We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs)array,with a single-mode pulse power of 108 mW at 13 K.The device utilizes a Talbot cavity to achieve phase locking among five ridge l...We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs)array,with a single-mode pulse power of 108 mW at 13 K.The device utilizes a Talbot cavity to achieve phase locking among five ridge lasers with first-order buried distributed feedback(DFB)grating,resulting in nearly five times amplification of the single-mode power.Due to the optimum length of Talbot cavity depends on wavelength,the combination of Talbot cavity with the DFB grating leads to better power amplification than the combination with multimode Fabry-Perot(F-P)cavities.The Talbot cavity facet reflects light back to the ridge array direction and achieves self-imaging in the array,enabling phase-locked operation of ridges.We set the spacing between adjacent elements to be 220μm,much larger than the free-space wavelength,ensuring the operation of the fundamental supermode throughout the laser's dynamic range and obtaining a high-brightness far-field distribution.This scheme provides a new approach for enhancing the single-mode power of THz QCLs.展开更多
The single event effect of a silicon–germanium heterojunction bipolar transistor(SiGe HBT) was thoroughly investigated. By considering the worst bias condition, the sensitive area of the proposed device was scanned w...The single event effect of a silicon–germanium heterojunction bipolar transistor(SiGe HBT) was thoroughly investigated. By considering the worst bias condition, the sensitive area of the proposed device was scanned with a pulsed laser.With variation of the collector bias and pulsed laser incident energy, the single event transient of the SiGe HBT was studied.Moreover, the single event transient produced by laser irradiation at a wavelength of 532 nm was more pronounced than at a wavelength of 1064 nm. Finally, the impact of the equivalent linear energy transfer of the 1064 nm pulsed laser on the single event transient was qualitatively examined by performing technology computer-aided design simulations, and a good consistency between the experimental data and the simulated outcomes was attained.展开更多
The dense and accurate measurement of 3D texture is helpful in evaluating the pavement function.To form dense mandatory constraints and improve matching accuracy,the traditional binocular reconstruction technology was...The dense and accurate measurement of 3D texture is helpful in evaluating the pavement function.To form dense mandatory constraints and improve matching accuracy,the traditional binocular reconstruction technology was improved threefold.First,a single moving laser line was introduced to carry out global scanning constraints on the target,which would well overcome the difficulty of installing and recognizing excessive laser lines.Second,four kinds of improved algorithms,namely,disparity replacement,superposition synthesis,subregion segmentation,and subregion segmentation centroid enhancement,were established based on different constraint mechanism.Last,the improved binocular reconstruction test device was developed to realize the dual functions of 3D texture measurement and precision self-evaluation.Results show that compared with traditional algorithms,the introduction of a single laser line scanning constraint is helpful in improving the measurement’s accuracy.Among various improved algorithms,the improvement effect of the subregion segmentation centroid enhancement method is the best.It has a good effect on both overall measurement and single pointmeasurement,which can be considered to be used in pavement function evaluation.展开更多
Single event effects of 1-T structure programmable read-only memory(PROM) devices fabricated with a 130-nm complementary metal oxide semiconductorbased thin/thick gate oxide anti-fuse process were investigated using h...Single event effects of 1-T structure programmable read-only memory(PROM) devices fabricated with a 130-nm complementary metal oxide semiconductorbased thin/thick gate oxide anti-fuse process were investigated using heavy ions and a picosecond pulsed laser. The cross sections of a single event upset(SEU) for radiationhardened PROMs were measured using a linear energy transfer(LET) ranging from 9.2 to 95.6 MeV cm^2mg^(-1).The result indicated that the LET threshold for a dynamic bit upset was ~ 9 MeV cm^2mg^(-1), which was lower than the threshold of ~ 20 MeV cm^2mg^(-1) for an address counter upset owing to the additional triple modular redundancy structure present in the latch. In addition, a slight hard error was observed in the anti-fuse structure when employing209 Bi ions with extremely high LET values(~ 91.6 MeV cm^2mg^(-1)) and large ion fluence(~ 1×10~8 ions cm^(-2)). To identify the detailed sensitive position of a SEU in PROMs, a pulsed laser with a 5-μm beam spot was used to scan the entire surface of the device.This revealed that the upset occurred in the peripheral circuits of the internal power source and I/O pairs rather than in the internal latches and buffers. This was subsequently confirmed by a ^(181)Ta experiment. Based on the experimental data and a rectangular parallelepiped model of the sensitive volume, the space error rates for the used PROMs were calculated using the CRèME-96 prediction tool. The results showed that this type of PROM was suitable for specific space applications, even in the geosynchronous orbit.展开更多
In this paper, we investigate the single event transient (SET) occurring in partially depleted silicon-on-insulator (PDSOI) metal-oxide-semiconductor (MOS) devices irradiated by pulsed laser beams. Transient sig...In this paper, we investigate the single event transient (SET) occurring in partially depleted silicon-on-insulator (PDSOI) metal-oxide-semiconductor (MOS) devices irradiated by pulsed laser beams. Transient signal characteristics of a 0.18-p.m single MOS device, such as SET pulse width, pulse maximum, and collected charge, are measured and an- alyzed at wafer level. We analyze in detail the influences of supply voltage and pulse energy on the SET characteristics of the device under test (DUT). The dependences of SET characteristics on drain-induced barrier lowering (DIBL) and the parasitic bipolar junction transistor (PBJT) are also discussed. These results provide a guide for radiation-hardened deep sub-micrometer PDSOI technology for space electronics applications.展开更多
We present a stable linear-cavity single longitudinal mode (SLM) erbium-doped silica fiber laser. It consists of four fiber Bragg gratings (FBGs) directly written in a section of photosensitive erbium-doped fiber ...We present a stable linear-cavity single longitudinal mode (SLM) erbium-doped silica fiber laser. It consists of four fiber Bragg gratings (FBGs) directly written in a section of photosensitive erbium-doped fiber (EDF) to form an asymmetric three-cavity structure. The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio (OSNR) of about 60 dB is verified experimentally. Under laboratory conditions, the performance of a power fluctuation of less than 0.05 dB observed from the power meter for 6 h and a wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer (OSA) for about 1.5 h are demonstrated. The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure. The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.展开更多
We report a low noise continuous-wave (CW) single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate (PPLN). The SRO was ...We report a low noise continuous-wave (CW) single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate (PPLN). The SRO was pumped by a CW single-frequency Nd:YVO4 laser at 1.06μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±l.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit (SNL) at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.展开更多
A multi-hole vertical-cavity surface-emitting laser (VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of...A multi-hole vertical-cavity surface-emitting laser (VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of an oxidation- confined 850 nm VCSEL. The single-mode output power of 2.6 mW, threshold current of 0.6 mA, full width of half maximum lasing spectrum of less than 0.1 nm, side mode suppression ratio of 28.4 dB, and far-field divergence angle of about 10% are obtained. The effects of different hole depths on the optical characteristics are simulated and analysed, including far-field divergence, spectrum and lateral cavity mode. The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter hole spacing and the scattering loss at the bottom of the holes, particularly for higher order modes.展开更多
In this paper, TitaiJum dioxide (TiO2) rutile single crystal was irradiated by infrared femtosecond laser pulses with repetition rate of 250 kHz. For a P-polarized femtosecond laser, the periodic nanograting structu...In this paper, TitaiJum dioxide (TiO2) rutile single crystal was irradiated by infrared femtosecond laser pulses with repetition rate of 250 kHz. For a P-polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was formed . The periodicity is much less than the laser wavelength. The direction of nanograting alignment depends on the polarization laser beam. Micro-Raman spectra show that the intensity of Eg Raman vibrating mode of rutile phase increases and that of Alg Raman vibrating mode decreases apparently within the ablation crater. With the increase of irradiation time and laser average power, the Raman vibrating modes of anatase phase emerged. Rutile phase of TiO2 single crystal is partly transformed into anatase phase.展开更多
A study on the single event transient (SET) induced by a pulsed laser in a silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) is presented in this work. The impacts of laser energy and collector lo...A study on the single event transient (SET) induced by a pulsed laser in a silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) is presented in this work. The impacts of laser energy and collector load resistance on the SET are investigated in detail. The waveform, amplitude, and width of the SET pulse as well as collected charge are used to characterize the SET response. The experimental results are discussed in detail and it is demonstrated that the laser energy and load resistance significantly affect the SET in the SiGe HBT. Furthermore, the underlying physical mechanisms are analyzed and investigated, and a near-ideal exponential model is proposed for the first time to describe the discharge of laser-induced electrons via collector resistance to collector supply when both base-collector and collector-substrate junctions are reverse biased or weakly forward biased. Besides, it is found that an additional multi-path discharge would play an important role in the SET once the base-collector and collector-substrate junctions get strongly forward biased due to a strong transient step charge by the laser pulse.展开更多
Optimization of the high power single-lateral-mode double-trench ridge waveguide semiconductor laser based on InGaAsP/InP quantum-well heterostructures with a separate confinement layer is reported. Two different wave...Optimization of the high power single-lateral-mode double-trench ridge waveguide semiconductor laser based on InGaAsP/InP quantum-well heterostructures with a separate confinement layer is reported. Two different waveguide structures of Fabry-Perot lasers emitting at a wavelength of 1.55 μm are fabricated. The influence of an effective lateral refractive index step on the maximum output power is investigated. A cw single mode output power of 165mW is obtained for a 1-mm-long uncoated laser.展开更多
In this paper the single-event responses of the silicon germanium heterojunction bipolar transistors(SiGe HBTs) are investigated by TCAD simulations and laser microbeam experiment. A three-dimensional(3D) simulation m...In this paper the single-event responses of the silicon germanium heterojunction bipolar transistors(SiGe HBTs) are investigated by TCAD simulations and laser microbeam experiment. A three-dimensional(3D) simulation model is established, the single event effect(SEE) simulation is further carried out on the basis of Si Ge HBT devices, and then, together with the laser microbeam test, the charge collection behaviors are analyzed, including the single event transient(SET) induced transient terminal currents, and the sensitive area of SEE charge collection. The simulations and experimental results are discussed in detail and it is demonstrated that the nature of the current transient is controlled by the behaviors of the collector–substrate(C/S) junction and charge collection by sensitive electrodes, thereby giving out the sensitive area and electrode of SiGe HBT in SEE.展开更多
By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm i...By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.展开更多
<正> A single-mode laser with coupling between additive and multiplicative noise terms is investigated when themultiplicative noise and the coupling between two noise terms are colored fluctuations with finite c...<正> A single-mode laser with coupling between additive and multiplicative noise terms is investigated when themultiplicative noise and the coupling between two noise terms are colored fluctuations with finite correlation times T_1 andT_2.Combining the unified colored noise approximation(UCNA)and the functional analysis,the stationary probabilitydistribution(SPD)and the variance of the laser intensity is derived.It is found that the colored nature of multiplicativenoise and the coupling strength between two noise terms can affect both the structure and the height of the SPD,whilethe colored nature of the coupling between two noise terms can only affect the height of the SPD.The multiplicative noisecan enhance the intensity fluctuations while the additive noise can reduce the fluctuations in a laser system.Numericalsimulations are presented and consistent to the analytical results.展开更多
The influence of the single photon laser altimeter range-gate width on the detection probability and ranging accuracy is discussed and analyzed,according to the LiDAR equation,single photon detection equation and the ...The influence of the single photon laser altimeter range-gate width on the detection probability and ranging accuracy is discussed and analyzed,according to the LiDAR equation,single photon detection equation and the Monte Carlo method to simulate the experiment.The simulated results show that the probability of detection is not affected by the range gate,while the probability of false alarm is relative to the gate width.When the gate width is 100 ns,the ranging accuracy can accord with the requirements of satellite laser altimeter.But when the range gate width exceeds 400 ns,ranging accuracy will decline sharply.The noise ratio will be more as long as the range gate to get larger,so the refined filtering algorithm during the data processing is important to extract the useful photons effectively.In order to ensure repeated observation of the same point for 25 times,we deduce the quantitative relation between the footprint size,footprint,and frequency repetition according to the parameters of ICESat-2.The related conclusions can provide some references for the design and the development of the domestic single photon laser altimetry satellite.展开更多
We present a single-longitudinal-mode continuous-wave Ho^3+:YVO4 laser at 2.05 μm pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power a...We present a single-longitudinal-mode continuous-wave Ho^3+:YVO4 laser at 2.05 μm pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power achieved in the single longitudinal mode at 2052.5 nm is 282 mW at a slope efficiency of 6.9%, corresponding to an optical conversion efficiency of 3.0%. These features demonstrate that this single-longitudinal-mode Ho:YVO4 laser is suitable for use as a seed laser in some Lidar systems(e.g., coherent Lidar or differential absorption Lidar). To the best of our knowledge, this is the first report on such a single-longitudinal-mode Ho:YVO4 laser at 2.05 μm.展开更多
In this paper, we investigate the laser irradiation of ZnO single crystals and its influence on photoluminescence. Our study shows that the photoluminescence of ZnO single crystals strongly depends on surface morpholo...In this paper, we investigate the laser irradiation of ZnO single crystals and its influence on photoluminescence. Our study shows that the photoluminescence of ZnO single crystals strongly depends on surface morphologies. The ultraviolet emissions of laser treated-ZnO under 200 mJ/cm^2 become stronger, whereas for those deteriorated by irradiation above 200 mJ/cm^2, the green emissions centred at 2.53 eV are significantly enhanced with a red-shift to 2.19 eV, probably due to the changes in the charge states of the defects. Enhanced yellow-green emissions are well resolved into four peaks at around 1.98, 2.19, 2.36, and 2.53 eV due to a shallow irradiation depth. Possible origins are proposed and discussed.展开更多
Brillouin light scattering technique can be successfully used to determine the whole set of elastic and piezoelectric constants of a ZnO single crystal irradiated by different laser energy densities, into a micron ran...Brillouin light scattering technique can be successfully used to determine the whole set of elastic and piezoelectric constants of a ZnO single crystal irradiated by different laser energy densities, into a micron range (radiation layer thickness). It is found that the scattering intensity, the linewidth and the Brillouin scattering shift of acoustic phonons are all strongly dependent on laser energy density. Based on the sound propagation equations and these results, the directional dependences of the compressional and shear moduli of the irradiated ZnO sample in the (001) plane are investigated. It is found that under an appropriate laser condition, 248 nm KrF excimer laser irradiation can significantly improve the surface quality and increase the elastic properties of ZnO single crystal. This procedure has potential applications in the fabrication of ZnO-based surface acoustic wave and optic-electronic devices.展开更多
The 850-nm oxide-confined vertical-cavity surface-emitting lasers with petal-shape holey structures are presented. An area-weighted average refractive index model is given to analyse their effective index profiles, an...The 850-nm oxide-confined vertical-cavity surface-emitting lasers with petal-shape holey structures are presented. An area-weighted average refractive index model is given to analyse their effective index profiles, and the graded index distribution in the holey region is demonstrated. The index step between the optical aperture and the holey region is obtained which is related merely to the etching depth. Four types of holey vertical-cavity surface-emitting lasers with different parameters are fabricated as well as the conventional oxide-confined vertical-cavity surface-emitting laser. Compared with the conventional oxide-confined vertical-cavity surface-emitting laser without etched holes, the holey vertical-cavity surface-emitting laser possesses an improved beam quality due to its graded index distribution, but has a lower output power, higher threshold current and lower slope efficiency. With the hole number increased, the holey vertical-cavity surface-emitting laser can realize the single-mode operation throughout the entire current range, and reduces the beam divergence further. The loss mechanism is used to explain the single-mode characteristic, and the reduced beam divergence is attributed to the shallow etching. High coupling efficiency of 86% to a multi-mode fibre is achieved for the single-mode device in the experiment.展开更多
基金funded by National Natural Science Foundation of China,grant numbers 62335006,62274014,62235016,61734006,61835011,61991430was funded by Key Program of the Chinese Academy of Sciences,grant numbers XDB43000000,QYZDJSSWJSC027,and Beijing Municipal Science&Technology Commission,grant number Z221100002722018.
文摘We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs)array,with a single-mode pulse power of 108 mW at 13 K.The device utilizes a Talbot cavity to achieve phase locking among five ridge lasers with first-order buried distributed feedback(DFB)grating,resulting in nearly five times amplification of the single-mode power.Due to the optimum length of Talbot cavity depends on wavelength,the combination of Talbot cavity with the DFB grating leads to better power amplification than the combination with multimode Fabry-Perot(F-P)cavities.The Talbot cavity facet reflects light back to the ridge array direction and achieves self-imaging in the array,enabling phase-locked operation of ridges.We set the spacing between adjacent elements to be 220μm,much larger than the free-space wavelength,ensuring the operation of the fundamental supermode throughout the laser's dynamic range and obtaining a high-brightness far-field distribution.This scheme provides a new approach for enhancing the single-mode power of THz QCLs.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61574171, 61704127, 11875229,51872251, and 12027813)。
文摘The single event effect of a silicon–germanium heterojunction bipolar transistor(SiGe HBT) was thoroughly investigated. By considering the worst bias condition, the sensitive area of the proposed device was scanned with a pulsed laser.With variation of the collector bias and pulsed laser incident energy, the single event transient of the SiGe HBT was studied.Moreover, the single event transient produced by laser irradiation at a wavelength of 532 nm was more pronounced than at a wavelength of 1064 nm. Finally, the impact of the equivalent linear energy transfer of the 1064 nm pulsed laser on the single event transient was qualitatively examined by performing technology computer-aided design simulations, and a good consistency between the experimental data and the simulated outcomes was attained.
基金supported by National Natural Science Foundation of China (52178422)Doctoral Research Foundation of Hubei University of Arts and Science (2059047)National College Students’Innovation and Entrepreneurship Training Program (202210519021).
文摘The dense and accurate measurement of 3D texture is helpful in evaluating the pavement function.To form dense mandatory constraints and improve matching accuracy,the traditional binocular reconstruction technology was improved threefold.First,a single moving laser line was introduced to carry out global scanning constraints on the target,which would well overcome the difficulty of installing and recognizing excessive laser lines.Second,four kinds of improved algorithms,namely,disparity replacement,superposition synthesis,subregion segmentation,and subregion segmentation centroid enhancement,were established based on different constraint mechanism.Last,the improved binocular reconstruction test device was developed to realize the dual functions of 3D texture measurement and precision self-evaluation.Results show that compared with traditional algorithms,the introduction of a single laser line scanning constraint is helpful in improving the measurement’s accuracy.Among various improved algorithms,the improvement effect of the subregion segmentation centroid enhancement method is the best.It has a good effect on both overall measurement and single pointmeasurement,which can be considered to be used in pavement function evaluation.
基金supported by the National Natural Science Foundation of China(Nos.11690041,11805244,and 11675233)the Opening Project of Science and Technology on Reliability Physics and Application Technology of the Electronic Component Laboratory(No.ZHD 201604)
文摘Single event effects of 1-T structure programmable read-only memory(PROM) devices fabricated with a 130-nm complementary metal oxide semiconductorbased thin/thick gate oxide anti-fuse process were investigated using heavy ions and a picosecond pulsed laser. The cross sections of a single event upset(SEU) for radiationhardened PROMs were measured using a linear energy transfer(LET) ranging from 9.2 to 95.6 MeV cm^2mg^(-1).The result indicated that the LET threshold for a dynamic bit upset was ~ 9 MeV cm^2mg^(-1), which was lower than the threshold of ~ 20 MeV cm^2mg^(-1) for an address counter upset owing to the additional triple modular redundancy structure present in the latch. In addition, a slight hard error was observed in the anti-fuse structure when employing209 Bi ions with extremely high LET values(~ 91.6 MeV cm^2mg^(-1)) and large ion fluence(~ 1×10~8 ions cm^(-2)). To identify the detailed sensitive position of a SEU in PROMs, a pulsed laser with a 5-μm beam spot was used to scan the entire surface of the device.This revealed that the upset occurred in the peripheral circuits of the internal power source and I/O pairs rather than in the internal latches and buffers. This was subsequently confirmed by a ^(181)Ta experiment. Based on the experimental data and a rectangular parallelepiped model of the sensitive volume, the space error rates for the used PROMs were calculated using the CRèME-96 prediction tool. The results showed that this type of PROM was suitable for specific space applications, even in the geosynchronous orbit.
文摘In this paper, we investigate the single event transient (SET) occurring in partially depleted silicon-on-insulator (PDSOI) metal-oxide-semiconductor (MOS) devices irradiated by pulsed laser beams. Transient signal characteristics of a 0.18-p.m single MOS device, such as SET pulse width, pulse maximum, and collected charge, are measured and an- alyzed at wafer level. We analyze in detail the influences of supply voltage and pulse energy on the SET characteristics of the device under test (DUT). The dependences of SET characteristics on drain-induced barrier lowering (DIBL) and the parasitic bipolar junction transistor (PBJT) are also discussed. These results provide a guide for radiation-hardened deep sub-micrometer PDSOI technology for space electronics applications.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61077069 and 61107094)the Innovation Foundation for Excellent Doctoral Candidates of Beijing Jiaotong University, China (Grant No. 2011YJS202)
文摘We present a stable linear-cavity single longitudinal mode (SLM) erbium-doped silica fiber laser. It consists of four fiber Bragg gratings (FBGs) directly written in a section of photosensitive erbium-doped fiber (EDF) to form an asymmetric three-cavity structure. The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio (OSNR) of about 60 dB is verified experimentally. Under laboratory conditions, the performance of a power fluctuation of less than 0.05 dB observed from the power meter for 6 h and a wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer (OSA) for about 1.5 h are demonstrated. The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure. The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.
基金supported by the National Natural Science Foundation of China(Grant No.60878003)the Science Fund for Excellent Research Team of the National Natural Science Foundation of China(Grant No.60821004)the National Basic Research Program of China(Grant No.2010CB923101)
文摘We report a low noise continuous-wave (CW) single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate (PPLN). The SRO was pumped by a CW single-frequency Nd:YVO4 laser at 1.06μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±l.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit (SNL) at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2008AA03Z402)the National Natural Science Foundation of China (Grant No. 61076044)the Natural Science Foundation of Beijing,China(Grant Nos. 4092007 and 4102003)
文摘A multi-hole vertical-cavity surface-emitting laser (VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of an oxidation- confined 850 nm VCSEL. The single-mode output power of 2.6 mW, threshold current of 0.6 mA, full width of half maximum lasing spectrum of less than 0.1 nm, side mode suppression ratio of 28.4 dB, and far-field divergence angle of about 10% are obtained. The effects of different hole depths on the optical characteristics are simulated and analysed, including far-field divergence, spectrum and lateral cavity mode. The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter hole spacing and the scattering loss at the bottom of the holes, particularly for higher order modes.
基金Project supported by Shanghai Leading Academic Discipline Project, China (Grant No T0104), the Shanghai Nano-technology Promotion Center and Science & Technology of Shanghai Municipality, China (Grant No 0652nm005), Science Foundation of Shanghai Municipal Commission Education and Science and Technology Commission of Shanghai Municipal, China (Grant No 06PJ14042).
文摘In this paper, TitaiJum dioxide (TiO2) rutile single crystal was irradiated by infrared femtosecond laser pulses with repetition rate of 250 kHz. For a P-polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was formed . The periodicity is much less than the laser wavelength. The direction of nanograting alignment depends on the polarization laser beam. Micro-Raman spectra show that the intensity of Eg Raman vibrating mode of rutile phase increases and that of Alg Raman vibrating mode decreases apparently within the ablation crater. With the increase of irradiation time and laser average power, the Raman vibrating modes of anatase phase emerged. Rutile phase of TiO2 single crystal is partly transformed into anatase phase.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60976013)
文摘A study on the single event transient (SET) induced by a pulsed laser in a silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) is presented in this work. The impacts of laser energy and collector load resistance on the SET are investigated in detail. The waveform, amplitude, and width of the SET pulse as well as collected charge are used to characterize the SET response. The experimental results are discussed in detail and it is demonstrated that the laser energy and load resistance significantly affect the SET in the SiGe HBT. Furthermore, the underlying physical mechanisms are analyzed and investigated, and a near-ideal exponential model is proposed for the first time to describe the discharge of laser-induced electrons via collector resistance to collector supply when both base-collector and collector-substrate junctions are reverse biased or weakly forward biased. Besides, it is found that an additional multi-path discharge would play an important role in the SET once the base-collector and collector-substrate junctions get strongly forward biased due to a strong transient step charge by the laser pulse.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61274046 and 61474111the National Basic Research Program of China under Grant No 2013AA014202
文摘Optimization of the high power single-lateral-mode double-trench ridge waveguide semiconductor laser based on InGaAsP/InP quantum-well heterostructures with a separate confinement layer is reported. Two different waveguide structures of Fabry-Perot lasers emitting at a wavelength of 1.55 μm are fabricated. The influence of an effective lateral refractive index step on the maximum output power is investigated. A cw single mode output power of 165mW is obtained for a 1-mm-long uncoated laser.
基金supported by the National Natural Science Foundation of China(Grant No.61274106)
文摘In this paper the single-event responses of the silicon germanium heterojunction bipolar transistors(SiGe HBTs) are investigated by TCAD simulations and laser microbeam experiment. A three-dimensional(3D) simulation model is established, the single event effect(SEE) simulation is further carried out on the basis of Si Ge HBT devices, and then, together with the laser microbeam test, the charge collection behaviors are analyzed, including the single event transient(SET) induced transient terminal currents, and the sensitive area of SEE charge collection. The simulations and experimental results are discussed in detail and it is demonstrated that the nature of the current transient is controlled by the behaviors of the collector–substrate(C/S) junction and charge collection by sensitive electrodes, thereby giving out the sensitive area and electrode of SiGe HBT in SEE.
基金Supported by the International Cooperation Projects of Ministry of Science and Technology under Grant No 2012DFB10120the National Natural Science Foundation of China under Grant No 61177059
文摘By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.
基金The project supported by National Natural Science Foundation of China under Grant No. 10547130 and Natural Science Foundation of Jiangsu Province of China under Grant No. BK2001138
文摘<正> A single-mode laser with coupling between additive and multiplicative noise terms is investigated when themultiplicative noise and the coupling between two noise terms are colored fluctuations with finite correlation times T_1 andT_2.Combining the unified colored noise approximation(UCNA)and the functional analysis,the stationary probabilitydistribution(SPD)and the variance of the laser intensity is derived.It is found that the colored nature of multiplicativenoise and the coupling strength between two noise terms can affect both the structure and the height of the SPD,whilethe colored nature of the coupling between two noise terms can only affect the height of the SPD.The multiplicative noisecan enhance the intensity fluctuations while the additive noise can reduce the fluctuations in a laser system.Numericalsimulations are presented and consistent to the analytical results.
基金National Natural Science Foundation of China(No.41871382)Open Foundation of the Key Laboratory of Space Active Opto-electronics Technologyand Chinese Academy of Sciences(No.2018-ZDKF-1)。
文摘The influence of the single photon laser altimeter range-gate width on the detection probability and ranging accuracy is discussed and analyzed,according to the LiDAR equation,single photon detection equation and the Monte Carlo method to simulate the experiment.The simulated results show that the probability of detection is not affected by the range gate,while the probability of false alarm is relative to the gate width.When the gate width is 100 ns,the ranging accuracy can accord with the requirements of satellite laser altimeter.But when the range gate width exceeds 400 ns,ranging accuracy will decline sharply.The noise ratio will be more as long as the range gate to get larger,so the refined filtering algorithm during the data processing is important to extract the useful photons effectively.In order to ensure repeated observation of the same point for 25 times,we deduce the quantitative relation between the footprint size,footprint,and frequency repetition according to the parameters of ICESat-2.The related conclusions can provide some references for the design and the development of the domestic single photon laser altimetry satellite.
基金supported by the National Natural Science Foundation of China(Grant Nos.61308009 and 61405047)the China Postdoctoral Science Foundation(Grant Nos.2016T90287 and 2015M570290)+1 种基金the Fundamental Research Funds for the Central Universities of China(Grant No.HIT.NSRIF.2015042)the Postdoctoral Science Foundation of Heilongjiang Province,China(Grant No.LBH-Z14085)
文摘We present a single-longitudinal-mode continuous-wave Ho^3+:YVO4 laser at 2.05 μm pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power achieved in the single longitudinal mode at 2052.5 nm is 282 mW at a slope efficiency of 6.9%, corresponding to an optical conversion efficiency of 3.0%. These features demonstrate that this single-longitudinal-mode Ho:YVO4 laser is suitable for use as a seed laser in some Lidar systems(e.g., coherent Lidar or differential absorption Lidar). To the best of our knowledge, this is the first report on such a single-longitudinal-mode Ho:YVO4 laser at 2.05 μm.
基金Project supported by the National Natural Science Foundation of China(Grant No.10974009)
文摘In this paper, we investigate the laser irradiation of ZnO single crystals and its influence on photoluminescence. Our study shows that the photoluminescence of ZnO single crystals strongly depends on surface morphologies. The ultraviolet emissions of laser treated-ZnO under 200 mJ/cm^2 become stronger, whereas for those deteriorated by irradiation above 200 mJ/cm^2, the green emissions centred at 2.53 eV are significantly enhanced with a red-shift to 2.19 eV, probably due to the changes in the charge states of the defects. Enhanced yellow-green emissions are well resolved into four peaks at around 1.98, 2.19, 2.36, and 2.53 eV due to a shallow irradiation depth. Possible origins are proposed and discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10974009)
文摘Brillouin light scattering technique can be successfully used to determine the whole set of elastic and piezoelectric constants of a ZnO single crystal irradiated by different laser energy densities, into a micron range (radiation layer thickness). It is found that the scattering intensity, the linewidth and the Brillouin scattering shift of acoustic phonons are all strongly dependent on laser energy density. Based on the sound propagation equations and these results, the directional dependences of the compressional and shear moduli of the irradiated ZnO sample in the (001) plane are investigated. It is found that under an appropriate laser condition, 248 nm KrF excimer laser irradiation can significantly improve the surface quality and increase the elastic properties of ZnO single crystal. This procedure has potential applications in the fabrication of ZnO-based surface acoustic wave and optic-electronic devices.
基金supported by the National Key Basic Research Special Foundation of China (Grant No. 2011CB922000)the National Natural Science Foundation of China (Grant Nos. 61025025 and 60838003)the National High Technology Research and Development Program of China (Grant Nos. 2007AA03Z410 and 2007AA03Z408)
文摘The 850-nm oxide-confined vertical-cavity surface-emitting lasers with petal-shape holey structures are presented. An area-weighted average refractive index model is given to analyse their effective index profiles, and the graded index distribution in the holey region is demonstrated. The index step between the optical aperture and the holey region is obtained which is related merely to the etching depth. Four types of holey vertical-cavity surface-emitting lasers with different parameters are fabricated as well as the conventional oxide-confined vertical-cavity surface-emitting laser. Compared with the conventional oxide-confined vertical-cavity surface-emitting laser without etched holes, the holey vertical-cavity surface-emitting laser possesses an improved beam quality due to its graded index distribution, but has a lower output power, higher threshold current and lower slope efficiency. With the hole number increased, the holey vertical-cavity surface-emitting laser can realize the single-mode operation throughout the entire current range, and reduces the beam divergence further. The loss mechanism is used to explain the single-mode characteristic, and the reduced beam divergence is attributed to the shallow etching. High coupling efficiency of 86% to a multi-mode fibre is achieved for the single-mode device in the experiment.