REPORTS imental evidence. From this measurement, we 12. M. Wittman, A Nazarkin, G. Korn, Phys. Rev. Lett. 84, 22. In the limit of AApmal <k lp l the change also learn that the electric field points toward lectrons'final kinetic energy is given by Al the electron detector at the pulse peak and that 13. Y Kobayashi, K. Torizuka, Opt Lett. 25, 856(2000) (8W Uema where Up Yin, S.E. over an its strength is 7 X 107 V/cm. With the tem- Harris, Phys. Rev. Lett. 87, 033402(2001) poral evolution, strength, and direction of E,(n 15. K Yamane et al. Opt Lett. 28, 2258(2003) 23. Increase of the excitation energy ho tends to measured,we have performed a complete char- 16.MY Shverdin, D R Walker: D. D: Yavuz, g, Y Yin field ionization and ensuring a high acterization of a light pulse in terms of ev.Mod.Phys.72.545(2000 classical electric field. Direct probing of light-field oscillations ashington, DC, 2004). Postdeadline paper CPDC1 represents what we believe to be a substantial extension of the basic repertoire of modern Lasers and Electro-Optics experimental science. The door to practica pplications is opened by the creation of the 18.R Kienberger et al. Science 297, 1144(2002) key element of the demonstrated light-field 19. A D. Bandrauk, Sz Chelkowski, N H Shon, Phys. Rev. Technology fellowship to R K from the Austrian detector, the synchronized attosecond elec- Academy of Sciences. our intense <5-fs laser pulse appears to be 21. R Kienberger et al, Nature 427, 817(2004) 28 May 2004: accepted 20 July 2004 apable of producing the necessary XUV trigger burst without suffering any noticeable back-action to its own temporal shape(Fig. Nanoribbon Waveguides for the attosecond photon probe, this powerful few-femtosecond Subwavelength photonics pulse is ideally suited for the synthesis of Itrabroadband, few-cycle, opticalwave- Integration forms (5-17). Being composed of radiation extending from the infrared through the vis- Matt Law,, 2* Donald J. Sirbuly, , Z* Justin C. Johnson, ible to the ultraviolet region. the resultant Josh Goldberger ,Richard J Saykally, Peidong Ya ew-cycle, monocycle, and conceivably ever subcycle waveforms will offer a marked de- Although the electrical integration of chemically synthesized nanowires has been gree of control over the temporal variation of achieved with lithography, optical integration, which promises high speeds and electric and magnetic forces on molecular greater device versatility, remains unexplored. We describe the properties and and atomic time scales functions of individual crystalline oxide nanoribbons that act as subwavelength These light forces, in turm, afford the pro optical waveguides and assess their applicability as nanoscale photonic elements of controlling quantum transitions of electrons in The length, flexibility, and strength of these structures enable their manipulation toms and molecules and-at relativistic inten- on surfaces, including the optical linking of nanoribbon waveguides and other sities-their center-of-mass motion. Reproduc nanowire elements to form networks and device components, We demonstrate the ible ultrabroadband light wave synthesis, a pre assembly of ribbon waveguides with nanowire light sources and detectors as a first requisite for these prospects to materialize, is step toward building nanowire photonic circuitry inconceivable without subfemtosecond measure ment of the synthesized waveforms. Beyond Photonics, the optical analog of electronics, versity of optical and electrical properties, providing the subfemtosecond electron probe for shares the logic of miniaturization that drives good size control, low surface roughness, these measurements, the substantial experimen- research in semiconductor and information and, in principle, the ability to operate above tal efforts associated with the construction and technology. The ability to manipulate pulses and below the diffraction limit. The toolbox reliable operation of a subfemtosecond photon of light within sub-micrometer volumes is of nanowire device elements already includes source will pay off in yet another way. The vital for highly integrated light-based devic- various types of transistors(5), light-emitting envisioned control of electronic motion with es, such as optical computers, to be realized. diodes(6), lasers(7,8), and photodetectors light forces can only be regarded as accom. Recent advances in the use of photonic band (9). An important step toward nanowire pho- plished once it has been measured. Owing to gap(1, 2)and plasmonic (3, 4) phenomena to tonics is to develop a nanowire waveguid eir perfect synchronism with the synthesized control the flow of light are impressive in this that can link these various elements and pro- light waveforms, the subfemtosecond photon regard. One alternative route to integrated vide the flexibility in interconnection patterns obe will allow us to test the degree of control photonics is to assemble photonic circuits that is needed to carry out complex tasks such achieved by tracking the triggered (and hopeful- from a collection of nanowire elements that as logic operations(10). Our demonstration ly steered) motion in a time-resolved fashion. assume different functions, such as light cre- of nanowire-based photonics complements ation, routing, and detection. Chemically syn- and expands upon recent work on optical thesized nanowires have several features that beam steering in mesostructured silica cavi- 1. R. Trereinoc es al,ge. te. strum. 68. 3277(1997) make them good photonic building blocks, ties(n) and on subwavelength structures 2. C laconia, L.A. Walmsley, Opt. Lett. 23, 792(1998). including inherent one-dimensionality, a di- made lithographically (12, 13)and by the 3. G.G. Paulus et al, Phys. Rev. Lett. 91, 253004(2003) drawing of silica microfibers (14) 4. T. Brabec, F. Krausz, Phys. Rev. Lett. 78, 3282( 1997) Nanoscale ribbon-shaped crystals of bina- 6.5 nikawa T Imasaka, Op比Cmn969(9BD erkeley. CA 94> Chemistry. University of Califonia, ry oxides exhibit a range of interesting prop 7. AE Kaplan, P L Shkolnikov, Phys. Rev. Lett. 73, 1243 Lawrence Berkeley National Laboratory, 1 Cyclotro erties including extreme mechanical oad, Berkeley, CA 94720, USA ity, surface-mediated electrical conductivity of a rece 10.A Nazarkin, G. Korn, Phys. Rev. Lett. 83, 4748(1999). To whom correspondence should be addressed. E- study of the photoluminescence(PL)of SnO2 11. 0. Albert, G Mourou, Appl. Phys. B 69, 207( 1999). mail: P_yang @ucink berkeley edu nanoribbons, we noted that ribbons with high .sciencemag. org SCIENCE VOL 305 27 AUGUST 2004 1269imental evidence. From this measurement, we also learn that the electric field points toward the electron detector at the pulse peak and that its strength is
7 107 V/cm. With the tem￾poral evolution, strength, and direction of EL(t) measured, we have performed a complete char￾acterization of a light pulse in terms of its classical electric field. Direct probing of light-field oscillations represents what we believe to be a substantial extension of the basic repertoire of modern experimental science. The door to practical applications is opened by the creation of the key element of the demonstrated light-field detector, the synchronized attosecond elec￾tron probe, in a noninvasive manner. In fact, our intense 5-fs laser pulse appears to be capable of producing the necessary XUV trigger burst without suffering any noticeable back-action to its own temporal shape (Fig. 3). After having produced the attosecond photon probe, this powerful few-femtosecond pulse is ideally suited for the synthesis of ultrabroadband, few-cycle, optical wave￾forms (5–17). Being composed of radiation extending from the infrared through the vis￾ible to the ultraviolet region, the resultant few-cycle, monocycle, and conceivably even subcycle waveforms will offer a marked de￾gree of control over the temporal variation of electric and magnetic forces on molecular and atomic time scales. These light forces, in turn, afford the promise of controlling quantum transitions of electrons in atoms and molecules and—at relativistic inten￾sities—their center-of-mass motion. Reproduc￾ible ultrabroadband light wave synthesis, a pre￾requisite for these prospects to materialize, is inconceivable without subfemtosecond measure￾ment of the synthesized waveforms. Beyond providing the subfemtosecond electron probe for these measurements, the substantial experimen￾tal efforts associated with the construction and reliable operation of a subfemtosecond photon source will pay off in yet another way. The envisioned control of electronic motion with light forces can only be regarded as accom￾plished once it has been measured. Owing to their perfect synchronism with the synthesized light waveforms, the subfemtosecond photon probe will allow us to test the degree of control achieved by tracking the triggered (and hopeful￾ly steered) motion in a time-resolved fashion. References and Notes 1. R. Trebino et al., Rev. Sci. Instrum. 68, 3277 (1997). 2. C. Iaconis, I. A. Walmsley, Opt. Lett. 23, 792 (1998). 3. G. G. Paulus et al., Phys. Rev. Lett. 91, 253004 (2003). 4. T. Brabec, F. Krausz, Phys. Rev. Lett. 78, 3282 (1997). 5 . T. W. Ha¨nsch, Opt. Commun. 80, 71 (1990). 6. S. Yoshikawa, T. Imasaka, Opt. Commun. 96, 94 (1993). 7. A. E. Kaplan, P. L. Shkolnikov, Phys. Rev. Lett. 73, 1243 (1994). 8. K. Shimoda, Jpn. J. Appl. Phys. 34, 3566 (1995). 9. S. E. Harris, A. V. Sokolov, Phys. Rev. Lett. 81, 2894 (1998). 10. A. Nazarkin, G. Korn, Phys. Rev. Lett. 83, 4748 (1999). 11. O. Albert, G. Mourou, Appl. Phys. B 69, 207 (1999). 12. M. Wittman, A. Nazarkin, G. Korn, Phys. Rev. Lett. 84, 5508 (2000). 13. Y. Kobayashi, K. Torizuka, Opt. Lett. 25, 856 (2000). 14. A. V. Sokolov, D. R. Walker, D. D. Yavuz, G. Y. Yin, S. E. Harris, Phys. Rev. Lett. 87, 033402 (2001). 15. K. Yamane et al., Opt. Lett. 28, 2258 (2003). 16. M. Y. Shverdin, D. R. Walker, D. D. Yavuz, G. Y. Yin, S. E. Harris, in OSA Trends in Optics and Photonics Series (TOPS) Vol. 96, Conference on Lasers and Electro-Optics (CLEO) (Optical Society of America, Washington, DC, 2004), Postdeadline paper CPDC1. 17. K. Yamane, T. Kito, R. Morita, M. Yamashita, in OSA Trends in Optics and Photonics Series (TOPS), vol. 96, Conference on Lasers and Electro-Optics (CLEO), (Optical Society of America, Washington, DC, 2004), Postdeadline paper CPDC2. 18. R. Kienberger et al., Science 297, 1144 (2002). 19. A. D. Bandrauk, Sz. Chelkowski, N. H. Shon, Phys. Rev. Lett. 89, 283903 (2002). 20. A. Baltuska et al., Nature 421, 611 (2003). 21. R. Kienberger et al., Nature 427, 817 (2004). 22. In the limit of
pmax

pi
, the change in the electrons’ final kinetic energy is given by Wmax [8Wi Up,max] 1/2, where Up,max  e2E0 2/4meL 2 is the electrons’ quiver energy averaged over an optical cycle at the peak of the light pulse. 23. Increase of the excitation energy
xuv tends to reconcile the conflicting requirements of avoiding field ionization and ensuring a high dynamic range. 24. T. Brabec, F. Krausz, Rev. Mod. Phys. 72, 545 (2000). 25. We are grateful to B. Ferus for creating the artwork. Sponsored by the fonds zur Fo¨rderung der Wissen￾schafllichen Forschung (Austria, grant nos. Y44-PHY, P15382, and F016), the Deutsche Forschungsgemein￾schaft and the Volkswagenstiftung (Germany), the European ATTO and Ultrashort XUV Pulses for Time￾Resolved and Non-Linear Applications networks, and an Austrian Programme for Advanced Research and Technology fellowship to R.K. from the Austrian Academy of Sciences. 28 May 2004; accepted 20 July 2004 Nanoribbon Waveguides for Subwavelength Photonics Integration Matt Law,1,2* Donald J. Sirbuly,1,2* Justin C. Johnson,1 Josh Goldberger,1 Richard J. Saykally,1 Peidong Yang1,2† Although the electrical integration of chemically synthesized nanowires has been achieved with lithography, optical integration, which promises high speeds and greater device versatility, remains unexplored. We describe the properties and functions of individual crystalline oxide nanoribbons that act as subwavelength optical waveguides and assess their applicability as nanoscale photonic elements. The length, flexibility, and strength of these structures enable their manipulation on surfaces, including the optical linking of nanoribbon waveguides and other nanowire elements to form networks and device components. We demonstrate the assembly of ribbon waveguides with nanowire light sources and detectors as a first step toward building nanowire photonic circuitry. Photonics, the optical analog of electronics, shares the logic of miniaturization that drives research in semiconductor and information technology. The ability to manipulate pulses of light within sub-micrometer volumes is vital for highly integrated light-based devic￾es, such as optical computers, to be realized. Recent advances in the use of photonic band gap (1, 2) and plasmonic (3, 4) phenomena to control the flow of light are impressive in this regard. One alternative route to integrated photonics is to assemble photonic circuits from a collection of nanowire elements that assume different functions, such as light cre￾ation, routing, and detection. Chemically syn￾thesized nanowires have several features that make them good photonic building blocks, including inherent one-dimensionality, a di￾versity of optical and electrical properties, good size control, low surface roughness, and, in principle, the ability to operate above and below the diffraction limit. The toolbox of nanowire device elements already includes various types of transistors (5), light-emitting diodes (6), lasers (7, 8), and photodetectors (9). An important step toward nanowire pho￾tonics is to develop a nanowire waveguide that can link these various elements and pro￾vide the flexibility in interconnection patterns that is needed to carry out complex tasks such as logic operations (10). Our demonstration of nanowire-based photonics complements and expands upon recent work on optical beam steering in mesostructured silica cavi￾ties (11) and on subwavelength structures made lithographically (12, 13) and by the drawing of silica microfibers (14). Nanoscale ribbon-shaped crystals of bina￾ry oxides exhibit a range of interesting prop￾erties including extreme mechanical flexibil￾ity, surface-mediated electrical conductivity (15), and lasing (16). As part of a recent study of the photoluminescence (PL) of SnO2 nanoribbons, we noted that ribbons with high 1 Department of Chemistry, University of California, Berkeley, CA 94720, USA. 2 Materials Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA. *These authors contributed equally to this work. †To whom correspondence should be addressed. E￾mail: p_yang@uclink.berkeley.edu R EPORTS www.sciencemag.org SCIENCE VOL 30527 AUGUST 2004 1269