High power and high-slope efficiency 650nm band real-refractive-index ridge w aveguide AlGaInP laser diodes with compressive strained MQW active layer are for med by pure Ar ion beam etching process.Symmetric laser me...High power and high-slope efficiency 650nm band real-refractive-index ridge w aveguide AlGaInP laser diodes with compressive strained MQW active layer are for med by pure Ar ion beam etching process.Symmetric laser mesas with high perpendi cularity,which are impossible to obtain by traditional wet etching method due to the use of a 15°-misoriented substrate,are obtained by this dry etching metho d.Laser diodes with 4μm wide,600μm long and 10%/90% coat are fabricated.Th e typical threshold current of these devices is 46mA at room temperature,and a s table fundamental-mode operation over 40mW is obtained.Very high slope efficien cy of 1.4W/A at 10mW and 1.1W/A at 40mW are realized.展开更多
With high hardness, high thermal and chemical stability and excellent optical performance, hard materials exhibit great potential applications in various fields, especially in harsh conditions. Femtosecond laser ablat...With high hardness, high thermal and chemical stability and excellent optical performance, hard materials exhibit great potential applications in various fields, especially in harsh conditions. Femtosecond laser ablation has the capability to fabricate three-dimensional micro/nanostructures in hard materials. However, the low efficiency, low precision and high surface roughness are the main stumbling blocks for femtosecond laser processing of hard materials. So far, etching- assisted femtosecond laser modification has demonstrated to be the efficient strategy to solve the above problems when processing hard materials, including wet etching and dry etching. In this review, femtosecond laser modification that would influence the etching selectivity is introduced. The fundamental and recent applications of the two kinds of etching assisted femtosecond laser modification technologies are summarized. In addition, the challenges and application prospects of these technologies are discussed.展开更多
Although femtosecond laser microfabrication is one of the most promising three-dimensional（3D） fabrication techniques, it could suffer from low fabrication efficiency for structures with high 3D complexities. By usi...Although femtosecond laser microfabrication is one of the most promising three-dimensional（3D） fabrication techniques, it could suffer from low fabrication efficiency for structures with high 3D complexities. By using etching as a main assistant technique, the processing can be speeded up and an improved structure surface quality can be provided. However,the assistance of a single technique cannot satisfy the increasing demands of fabrication and integration of highly functional 3D microstructures. Therefore, a multi-technique-based 3D microfabrication method is required. In this paper, we briefly review the recent development on etching-assisted femtosecond laser microfabrication（EAFLM）. Various processing approaches have been proposed to further strengthen the flexibilities of the EAFLM. With the use of the multi-technique-based microfabrication method, 3D microstructure arrays can be rapidly defined on planar or curved surfaces with high structure qualities.展开更多
Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular struct...Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared（IR） spectrometer, respectively. The laser induced damage thresholds（LIDTs） of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.展开更多
We demonstrate a method of fabricating through micro-holes and micro-hole arrays in silicon using femtosecond laser irradiation and selective chemical etching. The micro-hole formation mechanism is identified as the c...We demonstrate a method of fabricating through micro-holes and micro-hole arrays in silicon using femtosecond laser irradiation and selective chemical etching. The micro-hole formation mechanism is identified as the chemical reaction of the femtosecond laser-induced structure change zone and hydrofluoric acid solution. The morphologies of the through micro-holes and micro-hole arrays are characterized by using scanning electronic microscopy, The effects of the pulse number on the depth and diameter of the holes are investigated. Honeycomb arrays of through micro-holes fabricated at different laser powers and pulse numbers are demonstrated.展开更多
An effective method based on laser etching and driving layer strategy was proposed to prepare patterned Ag nanoparticles(Ag NPs)on fluorine-doped tin oxide(FTO)/glass substrate and thus to enhance the photoelectric pr...An effective method based on laser etching and driving layer strategy was proposed to prepare patterned Ag nanoparticles(Ag NPs)on fluorine-doped tin oxide(FTO)/glass substrate and thus to enhance the photoelectric properties.This method successively included depositing an aluminum-doped zinc oxide(AZO)driving layer,laser etching,depositing an Ag layer,furnace annealing and laser removal.Different AZO and Ag layer thicknesses were adopted,and the surface morphology,crystal structure and photoelectric properties were investigated.An Ag NPs/FTO/glass sample without an AZO driving layer was prepared for comparison.It was found that furnace annealing of the Ag layer combined with the AZO driving layer,rather than that without the AZO driving layer,was more conducive to generating patterned Ag NPs.Using a 20-nmthick AZO layer and a 150-nm-thick Ag layer led to the formation of uniformly distributed Ag NPs being aligned along the laser-etched grooves to form a pattern.The as-obtained sample had the best comprehensive photoelectric property with an average transmittance of 79.95%,a sheet resistance of 7.11Ω/sq and the highest figure of merit of 1.50×10^(-2)Ω^(-1),confirming the feasibility of the proposed method and providing enlightenment for related researches of transparent conductive oxide-based films.展开更多
In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was reported.To improve just-for-once successive rate of specimen preparation and ge...In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was reported.To improve just-for-once successive rate of specimen preparation and get good characterization results,an improving specimen preparation method of freezing etching was developed.Size,distribution and morphology of NANDS were directly visualized.Some information of particle dispersion feature and particle density can also be obtained.Reproductivity of the FETEM characterization is excellent.Comparing with laser scattering method,which is liable to give positive error especially for small size particle anchoring disperser,FETEM characterization can give more accurate measurement of particle size.Moreover,FETEM can give dispersion feature of nanoparticle in non-aqueous medium.展开更多
Gallium nitride(GaN)/porous silicon(PSi)film was prepared using a pulsed laser deposition method and 1064 nm Nd:YAG laser for optoelectronic applications and a series of Psi substrates were fabricated using a photoele...Gallium nitride(GaN)/porous silicon(PSi)film was prepared using a pulsed laser deposition method and 1064 nm Nd:YAG laser for optoelectronic applications and a series of Psi substrates were fabricated using a photoelectrochemical etching method assisted by laser at different etching times for 2.5–15 min at 2.5 min intervals.X-ray diffraction,room-temperature photoluminescence,atomic force microscopy and field emission scanning electron microscopy images,and electrical characteristics in the prepared GaN on the Psi film were investigated.The optimum Psi substrate was obtained under the following conditions:10 min,10 mA/cm^(2),and 24%hydrofluoric acid.The substrate exhibited two highly cubic crystalline structures at(200)and(400)orientations and yellow visible band photoluminescence,and homogeneous pores formed over the entire surface.The pores had steep oval shapes and were accompanied by small dark pores that appeared topographically and morphologically.The GaN/Psi film fabricated through PLD exhibited a high and hexagonal crystallographic texture in the(002)plane.Spectroscopic properties results revealed that the photoluminescence emission of the deposited nano-GaN films was in the ultraviolet band(374 nm)related to GaN material and in the near-infrared band(730 nm)related to the Psi substrate.The topographical and morphological results of the GaN films confirmed that the deposited film contained spherical grains with an average diameter of 51.8 nm and surface roughness of 4.8 nm.The GaN/Psi surface showed a cauliflower-like morphology,and the built-in voltage decreased from 3.4 to 2.7 eV after deposition.The fabricated GaN/Psi film exhibited good electrical characteristics.展开更多
Laser etching and laser chemical vapor deposition(LCVD)techniques were proposed for the rapid preparation of high-purity,strongly bonded SiC porous micro-nano-coatings on quartz substrates.The laser serves as an exter...Laser etching and laser chemical vapor deposition(LCVD)techniques were proposed for the rapid preparation of high-purity,strongly bonded SiC porous micro-nano-coatings on quartz substrates.The laser serves as an external driving force for the vertical growth of SiC whiskers,facilitating the formation of a porous nanostructure that resembles coral models found in the macroscopic biological world.The porous nanostructures are beneficial for reducing thermal expansion mismatch and relieving residual stress.It is capable of eliminating the cracks on the surface of SiC coatings as well as enhancing the bonding of SiC coatings with quartz substrates to avoid coating detachment.展开更多
Bending optofluidic waveguides are essential for developing high-performance fluid-based photonic circuits and systems.The combination of femtosecond(fs)-laser-assisted etching of high-precision microchannels and vacu...Bending optofluidic waveguides are essential for developing high-performance fluid-based photonic circuits and systems.The combination of femtosecond(fs)-laser-assisted etching of high-precision microchannels and vacuum-assisted liquid-core filling allows the controllable fabrication of low-loss optofluidic waveguides in fused silica.展开更多
Revealing grains and very fine dendrites in a solidified weld metal of aluminum–magnesium–silicon alloys is difficult and thus,there is no evidence to validate the micro-and meso-scale physical models for hot cracks...Revealing grains and very fine dendrites in a solidified weld metal of aluminum–magnesium–silicon alloys is difficult and thus,there is no evidence to validate the micro-and meso-scale physical models for hot cracks. In this research, the effect of preheating on the microstructure and hot crack creation in the pulsed laser welding of AA 6061 was investigated by an optical microscope and field emission electron microscopy. Etching was carried out in the gas phase using fresh Keller’s reagent for 600 s. The results showed that the grain size of the weld metal was proportional to the grain size of the base metal and was independent of the preheating temperature. Hot cracks passed the grain boundaries of the weld and the base metal. Lower solidification rates in the preheated samples led to coarser arm spacing;therefore, a lower cooling rate. Despite the results predicted by the micro and meso-scale models, lower cooling rates resulted in increased hot cracks. The cracks could grow in the weld metal after solidification;therefore, hot cracks were larger than predicted by the hot crack prediction models.展开更多
The effect of mesa size on th e thermal characteristics of etched mesa vertical-cavity surface-emitting lase rs(VCSELs) is studied. The numerical results show that the mesa size of the top mirror strongly influences t...The effect of mesa size on th e thermal characteristics of etched mesa vertical-cavity surface-emitting lase rs(VCSELs) is studied. The numerical results show that the mesa size of the top mirror strongly influences the temperature distribution inside the etched mesa V CSEL. Under a certain driving voltage, with decreasing mesa size, the location o f the maximal temperature moves towards the p-contact metal, the temperature in the core region of the active layer rises greatly, and the thermal characterist ics of the etched mesa VCSELs will deteriorate.展开更多
文摘High power and high-slope efficiency 650nm band real-refractive-index ridge w aveguide AlGaInP laser diodes with compressive strained MQW active layer are for med by pure Ar ion beam etching process.Symmetric laser mesas with high perpendi cularity,which are impossible to obtain by traditional wet etching method due to the use of a 15°-misoriented substrate,are obtained by this dry etching metho d.Laser diodes with 4μm wide,600μm long and 10%/90% coat are fabricated.Th e typical threshold current of these devices is 46mA at room temperature,and a s table fundamental-mode operation over 40mW is obtained.Very high slope efficien cy of 1.4W/A at 10mW and 1.1W/A at 40mW are realized.
基金This work was supported by the National Key Research and Development Program of China and National Natural Science Foundation of China (NSFC) under Grants 2017YFB1104300,61590930,61825502,61805098 and 61960206003.
文摘With high hardness, high thermal and chemical stability and excellent optical performance, hard materials exhibit great potential applications in various fields, especially in harsh conditions. Femtosecond laser ablation has the capability to fabricate three-dimensional micro/nanostructures in hard materials. However, the low efficiency, low precision and high surface roughness are the main stumbling blocks for femtosecond laser processing of hard materials. So far, etching- assisted femtosecond laser modification has demonstrated to be the efficient strategy to solve the above problems when processing hard materials, including wet etching and dry etching. In this review, femtosecond laser modification that would influence the etching selectivity is introduced. The fundamental and recent applications of the two kinds of etching assisted femtosecond laser modification technologies are summarized. In addition, the challenges and application prospects of these technologies are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant No.51501070)
文摘Although femtosecond laser microfabrication is one of the most promising three-dimensional（3D） fabrication techniques, it could suffer from low fabrication efficiency for structures with high 3D complexities. By using etching as a main assistant technique, the processing can be speeded up and an improved structure surface quality can be provided. However,the assistance of a single technique cannot satisfy the increasing demands of fabrication and integration of highly functional 3D microstructures. Therefore, a multi-technique-based 3D microfabrication method is required. In this paper, we briefly review the recent development on etching-assisted femtosecond laser microfabrication（EAFLM）. Various processing approaches have been proposed to further strengthen the flexibilities of the EAFLM. With the use of the multi-technique-based microfabrication method, 3D microstructure arrays can be rapidly defined on planar or curved surfaces with high structure qualities.
基金Project supported by the China Postdoctoral Science Foundation(Grant No.2016M592709)the National Natural Science Foundation of China(Grant No.51535003)
文摘Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared（IR） spectrometer, respectively. The laser induced damage thresholds（LIDTs） of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.
基金Supported by the National Basic Research Program of China under Grant No 2012CB921804the National Natural Science Foundation of China under Grant Nos 11204236 and 61308006the Collaborative Innovation Center of Suzhou Nano Science and Technology
文摘We demonstrate a method of fabricating through micro-holes and micro-hole arrays in silicon using femtosecond laser irradiation and selective chemical etching. The micro-hole formation mechanism is identified as the chemical reaction of the femtosecond laser-induced structure change zone and hydrofluoric acid solution. The morphologies of the through micro-holes and micro-hole arrays are characterized by using scanning electronic microscopy, The effects of the pulse number on the depth and diameter of the holes are investigated. Honeycomb arrays of through micro-holes fabricated at different laser powers and pulse numbers are demonstrated.
基金supported by the National Natural Science Foundation of China(Nos.51805220 and 61405078)the Jiangsu University Study-abroad Fund(No.UJS-2017-013)support of the Young Backbone Teacher Cultivating Project of Jiangsu University(No.5521220008)。
文摘An effective method based on laser etching and driving layer strategy was proposed to prepare patterned Ag nanoparticles(Ag NPs)on fluorine-doped tin oxide(FTO)/glass substrate and thus to enhance the photoelectric properties.This method successively included depositing an aluminum-doped zinc oxide(AZO)driving layer,laser etching,depositing an Ag layer,furnace annealing and laser removal.Different AZO and Ag layer thicknesses were adopted,and the surface morphology,crystal structure and photoelectric properties were investigated.An Ag NPs/FTO/glass sample without an AZO driving layer was prepared for comparison.It was found that furnace annealing of the Ag layer combined with the AZO driving layer,rather than that without the AZO driving layer,was more conducive to generating patterned Ag NPs.Using a 20-nmthick AZO layer and a 150-nm-thick Ag layer led to the formation of uniformly distributed Ag NPs being aligned along the laser-etched grooves to form a pattern.The as-obtained sample had the best comprehensive photoelectric property with an average transmittance of 79.95%,a sheet resistance of 7.11Ω/sq and the highest figure of merit of 1.50×10^(-2)Ω^(-1),confirming the feasibility of the proposed method and providing enlightenment for related researches of transparent conductive oxide-based films.
基金Funded by National Natural Science Foundation of China(No.50572121) Key Pre-research Foundation of Weapon and Equipment(No. 9140A27010206JB35)
文摘In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was reported.To improve just-for-once successive rate of specimen preparation and get good characterization results,an improving specimen preparation method of freezing etching was developed.Size,distribution and morphology of NANDS were directly visualized.Some information of particle dispersion feature and particle density can also be obtained.Reproductivity of the FETEM characterization is excellent.Comparing with laser scattering method,which is liable to give positive error especially for small size particle anchoring disperser,FETEM characterization can give more accurate measurement of particle size.Moreover,FETEM can give dispersion feature of nanoparticle in non-aqueous medium.
文摘Gallium nitride(GaN)/porous silicon(PSi)film was prepared using a pulsed laser deposition method and 1064 nm Nd:YAG laser for optoelectronic applications and a series of Psi substrates were fabricated using a photoelectrochemical etching method assisted by laser at different etching times for 2.5–15 min at 2.5 min intervals.X-ray diffraction,room-temperature photoluminescence,atomic force microscopy and field emission scanning electron microscopy images,and electrical characteristics in the prepared GaN on the Psi film were investigated.The optimum Psi substrate was obtained under the following conditions:10 min,10 mA/cm^(2),and 24%hydrofluoric acid.The substrate exhibited two highly cubic crystalline structures at(200)and(400)orientations and yellow visible band photoluminescence,and homogeneous pores formed over the entire surface.The pores had steep oval shapes and were accompanied by small dark pores that appeared topographically and morphologically.The GaN/Psi film fabricated through PLD exhibited a high and hexagonal crystallographic texture in the(002)plane.Spectroscopic properties results revealed that the photoluminescence emission of the deposited nano-GaN films was in the ultraviolet band(374 nm)related to GaN material and in the near-infrared band(730 nm)related to the Psi substrate.The topographical and morphological results of the GaN films confirmed that the deposited film contained spherical grains with an average diameter of 51.8 nm and surface roughness of 4.8 nm.The GaN/Psi surface showed a cauliflower-like morphology,and the built-in voltage decreased from 3.4 to 2.7 eV after deposition.The fabricated GaN/Psi film exhibited good electrical characteristics.
基金Funded by the International Science&Technology Cooperation Program of Hubei Province of China(No.2022EHB024)the National Key Research and Development Plan(Nos.2018YFE0103600 and 2021YFB3703100)+1 种基金the National Natural Science Foundation of China(Nos.51872212,51972244,52002075,and 52102066)the 111 Project(No.B13035)。
文摘Laser etching and laser chemical vapor deposition(LCVD)techniques were proposed for the rapid preparation of high-purity,strongly bonded SiC porous micro-nano-coatings on quartz substrates.The laser serves as an external driving force for the vertical growth of SiC whiskers,facilitating the formation of a porous nanostructure that resembles coral models found in the macroscopic biological world.The porous nanostructures are beneficial for reducing thermal expansion mismatch and relieving residual stress.It is capable of eliminating the cracks on the surface of SiC coatings as well as enhancing the bonding of SiC coatings with quartz substrates to avoid coating detachment.
基金National Natural Science Foundation of China(12174107,11933005,61991444,12192251,12334014)National Key Research and Development Program of China(2019YFA0705000)Fundamental Research Funds for the Central Universities.
文摘Bending optofluidic waveguides are essential for developing high-performance fluid-based photonic circuits and systems.The combination of femtosecond(fs)-laser-assisted etching of high-precision microchannels and vacuum-assisted liquid-core filling allows the controllable fabrication of low-loss optofluidic waveguides in fused silica.
基金The authors would like to thank the metallography laboratory personnel of University of Tehran for their cooperation.
文摘Revealing grains and very fine dendrites in a solidified weld metal of aluminum–magnesium–silicon alloys is difficult and thus,there is no evidence to validate the micro-and meso-scale physical models for hot cracks. In this research, the effect of preheating on the microstructure and hot crack creation in the pulsed laser welding of AA 6061 was investigated by an optical microscope and field emission electron microscopy. Etching was carried out in the gas phase using fresh Keller’s reagent for 600 s. The results showed that the grain size of the weld metal was proportional to the grain size of the base metal and was independent of the preheating temperature. Hot cracks passed the grain boundaries of the weld and the base metal. Lower solidification rates in the preheated samples led to coarser arm spacing;therefore, a lower cooling rate. Despite the results predicted by the micro and meso-scale models, lower cooling rates resulted in increased hot cracks. The cracks could grow in the weld metal after solidification;therefore, hot cracks were larger than predicted by the hot crack prediction models.
基金National High Technology Research and Development Programof China(2001AA312180)
文摘The effect of mesa size on th e thermal characteristics of etched mesa vertical-cavity surface-emitting lase rs(VCSELs) is studied. The numerical results show that the mesa size of the top mirror strongly influences the temperature distribution inside the etched mesa V CSEL. Under a certain driving voltage, with decreasing mesa size, the location o f the maximal temperature moves towards the p-contact metal, the temperature in the core region of the active layer rises greatly, and the thermal characterist ics of the etched mesa VCSELs will deteriorate.
