We present a compact injection-locking diode laser module to generate 671 nm laser light with a high output power up to 150 m W.The module adopts a master-slave injection-locking scheme,and the injection-locking state...We present a compact injection-locking diode laser module to generate 671 nm laser light with a high output power up to 150 m W.The module adopts a master-slave injection-locking scheme,and the injection-locking state is monitored using the transmission spectrum from a Fabry-Perot interferometer.Beat frequency spectrum measurement shows that the injection-locked slave laser has no other frequency components within the 150-MHz detection bandwidth.It is found that without additional electronic feedback,the slave laser can follow the master laser over a wide range of 6 GHz.All the elements of the module are commercially available,which favors fast construction of a complete 671-nm laser system for the preparation of cold^(6)Li atoms with only one research-grade diode laser as the seeding source.展开更多
Tunable diode laser absorption spectroscopy (TDLAS) has been widely employed in atmospheric trace gases detection. The ratio of the second-harmonic signal to the intensity of laser beam incident to the multi-pass ce...Tunable diode laser absorption spectroscopy (TDLAS) has been widely employed in atmospheric trace gases detection. The ratio of the second-harmonic signal to the intensity of laser beam incident to the multi-pass cell is proved to be proportional to the product of the path length and the gas concentration under any condition. A new calibration method based on this relation in TDLAS system for the measurement of trace gas concentration is proposed for the first time. The detection limit and the sensitivity of the system are below 110 and 31ppbv (parts-per-billion in volume), respectively.展开更多
The laser provides a controllable means of supplying localized energy for solder joint formation and is a valuable tool in electronics manufacture.Diode laser soldering for fine pitch QFP devices were carried out with...The laser provides a controllable means of supplying localized energy for solder joint formation and is a valuable tool in electronics manufacture.Diode laser soldering for fine pitch QFP devices were carried out with Sn-Ag-Cu lead-free solder and Sn-Pb solder respectively,and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR-1000 micro-joints tester.The results indicate that sound QFP micro-joints without bridging or solder ball are gained by means of diode laser soldering method with appropriate laser processing parameters,and the pitch of the QFP devices is as fine as to 0.4mm.Tensile strength of QFP micro-joints increases gradually with the increase of laser output power,the maximum tensile strength presents when the laser output power increase to a certain value.The results also indicate that the mechanical properties of QFP micro-joints soldered by diode laser soldering system are better than those of QFP micro-joints soldered by IR reflow soldering method.The experimental results may provide a theory guide for investigation of diode laser soldering.展开更多
As being an effective real-time method of monitoring vehicle emissions on-road, a remote sensing system based on the tunable diode laser (TDL) technology was presented, and the key technologies were discussed. A fie...As being an effective real-time method of monitoring vehicle emissions on-road, a remote sensing system based on the tunable diode laser (TDL) technology was presented, and the key technologies were discussed. A field test in Guangzhou(Guangdong, China) was performed and was found that the factors, such as slope, instantaneous speed and acceleration, had significant influence on the detectable rate of the system. Based on the results, the proposal choice of testing site was presented.展开更多
Interference filter-stabilized external cavity diode lasers (ECDLs) have properties of simple configurations, high sta- bilities, and narrow linewidths. However, the interference filter used in common ECDL designs r...Interference filter-stabilized external cavity diode lasers (ECDLs) have properties of simple configurations, high sta- bilities, and narrow linewidths. However, the interference filter used in common ECDL designs requires an ultra-narrow bandwidth (about 0.3 nm) to achieve mode selection, that is considerably expensive and not yet available for a wide range of wavelengths. In this paper, a robust ECDL using an available broad bandwidth (about 4 nm) interference filter as the wavelength discriminator is constructed and tested. The ECDL demonstrated a narrow Lorentzian fitted linewidth of 95 kHz and a spectral purity of 2.9 MHz. The long-term frequency stability of the ECDL reaches 5.59 x 10 12.展开更多
We report a robust method of directly stabilizing a grating feedback diode laser to an arbitrary frequency in a large range. The error signal, induced from the difference between the frequency measured by a wavelength...We report a robust method of directly stabilizing a grating feedback diode laser to an arbitrary frequency in a large range. The error signal, induced from the difference between the frequency measured by a wavelength meter and the preset target frequency, is fed back to the piezoelectric transducer module of the diode laser via a sound card in the computer. A visual Labview procedure is developed to realize a feedback system. In our experiment the frequency drift of the diode laser is reduced to 8 MHz within 25 min. The robust scheme can be adapted to realize the arbitrary frequency stabilization for many other kinds of lasers.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
AIM:To investigate the effects of diode laser treatment on ocular biometric parameters in premature infants with retinopathy of prematurity(ROP).METHODS:Premature infants who received diode laser treatment for ROP(n=6...AIM:To investigate the effects of diode laser treatment on ocular biometric parameters in premature infants with retinopathy of prematurity(ROP).METHODS:Premature infants who received diode laser treatment for ROP(n=68)and premature infants with spontaneous regressed ROP without treatment(n=50)were performed longitudinal ocular biometric measurements including anterior chamber depth,lens thickness and axial length as follows:1 d prior to laser treatment,and 3,6,9,and 12 mo after the laser treatment.RESULTS:The mean birth weight,gestational age and initial examination time values were 936.53±302.07 g,26.66±2.42 wk,36.26±2.73 wk in the treatment group and 959.78±260.08 g,27.28±2.10 wk,36.56±2.54 wk in the control group.There was no statistically significant difference in these demographic characteristics of the groups.Anterior chamber depth,lens thickness and axial length demonstrated statistically significant linear increases during the study period in the two groups(P<0.001 for each).There were no statistically significant differences between the two groups in terms of anterior chamber depth after laser treatment.Measurements of the lens thickness at 9 th and 12 th months(9 th month 3.70±0.22 vs 3.60±0.21 mm,P=0.017;12 th month 3.81±0.21 vs 3.69±0.22 mm,P=0.002)and the axial length at 12 th month(19.35±0.79 vs 19.13±0.54 mm,P=0.031)after laser treatment were statistically higher in the treatment group.CONCLUSION:Diode laser retinal photocoagulation treatment in premature infants seems to increase the lens thickness and axial length.展开更多
As a step toward realizing magnesium civilization,which needs a sustainable Mg production process,the reduction of MgO to Mg has been investigated.Direct diode laser(DDL)produces high power and continuous beam in tiny...As a step toward realizing magnesium civilization,which needs a sustainable Mg production process,the reduction of MgO to Mg has been investigated.Direct diode laser(DDL)produces high power and continuous beam in tiny spots.The laser with energy density up to 83*10^(5) W/cm^(2) is focused on MgO/Si target inside the vacuum chamber,creating the high temperature zone,which stimulates the Mg production reaction.The vapor is collected on the copper plate;and then,analyzed chemically in terms of Mg production efficiency.The largest reduction and energy efficiencies in Ar atmosphere were 41%and 15.3 mg kJ^(−1),while in the vacuum,13.5%and 15.8 mg kJ^(−1) were attainable.The reactions of MgO and Si have been investigated.Calculations revealed that the MgO reduction with Si proceeds as heterogeneous reaction.The rate of reaction of Si with MgO is faster than the rate of MgO evaporation and Mg vapor deposition.展开更多
An NO2 photoacoustic sensor system with a high reflective mirror based on a low power blue diode laser is developed in this work. The excitation power is enhanced by increasing the number of reflections. Comparing wit...An NO2 photoacoustic sensor system with a high reflective mirror based on a low power blue diode laser is developed in this work. The excitation power is enhanced by increasing the number of reflections. Comparing with a traditional photoacoustic system, the pool constant is improved from 300.24(Pa·cm)/W to 1450.64(Pa·cm)/W, and the signal sensitivity of the photoacoustic sensor is increased from 0.016 μV/ppb to 0.2562 μV/ppb. The characteristics of temperature and humidity of the new photoacoustic sensor are also obtained, and the algorithm is adjusted to provide a quantitative response and drift of the resonance frequency. The results of this research provide a new method and concept for further developing the NO2 photoacoustic sensors.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
Densities of Ar metastable states 1s5 and 1s3 are measured by using the tunable diode laser absorption spectroscopy(TDLAS) in Ar and Ar/O2 mixture dual-frequency capacitively coupled plasma(DF-CCP). We investigate...Densities of Ar metastable states 1s5 and 1s3 are measured by using the tunable diode laser absorption spectroscopy(TDLAS) in Ar and Ar/O2 mixture dual-frequency capacitively coupled plasma(DF-CCP). We investigate the effects of high-frequency(HF, 60 MHz) power, low-frequency(LF, 2 MHz) power, and working pressure on the density of Ar metastable states for three different gas components(0%, 5%, and 10% oxygen mixed in argon). The dependence of Ar metastable state density on the oxygen content is also studied at different working pressures. It is found that densities of Ar metastable states in discharges with different gas components exhibit different behaviors as HF power increases. With the increase of HF power, the metastable density increases rapidly at the initial stage, and then tends to be saturated at a higher HF power. With a small fraction(5% or 10%) of oxygen added in argon plasma, a similar change of the Ar metastable density with HF power can be observed, but the metastable density is saturated at a higher HF power than in the pure argon discharge. In the DF-CCP, the metastable density is found to be higher than in a single frequency discharge, and has weak dependence on LF power. As working pressure increases, the metastable state density first increases and then decreases,and the pressure value, at which the density maximum occurs, decreases with oxygen content increasing. Besides, adding a small fraction of oxygen into argon plasma will significantly dwindle the metastable state density as a result of quenching loss by oxygen molecules.展开更多
A compact optical setup for quantitative and spatially resolved measurement of atomic alkali concentration in combustion is demonstrated. Tunable diode laser absorption spectroscopy and laser-induced fluorescence are ...A compact optical setup for quantitative and spatially resolved measurement of atomic alkali concentration in combustion is demonstrated. Tunable diode laser absorption spectroscopy and laser-induced fluorescence are combined using a single continuous wave diode laser to measure the line-integration concentration and the relative distribution simultaneously, thereby obtaining the absolute concentration distribution along the laser beam. The results indicate the good performance of this method for one-dimensional quantitative measurement.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
A 1550-nm linearly tunable continuous wave (CW) single-mode external cavity diode laser (ECDL) based on a singlecavity all-dielectric thin-film Fabry-Pérot filter (s-AFPF) is proposed and realized in this p...A 1550-nm linearly tunable continuous wave (CW) single-mode external cavity diode laser (ECDL) based on a singlecavity all-dielectric thin-film Fabry-Pérot filter (s-AFPF) is proposed and realized in this paper. Its internal optical components as well as their operation mechanisms are introduced first, and then its longitudinal mode output characteristic is theoretically analyzed. Afterwards, we set up the experimental platform for the output characteristic measurement of this tunable ECDL; under different experimental conditions, we execute accurate and real-time measurements for the output central wavelength, output optical power, output longitudinal mode distribution, and the line-width of the tunable ECDL in its tuning process. By summing up the optimal experimental condition from the measured data, we obtain the optimal tunable ECDL relevant parameters: the tunable ECDL has a linear mode-hop-free wavelength tuning region of 1547.203 nm-1552.426 nm, a stable output optical power in the range of 40 μW-50 μW, and a stable output longitudinal mode distribution of a single longitudinal mode with a line-width in the range of 100 MHz-150 MHz. This tunable ECDL can be used in environmental gas monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.展开更多
We report a 42Ohm external cavity diode laser with an interference filter (IF) of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye refle...We report a 42Ohm external cavity diode laser with an interference filter (IF) of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye reflector are used for selecting wavelength and light feedback, respectively. The measured laser linewidth is 24 kHz when the diode laser is free running. Using this narrow-linewidth IF blue diode laser, we realize a compact Rb optical frequency standard without a complicated PDH system. The preliminary stability of the Rb optical frequency standard is 2 × 10^-13 at I s and decreases to 1.9 ×10^-14 at 1000s. The narrow-linewidth characteristic makes the IF blue diode laser a well suited candidate for the compact Rb optical frequency standard.展开更多
We demonstrate an atmospheric transfer of microwave signal over a 120 m outdoor free-space link using a compact diode laser with a timing fluctuation suppression technique.Timing fluctuation and Allan Deviation are bo...We demonstrate an atmospheric transfer of microwave signal over a 120 m outdoor free-space link using a compact diode laser with a timing fluctuation suppression technique.Timing fluctuation and Allan Deviation are both measured to characterize the instability of transferred frequency incurred during the transfer process.By transferring a 100 MHz microwave signal within 4500 s,the total root-mean-square(RMS)timing fluctuation was measured to be about 6 ps,with a fractional frequency instability on the order of 1×10-12 at 1 s,and order of 7×10-15 at 1000 s.This portable atmospheric frequency transfer scheme with timing fluctuation suppression can be used to distribute an atomic clock-based frequency over a free-space link.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
Background:Laser photocoagulation restricted to ablation of the avascular retina has been the conventional but not a completely effective treatment strategy in the management of threshold retinopathy of prematurity(RO...Background:Laser photocoagulation restricted to ablation of the avascular retina has been the conventional but not a completely effective treatment strategy in the management of threshold retinopathy of prematurity(ROP).The purpose of this study was to compare the structural outcomes of additional posterior to ridge diode laser compared to conventional diode laser to avascular retina alone in threshold stage III ROP.Methods:This was a prospective,randomized study involving infants diagnosed with threshold stage III ROP in one or both the eyes.The infants were randomized into control and study groups.Infants under the control group underwent conventional laser to avascular retina alone while infants under the study group received additional two rows of laser posterior to the ridge in the vascular retina.The infants were followed up at 2 weeks,1 month and up to 6 months after the laser procedure.Results:During the study period of 1 year,42 eyes of 24 infants were recruited into this study with 21 eyes in each group.The mean birth weight was 1,310.48±400.92 g in the test group and 1,341.9±396.2 g in the control group.The mean post conceptional age at the time of intervention was 36.43±2.79 weeks in test group and 36.29±2.55 weeks in the control group.At 1-month post laser,19 eyes in the study group showed regression of neovascularization laser compared to 18 eyes in the control group.However at the end of 3 and 6 months post laser,both groups had showed similar rates regression of neovascularization(19 of 21 eyes in both groups).Five eyes in the study group and six in the control group required additional laser treatment.Two eyes in the study group and one eye in the control group developed post laser vitreous hemorrhage.Conclusions:Posterior to ridge laser treatment for severe stage 3 ROP did not show any additional benefit compared to conventional laser.展开更多
Objective: This study aims to describe the experience with diode laser cyclophotocoagulation in the control of intraocular pressure and resolution of pain in patients with refractory glaucoma. Methods: Retrospective s...Objective: This study aims to describe the experience with diode laser cyclophotocoagulation in the control of intraocular pressure and resolution of pain in patients with refractory glaucoma. Methods: Retrospective study. 64 eyes of 60 patients who underwent cyclophotocoagulation between January 2008 and March 2014. Evaluation of the pre- and post-operative intraocular pressure, the control of ocular pain, the number of anti-glaucoma drugs used in pre- and post-intervention, the rate of complications and the success rate. Results: There was an overall success rate of 81.3%, with 9 eyes needing a second intervention. There was a mean reduction of 52.6% of the preoperative mean intraocular pressure of 41.25 to 19.56 mmHg at 12 months observation (p < 0.001). There was also a statistically significant reduction in the number of anti-glaucoma drugs used from 3.19 to 2.01 per eye and the resolution of pain in 75% of patients. Conclusions: cyclophotocoagulation is an effective procedure, with an expected positive impact on quality of life of patients as a result from the decreased number of anti-glaucoma drugs, sustained intraocular pressure reduction and resolution of pain.展开更多
基金the National Natural Science Foundation of China(Grant Nos.12035006,12205095,and12147219)the Natural Science Foundation of Zhejiang Province(Grant No.LQ21A040001)。
文摘We present a compact injection-locking diode laser module to generate 671 nm laser light with a high output power up to 150 m W.The module adopts a master-slave injection-locking scheme,and the injection-locking state is monitored using the transmission spectrum from a Fabry-Perot interferometer.Beat frequency spectrum measurement shows that the injection-locked slave laser has no other frequency components within the 150-MHz detection bandwidth.It is found that without additional electronic feedback,the slave laser can follow the master laser over a wide range of 6 GHz.All the elements of the module are commercially available,which favors fast construction of a complete 671-nm laser system for the preparation of cold^(6)Li atoms with only one research-grade diode laser as the seeding source.
基金Project supported by the National Natural Science Foundation of China (Grant No 10274080) and the National High Technology Research and Development Program of China (Grant No 2003AA641010).
文摘Tunable diode laser absorption spectroscopy (TDLAS) has been widely employed in atmospheric trace gases detection. The ratio of the second-harmonic signal to the intensity of laser beam incident to the multi-pass cell is proved to be proportional to the product of the path length and the gas concentration under any condition. A new calibration method based on this relation in TDLAS system for the measurement of trace gas concentration is proposed for the first time. The detection limit and the sensitivity of the system are below 110 and 31ppbv (parts-per-billion in volume), respectively.
基金supported by Nanjing University of Aeronautics and Astronautics Doctoral Dissertation Innovation and Excellence Producing Foundation of China (Grant No. BCXJ09-07)Jiangsu Provincial General Colleges and Universities Postgraduate Scientific Research Innovative Plan of China (Grant No. CX09B_074Z)the Six Kind Skilled Personnel Project of Jiangsu Province of China(Grant No. 06-E-020)
文摘The laser provides a controllable means of supplying localized energy for solder joint formation and is a valuable tool in electronics manufacture.Diode laser soldering for fine pitch QFP devices were carried out with Sn-Ag-Cu lead-free solder and Sn-Pb solder respectively,and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR-1000 micro-joints tester.The results indicate that sound QFP micro-joints without bridging or solder ball are gained by means of diode laser soldering method with appropriate laser processing parameters,and the pitch of the QFP devices is as fine as to 0.4mm.Tensile strength of QFP micro-joints increases gradually with the increase of laser output power,the maximum tensile strength presents when the laser output power increase to a certain value.The results also indicate that the mechanical properties of QFP micro-joints soldered by diode laser soldering system are better than those of QFP micro-joints soldered by IR reflow soldering method.The experimental results may provide a theory guide for investigation of diode laser soldering.
文摘As being an effective real-time method of monitoring vehicle emissions on-road, a remote sensing system based on the tunable diode laser (TDL) technology was presented, and the key technologies were discussed. A field test in Guangzhou(Guangdong, China) was performed and was found that the factors, such as slope, instantaneous speed and acceleration, had significant influence on the detectable rate of the system. Based on the results, the proposal choice of testing site was presented.
基金Project supported by the Foundation of Based Technology of China(Grant No.YXBGD20151JL01)the National Natural Science Foundation of China(Grant Nos.61376049,61604007,11674016,61378058,61575008,and 61574011)+1 种基金the Natural Science Foundation of Beijing City,China(Grant Nos.4172009 and4152003)the Beijing Municipal Commission of Education of China(Grant Nos.PXM2017 014204 500034 and PXM2016 014204 500018)
文摘Interference filter-stabilized external cavity diode lasers (ECDLs) have properties of simple configurations, high sta- bilities, and narrow linewidths. However, the interference filter used in common ECDL designs requires an ultra-narrow bandwidth (about 0.3 nm) to achieve mode selection, that is considerably expensive and not yet available for a wide range of wavelengths. In this paper, a robust ECDL using an available broad bandwidth (about 4 nm) interference filter as the wavelength discriminator is constructed and tested. The ECDL demonstrated a narrow Lorentzian fitted linewidth of 95 kHz and a spectral purity of 2.9 MHz. The long-term frequency stability of the ECDL reaches 5.59 x 10 12.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB921603)the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(Grant No.IRT13076)+4 种基金the Major Research Plan of the National Natural Science Foundation of China(Grant No.91436108)the National Natural Science Foundation of China(Grant Nos.61378014,61308023,61378015,and 11434007)the Fund for Fostering Talents in Basic Science of the National Natural Science Foundation of China(Grant No.J1103210)the New Teacher Fund of the Ministry of Education of China(Grant No.20131401120012)the Natural Science Foundation for Young Scientists of Shanxi Province,China(Grant No.2013021005-1)
文摘We report a robust method of directly stabilizing a grating feedback diode laser to an arbitrary frequency in a large range. The error signal, induced from the difference between the frequency measured by a wavelength meter and the preset target frequency, is fed back to the piezoelectric transducer module of the diode laser via a sound card in the computer. A visual Labview procedure is developed to realize a feedback system. In our experiment the frequency drift of the diode laser is reduced to 8 MHz within 25 min. The robust scheme can be adapted to realize the arbitrary frequency stabilization for many other kinds of lasers.
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.
文摘AIM:To investigate the effects of diode laser treatment on ocular biometric parameters in premature infants with retinopathy of prematurity(ROP).METHODS:Premature infants who received diode laser treatment for ROP(n=68)and premature infants with spontaneous regressed ROP without treatment(n=50)were performed longitudinal ocular biometric measurements including anterior chamber depth,lens thickness and axial length as follows:1 d prior to laser treatment,and 3,6,9,and 12 mo after the laser treatment.RESULTS:The mean birth weight,gestational age and initial examination time values were 936.53±302.07 g,26.66±2.42 wk,36.26±2.73 wk in the treatment group and 959.78±260.08 g,27.28±2.10 wk,36.56±2.54 wk in the control group.There was no statistically significant difference in these demographic characteristics of the groups.Anterior chamber depth,lens thickness and axial length demonstrated statistically significant linear increases during the study period in the two groups(P<0.001 for each).There were no statistically significant differences between the two groups in terms of anterior chamber depth after laser treatment.Measurements of the lens thickness at 9 th and 12 th months(9 th month 3.70±0.22 vs 3.60±0.21 mm,P=0.017;12 th month 3.81±0.21 vs 3.69±0.22 mm,P=0.002)and the axial length at 12 th month(19.35±0.79 vs 19.13±0.54 mm,P=0.031)after laser treatment were statistically higher in the treatment group.CONCLUSION:Diode laser retinal photocoagulation treatment in premature infants seems to increase the lens thickness and axial length.
文摘As a step toward realizing magnesium civilization,which needs a sustainable Mg production process,the reduction of MgO to Mg has been investigated.Direct diode laser(DDL)produces high power and continuous beam in tiny spots.The laser with energy density up to 83*10^(5) W/cm^(2) is focused on MgO/Si target inside the vacuum chamber,creating the high temperature zone,which stimulates the Mg production reaction.The vapor is collected on the copper plate;and then,analyzed chemically in terms of Mg production efficiency.The largest reduction and energy efficiencies in Ar atmosphere were 41%and 15.3 mg kJ^(−1),while in the vacuum,13.5%and 15.8 mg kJ^(−1) were attainable.The reactions of MgO and Si have been investigated.Calculations revealed that the MgO reduction with Si proceeds as heterogeneous reaction.The rate of reaction of Si with MgO is faster than the rate of MgO evaporation and Mg vapor deposition.
基金National Natural Science Foundation of China(Grant Nos.91644107,61575206,51904009,and 41905130)National Key Research and Development Program of China(Grant Nos.2017YFC0209401,2017YFC0209403,and 2017YFC0209902)the Outstanding Young Talents Program of Anhui University,China(Grant No.gxyq2019022).
文摘An NO2 photoacoustic sensor system with a high reflective mirror based on a low power blue diode laser is developed in this work. The excitation power is enhanced by increasing the number of reflections. Comparing with a traditional photoacoustic system, the pool constant is improved from 300.24(Pa·cm)/W to 1450.64(Pa·cm)/W, and the signal sensitivity of the photoacoustic sensor is increased from 0.016 μV/ppb to 0.2562 μV/ppb. The characteristics of temperature and humidity of the new photoacoustic sensor are also obtained, and the algorithm is adjusted to provide a quantitative response and drift of the resonance frequency. The results of this research provide a new method and concept for further developing the NO2 photoacoustic sensors.
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 the National Natural Science Foundation of China(Grant Nos.11335004,11722541,11675039,and 11747153)the Important National Science and Technology Specific Project,China(Grant No.2011ZX02403-001)
文摘Densities of Ar metastable states 1s5 and 1s3 are measured by using the tunable diode laser absorption spectroscopy(TDLAS) in Ar and Ar/O2 mixture dual-frequency capacitively coupled plasma(DF-CCP). We investigate the effects of high-frequency(HF, 60 MHz) power, low-frequency(LF, 2 MHz) power, and working pressure on the density of Ar metastable states for three different gas components(0%, 5%, and 10% oxygen mixed in argon). The dependence of Ar metastable state density on the oxygen content is also studied at different working pressures. It is found that densities of Ar metastable states in discharges with different gas components exhibit different behaviors as HF power increases. With the increase of HF power, the metastable density increases rapidly at the initial stage, and then tends to be saturated at a higher HF power. With a small fraction(5% or 10%) of oxygen added in argon plasma, a similar change of the Ar metastable density with HF power can be observed, but the metastable density is saturated at a higher HF power than in the pure argon discharge. In the DF-CCP, the metastable density is found to be higher than in a single frequency discharge, and has weak dependence on LF power. As working pressure increases, the metastable state density first increases and then decreases,and the pressure value, at which the density maximum occurs, decreases with oxygen content increasing. Besides, adding a small fraction of oxygen into argon plasma will significantly dwindle the metastable state density as a result of quenching loss by oxygen molecules.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91541119 and 91541203
文摘A compact optical setup for quantitative and spatially resolved measurement of atomic alkali concentration in combustion is demonstrated. Tunable diode laser absorption spectroscopy and laser-induced fluorescence are combined using a single continuous wave diode laser to measure the line-integration concentration and the relative distribution simultaneously, thereby obtaining the absolute concentration distribution along the laser beam. The results indicate the good performance of this method for one-dimensional quantitative measurement.
基金Project supported by the Major Program of the National Natural Science Foundation of China(Grant No.61790581)the Key Area Research and Development Program of Guangdong Province,China(Grant No.2020B0303020001).
文摘We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength.The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector.The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper.And the quantum well cascade laser with 100-μm-wide,2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature.The characteristic temperature T_(0) is estimated at above 60 K.
基金the Key Laboratory of Functional Crystals and Laser Technology,Chinese Academy of Sciences(Grant No.JTJG201109)the Guangdong Province&Chinese Academy of Sciences Comprehensive Strategic Cooperation Project(Grant No.2010A090100014)the 2009 Technology Research and Development Fund of Shenzhen,China(Grant No.O702011001)
文摘A 1550-nm linearly tunable continuous wave (CW) single-mode external cavity diode laser (ECDL) based on a singlecavity all-dielectric thin-film Fabry-Pérot filter (s-AFPF) is proposed and realized in this paper. Its internal optical components as well as their operation mechanisms are introduced first, and then its longitudinal mode output characteristic is theoretically analyzed. Afterwards, we set up the experimental platform for the output characteristic measurement of this tunable ECDL; under different experimental conditions, we execute accurate and real-time measurements for the output central wavelength, output optical power, output longitudinal mode distribution, and the line-width of the tunable ECDL in its tuning process. By summing up the optimal experimental condition from the measured data, we obtain the optimal tunable ECDL relevant parameters: the tunable ECDL has a linear mode-hop-free wavelength tuning region of 1547.203 nm-1552.426 nm, a stable output optical power in the range of 40 μW-50 μW, and a stable output longitudinal mode distribution of a single longitudinal mode with a line-width in the range of 100 MHz-150 MHz. This tunable ECDL can be used in environmental gas monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.
基金Supported by the China Academy of Space Technology Foundation under Grant No CAST-2015-5-10the National Hi-Tech Research and Development Programthe National Natural Science Foundation of China under Grant No 91436210
文摘We report a 42Ohm external cavity diode laser with an interference filter (IF) of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye reflector are used for selecting wavelength and light feedback, respectively. The measured laser linewidth is 24 kHz when the diode laser is free running. Using this narrow-linewidth IF blue diode laser, we realize a compact Rb optical frequency standard without a complicated PDH system. The preliminary stability of the Rb optical frequency standard is 2 × 10^-13 at I s and decreases to 1.9 ×10^-14 at 1000s. The narrow-linewidth characteristic makes the IF blue diode laser a well suited candidate for the compact Rb optical frequency standard.
基金supported by ZTE Industry-Academia-Research Cooperation Funds,the National Natural Science Foundation of China under Grant Nos.61871084 and 61601084the National Key Research and Development Program of China under Grant No.2016YFB0502003the State Key Laboratory of Advanced Optical Communication Systems and Networks,China
文摘We demonstrate an atmospheric transfer of microwave signal over a 120 m outdoor free-space link using a compact diode laser with a timing fluctuation suppression technique.Timing fluctuation and Allan Deviation are both measured to characterize the instability of transferred frequency incurred during the transfer process.By transferring a 100 MHz microwave signal within 4500 s,the total root-mean-square(RMS)timing fluctuation was measured to be about 6 ps,with a fractional frequency instability on the order of 1×10-12 at 1 s,and order of 7×10-15 at 1000 s.This portable atmospheric frequency transfer scheme with timing fluctuation suppression can be used to distribute an atomic clock-based frequency over a free-space link.
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Background:Laser photocoagulation restricted to ablation of the avascular retina has been the conventional but not a completely effective treatment strategy in the management of threshold retinopathy of prematurity(ROP).The purpose of this study was to compare the structural outcomes of additional posterior to ridge diode laser compared to conventional diode laser to avascular retina alone in threshold stage III ROP.Methods:This was a prospective,randomized study involving infants diagnosed with threshold stage III ROP in one or both the eyes.The infants were randomized into control and study groups.Infants under the control group underwent conventional laser to avascular retina alone while infants under the study group received additional two rows of laser posterior to the ridge in the vascular retina.The infants were followed up at 2 weeks,1 month and up to 6 months after the laser procedure.Results:During the study period of 1 year,42 eyes of 24 infants were recruited into this study with 21 eyes in each group.The mean birth weight was 1,310.48±400.92 g in the test group and 1,341.9±396.2 g in the control group.The mean post conceptional age at the time of intervention was 36.43±2.79 weeks in test group and 36.29±2.55 weeks in the control group.At 1-month post laser,19 eyes in the study group showed regression of neovascularization laser compared to 18 eyes in the control group.However at the end of 3 and 6 months post laser,both groups had showed similar rates regression of neovascularization(19 of 21 eyes in both groups).Five eyes in the study group and six in the control group required additional laser treatment.Two eyes in the study group and one eye in the control group developed post laser vitreous hemorrhage.Conclusions:Posterior to ridge laser treatment for severe stage 3 ROP did not show any additional benefit compared to conventional laser.
文摘Objective: This study aims to describe the experience with diode laser cyclophotocoagulation in the control of intraocular pressure and resolution of pain in patients with refractory glaucoma. Methods: Retrospective study. 64 eyes of 60 patients who underwent cyclophotocoagulation between January 2008 and March 2014. Evaluation of the pre- and post-operative intraocular pressure, the control of ocular pain, the number of anti-glaucoma drugs used in pre- and post-intervention, the rate of complications and the success rate. Results: There was an overall success rate of 81.3%, with 9 eyes needing a second intervention. There was a mean reduction of 52.6% of the preoperative mean intraocular pressure of 41.25 to 19.56 mmHg at 12 months observation (p < 0.001). There was also a statistically significant reduction in the number of anti-glaucoma drugs used from 3.19 to 2.01 per eye and the resolution of pain in 75% of patients. Conclusions: cyclophotocoagulation is an effective procedure, with an expected positive impact on quality of life of patients as a result from the decreased number of anti-glaucoma drugs, sustained intraocular pressure reduction and resolution of pain.