Semiconductor and laser single crystals are usually brittle and hard,which need to be ground to have satisfactory surface integrity and dimensional precision prior to their applications.Improvement of the surface inte...Semiconductor and laser single crystals are usually brittle and hard,which need to be ground to have satisfactory surface integrity and dimensional precision prior to their applications.Improvement of the surface integrity of a ground crystal can shorten the time of a subsequent polishing process,thus reducing the manufacturing cost.The development of cost-effective grinding technologies for those crystals requires an in-depth understanding of their deformation and removal mechanisms.As a result,a great deal of research efforts were directed towards studying this topic in the past two or three decades.In this review,we aimed to summarize the deformation and removal characteristics of representative semiconductor and laser single crystals in accordance with the scale of mechanical loading,especially at extremely small scales.Their removal mechanisms were critically examined based on the evidence obtained from highresolution TEM analyses.The relationships between machining conditions and removal behaviors were discussed to provide a guidance for further advancing of the grinding technologies for those crystals.展开更多
Based on a theoretical model of Q-switched laser with the influences of the driving signal sent to the Pockels cell and the doping concentration of the gain medium taken into account,a method of achieving high energy ...Based on a theoretical model of Q-switched laser with the influences of the driving signal sent to the Pockels cell and the doping concentration of the gain medium taken into account,a method of achieving high energy sub-nanosecond Q-switched lasers is proposed and verified in experiment.When a Nd:YVO4 crystal with a doping concentration of 0.7 at.%is used as a gain medium and a driving signal with the optimal high-level voltage is applied to the Pockels cell,a stable single-transverse-mode electro-optical Q-switched laser with a pulse width of 0.77 ns and a pulse energy of 1.04 mJ operating at the pulse repetition frequency of 1 kHz is achieved.The precise tuning of the pulse width is also demonstrated.展开更多
We report the repetitively Q-switched laser operation of the Yb-doped calcium niobium gallium garnet disordered garnet crystal, achieved with an acousto-optic modulator in a compact plano-concave resonator that is end...We report the repetitively Q-switched laser operation of the Yb-doped calcium niobium gallium garnet disordered garnet crystal, achieved with an acousto-optic modulator in a compact plano-concave resonator that is endpumped by a 935-nm diode laser. An average output power of 1.96 W is produced at pulse repetition rate of50 k Hz at emission wavelengths around 1035 nm, with a slope efficiency of 16%. The highest pulse energy of 269 μJ is generated at pulse repetition rate of 1 k Hz, with pulse width 12.1 ns and peak power 20.53 kW.展开更多
The crystallization behaviour of the laser synthesized nanometric amorphous Si3N4 powders with the particle size of 15 nm in diameter has been studied between 1200° and 1700℃ by XRD,TEM and FTIR techniques. A sm...The crystallization behaviour of the laser synthesized nanometric amorphous Si3N4 powders with the particle size of 15 nm in diameter has been studied between 1200° and 1700℃ by XRD,TEM and FTIR techniques. A small amount of β-Si3N4 formed at 1250℃ and increased slowly until the α- β transformation happened at 1700℃, whereas α-Si3N4 appeared at 1300℃ andincreased rapidly between 1500-1600℃. The formation of β phase at the lower temperature was caused by the nitridation of free Si due to the preexisted β-nuclei in the Si3N4 particles, whereasthe α phase was formed by solid crystallization from the amorphous matrix. There were α and β SiC formed at 1700℃ due to the presence of Sio and Co gases in the system. FTIR analysis shows that two new IR absorption at 1356 and 1420 cm-1, and an overall strong absorption in wide wavenumber range resulted from the powders annealed at 1600 and 1700℃展开更多
This article summarizes work at the Laser Thermal Laboratory and discusses related studies on the laser synthesis and functionalization of semiconductor nanostructures and two-dimensional(2D)semiconductor materials.Re...This article summarizes work at the Laser Thermal Laboratory and discusses related studies on the laser synthesis and functionalization of semiconductor nanostructures and two-dimensional(2D)semiconductor materials.Research has been carried out on the laser-induced crystallization of thin films and nanostructures.The in situ transmission electron microscopy(TEM)monitoring of the crystallization of amorphous precursors in nanodomains is discussed herein.The directed assembly of silicon nanoparticles and the modulation of their optical properties by phase switching is presented.The vapor-liquid-solid mechanism has been adopted as a bottom-up approach in the synthesis of semiconducting nanowires(NWs).In contrast to furnace heating methods,laser irradiation offers high spatial selectivity and precise control of the heating mechanism in the time domain.These attributes enabled the investigation of NW nucleation and the early stage of nanostructure growth.Site-and shape-selective,on-demand direct integration of oriented NWs was accomplished.Growth of discrete silicon NWs with nanoscale location selectivity by employing near-field laser illumination is also reported herein.Tuning the properties of 2D transition metal dichalcogenides(TMDCs)by modulating the free carrier type,density,and composition can offer an exciting new pathway to various practical nanoscale electronics.In situ Raman probing of laser-induced processing of TMDC flakes was conducted in a TEM instrument.展开更多
Direct growth and patterning of atomically thin two-dimensional(2D)materials on various substrates are essential steps towards enabling their potential for use in the next generation of electronic and optoelectronic d...Direct growth and patterning of atomically thin two-dimensional(2D)materials on various substrates are essential steps towards enabling their potential for use in the next generation of electronic and optoelectronic devices.The conventional gas-phase growth techniques,however,are not compatible with direct patterning processes.Similarly,the condensed-phase methods,based on metal oxide deposition and chalcogenization processes,require lengthy processing times and high temperatures.Here,a novel self-limiting laser crystallization process for direct crystallization and patterning of 2D materials is demonstrated.It takes advantage of significant differences between the optical properties of the amorphous and crystalline phases.Pulsed laser deposition is used to deposit a thin layer of stoichiometric amorphous molybdenum disulfide(MoS2)film(∼3 nm)onto the fused silica substrates.A tunable nanosecond infrared(IR)laser(1064 nm)is then employed to couple a precise amount of power and number of pulses into the amorphous materials for controlled crystallization and direct writing processes.The IR laser interaction with the amorphous layer results in fast heating,crystallization,and/or evaporation of the materials within a narrow processing window.However,reduction of the midgap and defect states in the as crystallized layers decreases the laser coupling efficiency leading to higher tolerance to process parameters.The deliberate design of such laser 2D material interactions allows the selflimiting crystallization phenomena to occur with increased quality and a much broader processing window.This unique laser processing approach allows high-quality crystallization,direct writing,patterning,and the integration of various 2D materials into future functional devices.展开更多
The single and coupled photonic crystal nanocavity lasers are fabricated in the InGaAsP material system and their static and dynamic features are compared. The coupled-cavity lasers show a larger lasing efficiency and...The single and coupled photonic crystal nanocavity lasers are fabricated in the InGaAsP material system and their static and dynamic features are compared. The coupled-cavity lasers show a larger lasing efficiency and generate an output power higher than the single-cavity lasers, results that are consistent with the theoretical results obtained by rate equations. In dynamic regime, the single-cavity lasers produce pulses as short as 113 ps,while the coupled-cavity lasers show a significantly longer lasing duration. These results indicate that the photonic crystal laser is a promising candidate for the light source in high-speed photonic integrated circuit.展开更多
Femtosecond laser inscription or writing has been recognized as a powerful technique to engineer various materials toward a number of applications.By efficient modification of refractive indices of dielectric crystals...Femtosecond laser inscription or writing has been recognized as a powerful technique to engineer various materials toward a number of applications.By efficient modification of refractive indices of dielectric crystals,optical waveguides with diverse configurations have been produced by femtosecond laser writing.The waveguiding properties depend not only on the parameters of the laser writing but also on the nature of the crystals.The mode profile tailoring and polarization engineering are realizable by selecting appropriate fabrication conditions.In addition,regardless of the complexity of crystal refractive index changes induced by ultrafast pulses,several three-dimensional geometries have been designed and implemented that are useful for the fabrication of laser-written photonic chips.Some intriguing devices,e.g.,waveguide lasers,wavelength converters,and quantum memories,have been made,exhibiting potential for applications in various areas.Our work gives a concise review of the femtosecond laser-inscribed waveguides in dielectric crystals and focuses on the recent advances of this research area,including the fundamentals,fabrication,and selected photonic applications.展开更多
The crystal of high concentration Nd:YAG was grown by flux method and diode pu mp microcavity laser was studied.High efficiency and frequency solid state lase r was built on research and development.some applications ...The crystal of high concentration Nd:YAG was grown by flux method and diode pu mp microcavity laser was studied.High efficiency and frequency solid state lase r was built on research and development.some applications such as target designa tion,laser radar,rangefinder,CATV etc. In order to maximize pump efficiency and power output,the Nd concentration shoul d be made as high as possible without degrading the gain through concentration q uenching.In crystal grown by Czochraski method.it is difficult to increase the N d concentration over 1.2% because of Nd segregation in the melt (yttrium aluminum garnet),which leads to large nonuniformities in doping.However,by using the f lux met hod growth technique,it is possible to grow uniformly doped crystal as much as 4 % Nd concentration YAG.展开更多
The KGd(WO 4) 2[KGW] crystal has a structure belonging to the monoclinic sys tem with space group C 2/ c and with unit cell dimensions a =1.068mm, b =1.043nm, c =0.76nm, β =130°.This crystal is an excellent host...The KGd(WO 4) 2[KGW] crystal has a structure belonging to the monoclinic sys tem with space group C 2/ c and with unit cell dimensions a =1.068mm, b =1.043nm, c =0.76nm, β =130°.This crystal is an excellent host material for solid state lasers.The threshold of the laser oscillations in a Nd 3+ d oped KGW laser crystal is considerable low and has a higher emissive section.T he fluorescent concentration quench effect of the Nd 3+ ion in the KGW crystal may be weakened due to the W O covalent bond,so this crystal has a higher dopi ng concentration of active ion.Furthermore,the absorption band at 808nm of Nd 3+ in the KGW crystal,which has 12nm FWHM,is well matched with the emission w avelength of a laser diode ,a solid state laser pump that is very convenient and popular in laser science and technology today.Therefore the KGW crystal has a l aser emission with higher output and higher efficiency.Scientists of laser techn ology circles are very interested in Yb 3+ doped laser crystals because they have four advanta ges when they are compared with Nd 3+ doped laser crystals.Firstly,their flu orescent lifetimes are three or four times as many as that of Nd 3+ doped la ser crystals,which is beneficial to reserving the energy.Secondly,the heat energ y,which is formed when laser is operating,will be decreased because the pumping band is close to the upper energy level.Not only will the use ratio of energy be increased but also the damage effect to laser properties will be decreased.Thir dly,there is no absorption problems of excite state because the energy level of Yb 3+ is simple.Finally,the higher optical quality crystals are easier to gr ow because the radius of Yb 3+ is closer to that of Gd 3+ .Furthermore,Y b 3+ doped laser crystals can substitute the Ti sapphire for the psec laser .展开更多
Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic...Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic requests are high figure of merit(FOM),high damage threshold,good chemical stability and mechanical properties.Perfection and growth characters are also important for a practical SFD crystal. In recent years,the discovery of rare earth calcium oxyborates has resulted in the renewal in the field of SFD crystal.ReCaO(BO 3) 3(ReCOB)is a new type of novel nonlinear optical crystals which is nearly congruently melt and can be grown with Czochralski method.ReCOB crystals possess high nonlinear coefficients and damage thresholds.They are non hydroscopic and easy cutting and polishing.They belong to monoclinic with point group m and space group cm.The strong anisotropy originated from the low symmetry makes the measurement and application of the crystal more complicated.More than half of naturally existed crystals belongs to low symmetry,consequently,the research on the nonlinear and anisotropic laser optical properties are not only important for ReCOB crystal,but also useful for the applications of other low symmetry crystals.展开更多
Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re...Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re∶GdYCOB single crystals growth were synthesized by multistage solid phase reaction method.Re∶GdYCOB single crystals were grown by Czochralski technique.The pulling rates are 0.5-2mm/h and the rotation rates are 10-30r/min.Usually 65-75% polycrystalline materials can be transformed into good quality single crystals under our growth conditions. The structures of some as grown Re∶GdYCOB single crystals were measured by using a four circle diffractometer.The results measured show that the space group of the crystals is C 3 s Cm.The determined lattice constants of 8 at% Nd doped Ca 4YO(BO 3) 3 single crystal are a =0.8076nm, b =1.6020nm, c =0.3527nm , β =101.23°.展开更多
The 3μm laser emission of Er 3+ ( 4 I 11/2 → 4 I 13/2 )in the YAG crystal is,in principle,selfsaturation transition,the lifetime of the upper laser level( 4 I 11/2 )being smaller than that of the olwer one( 4 I 13/2...The 3μm laser emission of Er 3+ ( 4 I 11/2 → 4 I 13/2 )in the YAG crystal is,in principle,selfsaturation transition,the lifetime of the upper laser level( 4 I 11/2 )being smaller than that of the olwer one( 4 I 13/2 ).The effect of the selfsaturation limit the laser output. In present work,for the first time,we report on the investigation of the utility of Pr 3+ as a sensitizer of Er 3+ ion,using Pr 3+ 4 f 2-4 f5d transition.The radiation emission from 4f5d configuration of Pr 3+ ion have been observed in the YAG∶Pr 3+ crystal.This shows that under suitable conditions this radiant process can compete successfully by non radiative decay to the 4 f configuration.Using Er 3+ Pr 3 codoped YAG it is possible to predict the position of the lowest 4 f 2-4 f5d absorption bands of Pr 3+ ion in the ultraviolet range and to present the occurrence of the energy transfer from Pr 3+ to Er 3+ ion.By xenon flash lamp pumped 2.93μm laser action in the YAG∶(Er 3+ ,Pr 3+ ) crystals was demonstrated at room temperature.展开更多
Tunable color center lasers making use of electron trapping defects such as F A and F + 2 like centers in alkali halide crystals can deliver broadly tunable power over the near infrared 0.8—4.0μm range.The tunable r...Tunable color center lasers making use of electron trapping defects such as F A and F + 2 like centers in alkali halide crystals can deliver broadly tunable power over the near infrared 0.8—4.0μm range.The tunable range and their impressive feature of narrow linewidth make these solid state lasers important to molecular spectroscopy,pollution detection,fiber optics communication and other scientific research fields.The( F + 2) H center consisting of an F + 2 center and an neibouring O 2- ion,is one of the most important color centers.In this paper,we will study the preparation,absorption and emission spectra of the ( F + 2) H center in mixed crystal KCl KBr∶OH -. Single crystals of KCl,KBr and different compositions of KCl x Br 1-x solid solutions are growtn with 0.1mol%—0.3mol% KOH in the melt by the Czochralski technique in air.展开更多
Starting from the data obtained recently,that the crystal yttrium aluminum borat e(NAB)is an ideal material for LD pumped microchip laser is demonstrated.Coopera ting with Material Physics Department of Autonoma Unive...Starting from the data obtained recently,that the crystal yttrium aluminum borat e(NAB)is an ideal material for LD pumped microchip laser is demonstrated.Coopera ting with Material Physics Department of Autonoma University of Madrid,Ti:sappir e laser was used to simulate laser diode to pump a NAB crystal sample of 0.3mm t hickness.For incident pump power of 375mW,laser output power at 1.064μm reach 1 57mW with optical to optical efficiency as high as 42%.The corresponding effici e ncy at 1.341μm is 25%.Output laser beams belong to TEM 00 mode.The thresho ld of laser oscillation at 1.064μm were 13,18,30,100 and 140mW for output mirr ors with transmittance of 0.36%,1%,2%,4% and 6% respectively.NAB crystal has a wide and flat absorption band with half high width of 45nm for pump light and so th e temperature shift of the laser diode wavelength will not affect the pumping effi ciency.All the advantages mentioned show the this crystal is obviously an ideal material for LD pumped microchip laser. Therefrom,the possible application of a series of self ativated laser crystal developed in the seventies years 20th century will be discussed in the case of L D lasers have been well developed.展开更多
In recent years,from the laser experimental study of neodymium doped potassium g adolinium tungstate,i.e.KGd(WO 4) 2 (KGW),laser scientific workers had discove r ed that it has many advantages,as compared to YAG and o...In recent years,from the laser experimental study of neodymium doped potassium g adolinium tungstate,i.e.KGd(WO 4) 2 (KGW),laser scientific workers had discove r ed that it has many advantages,as compared to YAG and other tungstate crystals u n der indentical experimental conditions,such as low lasing threshold,high output energy o r power and high efficiency et al.Especially,as seen on the absorption spectra o f Nd:YAG and Nd:KGW reported by V.Kushawaha et al,a strong and broad absorption line around 808nm is much wider (～12nmFWHM) in Nd:KGW as compared to the Nd:YAG (～1.5nm FWHM),and this wavelength is just during the main peak area emitted by diode laser,so that Nd:KGW may be a excellent candidate for efficient diode pum ping at 808nm.Therefore the research and development of KGW crystals and laser d evices has been bestowed great attention in interational laser science area.For the laser rod with dimensions of 5mm×8mm and 6.3mm×75mm,the xenon flashlamp pumping KGW laser have achieved more laser output and higher efficie n ies than the YAG crystals under identical experimental conditions,by V.Kushawaha et al.In Unite State and K.A.Stankov et al.in Germang respectively.展开更多
With the development of the diode laser pump sources,the Yb 3+ doped crystals have brought much attention which is not suitable for flash light pump source since they are not match in spectrum region.Comparing with Nd...With the development of the diode laser pump sources,the Yb 3+ doped crystals have brought much attention which is not suitable for flash light pump source since they are not match in spectrum region.Comparing with Nd 3+ doped crystals,Yb 3+ doped crystals have many advantages,for example, (1)Yb 3+ doped crystals have very low thermal load,(only about 1/3 of that of Nd 3+ doped crystals) therefore,the systems can obtain lasers with higher optical quality and higher average power. (2)The energy stored up ability of Yb 3+ doped crystals is about 5 times as much as that of Nd 3+ doped crystals. (3)The position of main absorption peak of Yb 3+ matches to the pumping InGaAs diode emission,which is more durable than the AlGaAs diode used to pump the Nd 3+ . (4)The full width at half maximum of Yb 3+ doped crystals is 10 times as much as that of Nd 3+ doped crystals,so,the temperature control requirement of laser diode is relatively moderate. (5)From the point of view of energy transfer,because of the inherently small quantum defect of the Yb 3+ ,the theoredtical quantum efficiency can get up to 91%.展开更多
After 40 years of development,laser crystals have established a firm foundation for solid state laser technology.The improvements of the crystals now on hand and the exploration of new crystals are still going on acti...After 40 years of development,laser crystals have established a firm foundation for solid state laser technology.The improvements of the crystals now on hand and the exploration of new crystals are still going on actively. 1 Development of the laser crystals now on hand 1.1 YAG YAG is a laser crystal with good property,extensive application and wide scale manufacturing.Aimed at the need of LD pumping,many new varieties of garnet have been developed,with the goal of enlarging the absorption of line width.The idea of this development is chiefly as the follows:(1)Enlarge the lattice constant through substitution of cations;(2)Waiden the absorption spectrum through the vacancy of cations;(3)Using cations with host sensitization,such as Mn 2+ ,etc.The author has considered several optional varieties:Y 2.7 La 0.25 Nd 0.05 Al 3.5 Nb 0.9 O 12 (calculating lattice constant: a 0～1.202nm,in contrast of that of YAG: a 0～1.200nm);Y 1.5 LaMn 2+ 0.5 Al 4.5 Si 0.5 O 12 ( a 0～1.205nm);and YLaMn 2+ Al 4(Nb,V) 5+ 0.6 O 12 ( a 0～1.204nm);etc.展开更多
We report the observation of electric field induced random lasing in a dye doped liquid crystal system. This was achieved by using a liquid crystal host with negative dielectric anisotropy doped with laser dye PM 597 ...We report the observation of electric field induced random lasing in a dye doped liquid crystal system. This was achieved by using a liquid crystal host with negative dielectric anisotropy doped with laser dye PM 597 in a 75 μm cell with a homeotropic alignment layer. In the absence of an applied field, only amplified spontaneous emission was observed since the liquid crystal orientation was uniform. However, application of a field resulted in a fieldinduced planar-like configuration with local nonuniformity in liquid crystal orientation. This led to random lasing in the energized state(voltage greater than a transition threshold). The onset of lasing occurs by application of either a spatially homogenous or a spatially inhomogeneous electric field across the liquid crystal. The characteristics of the emission spectra as a function of different(i) dye concentration and(ii) applied voltage were investigated using nanosecond pulsed laser excitation at 532 nm. The effects of using an inhomogeneous field were compared to the use of a homogenous field and reported. It is shown that the spatial configuration can be used to alter the emission spectra of the system. The work is used to suggest a new configuration, referred to here as"reverse mode," for liquid crystal-based random lasers. This new configuration may provide additional avenues for their use in commercial devices.展开更多
Laser displays,benefiting from the characteristic merits of lasers,have led to the revolution of next-generation display technologies owing to their superior color expression.However,the acquisition of pixelated laser...Laser displays,benefiting from the characteristic merits of lasers,have led to the revolution of next-generation display technologies owing to their superior color expression.However,the acquisition of pixelated laser arrays as self-emissive panels for flat-panel laser displays remains challenging.Liquid crystal(LC)materials with excellent processability and optoelectronic properties offer considerable potential for the construction of highly ordered multicolor laser arrays.Here,we demonstrate flat-panel laser displays on LC microlaser pixel arrays through a microtemplate-assisted inkjet printing method.Individual organic red-green-blue(RGB)microlaser pixel arrays were obtained by doping dyes into LCs with photonic band edges to obtain single-mode RGB lasing,leading to a much broader color gamut,compared with the standard RGB color space.Then we acquired periodically patterned RGB pixel matrices by positioning LC microlasers precisely into highly ordered arrays,according to the well-organized geometry of the microtemplates.Subsequently,we demonstrated full-color flat-panel laser displays using the LC microlaser pixel matrices as self-emissive panels.These results provide valuable enlightenment for the construction of next-generation flat-panel laser display devices.展开更多
基金The authors would like to acknowledge the financial supports from Australia Research Council(ARC)under Discovery Projects program(DP180103275)It is also supported by the Scientific Research Funds of Huaqiao University(605-50Y19022)Certain images in this publication have been obtained by the author(s)from the Wikipedia/Wikimedia website,where they were made available under a Creative Commons licence or stated to be in the public domain.Please see individual captions in this publications for details.To the extent that the law allows,IOP Publishing disclaim any liability that any person may suffer as a result of accessing,using or forwarding the image(s).Any reuse rights should be checked and permission should be sought if necessary from the Wikipedia/Wikimedia and/or the copyright owner(as appropriate)before using or forwarding the image(s).
文摘Semiconductor and laser single crystals are usually brittle and hard,which need to be ground to have satisfactory surface integrity and dimensional precision prior to their applications.Improvement of the surface integrity of a ground crystal can shorten the time of a subsequent polishing process,thus reducing the manufacturing cost.The development of cost-effective grinding technologies for those crystals requires an in-depth understanding of their deformation and removal mechanisms.As a result,a great deal of research efforts were directed towards studying this topic in the past two or three decades.In this review,we aimed to summarize the deformation and removal characteristics of representative semiconductor and laser single crystals in accordance with the scale of mechanical loading,especially at extremely small scales.Their removal mechanisms were critically examined based on the evidence obtained from highresolution TEM analyses.The relationships between machining conditions and removal behaviors were discussed to provide a guidance for further advancing of the grinding technologies for those crystals.
基金the National Key Research and Development Program of China(Grant No.2017YFB0405203)the Shanxi“1331 Project”Key Subjects Construction,China(Grant No.1331KSC).
文摘Based on a theoretical model of Q-switched laser with the influences of the driving signal sent to the Pockels cell and the doping concentration of the gain medium taken into account,a method of achieving high energy sub-nanosecond Q-switched lasers is proposed and verified in experiment.When a Nd:YVO4 crystal with a doping concentration of 0.7 at.%is used as a gain medium and a driving signal with the optimal high-level voltage is applied to the Pockels cell,a stable single-transverse-mode electro-optical Q-switched laser with a pulse width of 0.77 ns and a pulse energy of 1.04 mJ operating at the pulse repetition frequency of 1 kHz is achieved.The precise tuning of the pulse width is also demonstrated.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274188 and 11574170
文摘We report the repetitively Q-switched laser operation of the Yb-doped calcium niobium gallium garnet disordered garnet crystal, achieved with an acousto-optic modulator in a compact plano-concave resonator that is endpumped by a 935-nm diode laser. An average output power of 1.96 W is produced at pulse repetition rate of50 k Hz at emission wavelengths around 1035 nm, with a slope efficiency of 16%. The highest pulse energy of 269 μJ is generated at pulse repetition rate of 1 k Hz, with pulse width 12.1 ns and peak power 20.53 kW.
文摘The crystallization behaviour of the laser synthesized nanometric amorphous Si3N4 powders with the particle size of 15 nm in diameter has been studied between 1200° and 1700℃ by XRD,TEM and FTIR techniques. A small amount of β-Si3N4 formed at 1250℃ and increased slowly until the α- β transformation happened at 1700℃, whereas α-Si3N4 appeared at 1300℃ andincreased rapidly between 1500-1600℃. The formation of β phase at the lower temperature was caused by the nitridation of free Si due to the preexisted β-nuclei in the Si3N4 particles, whereasthe α phase was formed by solid crystallization from the amorphous matrix. There were α and β SiC formed at 1700℃ due to the presence of Sio and Co gases in the system. FTIR analysis shows that two new IR absorption at 1356 and 1420 cm-1, and an overall strong absorption in wide wavenumber range resulted from the powders annealed at 1600 and 1700℃
基金The research was performed at the Laser Thermal Laboratory by Drs David J Hwang,Sang-gil Ryu,Eunpa Kim,Jung Bin In,and the current students,Letian Wang,Yoonsoo Rho and Matthew Eliceiri.Professors Andrew M Minor,Junqiao Wu,Oscar D Dubon,Drs Bin Xiang,Frances I Allen,and Changhyun Ko of UCB Materials Science and Engineering,and Dr Carlo Carraro of UCB Chem.Engineering contributed to the work.The research was supported by DARPA/MTO under TBN grant N66001-08-1-2041,the US Department of Energy SBIR grant(DE-FG02-07ER84813),Samsung GRO,and NSF CMMI-1363392.The in situ experiments were performed at the National Center for Electron Microscopy at the Lawrence Berkeley National Laboratory,which is supported by the Office of Science,Office of Basic Energy Sciences,Scientific User Facilities Division,of the US Department of Energy under Contract No.DE-AC02-05CH11231.The laser-induced nanowire growth and doping was conducted on the LACVD apparatus in the UC Berkeley Marvell Nanofabrication Laboratory.
文摘This article summarizes work at the Laser Thermal Laboratory and discusses related studies on the laser synthesis and functionalization of semiconductor nanostructures and two-dimensional(2D)semiconductor materials.Research has been carried out on the laser-induced crystallization of thin films and nanostructures.The in situ transmission electron microscopy(TEM)monitoring of the crystallization of amorphous precursors in nanodomains is discussed herein.The directed assembly of silicon nanoparticles and the modulation of their optical properties by phase switching is presented.The vapor-liquid-solid mechanism has been adopted as a bottom-up approach in the synthesis of semiconducting nanowires(NWs).In contrast to furnace heating methods,laser irradiation offers high spatial selectivity and precise control of the heating mechanism in the time domain.These attributes enabled the investigation of NW nucleation and the early stage of nanostructure growth.Site-and shape-selective,on-demand direct integration of oriented NWs was accomplished.Growth of discrete silicon NWs with nanoscale location selectivity by employing near-field laser illumination is also reported herein.Tuning the properties of 2D transition metal dichalcogenides(TMDCs)by modulating the free carrier type,density,and composition can offer an exciting new pathway to various practical nanoscale electronics.In situ Raman probing of laser-induced processing of TMDC flakes was conducted in a TEM instrument.
基金This work is supported by the Intermural Grant Program(IGP)at Auburn University.
文摘Direct growth and patterning of atomically thin two-dimensional(2D)materials on various substrates are essential steps towards enabling their potential for use in the next generation of electronic and optoelectronic devices.The conventional gas-phase growth techniques,however,are not compatible with direct patterning processes.Similarly,the condensed-phase methods,based on metal oxide deposition and chalcogenization processes,require lengthy processing times and high temperatures.Here,a novel self-limiting laser crystallization process for direct crystallization and patterning of 2D materials is demonstrated.It takes advantage of significant differences between the optical properties of the amorphous and crystalline phases.Pulsed laser deposition is used to deposit a thin layer of stoichiometric amorphous molybdenum disulfide(MoS2)film(∼3 nm)onto the fused silica substrates.A tunable nanosecond infrared(IR)laser(1064 nm)is then employed to couple a precise amount of power and number of pulses into the amorphous materials for controlled crystallization and direct writing processes.The IR laser interaction with the amorphous layer results in fast heating,crystallization,and/or evaporation of the materials within a narrow processing window.However,reduction of the midgap and defect states in the as crystallized layers decreases the laser coupling efficiency leading to higher tolerance to process parameters.The deliberate design of such laser 2D material interactions allows the selflimiting crystallization phenomena to occur with increased quality and a much broader processing window.This unique laser processing approach allows high-quality crystallization,direct writing,patterning,and the integration of various 2D materials into future functional devices.
基金Supported by the National Key Basic Research Special Fund/CNKBRSF of China under Grant Nos 2012CB933501,2016YFA0301102,2016YFB0401804 and 2016YFB0402203the National Natural Science Foundation of China under Grant Nos61535013,61321063 and 61137003+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant Nos XDB24010100,XDB24010200,XDB24020100 and XDB24030100the One Hundred Person Project of the Chinese Academy of Sciences
文摘The single and coupled photonic crystal nanocavity lasers are fabricated in the InGaAsP material system and their static and dynamic features are compared. The coupled-cavity lasers show a larger lasing efficiency and generate an output power higher than the single-cavity lasers, results that are consistent with the theoretical results obtained by rate equations. In dynamic regime, the single-cavity lasers produce pulses as short as 113 ps,while the coupled-cavity lasers show a significantly longer lasing duration. These results indicate that the photonic crystal laser is a promising candidate for the light source in high-speed photonic integrated circuit.
基金financially supported by the National Natural Science Foundation of China (Nos. 12174222 and 61775120)the Natural Science Foundation of Shandong Province (ZR2021ZD02)Taishan Scholars Program of Shandong Province
文摘Femtosecond laser inscription or writing has been recognized as a powerful technique to engineer various materials toward a number of applications.By efficient modification of refractive indices of dielectric crystals,optical waveguides with diverse configurations have been produced by femtosecond laser writing.The waveguiding properties depend not only on the parameters of the laser writing but also on the nature of the crystals.The mode profile tailoring and polarization engineering are realizable by selecting appropriate fabrication conditions.In addition,regardless of the complexity of crystal refractive index changes induced by ultrafast pulses,several three-dimensional geometries have been designed and implemented that are useful for the fabrication of laser-written photonic chips.Some intriguing devices,e.g.,waveguide lasers,wavelength converters,and quantum memories,have been made,exhibiting potential for applications in various areas.Our work gives a concise review of the femtosecond laser-inscribed waveguides in dielectric crystals and focuses on the recent advances of this research area,including the fundamentals,fabrication,and selected photonic applications.
文摘The crystal of high concentration Nd:YAG was grown by flux method and diode pu mp microcavity laser was studied.High efficiency and frequency solid state lase r was built on research and development.some applications such as target designa tion,laser radar,rangefinder,CATV etc. In order to maximize pump efficiency and power output,the Nd concentration shoul d be made as high as possible without degrading the gain through concentration q uenching.In crystal grown by Czochraski method.it is difficult to increase the N d concentration over 1.2% because of Nd segregation in the melt (yttrium aluminum garnet),which leads to large nonuniformities in doping.However,by using the f lux met hod growth technique,it is possible to grow uniformly doped crystal as much as 4 % Nd concentration YAG.
文摘The KGd(WO 4) 2[KGW] crystal has a structure belonging to the monoclinic sys tem with space group C 2/ c and with unit cell dimensions a =1.068mm, b =1.043nm, c =0.76nm, β =130°.This crystal is an excellent host material for solid state lasers.The threshold of the laser oscillations in a Nd 3+ d oped KGW laser crystal is considerable low and has a higher emissive section.T he fluorescent concentration quench effect of the Nd 3+ ion in the KGW crystal may be weakened due to the W O covalent bond,so this crystal has a higher dopi ng concentration of active ion.Furthermore,the absorption band at 808nm of Nd 3+ in the KGW crystal,which has 12nm FWHM,is well matched with the emission w avelength of a laser diode ,a solid state laser pump that is very convenient and popular in laser science and technology today.Therefore the KGW crystal has a l aser emission with higher output and higher efficiency.Scientists of laser techn ology circles are very interested in Yb 3+ doped laser crystals because they have four advanta ges when they are compared with Nd 3+ doped laser crystals.Firstly,their flu orescent lifetimes are three or four times as many as that of Nd 3+ doped la ser crystals,which is beneficial to reserving the energy.Secondly,the heat energ y,which is formed when laser is operating,will be decreased because the pumping band is close to the upper energy level.Not only will the use ratio of energy be increased but also the damage effect to laser properties will be decreased.Thir dly,there is no absorption problems of excite state because the energy level of Yb 3+ is simple.Finally,the higher optical quality crystals are easier to gr ow because the radius of Yb 3+ is closer to that of Gd 3+ .Furthermore,Y b 3+ doped laser crystals can substitute the Ti sapphire for the psec laser .
文摘Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic requests are high figure of merit(FOM),high damage threshold,good chemical stability and mechanical properties.Perfection and growth characters are also important for a practical SFD crystal. In recent years,the discovery of rare earth calcium oxyborates has resulted in the renewal in the field of SFD crystal.ReCaO(BO 3) 3(ReCOB)is a new type of novel nonlinear optical crystals which is nearly congruently melt and can be grown with Czochralski method.ReCOB crystals possess high nonlinear coefficients and damage thresholds.They are non hydroscopic and easy cutting and polishing.They belong to monoclinic with point group m and space group cm.The strong anisotropy originated from the low symmetry makes the measurement and application of the crystal more complicated.More than half of naturally existed crystals belongs to low symmetry,consequently,the research on the nonlinear and anisotropic laser optical properties are not only important for ReCOB crystal,but also useful for the applications of other low symmetry crystals.
文摘Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re∶GdYCOB single crystals growth were synthesized by multistage solid phase reaction method.Re∶GdYCOB single crystals were grown by Czochralski technique.The pulling rates are 0.5-2mm/h and the rotation rates are 10-30r/min.Usually 65-75% polycrystalline materials can be transformed into good quality single crystals under our growth conditions. The structures of some as grown Re∶GdYCOB single crystals were measured by using a four circle diffractometer.The results measured show that the space group of the crystals is C 3 s Cm.The determined lattice constants of 8 at% Nd doped Ca 4YO(BO 3) 3 single crystal are a =0.8076nm, b =1.6020nm, c =0.3527nm , β =101.23°.
文摘The 3μm laser emission of Er 3+ ( 4 I 11/2 → 4 I 13/2 )in the YAG crystal is,in principle,selfsaturation transition,the lifetime of the upper laser level( 4 I 11/2 )being smaller than that of the olwer one( 4 I 13/2 ).The effect of the selfsaturation limit the laser output. In present work,for the first time,we report on the investigation of the utility of Pr 3+ as a sensitizer of Er 3+ ion,using Pr 3+ 4 f 2-4 f5d transition.The radiation emission from 4f5d configuration of Pr 3+ ion have been observed in the YAG∶Pr 3+ crystal.This shows that under suitable conditions this radiant process can compete successfully by non radiative decay to the 4 f configuration.Using Er 3+ Pr 3 codoped YAG it is possible to predict the position of the lowest 4 f 2-4 f5d absorption bands of Pr 3+ ion in the ultraviolet range and to present the occurrence of the energy transfer from Pr 3+ to Er 3+ ion.By xenon flash lamp pumped 2.93μm laser action in the YAG∶(Er 3+ ,Pr 3+ ) crystals was demonstrated at room temperature.
文摘Tunable color center lasers making use of electron trapping defects such as F A and F + 2 like centers in alkali halide crystals can deliver broadly tunable power over the near infrared 0.8—4.0μm range.The tunable range and their impressive feature of narrow linewidth make these solid state lasers important to molecular spectroscopy,pollution detection,fiber optics communication and other scientific research fields.The( F + 2) H center consisting of an F + 2 center and an neibouring O 2- ion,is one of the most important color centers.In this paper,we will study the preparation,absorption and emission spectra of the ( F + 2) H center in mixed crystal KCl KBr∶OH -. Single crystals of KCl,KBr and different compositions of KCl x Br 1-x solid solutions are growtn with 0.1mol%—0.3mol% KOH in the melt by the Czochralski technique in air.
文摘Starting from the data obtained recently,that the crystal yttrium aluminum borat e(NAB)is an ideal material for LD pumped microchip laser is demonstrated.Coopera ting with Material Physics Department of Autonoma University of Madrid,Ti:sappir e laser was used to simulate laser diode to pump a NAB crystal sample of 0.3mm t hickness.For incident pump power of 375mW,laser output power at 1.064μm reach 1 57mW with optical to optical efficiency as high as 42%.The corresponding effici e ncy at 1.341μm is 25%.Output laser beams belong to TEM 00 mode.The thresho ld of laser oscillation at 1.064μm were 13,18,30,100 and 140mW for output mirr ors with transmittance of 0.36%,1%,2%,4% and 6% respectively.NAB crystal has a wide and flat absorption band with half high width of 45nm for pump light and so th e temperature shift of the laser diode wavelength will not affect the pumping effi ciency.All the advantages mentioned show the this crystal is obviously an ideal material for LD pumped microchip laser. Therefrom,the possible application of a series of self ativated laser crystal developed in the seventies years 20th century will be discussed in the case of L D lasers have been well developed.
文摘In recent years,from the laser experimental study of neodymium doped potassium g adolinium tungstate,i.e.KGd(WO 4) 2 (KGW),laser scientific workers had discove r ed that it has many advantages,as compared to YAG and other tungstate crystals u n der indentical experimental conditions,such as low lasing threshold,high output energy o r power and high efficiency et al.Especially,as seen on the absorption spectra o f Nd:YAG and Nd:KGW reported by V.Kushawaha et al,a strong and broad absorption line around 808nm is much wider (～12nmFWHM) in Nd:KGW as compared to the Nd:YAG (～1.5nm FWHM),and this wavelength is just during the main peak area emitted by diode laser,so that Nd:KGW may be a excellent candidate for efficient diode pum ping at 808nm.Therefore the research and development of KGW crystals and laser d evices has been bestowed great attention in interational laser science area.For the laser rod with dimensions of 5mm×8mm and 6.3mm×75mm,the xenon flashlamp pumping KGW laser have achieved more laser output and higher efficie n ies than the YAG crystals under identical experimental conditions,by V.Kushawaha et al.In Unite State and K.A.Stankov et al.in Germang respectively.
文摘With the development of the diode laser pump sources,the Yb 3+ doped crystals have brought much attention which is not suitable for flash light pump source since they are not match in spectrum region.Comparing with Nd 3+ doped crystals,Yb 3+ doped crystals have many advantages,for example, (1)Yb 3+ doped crystals have very low thermal load,(only about 1/3 of that of Nd 3+ doped crystals) therefore,the systems can obtain lasers with higher optical quality and higher average power. (2)The energy stored up ability of Yb 3+ doped crystals is about 5 times as much as that of Nd 3+ doped crystals. (3)The position of main absorption peak of Yb 3+ matches to the pumping InGaAs diode emission,which is more durable than the AlGaAs diode used to pump the Nd 3+ . (4)The full width at half maximum of Yb 3+ doped crystals is 10 times as much as that of Nd 3+ doped crystals,so,the temperature control requirement of laser diode is relatively moderate. (5)From the point of view of energy transfer,because of the inherently small quantum defect of the Yb 3+ ,the theoredtical quantum efficiency can get up to 91%.
文摘After 40 years of development,laser crystals have established a firm foundation for solid state laser technology.The improvements of the crystals now on hand and the exploration of new crystals are still going on actively. 1 Development of the laser crystals now on hand 1.1 YAG YAG is a laser crystal with good property,extensive application and wide scale manufacturing.Aimed at the need of LD pumping,many new varieties of garnet have been developed,with the goal of enlarging the absorption of line width.The idea of this development is chiefly as the follows:(1)Enlarge the lattice constant through substitution of cations;(2)Waiden the absorption spectrum through the vacancy of cations;(3)Using cations with host sensitization,such as Mn 2+ ,etc.The author has considered several optional varieties:Y 2.7 La 0.25 Nd 0.05 Al 3.5 Nb 0.9 O 12 (calculating lattice constant: a 0～1.202nm,in contrast of that of YAG: a 0～1.200nm);Y 1.5 LaMn 2+ 0.5 Al 4.5 Si 0.5 O 12 ( a 0～1.205nm);and YLaMn 2+ Al 4(Nb,V) 5+ 0.6 O 12 ( a 0～1.204nm);etc.
文摘We report the observation of electric field induced random lasing in a dye doped liquid crystal system. This was achieved by using a liquid crystal host with negative dielectric anisotropy doped with laser dye PM 597 in a 75 μm cell with a homeotropic alignment layer. In the absence of an applied field, only amplified spontaneous emission was observed since the liquid crystal orientation was uniform. However, application of a field resulted in a fieldinduced planar-like configuration with local nonuniformity in liquid crystal orientation. This led to random lasing in the energized state(voltage greater than a transition threshold). The onset of lasing occurs by application of either a spatially homogenous or a spatially inhomogeneous electric field across the liquid crystal. The characteristics of the emission spectra as a function of different(i) dye concentration and(ii) applied voltage were investigated using nanosecond pulsed laser excitation at 532 nm. The effects of using an inhomogeneous field were compared to the use of a homogenous field and reported. It is shown that the spatial configuration can be used to alter the emission spectra of the system. The work is used to suggest a new configuration, referred to here as"reverse mode," for liquid crystal-based random lasers. This new configuration may provide additional avenues for their use in commercial devices.
基金supported financially by the Ministry of Science and Technology of China(no.2017YFA0204502)the National Natural Science Foundation of China(grant nos.21533013 and 21790364).
文摘Laser displays,benefiting from the characteristic merits of lasers,have led to the revolution of next-generation display technologies owing to their superior color expression.However,the acquisition of pixelated laser arrays as self-emissive panels for flat-panel laser displays remains challenging.Liquid crystal(LC)materials with excellent processability and optoelectronic properties offer considerable potential for the construction of highly ordered multicolor laser arrays.Here,we demonstrate flat-panel laser displays on LC microlaser pixel arrays through a microtemplate-assisted inkjet printing method.Individual organic red-green-blue(RGB)microlaser pixel arrays were obtained by doping dyes into LCs with photonic band edges to obtain single-mode RGB lasing,leading to a much broader color gamut,compared with the standard RGB color space.Then we acquired periodically patterned RGB pixel matrices by positioning LC microlasers precisely into highly ordered arrays,according to the well-organized geometry of the microtemplates.Subsequently,we demonstrated full-color flat-panel laser displays using the LC microlaser pixel matrices as self-emissive panels.These results provide valuable enlightenment for the construction of next-generation flat-panel laser display devices.
