NSOM近場(chǎng)光學(xué)

1、NSOM 近場(chǎng)光學(xué) 界面和倏逝場(chǎng)透射和反射系數(shù)近場(chǎng)光學(xué)近場(chǎng)光學(xué)的歷史1928 AD E. H. Synge ( England )1973 AD Ash & Nichols 微波實(shí)驗(yàn)證實(shí) 1956 AD OKeefe 相關(guān)理論的提出1982 AD G. Binning & H. Rohrer 第一步STM誕生1984 AD D. W. Phol 等人 近場(chǎng)光學(xué)技術(shù)與STM結(jié)合1989 AD R. C. Reddick 等人 發(fā)展具有光學(xué)回饋的NSOM且開 啟了以腐蝕方法制作探針1992 AD Eric Betzig 近場(chǎng)光學(xué)技術(shù)與AFM的結(jié)合近場(chǎng)顯微術(shù) The near field decay

2、s exponentially with distance The tip should be kept at a controllede distance from the sample surface Feed back mechanism: shear force (similar to AFM tapping mode) Feedback detection: quartz oscillator (STM current is not suitable for biological samples; optical methods are disturbing the optical

3、response).xyz piezoFeedbackImpedance detectorElectrodesPiezo actuatorAperture SNOMAperture SNOMIlluminationCollectionIlluminationcollectionReflectioncollectionTransmissionilluminationTransmission collectionOperational modes Typical set upAperture SNOMLaserPol. controlfeedbackcontrolxyzScannerDetecto

4、rTopographic imagenf optical imageInvertedoptical microscopeOptical fiberMonochromator SNOM tipsAperture SNOMpullingbreakingheatingHeating and pulling methodTurner etching methodHydrofluoric acidChemical etchingAluminum vaporGlassAl coatingOptical fiber SNOM tips Calculation of the distribution of e

5、lectric field as a function of the tip geometryAperture SNOMSource: InAs QdotPoint like source l/40 below the surface SNOM tips - pullingAperture SNOMLight propagation SNOM tips - etchingAperture SNOMLight propagationHoles are dug by various methods:The best results are obtained by FIB NSOM 應(yīng)用的優(yōu)點(diǎn) 與傳

6、統(tǒng)光學(xué)顯微鏡比較衍射極限的突破 大幅降低設(shè)備成本理想透鏡可分辨的最小距離 D D = 0.61NA：入射光波長(zhǎng)NA：透鏡的數(shù)值孔徑與電子掃描式顯微鏡 ( AFM、STM)比較非破壞性測(cè)量 可偵測(cè)到真實(shí)的表面 ( Real Surface Measurement )樣品不需繁復(fù)的制備手續(xù)無需在真空下檢測(cè)具有其他光學(xué)性質(zhì)的優(yōu)點(diǎn)應(yīng) 用近場(chǎng)光學(xué)原理除了 應(yīng)用于近場(chǎng)光學(xué)顯微鏡、作為納米尺寸的局部光學(xué)強(qiáng)度與材料的光學(xué)特性等測(cè)量用外，由于此技術(shù)同時(shí)具有納米尺寸加工與曝光的能力，故還可用于制作單電子晶體管、量子阱等納米元件，以及應(yīng)用于更高密度的存儲(chǔ)器上。 optical quantum corralApert

7、ure SNOMThe experiment:Testing the subwavelkenght modulation induced on the local density of states of the optical modes by the fabrication of nanometric opticla corralsSubstrate ITOModulators 100nm100nm50nm gold particles deposited by e-beam lithographyTo test the real LDOS the tip should act as a

8、perfetct dipole at a nanometric distance from the surface.Real tips always pertirb the LDOS and what is measured is the combined LDOS of the sample and the tip!optical quantum corralLight Polarization controlElliptical mirros that selects only the near field radiation (propagating radiation is not allowed in the “forbidden light region with qqcThe signal is 0 only closo to the sampleoptical quantum corralTeorical optical LDOS in x, y and z directionoptical quantum corralNear field results in trasmission.Best results obtained with a gold coated tip without ape