简介:针对使用单一频率飞秒激光纵模间拍信号测距时测量分辨力和最大非模糊距离之间的矛盾,提出了一种同时使用不同频率的微波信号对距离进行测量并逐级合成测量结果的方法。分别选取频率为100MHz和1GHz的纵模间拍信号测量目标距离,之后调整飞秒激光器的重复频率,使1GHz的纵模间拍信号频率变化1MHz后再次测量,借助频率变化进一步得到更大的合成波长,最后将三次测量的结果逐级合成,在扩展最大非模糊距离的同时保证了测量结果的高精度。实验结果表明,这种方法能够将最大非模糊距离扩展到150m,对目标绝对距离的测量结果不确定度为25.8μm。该方法不需要改变光路结构,测量过程简便,能很好地实现大尺寸高精度的绝对距离测量。
简介:WeinvestigatereactivefluorineatomspectroscopiccharacterizationinatmosphericpressureofHe/SF6plasmausingatomicemissionspectrometry.Asinputradiofrequency(RF)powerlevelsareraisedfrom140to220W,theemissionspectraof685.60(3p4D→3s4Ptransition)and739.87nm(3p4P→3s4Ptransition)increasesignificantly.Moreover,anoptimalvalueofSF6volumeconcentrationintheproductionoffluorineradicals,whichis0.8%isachieved.AdditionofcertainamountsofO2intoHe/SF6plasmaresultsinthepromotionofSF6dissociation.EmissionintensitiesoffluorineatomsshowthemaximumattheO2/SF6ratioof0.4.
简介:Wereportthefabricationofsubmicrometerpitsarray(SP-array)on6H-SiCsurfacebytheinterferenceoftwofemtosecondlaserbeams.FormationmechanismsandopticalabsorptionofSP-arrayarestudied.Therelativereflectivityandtransmissivityofwhitelightdecreaseto10%ofthevaluesofSiCcrystal,andtheopticalabsorptionisenhancedto97%.Therelativereflectivityandtransmissivityofincidentangleswithintherangeof20°-60°arekeptbelow25%.TheenhancementmechanismofopticalabsorptionoftheSP-arrayisalsodiscussed.