View source for Photon-Induced Near-field Electron Microscopy

{{short description|Electron microscope technique}}
'''Photon-Induced Near-field Electron Microscopy''' ('''PINEM''') is a variant of the [[Engineering:Transmission electron microscopy#Ultrafast and dynamic TEM|Ultrafast Transmission Electron Microscopy]] technique and is based on the inelastic coupling between electrons and photons in presence of a surface or a nanostructure.<ref name="BarwickFlanniganZewail2009">{{cite journal | last1 = Barwick | first1 = Brett | last2 = Flannigan | first2 = David J. | last3 = Zewail | first3 = Ahmed H. | title = Photon-induced near-field electron microscopy | journal = Nature | date = December 2009 | volume = 462 | issue = 7275 | pages = 902–906 | issn = 0028-0836 | eissn = 1476-4687 | doi = 10.1038/nature08662 | pmid = 20016598 | s2cid = 4423704 | url = https://authors.library.caltech.edu/42870/}}</ref> This method allows one to investigate time-varying nanoscale electromagnetic fields in an electron microscope.<ref name="PiazzaLummenQuiñonez2015">{{cite journal | last1 = Piazza | first1 = L | last2 = Lummen | first2 = T.T.A. | last3 = Quiñonez | first3 = E | last4 = Murooka | first4 = Y | last5 = Reed | first5 = B.W. | last6 = Barwick | first6 = B | last7 = Carbone | first7 = F | title = Simultaneous observation of the quantization and the interference pattern of a plasmonic near-field | journal = Nature Communications | date = 2 March 2015 | volume = 6 | issue = 1 | page = 6407 | eissn = 2041-1723 | doi = 10.1038/ncomms7407 | pmid = 25728197 | pmc = 4366487 | url = }}</ref><ref>{{Cite journal |last1=Barwick |first1=Brett |last2=Zewail |first2=Ahmed H. |date=2015-10-21 |title=Photonics and Plasmonics in 4D Ultrafast Electron Microscopy |journal=ACS Photonics |language=en |volume=2 |issue=10 |pages=1391–1402 |doi=10.1021/acsphotonics.5b00427 |issn=2330-4022|doi-access=free }}</ref>

For visible light, such inelastic coupling between electrons and light, i.e. direct absorption or emission of photons, is forbidden in free space (vacuum) since it is not possible to simultaneously conserve both energy and momentum. This constraint can be circumvented when photon momentum is broadened as a result of light being reflected or scattered from a surface or nanostructure. This process would then generate evanescently confined near-fields with a broad momentum distribution, reaching high intensities in a nanoconfined space and thus also boosting the cross section of electron-light coupling.

Theoretically, the analytical description of the phenomenon has been provided by Park et al.,<ref>{{cite journal |author1 = S. T. Park |author2 = M. Lin |author3 = A. H. Zewail |date = December 2010 |title = Photon-induced near-field electron microscopy (PINEM): theoretical and experimental |journal = New Journal of Physics |volume  = 12 |issue = 12 |pages = 123028 |doi = 10.1088/1367-2630/12/12/123028|s2cid = 9985483 |doi-access = free }}</ref> Garcia de Abajo et al.<ref>{{cite journal |author1 = F. J. García de Abajo |author2 = A. Asenjo-Garcia |author3 = M. Kociak |date = April 2010 |title = Multiphoton Absorption and Emission by Interaction of Swift Electrons with Evanescent Light Fields |journal = Nano Letters |volume  = 10 |issue = 5 |pages = 1859–1863 |url = https://pubs.acs.org/doi/full/10.1021/nl100613s |doi = 10.1021/nl100613s|pmid = 20415459 }}</ref> and Feist et al.<ref name=Feist2015>{{cite journal |author1 = A. Feist |author2 = K. E. Echternkamp |author3 = J. Schauss |author4 = S. V. Yalunin |author5 = S. Schäfer |author6 = C. Ropers |date = May 2015 |title = Quantum coherent optical phase modulation in an ultrafast transmission electron microscope |journal = Nature |volume  = 521 |issue = 7551 |pages = 200–203 |url = https://www.nature.com/articles/nature14463 |doi = 10.1038/nature14463|pmid = 25971512 |s2cid = 4447578 }}</ref> In these works the authors demonstrated that the strength of electron-light interaction depends on the linear coupling to the electric field projection along the electron propagation direction. In particular, Feist et al.<ref name=Feist2015 /> also experimentally demonstrated that the interaction process results in a coherent spectral redistribution of the electron wave packet producing Rabi oscillations of a multi-level quantum ladder in which the states are separated by the photon energy.

Particularly appealing for photonics application is the fact that the spectral, spatial and momentum distributions of the electrons subjected to such inelastic scattering process are strictly correlated with the near-field distribution mediating the electron-light coupling. The latter can be thus mapped in space and time with ultrafast electron microscopy methods, providing femtosecond movies of nanoscale fields in and around nanostructures.<ref>{{cite journal |author1 = I. Madan |author2 = G. M. Vanacore |author3 = E. Pomarico |author4 = G. Berruto |author5 = R. J. Lamb |author6 = D. McGrouther |author7 = T. T. A. Lummen |author8 =  T. Latychevskaia |author9 = F. J. García de Abajo |author10 = F. Carbone |date = May 2019 |title = Holographic imaging of electromagnetic fields via electron-light quantum interference |journal = Science Advances |volume  = 5 |issue = 5 |pages = eaav8358 |doi = 10.1126/sciadv.aav8358 |pmid = 31058225 |pmc = 6499551 }}</ref><ref>{{Cite journal |last1=Wang |first1=Kangpeng |last2=Dahan |first2=Raphael |last3=Shentcis |first3=Michael |last4=Kauffmann |first4=Yaron |last5=Ben Hayun |first5=Adi |last6=Reinhardt |first6=Ori |last7=Tsesses |first7=Shai |last8=Kaminer |first8=Ido |date=2020-06-04 |title=Coherent interaction between free electrons and a photonic cavity |url=http://www.nature.com/articles/s41586-020-2321-x |journal=Nature |language=en |volume=582 |issue=7810 |pages=50–54 |doi=10.1038/s41586-020-2321-x |pmid=32494081 |arxiv=1908.06206 |s2cid=219281767 |issn=0028-0836}}</ref><ref>{{Cite journal |last1=Kfir |first1=Ofer |last2=Lourenço-Martins |first2=Hugo |last3=Storeck |first3=Gero |last4=Sivis |first4=Murat |last5=Harvey |first5=Tyler R. |last6=Kippenberg |first6=Tobias J. |last7=Feist |first7=Armin |last8=Ropers |first8=Claus |date=2020-06-04 |title=Controlling free electrons with optical whispering-gallery modes |url=http://www.nature.com/articles/s41586-020-2320-y |journal=Nature |language=en |volume=582 |issue=7810 |pages=46–49 |doi=10.1038/s41586-020-2320-y |pmid=32494079 |arxiv=1910.09540 |s2cid=204823876 |issn=0028-0836}}</ref>

More interestingly, the PINEM method can also be used to dynamically manipulate the wave properties of the electron beam by using suitably prepared electromagnetic field configuration. In such a way, one can modulate coherently the amplitude and phase of the electron beam along both the longitudinal and the transverse directions.<ref name=Feist2015 /><ref name="MorimotoBaum2017">{{cite journal | last1 = Morimoto | first1 = Yuya | last2 = Baum | first2 = Peter | title = Diffraction and microscopy with attosecond electron pulse trains | journal = Nature Physics | date = 27 November 2017 | volume = 14 | issue = 3 | pages = 252–256 | issn = 1745-2473 | eissn = 1745-2481 | doi = 10.1038/s41567-017-0007-6 | pmid = | s2cid = 125210956 | url = http://nbn-resolving.de/urn:nbn:de:bsz:352-2-ct2lzpyprxx10}}</ref><ref name="KozákEcksteinSchönenberger2017">{{cite journal | last1 = Kozák | first1 = M. | last2 = Eckstein | first2 = T. | last3 = Schönenberger | first3 = N. | last4 = Hommelhoff | first4 = P. | title = Inelastic ponderomotive scattering of electrons at a high-intensity optical travelling wave in vacuum | journal = Nature Physics | date = 9 October 2017 | volume = 14 | issue = 2 | pages = 121–125 | issn = 1745-2473 | eissn = 1745-2481 | doi = 10.1038/nphys4282 | pmid = | s2cid = 126006282 | url = | arxiv = 1905.05240 }}</ref><ref>{{Cite journal |last1=Priebe |first1=Katharina E. |last2=Rathje |first2=Christopher |last3=Yalunin |first3=Sergey V. |last4=Hohage |first4=Thorsten |last5=Feist |first5=Armin |last6=Schäfer |first6=Sascha |last7=Ropers |first7=Claus |date=December 2017 |title=Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy |url=http://www.nature.com/articles/s41566-017-0045-8 |journal=Nature Photonics |language=en |volume=11 |issue=12 |pages=793–797 |doi=10.1038/s41566-017-0045-8 |arxiv=1706.03680 |s2cid=119105731 |issn=1749-4885}}</ref><ref name="VanacoreMadanBerruto2018">{{cite journal | last1 = Vanacore | first1 = G. M. | last2 = Madan | first2 = I. | last3 = Berruto | first3 = G. | last4 = Wang | first4 = K. | last5 = Pomarico | first5 = E. | last6 = Lamb | first6 = R. J. | last7 = McGrouther | first7 = D. | last8 = Kaminer | first8 = I. | last9 = Barwick | first9 = B. | last10 = García de Abajo | first10 = F. Javier | last11 = Carbone | first11 = F. | title = Attosecond coherent control of free-electron wave functions using semi-infinite light fields | journal = Nature Communications | date = 12 July 2018 | volume = 9 | issue = 1 | page = 2694 | eissn = 2041-1723 | doi = 10.1038/s41467-018-05021-x | pmid = 30002367 | pmc = 6043599 | url = }}</ref><ref>{{cite journal |author1 = K. E. Echternkamp |author2 = A. Feist |author3 = S. Schäfer |author4 = C. Ropers |date = August 2016 |title = Ramsey-type phase control of free-electron beams |journal = Nature Physics |volume  = 12 |issue = 11 |pages = 1000–1004 |url = https://www.nature.com/articles/nphys3844 |doi = 10.1038/NPHYS3844 |arxiv = 1605.00534 |s2cid = 119214197 }}</ref><ref>{{cite journal |author1 = G. M. Vanacore |author2 = G. Berruto |author3 = I. Madan |author4 = E. Pomarico |author5 = P. Biagioni |author6 = R. J. Lamb |author7 = D. McGrouther |author8 = O. Reinhardt |author9 = I. Kaminer |author10 = B. Barwick |author11 = H. Larocque |author12 = V. Grillo |author13 = E. Karimi |author14 = F. J. García de Abajo |author15 = F. Carbone |date = May 2019 |title = Ultrafast generation and control of an electron vortex beam via chiral plasmonic near fields |journal = Nature Materials |volume  = 18 |issue = 6 |pages = 573–579 |url = https://www.nature.com/articles/s41563-019-0336-1 |doi = 10.1038/s41563-019-0336-1 |pmid = 31061485 |s2cid = 119186105 |arxiv = 1806.00366 }}</ref>

==See also==
*[[Engineering:Transmission electron microscopy|Transmission electron microscopy]]
*[[Electron energy loss spectroscopy]] (EELS)
*[[Engineering:Energy filtered transmission electron microscopy|Energy filtered transmission electron microscopy]] (EFTEM)

==References==
{{reflist}}
{{DEFAULTSORT:Photon-Induced Near-Field Electron Microscopy}}
[[Category:Electron beam]]
[[Category:Scientific techniques]]
[[Category:Quantum electrodynamics]]
[[Category:Photonics]]

{{Sourceattribution|Photon-Induced Near-field Electron Microscopy}}