Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material inte...Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material interaction.Under the extreme nonequilibrium conditions imposed by femtosecond laser irradiation,many fundamental questions concerning the physical origin of the material removal process remain unanswered.In this review,cutting-edge ultrafast dynamic observation techniques for investigating the fundamental questions,including timeresolved pump-probe shadowgraphy,ultrafast continuous optical imaging,and four-dimensional ultrafast scanning electron microscopy,are comprehensively surveyed.Each technique is described in depth,beginning with its basic principle,followed by a description of its representative applications in laser-material interaction and its strengths and limitations.The consideration of temporal and spatial resolutions and panoramic measurement at different scales are two major challenges.Hence,the prospects for technical advancement in this field are discussed finally.展开更多
1.Introduction Today we live in a new era of economic globalization and rapid technological growth.The advancement of both our society and standard of living require us to delve into this new world and unleash the pos...1.Introduction Today we live in a new era of economic globalization and rapid technological growth.The advancement of both our society and standard of living require us to delve into this new world and unleash the possibilities our future.We need to broaden the horizons of our universe to discover a new realm where the future of humanity can flourish.We need to be unafraid to unveil the mysteries hidden within the depths of our oceans to unearth treasures that will benefit not only us,but the generations to come.To fulfill this vision,we must manufacture extremely large and extraordinarily fast equipment that will function seamlessly under the duress of extreme environments.On the other hand,matter is infinitely divisible.展开更多
The International Journal of Extreme Manufacturing is a leading,worldwide scientific journal focused on the fields of extreme manufacturing.Published within it are the latest scientific and engineering achievements in...The International Journal of Extreme Manufacturing is a leading,worldwide scientific journal focused on the fields of extreme manufacturing.Published within it are the latest scientific and engineering achievements in related fields,as well as pioneering scientific,technological,and engineering innovations and developments.展开更多
Urogenital system tumors include prostate cancer,bladder cancer,ovarian cancer,and other very common solid tumor diseases with high morbidity and high mortality.The unique physiological and anatomical features of the ...Urogenital system tumors include prostate cancer,bladder cancer,ovarian cancer,and other very common solid tumor diseases with high morbidity and high mortality.The unique physiological and anatomical features of the urogenital system render it particularly amenable to the application of tissue imaging techniques for diagnostic purposes.The advancement of aggregationinduced emission(AIE)materials has addressed the limitations associated with conventional fluorescentmaterials that are prone to aggregation-caused quenching.This advancement has facilitated the development of innovative AIE fluorescent materials characterized by enhanced photostability,an increased signal-to-noise ratio,and improved imaging quality.This article reviews the research progress of AIE biosensors in the diagnosis of urogenital tumors.Itmainly involves biomarker diagnostic in vitro and fluorescence imaging in urogenital solid tumors such as prostate cancer,uterine cancer,bladder cancer,and ovarian cancer,which are based on AIE biosensors.In addition,a comprehensive description of AIE biosensors’synthesis and application strategies is provided.This includes a detailed elucidation of in vitro diagnostic platforms and intracellular imaging mechanisms based on the basic principles ofAIE,accompanied by a presentation of quantitative analysis and cell imaging results.In addition,the limitations,challenges and suggestions of AIE biosensors application in the field of tumor diagnosis are summarized,and the development prospect of AIE biosensors in the field of tumor diagnosis is prospected.This article reviews the application of AIE biosensors in the diagnosis of urogenital tumors,and also provides a catalyst for exploring the characteristics of AIE biosensors and its wide application in the field of disease diagnosis.展开更多
Numerous valuable studies on electron dynamics have focussed on the extraordinary properties of molybdenum disulfide(MoS_(2));however,most of them were confined to the level below the damage threshold.Here the electro...Numerous valuable studies on electron dynamics have focussed on the extraordinary properties of molybdenum disulfide(MoS_(2));however,most of them were confined to the level below the damage threshold.Here the electron dynamics of MoS_(2) under intense ultrafast laser irradiation was investigated by experiments and simulations.Two kinds of ablation mechanisms were revealed,which led to two distinct types of electron dynamics and final ablation morphology.At a higher fluence,the emergence of superheated liquid induced a dramatic change in the transient reflectivity and micro-honeycomb structures.At a lower fluence,the material was just removed by sublimation,and the ablation structure was relatively flat.X-ray photoelectron spectroscopic(XPS)measurements demonstrated that thermal decomposition only occurred at the higher fluence.Furthermore,a theoretical model was developed to deeply reveal the ultrafast dynamics of MoS_(2) ablation.The simulation results were in good agreement with the temporal and spatial reflectivity distribution obtained from the experiment.The electron and lattice temperature evolution was also obtained to prove the ablation mechanism.Our results revealed ultrafast dynamics of MoS_(2) above the damage threshold and are helpful for understanding the interaction mechanism between MoS_(2) and intense ultrafast lasers,as well as for MoS_(2) processing applications.展开更多
Silkworm silk fiber is an attractive material owing to its remarkable mechanical characteristics,excellent optical properties,and good biocompatibility and biodegradability.However,nano-processing of the silk fiber is...Silkworm silk fiber is an attractive material owing to its remarkable mechanical characteristics,excellent optical properties,and good biocompatibility and biodegradability.However,nano-processing of the silk fiber is still a challenge limiting its applications in nanoengineering and related fields.Herein,we report localized near-field enhancement-assisted ablation with an ultrafast laser to break this bottleneck.Localized processing of silk fiber,including nano-holing,nano-grooving,and cutting could retain the key molecular structure building blocks and the pristine functionality of the silk fiber.An extremely narrow nanohole with a width of^64 nm was successfully achieved.The processed silk fiber can be used to transfer micro/nanoparticles and drugs,showing potential for biomedical engineering.The processing strategy developed in this study can also be extended to other materials,paving a new way for fabricating functional nanostructures with precisely controlled size and morphology.展开更多
Advanced micro/nanofabrication of functional materials and structures with various dimensions represents a key research topic in modem nanoscience and technology and becomes critically important for numerous emerging ...Advanced micro/nanofabrication of functional materials and structures with various dimensions represents a key research topic in modem nanoscience and technology and becomes critically important for numerous emerging technologies such as nanoelectronics, nanopho- tonics and micro/nanoelectromechanical systems. This review systematically explores the non-conventional material processing approaches in fabricating nanomaterials and micro/nanostructures of various dimensions which are challenging to be fabricated via conventional approaches. Research efforts are focused on laser-based techniques for the growth and fabrication of one-dimensional （1D）, two-dimensional （2D） and three-dimensional （3D） nanomaterials and micro/nanostructures. The following research topics are covered, including： 1） laser-assisted chemical vapor deposition （CVD） for highly efficient growth and integration of 1D nanomaterial of carbon nanotubes （CNTs）, 2） laser direct writing （LDW） of graphene ribbons under ambient conditions, and 3） LDW of 3D micro/nanostructures via additive and subtractive processes. Comparing with the conventional fabrication methods, the laser-based methods exhibit several unique advantages in the micro/nanofabrication of advanced functional materials and structures. For the 1D CNT growth, the laser-assisted CVD process can realize both rapid material synthesis and tight control of growth location and orientation of CNTs due to the highly intense energy delivery and laser-induced optical near-field effects. For the 2D graphene synthesis and patterning, roomtemperature and open-air fabrication of large-scale graphene patterns on dielectric surface has been successfully realized by a LDW process. For the 3D micro/nanofabrica- tion, the combination of additive two-photon polymeriza- tion （TPP） and subtractive multi-photon ablation （MPA） processes enables the fabrication of arbitrary complex 3D micro/nanostructures which tional fabrication methods are challenging for conven- Considering the numerous unique advantages of laser-based techniques, the laser- based micro/nanofabrication is expected to play a more and more important role in the fabrication of advanced functional micro/nano-devices.展开更多
Raman spectroscopy plays a crucial role in biochemical analysis.Recently,superhydrophobic surface-enhanced Raman scattering(SERS)substrates have enhanced detection limits by concentrating target molecules into small a...Raman spectroscopy plays a crucial role in biochemical analysis.Recently,superhydrophobic surface-enhanced Raman scattering(SERS)substrates have enhanced detection limits by concentrating target molecules into small areas.However,due to the wet transition phenomenon,further reduction of the droplet contact area is prevented,and the detection limit is restricted.This paper proposes a simple method involving femtosecond laser-induced forward transfer for preparing a hybrid superhydrophilic–superhydrophobic SERS(HS-SERS)substrate by introducing a superhydrophilic pattern to promote the target molecules to concentrate on it for ultratrace detection.Furthermore,the HS-SERS substrate is heated to promote a smaller concentrated area.The water vapor film formed by the contact of the solution with the substrate overcomes droplet collapse,and the target molecules are completely concentrated into the superhydrophilic region without loss during evaporation.Finally,the concentrated region is successfully reduced,and the detection limit is enhanced.The HS-SERS substrate achieved a final contact area of 0.013mm2,a 12.1-fold decrease from the unheated case.The reduction of the contact area led to a detection limit concentration as low as 10−16 M for a Rhodamine 6G solution.In addition,the HS-SERS substrate accurately controlled the size of the concentrated areas through the superhydrophilic pattern,which can be attributed to the favorable repeatability of the droplet concentration results.In addition,the preparation method is flexible and has the potential for fluid mixing,fluid transport,and biochemical sensors,etc.展开更多
Femtosecond laser-induced surface structures upon multiple pulses irradiation are strongly correlated with the pulse number,which in turn signifcantly afects successive laser-material interactions.By recording the dyn...Femtosecond laser-induced surface structures upon multiple pulses irradiation are strongly correlated with the pulse number,which in turn signifcantly afects successive laser-material interactions.By recording the dynamics of femtosecond laser ablation of silicon using time-resolved shadowgraphy,here we present direct visualization of the excitation of air plasma induced by the refected laser during the second pulse irradiation.Te interaction of the air plasma and silicon plasma is found to enhance the shockwave expansion induced by silicon ablation in the longitudinal direction,showing anisotropic expansion dynamics in diferent directions.We further demonstrate the vanishing of air plasma as the pulse number increases because of the generation of a rough surface without light focusing ability.In the scenario,the interaction of air plasma and silicon plasma disappears;the expansion of the silicon plasma and shockwave restores its original characteristic that is dominated by the laser-material coupling.Te results show that the excitation of air plasma and the laser-material coupling involved in laser-induced plasma and shockwave expansion are structure mediated and dependent on the pulse number,which is of fundamental importance for deep insight into the nature of laser-material interactions during multiple pulses ablation.展开更多
The dynamics of plasma and shockwave expansion during two femtosecond laser pulse ablation of fused silica are studied using a time-resolved shadowgraph imaging technique. The experimental results reveal that during t...The dynamics of plasma and shockwave expansion during two femtosecond laser pulse ablation of fused silica are studied using a time-resolved shadowgraph imaging technique. The experimental results reveal that during the second pulse irradiation on the crater induced by the first pulse, the expansion of the plasma and shockwave is enhanced in the longitudinal direction. The plasma model and Fresnel diffraction theory are combined to calculate the laser intensity distribution by considering the change in surface morphology and transient material properties. The theoretical results show that after the free electron density induced by the rising edge of the pulse reaches the critical density, the originally transparent surface is transformed into a transient high-reflectivity surface(metallic state). Thus, the crater with a concave-lens-like morphology can tremendously reflect and refocus the latter part of the laser pulse, leading to a strong laser field with an intensity even higher than the incident intensity. This strong refocused laser pulse results in a stronger laser-induced air breakdown and enhances the subsequent expansion of the plasma and shockwave. In addition, similar shadowgraphs are also recorded in the single-pulse ablation of a concave microlens, providing experimental evidence for the enhancement mechanism.展开更多
Cylindrical shockwaves inside polymethyl methacrylate(PMMA) generated simultaneously with two hemispherical shockwaves induced by a femtosecond Gaussian beam laser were investigated using an ultrafast pump–probe imag...Cylindrical shockwaves inside polymethyl methacrylate(PMMA) generated simultaneously with two hemispherical shockwaves induced by a femtosecond Gaussian beam laser were investigated using an ultrafast pump–probe imaging technique. The evolutions of these three shockwaves with probe delay and incident pulse number have been systematically analyzed. The plasma intensity and filament length in the center of cylindrical shockwave both decayed with pulse number. Moreover, the self-focused filament moved downstream towards the output surface with an increased pulse number. The experimental results and mechanism illustrated that energy deposition was suppressed by a degraded nonlinear effect due to a pre-ablated structure in multi-pulse irradiation.展开更多
Photonic integrated circuits （PIC） enable efficient and flex- ible control of photons within a compact space, thereby re- volutionizing both information technology and biological and chemical sensing. Currently, sem...Photonic integrated circuits （PIC） enable efficient and flex- ible control of photons within a compact space, thereby re- volutionizing both information technology and biological and chemical sensing. Currently, semiconductor materials including silicon, silicon nitride （SIN）, and indium phosphate （lnP） are still the prominent PIC platforms, which can be patterned using mature photolithographic technologies [1]. Being an intrinsically planar fabrication technology, increasing the integration density in the photolithography mainly depends on reducing the sizes of individual components.展开更多
基金supported by the National Natural Science Foundation of China under Grant Nos.51975054,61605140 and 11704028the National Key R&D Program of China(2017YFB1104300)。
文摘Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material interaction.Under the extreme nonequilibrium conditions imposed by femtosecond laser irradiation,many fundamental questions concerning the physical origin of the material removal process remain unanswered.In this review,cutting-edge ultrafast dynamic observation techniques for investigating the fundamental questions,including timeresolved pump-probe shadowgraphy,ultrafast continuous optical imaging,and four-dimensional ultrafast scanning electron microscopy,are comprehensively surveyed.Each technique is described in depth,beginning with its basic principle,followed by a description of its representative applications in laser-material interaction and its strengths and limitations.The consideration of temporal and spatial resolutions and panoramic measurement at different scales are two major challenges.Hence,the prospects for technical advancement in this field are discussed finally.
文摘1.Introduction Today we live in a new era of economic globalization and rapid technological growth.The advancement of both our society and standard of living require us to delve into this new world and unleash the possibilities our future.We need to broaden the horizons of our universe to discover a new realm where the future of humanity can flourish.We need to be unafraid to unveil the mysteries hidden within the depths of our oceans to unearth treasures that will benefit not only us,but the generations to come.To fulfill this vision,we must manufacture extremely large and extraordinarily fast equipment that will function seamlessly under the duress of extreme environments.On the other hand,matter is infinitely divisible.
文摘The International Journal of Extreme Manufacturing is a leading,worldwide scientific journal focused on the fields of extreme manufacturing.Published within it are the latest scientific and engineering achievements in related fields,as well as pioneering scientific,technological,and engineering innovations and developments.
基金National Natural Science Foundation of China(82102083,82471500)Guangdong Basic and Applied Basic Research Foundation(2022A1515011664)+2 种基金Guangzhou Municipal Science and Technology(2025A03J4319)Shenzhen Science and Technology Program(2023SC0005)the University Development Fund(UDF01002573).
文摘Urogenital system tumors include prostate cancer,bladder cancer,ovarian cancer,and other very common solid tumor diseases with high morbidity and high mortality.The unique physiological and anatomical features of the urogenital system render it particularly amenable to the application of tissue imaging techniques for diagnostic purposes.The advancement of aggregationinduced emission(AIE)materials has addressed the limitations associated with conventional fluorescentmaterials that are prone to aggregation-caused quenching.This advancement has facilitated the development of innovative AIE fluorescent materials characterized by enhanced photostability,an increased signal-to-noise ratio,and improved imaging quality.This article reviews the research progress of AIE biosensors in the diagnosis of urogenital tumors.Itmainly involves biomarker diagnostic in vitro and fluorescence imaging in urogenital solid tumors such as prostate cancer,uterine cancer,bladder cancer,and ovarian cancer,which are based on AIE biosensors.In addition,a comprehensive description of AIE biosensors’synthesis and application strategies is provided.This includes a detailed elucidation of in vitro diagnostic platforms and intracellular imaging mechanisms based on the basic principles ofAIE,accompanied by a presentation of quantitative analysis and cell imaging results.In addition,the limitations,challenges and suggestions of AIE biosensors application in the field of tumor diagnosis are summarized,and the development prospect of AIE biosensors in the field of tumor diagnosis is prospected.This article reviews the application of AIE biosensors in the diagnosis of urogenital tumors,and also provides a catalyst for exploring the characteristics of AIE biosensors and its wide application in the field of disease diagnosis.
基金supported by the National Natural Science Foundation of China(Grant No.11704028)the National Key R&D Program of China(Grant No.2017YFB1104300).
文摘Numerous valuable studies on electron dynamics have focussed on the extraordinary properties of molybdenum disulfide(MoS_(2));however,most of them were confined to the level below the damage threshold.Here the electron dynamics of MoS_(2) under intense ultrafast laser irradiation was investigated by experiments and simulations.Two kinds of ablation mechanisms were revealed,which led to two distinct types of electron dynamics and final ablation morphology.At a higher fluence,the emergence of superheated liquid induced a dramatic change in the transient reflectivity and micro-honeycomb structures.At a lower fluence,the material was just removed by sublimation,and the ablation structure was relatively flat.X-ray photoelectron spectroscopic(XPS)measurements demonstrated that thermal decomposition only occurred at the higher fluence.Furthermore,a theoretical model was developed to deeply reveal the ultrafast dynamics of MoS_(2) ablation.The simulation results were in good agreement with the temporal and spatial reflectivity distribution obtained from the experiment.The electron and lattice temperature evolution was also obtained to prove the ablation mechanism.Our results revealed ultrafast dynamics of MoS_(2) above the damage threshold and are helpful for understanding the interaction mechanism between MoS_(2) and intense ultrafast lasers,as well as for MoS_(2) processing applications.
基金the support from the National Key R&D Program of China(2017YFB1104300,2016YFA0200103 and 2018YFB1107200)the National Program for the Support of Top-notch Young Professionalsthe National Natural Science Foundation of China(51775303)。
文摘Silkworm silk fiber is an attractive material owing to its remarkable mechanical characteristics,excellent optical properties,and good biocompatibility and biodegradability.However,nano-processing of the silk fiber is still a challenge limiting its applications in nanoengineering and related fields.Herein,we report localized near-field enhancement-assisted ablation with an ultrafast laser to break this bottleneck.Localized processing of silk fiber,including nano-holing,nano-grooving,and cutting could retain the key molecular structure building blocks and the pristine functionality of the silk fiber.An extremely narrow nanohole with a width of^64 nm was successfully achieved.The processed silk fiber can be used to transfer micro/nanoparticles and drugs,showing potential for biomedical engineering.The processing strategy developed in this study can also be extended to other materials,paving a new way for fabricating functional nanostructures with precisely controlled size and morphology.
文摘Advanced micro/nanofabrication of functional materials and structures with various dimensions represents a key research topic in modem nanoscience and technology and becomes critically important for numerous emerging technologies such as nanoelectronics, nanopho- tonics and micro/nanoelectromechanical systems. This review systematically explores the non-conventional material processing approaches in fabricating nanomaterials and micro/nanostructures of various dimensions which are challenging to be fabricated via conventional approaches. Research efforts are focused on laser-based techniques for the growth and fabrication of one-dimensional （1D）, two-dimensional （2D） and three-dimensional （3D） nanomaterials and micro/nanostructures. The following research topics are covered, including： 1） laser-assisted chemical vapor deposition （CVD） for highly efficient growth and integration of 1D nanomaterial of carbon nanotubes （CNTs）, 2） laser direct writing （LDW） of graphene ribbons under ambient conditions, and 3） LDW of 3D micro/nanostructures via additive and subtractive processes. Comparing with the conventional fabrication methods, the laser-based methods exhibit several unique advantages in the micro/nanofabrication of advanced functional materials and structures. For the 1D CNT growth, the laser-assisted CVD process can realize both rapid material synthesis and tight control of growth location and orientation of CNTs due to the highly intense energy delivery and laser-induced optical near-field effects. For the 2D graphene synthesis and patterning, roomtemperature and open-air fabrication of large-scale graphene patterns on dielectric surface has been successfully realized by a LDW process. For the 3D micro/nanofabrica- tion, the combination of additive two-photon polymeriza- tion （TPP） and subtractive multi-photon ablation （MPA） processes enables the fabrication of arbitrary complex 3D micro/nanostructures which tional fabrication methods are challenging for conven- Considering the numerous unique advantages of laser-based techniques, the laser- based micro/nanofabrication is expected to play a more and more important role in the fabrication of advanced functional micro/nano-devices.
基金This work was supported by the National Key R&D Program of China(2018YFB1107200)the National Natural Science Foundation of China(51675049)+1 种基金the Natural Science Foundation of Beijing Municipality(3172027)the Young Elite Scientists Sponsorship Program(2016QNRC001).
文摘Raman spectroscopy plays a crucial role in biochemical analysis.Recently,superhydrophobic surface-enhanced Raman scattering(SERS)substrates have enhanced detection limits by concentrating target molecules into small areas.However,due to the wet transition phenomenon,further reduction of the droplet contact area is prevented,and the detection limit is restricted.This paper proposes a simple method involving femtosecond laser-induced forward transfer for preparing a hybrid superhydrophilic–superhydrophobic SERS(HS-SERS)substrate by introducing a superhydrophilic pattern to promote the target molecules to concentrate on it for ultratrace detection.Furthermore,the HS-SERS substrate is heated to promote a smaller concentrated area.The water vapor film formed by the contact of the solution with the substrate overcomes droplet collapse,and the target molecules are completely concentrated into the superhydrophilic region without loss during evaporation.Finally,the concentrated region is successfully reduced,and the detection limit is enhanced.The HS-SERS substrate achieved a final contact area of 0.013mm2,a 12.1-fold decrease from the unheated case.The reduction of the contact area led to a detection limit concentration as low as 10−16 M for a Rhodamine 6G solution.In addition,the HS-SERS substrate accurately controlled the size of the concentrated areas through the superhydrophilic pattern,which can be attributed to the favorable repeatability of the droplet concentration results.In addition,the preparation method is flexible and has the potential for fluid mixing,fluid transport,and biochemical sensors,etc.
基金Tis research was supported by the National Key R&D Program of China(grant no.2017YFB1104300)and the National Natural Science Foundation of China(grant nos.91323301,11704028).
文摘Femtosecond laser-induced surface structures upon multiple pulses irradiation are strongly correlated with the pulse number,which in turn signifcantly afects successive laser-material interactions.By recording the dynamics of femtosecond laser ablation of silicon using time-resolved shadowgraphy,here we present direct visualization of the excitation of air plasma induced by the refected laser during the second pulse irradiation.Te interaction of the air plasma and silicon plasma is found to enhance the shockwave expansion induced by silicon ablation in the longitudinal direction,showing anisotropic expansion dynamics in diferent directions.We further demonstrate the vanishing of air plasma as the pulse number increases because of the generation of a rough surface without light focusing ability.In the scenario,the interaction of air plasma and silicon plasma disappears;the expansion of the silicon plasma and shockwave restores its original characteristic that is dominated by the laser-material coupling.Te results show that the excitation of air plasma and the laser-material coupling involved in laser-induced plasma and shockwave expansion are structure mediated and dependent on the pulse number,which is of fundamental importance for deep insight into the nature of laser-material interactions during multiple pulses ablation.
基金National Natural Science Foundation of China(NSFC)(51605029,91323301)
文摘The dynamics of plasma and shockwave expansion during two femtosecond laser pulse ablation of fused silica are studied using a time-resolved shadowgraph imaging technique. The experimental results reveal that during the second pulse irradiation on the crater induced by the first pulse, the expansion of the plasma and shockwave is enhanced in the longitudinal direction. The plasma model and Fresnel diffraction theory are combined to calculate the laser intensity distribution by considering the change in surface morphology and transient material properties. The theoretical results show that after the free electron density induced by the rising edge of the pulse reaches the critical density, the originally transparent surface is transformed into a transient high-reflectivity surface(metallic state). Thus, the crater with a concave-lens-like morphology can tremendously reflect and refocus the latter part of the laser pulse, leading to a strong laser field with an intensity even higher than the incident intensity. This strong refocused laser pulse results in a stronger laser-induced air breakdown and enhances the subsequent expansion of the plasma and shockwave. In addition, similar shadowgraphs are also recorded in the single-pulse ablation of a concave microlens, providing experimental evidence for the enhancement mechanism.
基金supported by the National Key R&D Program of China(No.2018YFB1107200)the National Natural Science Foundation of China(Nos.51675048 and 11704028)
文摘Cylindrical shockwaves inside polymethyl methacrylate(PMMA) generated simultaneously with two hemispherical shockwaves induced by a femtosecond Gaussian beam laser were investigated using an ultrafast pump–probe imaging technique. The evolutions of these three shockwaves with probe delay and incident pulse number have been systematically analyzed. The plasma intensity and filament length in the center of cylindrical shockwave both decayed with pulse number. Moreover, the self-focused filament moved downstream towards the output surface with an increased pulse number. The experimental results and mechanism illustrated that energy deposition was suppressed by a degraded nonlinear effect due to a pre-ablated structure in multi-pulse irradiation.
文摘Photonic integrated circuits （PIC） enable efficient and flex- ible control of photons within a compact space, thereby re- volutionizing both information technology and biological and chemical sensing. Currently, semiconductor materials including silicon, silicon nitride （SIN）, and indium phosphate （lnP） are still the prominent PIC platforms, which can be patterned using mature photolithographic technologies [1]. Being an intrinsically planar fabrication technology, increasing the integration density in the photolithography mainly depends on reducing the sizes of individual components.
