mixtures of CCl2F2/O2 and H2/CH4 were used to f...We report comparatively on fabrication of two-section ridge-waveguide tapered 3 quantum well (QW) InGaAsP/InP (1300 nm) and 5 QW AlGaInAs/InP (1550 nm) diode lasers. Gas mixtures of CCl2F2/O2 and H2/CH4 were used to form ridge-waveguide on the lasers with InP-based material structures. As known, chlorine- and hydro-carbon based gases are used to fabricate ridge-waveguide structures. Here, we show the difference between the structures obtained by using the both gas mixtures in which surface and sidewall structures as well as performance of the lasers were analysed using scanning electron microscopy. It is demonstrated that gas mixtures of CCl2F2/O2 highly deteriorated the etched structures although different flow rates, rf powers and base pressures were tried. We also show that the structures etched with H2/CH4 gas mixtures produced much better results that led to the successful fabrication of two-section devices with ridge-waveguide. The lasers fabricated using H2/CH4 were characterized using output power-current (P-I) and spectral results.展开更多
We develop a high-performance ultraviolet(UV)frequency stabilization technique implemented directly on UV diode lasers by combining the dichroic atomic vapor laser lock and the resonant transfer cavity lock.As an exam...We develop a high-performance ultraviolet(UV)frequency stabilization technique implemented directly on UV diode lasers by combining the dichroic atomic vapor laser lock and the resonant transfer cavity lock.As an example,we demonstrate a stable locking with measured frequency standard deviations of approximately 200 kHz and 300 kHz for 399 nm and 370 nm diode lasers in 20 min.We achieve a long-term frequency drift of no more than 1 MHz for the target 370 nm laser within an hour,which is further verified with fluorescence count rates of a single trapped ^171Yb+ion.We also find strong linear correlations between lock points and environmental factors such as temperature and atmospheric pressure.Our approach provides a simple and stable solution at a relatively low cost,and features flexible control,high feedback bandwidth and minimal power consumption of the target UV laser.展开更多
GaSb-based diode lasers with emitting wavelength of 1.8-4μm have a wide range of applications due to advantages of compact in size,light in weight and electric drive.However,single emitter can not provide e-nough las...GaSb-based diode lasers with emitting wavelength of 1.8-4μm have a wide range of applications due to advantages of compact in size,light in weight and electric drive.However,single emitter can not provide e-nough laser power for practical applications.Therefore,methods of beam combination which have been successful-ly applied to diode lasers in near-infrared band are needed to be transplanted to mid-infrared band.In every method of beam combination,high efficiency beam shaping is basic and principal.A method of high efficiency beam sha-ping using multiple single diode lasers was demonstrated.A continuous-wave optical power of 1.93 W at wave-length of 1.94μm with efficiency of higher than 90%was achieved experimentally.This method of beam shaping can be utilized to build spectral or coherent beam combination.展开更多
We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength.The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector.Th...We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength.The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector.The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper.And the quantum well cascade laser with 100-μm-wide,2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature.The characteristic temperature T_(0) is estimated at above 60 K.展开更多
In laser hair removal treatments on dark skin, the high concentration of melanin in the skin competes with the melanin in the hair. During standard laser procedures, with wavelengths of 755 nm or 810 nm, a high level ...In laser hair removal treatments on dark skin, the high concentration of melanin in the skin competes with the melanin in the hair. During standard laser procedures, with wavelengths of 755 nm or 810 nm, a high level of laser light absorption by melanin in the skin is observed. Therefore, to avoid side effects, lower fluence values are used, which further reduces hair-removal efficacy. To improve results, 810 nm diode lasers operating in dynamic mode, with high frequency and multiple passes, are typically used. The aim of this study is to compare the efficacy and safety of triple-wavelength diode lasers (810 nm, 940 nm, 1060 nm) with that of 810 nm diode lasers on Indian patients. A side-by-side comparison was performed using a triple-wavelength diode laser in stamping mode on one side, and an 810 nm diode laser in dynamic mode on the other. Three subjects with skin type IV on the Fitzpatrick scale participated in the study. Efficacy was assessed through hair counting using clinical photographs, taken before and after the treatments, and the Global Aesthetic Improvement Scale (GAIS). Additionally, comparisons related to epidermal heating and thermal damage to the hair follicle were conducted through mathematical 3D simulations using COMSOL Multiphysics<sup>®</sup> software. Side effects were also evaluated. A superior end point was observed with triple wavelength compared to the 810 nm diode laser. Hair counting showed a 27% greater hair reduction with triple wavelength. No adverse effects were observed. Thermal simulations revealed 29% higher thermal damage with the triple-wavelength laser compared to the 810 nm diode laser. To conclude, on darker skin types, the triple-wavelength diode laser has been shown to be more effective at removing hair, compared to the 810 nm diode laser, while also being a safe procedure.展开更多
AlGaN-based deep-ultraviolet(DUV)laser diodes(LDs)face performance challenges due to elec-tron leakage and poor hole injection which is often worsened by polarization effects from conventional elec-tron blocking layer...AlGaN-based deep-ultraviolet(DUV)laser diodes(LDs)face performance challenges due to elec-tron leakage and poor hole injection which is often worsened by polarization effects from conventional elec-tron blocking layers(EBLs).To overcome these limitations,we propose an EBL-free DUV LD design incor-porating a 1-nm undoped Al_(0.8)Ga_(0.2)N thin strip layer after the last quantum barrier.Using PICS3D simula-tions,we evaluate the optical and electrical characteristics.Results show a significant increase in effective electron barrier height(from 158.2 meV to 420.7 meV)and a reduction in hole barrier height(from 149.2 meV to 62.8 meV),which enhance hole injection and reduce electron leakage.The optimized structure(LD3)achieves a 14%increase in output power,improved slope efficiency(1.85 W/A),and lower threshold current.This design also reduces the quantum confined Stark effect and forms dual hole accumulation regions,im-proving recombination efficiency.展开更多
A novel broad area slotted Fabry-Perot diode laser is designed and fabricated. Using a new semi- analytical method, we introduce effective refractive index perturbations in the form of etched slot features into a conv...A novel broad area slotted Fabry-Perot diode laser is designed and fabricated. Using a new semi- analytical method, we introduce effective refractive index perturbations in the form of etched slot features into a conventional 980 nm broad area Fabry-Perot cavity, and the spectral characteristics of the device are expected to be noticeably improved. A low density of slot features is formed by using standard optical lithography and inductively coupled plasma dry etching. The experimental results show that the full spectral width at half-maximum is less than 0.4 rim, meanwhile, the thermal shift of the emission spectrum is decreased from 0.26 to 0.07 nm/℃ over a temperature range of 10 to 60℃. The improved spectral characteristics of the device are proved to be attributed to such slotted Fabry-Perot laser structures.展开更多
The paper presents a study on the effects of low intensity laser irradiation on morphological changes in plants sprouted from maize hybrid seeds （two hybrids） and wheat seeds. Pre-sowing laser irradiation treatment ...The paper presents a study on the effects of low intensity laser irradiation on morphological changes in plants sprouted from maize hybrid seeds （two hybrids） and wheat seeds. Pre-sowing laser irradiation treatment on the seeds was done, intervals from 10 s to 15 min （approximately）, by using a diode laser output power of 12 mW at 904 nm wavelength or with He-Ne laser with output power of 50 mW and 632.8 nm wavelength. Before irradiation seeds were divided into groups （wet and dry, and then in subgroups-irradiated or control groups）. We used maize hybrids, Amilacea and Identata and wheat （Triticum aestivum）. The reflection coefficient in visible range was done for maize varieties. Obtained data show the influence of laser beam to better plant growth. Better results are obtained for dry seed irradiation than for wet. In order to investigate the effect of laser beam and in general to clarify a lot of unsolved photo processes related to bioorganisms at macroscopic and microscopic levels, some optical constants of selected plant families were researched. At the same time, the influence of laser beams of common wavelengths to the selected plants was monitored. Morphological processes of plants （seeds and leaves） irradiated under different conditions and plant growing dynamics were contemplated. The definite correlation analyses of obtained results were made, clearly speaking about the influence of small-dose radiation to characteristics （quantitative and other genetic, bio-stimulating effects） of future plant growth.展开更多
There is nonradiative recombination in waveguide region owing to severe carrier leakage,which in turn reduces output power and wall-plug efficiency.In this paper,we designed a novel epitaxial structure,which suppresse...There is nonradiative recombination in waveguide region owing to severe carrier leakage,which in turn reduces output power and wall-plug efficiency.In this paper,we designed a novel epitaxial structure,which suppresses carrier leakage by inserting n-Ga_(0.55)In_(0.45)P and p-GaAs_(0.6)P_(0.4) between barriers and waveguide layers,respectively,to modulate the energy band structure and to increase the height of barrier.The results show that the leakage current density reduces by 87.71%,compared to traditional structure.The nonradiative recombination current density of novel structure reduces to 37.411 A/cm^(2),and the output power reaches 12.80 W with wall-plug efficiency of 78.24%at an injection current density 5 A/cm^(2) at room temperature.In addition,the temperature drift coefficient of center wavelength is 0.206 nm/℃at the temperature range from 5℃to 65℃,and the slope of fitted straight line of threshold current with temperature variation is 0.00113.The novel epitaxial structure provides a theoretical basis for achieving high-power laser diode.展开更多
Stimulated emission and lasing of GaN-based laser diodes(LDs)were reported at 1995[1]and 1996[2],right after the breakthrough of p-type doping[3−5],material quality[6]and the invention of high-brightness GaN-based LED...Stimulated emission and lasing of GaN-based laser diodes(LDs)were reported at 1995[1]and 1996[2],right after the breakthrough of p-type doping[3−5],material quality[6]and the invention of high-brightness GaN-based LEDs[7,8].However,it took much longer time for GaN-based LDs to achieve high power,high wall plug efficiency,and long lifetime.Until 2019,Nichia reported blue LDs with these performances[9],which open wide applications with GaN-based blue LDs.展开更多
The packaging quality of coaxial laser diodes(CLDs)plays a pivotal role in determining their optical performance and long-term reliability.As the core packaging process,high-precision laser welding requires precise co...The packaging quality of coaxial laser diodes(CLDs)plays a pivotal role in determining their optical performance and long-term reliability.As the core packaging process,high-precision laser welding requires precise control of process parameters to suppress optical power loss.However,the complex nonlinear relationship between welding parameters and optical power loss renders traditional trial-and-error methods inefficient and imprecise.To address this challenge,a physics-informed(PI)and data-driven collaboration approach for welding parameter optimization is proposed.First,thermal-fluid-solid coupling finite element method(FEM)was employed to quantify the sensitivity of welding parameters to physical characteristics,including residual stress.This analysis facilitated the identification of critical factors contributing to optical power loss.Subsequently,a Gaussian process regression(GPR)model incorporating finite element simulation prior knowledge was constructed based on the selected features.By introducing physics-informed kernel(PIK)functions,stress distribution patterns were embedded into the prediction model,achieving high-precision optical power loss prediction.Finally,a Bayesian optimization(BO)algorithm with an adaptive sampling strategy was implemented for efficient parameter space exploration.Experimental results demonstrate that the proposedmethod effectively establishes explicit physical correlations between welding parameters and optical power loss.The optimized welding parameters reduced optical power loss by 34.1%,providing theoretical guidance and technical support for reliable CLD packaging.展开更多
A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The em...A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The emissions of the laser diode bar are coupled into multimode fiber array.The radi ation from individual ones of emitter regions is optically coupled into individu al ones of fiber array.Total coupling efficiency and fiber output power are 75% and 15W,respectively.展开更多
The 808nm laser diodes with a broad waveguide are designed and fabricated.The thickness of the Al_ 0.35 - Ga_ 0.65 As waveguide is increased to 0.9μm.In order to suppress the super modes,the thickness of the A...The 808nm laser diodes with a broad waveguide are designed and fabricated.The thickness of the Al_ 0.35 - Ga_ 0.65 As waveguide is increased to 0.9μm.In order to suppress the super modes,the thickness of the Al_ 0.55 Ga_ 0.45 As cladding layers is reduced to only 0.7μm while keeping the transverse radiation losses of the fundamental mode below 0.2cm -1 .The structures are grown by metal organic chemical vapour deposition.The devices show excellent performances.The maximum output power of 10.2W in the 100μm broad-area laser diodes is obtained.展开更多
The growth of multi-layer InGaAs/InAs/GaAs self-assembled quantum dots （QDs） by molecular beam epitaxy （MBE） is investigated,and a QD laser diode lasing at 1.33μm in continuous operation mode at room temperature ...The growth of multi-layer InGaAs/InAs/GaAs self-assembled quantum dots （QDs） by molecular beam epitaxy （MBE） is investigated,and a QD laser diode lasing at 1.33μm in continuous operation mode at room temperature is reported. The full width at half maximum of the band edge emitting peaks of the photoluminescence （PL） spectra at room temperature is less than 35meV for most of the multi-layer QD samples,revealing good,reproducible MBE growth conditions. Moreover,atomic force microscopy images show that the QD surface density can be controlled in the range from 1×10^10 to 7 ×10^10 cm^-2 . The best PL properties are obtained at a QD surface density of about 4×10^10cm^-2. Edge emitting lasers containing 3 and 5 stacked QD layers as the active layer lasing at room temperature in continuous wave operation mode are reported.展开更多
Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the...Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the tuning of the indium and nitrogen composition of the GalnNAs QWs, the emission wavelengths of the QWs can be tuned to 1.3μm. Ridge geometry waveguide laser diodes are fabricated. The lasing wavelength is 1.3μm under continuous current injection at room temperature with threshold current of 1kA/cm^2 for the laser diode structures with the cleaved facet mirrors. The output light power over 30mW is obtained.展开更多
We demonstrate an 852-nm external cavity diode laser（ECDL） system whose wavelength is mainly determined by an interference filter instead of other wavelength selective elements. The Lorentzian linewidth measured by ...We demonstrate an 852-nm external cavity diode laser（ECDL） system whose wavelength is mainly determined by an interference filter instead of other wavelength selective elements. The Lorentzian linewidth measured by the heterodyne beating between two identical lasers is 28.3 k Hz. Moreover, we test the application of the ECDL in the Faraday atomic filter.Besides saturated absorption spectrum, the transmission spectrum of the Faraday atomic filter at 852 nm is measured by using the ECDL. This interference filter ECDL method can also be extended to other wavelengths and widen the application range of diode laser.展开更多
A high power GaSb-based laser diode with lasing wavelength at 2 μm was fabricated and optimized. With the optimized epitaxial laser structure, the internal loss and the threshold current density decreased and the int...A high power GaSb-based laser diode with lasing wavelength at 2 μm was fabricated and optimized. With the optimized epitaxial laser structure, the internal loss and the threshold current density decreased and the internal quantum efficiency increased. For uncoated broad-area lasers, the threshold current density was as low as 144 A/cm2 （72 A/cm^2 per quantum well）, and the slope efficiency was 0.2 W/A. The internal loss was 11 cm^-1 and the internal quantum efficiency was 27.1%. The maximum output power of 357 mW under continuous-wave operation at room temperature was achieved. The electrical and optical properties of the laser diode were improved.展开更多
A 1.60μm laser diode and electroabsorption modulator monolithically integrated with a novel dual-waveguide spot-size converter output for low-loss coupling to a cleaved single-mode optical fiber are demonstrated.The ...A 1.60μm laser diode and electroabsorption modulator monolithically integrated with a novel dual-waveguide spot-size converter output for low-loss coupling to a cleaved single-mode optical fiber are demonstrated.The devices emit in a single transverse and quasi single longitudinal mode with an SMSR of 25.6dB.These devices exhibit a 3dB modulation bandwidth of 15.0GHz,and modulator DC extinction ratios of 16.2dB.The output beam divergence angles of the spot-size converter in the horizontal and vertical directions are as small as 7.3°×18.0°,respectively,resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.展开更多
基金This work was supported by the National Basic Research Program of China （No.2013BAK12B00 and No.2013CB834602） and the National Natural Science Foundation of China （No.21225314 and No.21427804）.
文摘Moisture measurement is of great needs in semiconductor industry, combustion diagnosis, meteorology, and atmospheric studies. We present an optical hygrometer based on cavity ring-down spectroscopy （CRDS）. By using different absorption lines of H20 in the 1.56 and 1.36 gm regions, we are able to determine the relative concentration （mole fraction） of water vapor from a few percent down to the 10-12 level. The quantitative accuracy is examined by comparing the CRDS hygrometer with a commercial chilled-mirror dew-point meter. The high sensitivity of the CRDS instrument allows a water detection limit of 8 pptv.
基金Supported by National Key R&D Project(2017YFB0405100)National Natural Science Foundation of China(61774024/61964007)Jilin province science and technology development plan(20190302007GX)。
文摘In long-cavity edge-emitting diode lasers,longitudinal spatial hole burning(LSHB),two-photon ab⁃sorption(TPA)and free carrier absorption(FCA)are among the key factors that affect the linear increase in out⁃put power at high injection currents.In this paper,a simplified numerical analysis model is proposed for 1.06μm long-cavity diode lasers by combining TPA and FCA losses with one-dimensional(1D)rate equations.The ef⁃fects of LSHB,TPA and FCA on the output characteristics are systematically analyzed,and it is proposed that ad⁃justing the front facet reflectivity and the position of the quantum well(QW)in the waveguide layer can improve the front facet output power.
基金the financial support of TUB-ITAK via Project 107E163.
文摘We report comparatively on fabrication of two-section ridge-waveguide tapered 3 quantum well (QW) InGaAsP/InP (1300 nm) and 5 QW AlGaInAs/InP (1550 nm) diode lasers. Gas mixtures of CCl2F2/O2 and H2/CH4 were used to form ridge-waveguide on the lasers with InP-based material structures. As known, chlorine- and hydro-carbon based gases are used to fabricate ridge-waveguide structures. Here, we show the difference between the structures obtained by using the both gas mixtures in which surface and sidewall structures as well as performance of the lasers were analysed using scanning electron microscopy. It is demonstrated that gas mixtures of CCl2F2/O2 highly deteriorated the etched structures although different flow rates, rf powers and base pressures were tried. We also show that the structures etched with H2/CH4 gas mixtures produced much better results that led to the successful fabrication of two-section devices with ridge-waveguide. The lasers fabricated using H2/CH4 were characterized using output power-current (P-I) and spectral results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11704408 and 91836106)the Beijing Natural Science Foundation,China(Grant No.Z180013)the Joint Fund of the Ministry of Education,China(Grant No.6141A020333xx).
文摘We develop a high-performance ultraviolet(UV)frequency stabilization technique implemented directly on UV diode lasers by combining the dichroic atomic vapor laser lock and the resonant transfer cavity lock.As an example,we demonstrate a stable locking with measured frequency standard deviations of approximately 200 kHz and 300 kHz for 399 nm and 370 nm diode lasers in 20 min.We achieve a long-term frequency drift of no more than 1 MHz for the target 370 nm laser within an hour,which is further verified with fluorescence count rates of a single trapped ^171Yb+ion.We also find strong linear correlations between lock points and environmental factors such as temperature and atmospheric pressure.Our approach provides a simple and stable solution at a relatively low cost,and features flexible control,high feedback bandwidth and minimal power consumption of the target UV laser.
基金Supported by National Natural Science Foundation of China(61307032)the Science Research Program of Jilin Province(20140520108JH)
文摘GaSb-based diode lasers with emitting wavelength of 1.8-4μm have a wide range of applications due to advantages of compact in size,light in weight and electric drive.However,single emitter can not provide e-nough laser power for practical applications.Therefore,methods of beam combination which have been successful-ly applied to diode lasers in near-infrared band are needed to be transplanted to mid-infrared band.In every method of beam combination,high efficiency beam shaping is basic and principal.A method of high efficiency beam sha-ping using multiple single diode lasers was demonstrated.A continuous-wave optical power of 1.93 W at wave-length of 1.94μm with efficiency of higher than 90%was achieved experimentally.This method of beam shaping can be utilized to build spectral or coherent beam combination.
基金Project supported by the Major Program of the National Natural Science Foundation of China(Grant No.61790581)the Key Area Research and Development Program of Guangdong Province,China(Grant No.2020B0303020001).
文摘We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength.The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector.The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper.And the quantum well cascade laser with 100-μm-wide,2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature.The characteristic temperature T_(0) is estimated at above 60 K.
文摘In laser hair removal treatments on dark skin, the high concentration of melanin in the skin competes with the melanin in the hair. During standard laser procedures, with wavelengths of 755 nm or 810 nm, a high level of laser light absorption by melanin in the skin is observed. Therefore, to avoid side effects, lower fluence values are used, which further reduces hair-removal efficacy. To improve results, 810 nm diode lasers operating in dynamic mode, with high frequency and multiple passes, are typically used. The aim of this study is to compare the efficacy and safety of triple-wavelength diode lasers (810 nm, 940 nm, 1060 nm) with that of 810 nm diode lasers on Indian patients. A side-by-side comparison was performed using a triple-wavelength diode laser in stamping mode on one side, and an 810 nm diode laser in dynamic mode on the other. Three subjects with skin type IV on the Fitzpatrick scale participated in the study. Efficacy was assessed through hair counting using clinical photographs, taken before and after the treatments, and the Global Aesthetic Improvement Scale (GAIS). Additionally, comparisons related to epidermal heating and thermal damage to the hair follicle were conducted through mathematical 3D simulations using COMSOL Multiphysics<sup>®</sup> software. Side effects were also evaluated. A superior end point was observed with triple wavelength compared to the 810 nm diode laser. Hair counting showed a 27% greater hair reduction with triple wavelength. No adverse effects were observed. Thermal simulations revealed 29% higher thermal damage with the triple-wavelength laser compared to the 810 nm diode laser. To conclude, on darker skin types, the triple-wavelength diode laser has been shown to be more effective at removing hair, compared to the 810 nm diode laser, while also being a safe procedure.
文摘AlGaN-based deep-ultraviolet(DUV)laser diodes(LDs)face performance challenges due to elec-tron leakage and poor hole injection which is often worsened by polarization effects from conventional elec-tron blocking layers(EBLs).To overcome these limitations,we propose an EBL-free DUV LD design incor-porating a 1-nm undoped Al_(0.8)Ga_(0.2)N thin strip layer after the last quantum barrier.Using PICS3D simula-tions,we evaluate the optical and electrical characteristics.Results show a significant increase in effective electron barrier height(from 158.2 meV to 420.7 meV)and a reduction in hole barrier height(from 149.2 meV to 62.8 meV),which enhance hole injection and reduce electron leakage.The optimized structure(LD3)achieves a 14%increase in output power,improved slope efficiency(1.85 W/A),and lower threshold current.This design also reduces the quantum confined Stark effect and forms dual hole accumulation regions,im-proving recombination efficiency.
基金Project supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(No.ISCAS2008T12)
文摘A novel broad area slotted Fabry-Perot diode laser is designed and fabricated. Using a new semi- analytical method, we introduce effective refractive index perturbations in the form of etched slot features into a conventional 980 nm broad area Fabry-Perot cavity, and the spectral characteristics of the device are expected to be noticeably improved. A low density of slot features is formed by using standard optical lithography and inductively coupled plasma dry etching. The experimental results show that the full spectral width at half-maximum is less than 0.4 rim, meanwhile, the thermal shift of the emission spectrum is decreased from 0.26 to 0.07 nm/℃ over a temperature range of 10 to 60℃. The improved spectral characteristics of the device are proved to be attributed to such slotted Fabry-Perot laser structures.
文摘The paper presents a study on the effects of low intensity laser irradiation on morphological changes in plants sprouted from maize hybrid seeds （two hybrids） and wheat seeds. Pre-sowing laser irradiation treatment on the seeds was done, intervals from 10 s to 15 min （approximately）, by using a diode laser output power of 12 mW at 904 nm wavelength or with He-Ne laser with output power of 50 mW and 632.8 nm wavelength. Before irradiation seeds were divided into groups （wet and dry, and then in subgroups-irradiated or control groups）. We used maize hybrids, Amilacea and Identata and wheat （Triticum aestivum）. The reflection coefficient in visible range was done for maize varieties. Obtained data show the influence of laser beam to better plant growth. Better results are obtained for dry seed irradiation than for wet. In order to investigate the effect of laser beam and in general to clarify a lot of unsolved photo processes related to bioorganisms at macroscopic and microscopic levels, some optical constants of selected plant families were researched. At the same time, the influence of laser beams of common wavelengths to the selected plants was monitored. Morphological processes of plants （seeds and leaves） irradiated under different conditions and plant growing dynamics were contemplated. The definite correlation analyses of obtained results were made, clearly speaking about the influence of small-dose radiation to characteristics （quantitative and other genetic, bio-stimulating effects） of future plant growth.
文摘There is nonradiative recombination in waveguide region owing to severe carrier leakage,which in turn reduces output power and wall-plug efficiency.In this paper,we designed a novel epitaxial structure,which suppresses carrier leakage by inserting n-Ga_(0.55)In_(0.45)P and p-GaAs_(0.6)P_(0.4) between barriers and waveguide layers,respectively,to modulate the energy band structure and to increase the height of barrier.The results show that the leakage current density reduces by 87.71%,compared to traditional structure.The nonradiative recombination current density of novel structure reduces to 37.411 A/cm^(2),and the output power reaches 12.80 W with wall-plug efficiency of 78.24%at an injection current density 5 A/cm^(2) at room temperature.In addition,the temperature drift coefficient of center wavelength is 0.206 nm/℃at the temperature range from 5℃to 65℃,and the slope of fitted straight line of threshold current with temperature variation is 0.00113.The novel epitaxial structure provides a theoretical basis for achieving high-power laser diode.
基金supported by the Natural Science Foundation of Jiangsu Province(Grant.BK20232042).
文摘Stimulated emission and lasing of GaN-based laser diodes(LDs)were reported at 1995[1]and 1996[2],right after the breakthrough of p-type doping[3−5],material quality[6]and the invention of high-brightness GaN-based LEDs[7,8].However,it took much longer time for GaN-based LDs to achieve high power,high wall plug efficiency,and long lifetime.Until 2019,Nichia reported blue LDs with these performances[9],which open wide applications with GaN-based blue LDs.
基金funded by the National Key R&D Program of China,Grant No.2024YFF0504904.
文摘The packaging quality of coaxial laser diodes(CLDs)plays a pivotal role in determining their optical performance and long-term reliability.As the core packaging process,high-precision laser welding requires precise control of process parameters to suppress optical power loss.However,the complex nonlinear relationship between welding parameters and optical power loss renders traditional trial-and-error methods inefficient and imprecise.To address this challenge,a physics-informed(PI)and data-driven collaboration approach for welding parameter optimization is proposed.First,thermal-fluid-solid coupling finite element method(FEM)was employed to quantify the sensitivity of welding parameters to physical characteristics,including residual stress.This analysis facilitated the identification of critical factors contributing to optical power loss.Subsequently,a Gaussian process regression(GPR)model incorporating finite element simulation prior knowledge was constructed based on the selected features.By introducing physics-informed kernel(PIK)functions,stress distribution patterns were embedded into the prediction model,achieving high-precision optical power loss prediction.Finally,a Bayesian optimization(BO)algorithm with an adaptive sampling strategy was implemented for efficient parameter space exploration.Experimental results demonstrate that the proposedmethod effectively establishes explicit physical correlations between welding parameters and optical power loss.The optimized welding parameters reduced optical power loss by 34.1%,providing theoretical guidance and technical support for reliable CLD packaging.
文摘A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The emissions of the laser diode bar are coupled into multimode fiber array.The radi ation from individual ones of emitter regions is optically coupled into individu al ones of fiber array.Total coupling efficiency and fiber output power are 75% and 15W,respectively.
文摘The 808nm laser diodes with a broad waveguide are designed and fabricated.The thickness of the Al_ 0.35 - Ga_ 0.65 As waveguide is increased to 0.9μm.In order to suppress the super modes,the thickness of the Al_ 0.55 Ga_ 0.45 As cladding layers is reduced to only 0.7μm while keeping the transverse radiation losses of the fundamental mode below 0.2cm -1 .The structures are grown by metal organic chemical vapour deposition.The devices show excellent performances.The maximum output power of 10.2W in the 100μm broad-area laser diodes is obtained.
文摘The growth of multi-layer InGaAs/InAs/GaAs self-assembled quantum dots （QDs） by molecular beam epitaxy （MBE） is investigated,and a QD laser diode lasing at 1.33μm in continuous operation mode at room temperature is reported. The full width at half maximum of the band edge emitting peaks of the photoluminescence （PL） spectra at room temperature is less than 35meV for most of the multi-layer QD samples,revealing good,reproducible MBE growth conditions. Moreover,atomic force microscopy images show that the QD surface density can be controlled in the range from 1×10^10 to 7 ×10^10 cm^-2 . The best PL properties are obtained at a QD surface density of about 4×10^10cm^-2. Edge emitting lasers containing 3 and 5 stacked QD layers as the active layer lasing at room temperature in continuous wave operation mode are reported.
文摘Material growth and device fabrication of the first 1.3μm quantum well （QW） edge emitting laser diodes in China are reported. Through the optimization of the molecular beam epitaxy （MBE） growth conditions and the tuning of the indium and nitrogen composition of the GalnNAs QWs, the emission wavelengths of the QWs can be tuned to 1.3μm. Ridge geometry waveguide laser diodes are fabricated. The lasing wavelength is 1.3μm under continuous current injection at room temperature with threshold current of 1kA/cm^2 for the laser diode structures with the cleaved facet mirrors. The output light power over 30mW is obtained.
基金supported by the National Natural Science Foundation of China(Grant No.91436210)the International Science and Technology Cooperation Program of China(Grant No.2010DFR10900)
文摘We demonstrate an 852-nm external cavity diode laser（ECDL） system whose wavelength is mainly determined by an interference filter instead of other wavelength selective elements. The Lorentzian linewidth measured by the heterodyne beating between two identical lasers is 28.3 k Hz. Moreover, we test the application of the ECDL in the Faraday atomic filter.Besides saturated absorption spectrum, the transmission spectrum of the Faraday atomic filter at 852 nm is measured by using the ECDL. This interference filter ECDL method can also be extended to other wavelengths and widen the application range of diode laser.
基金supported by the Beijing Natural Science Foundation, China (Grant No. 4112058)
文摘A high power GaSb-based laser diode with lasing wavelength at 2 μm was fabricated and optimized. With the optimized epitaxial laser structure, the internal loss and the threshold current density decreased and the internal quantum efficiency increased. For uncoated broad-area lasers, the threshold current density was as low as 144 A/cm2 （72 A/cm^2 per quantum well）, and the slope efficiency was 0.2 W/A. The internal loss was 11 cm^-1 and the internal quantum efficiency was 27.1%. The maximum output power of 357 mW under continuous-wave operation at room temperature was achieved. The electrical and optical properties of the laser diode were improved.
文摘A 1.60μm laser diode and electroabsorption modulator monolithically integrated with a novel dual-waveguide spot-size converter output for low-loss coupling to a cleaved single-mode optical fiber are demonstrated.The devices emit in a single transverse and quasi single longitudinal mode with an SMSR of 25.6dB.These devices exhibit a 3dB modulation bandwidth of 15.0GHz,and modulator DC extinction ratios of 16.2dB.The output beam divergence angles of the spot-size converter in the horizontal and vertical directions are as small as 7.3°×18.0°,respectively,resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.
