Theoretical Study of the Optical Manipulation of Semiconductor Nanoparticles under an Excitonic Resonance Condition + Reference + T.Iida and H.Ishihara, Phys.Rev.Lett. 90, (2003) ITOH Lab. Kei IMAIZUMI （ M1 ）

Abstract “Manipulation” means “skillful handling”. Optical manipulation is the technique of handling small objects using mechanical interaction between light and matter. Force ・ Manipulating the semiconductor nanoparticle ・ Size selective manipulation

Contents Introduction Application, History Maxwell stress tensor method Calculation Result The merit of using electronic resonance Heat problem Size selective manipulation Summary

Application Handling of DNA T. T. Perkins, D. E. Smith, S. Chu (1994) Biology, Chemistry, Material engineering… Kansai Advanced Research Center Polystyrene bead with a diameter of 1 μm captured by laser

History of optical manipulation 19c Lorentz derived the equation of motion of a charged particle. Laser was invented. A.Ashkin accelerated micro-size particles by laser. Laser cooling of atoms A.Ashkin demonstrated the trapping of dielectric particle with single focused laser beam. Bose Einstein condensation of atoms 1997 Nobel Prize S.Chu, C.Cohen-Tannoudi, W.D.Phillips 2001 Nobel Prize E.A.Cornell, W.Ketterle, C.E.Wieman

Difficulty of manipulating nano-particles Electronic Resonance Manipulating the nano-particles Size selective manipulation Atomic scale r ≪ λ μm r ≫ λ nm difficult ex.) atom trapping ex.) optical tweezer

Forces Scattering force, Absorbing force Gradient force Resonance The interaction between light and matter increases.

Maxwell stress tensor method Lorentz Force Maxwell Equations : time average T : Maxwell’s stress tensor n : normal vector S : Surface of the matter volume integral surface integral

resonance susceptibility E ob ， Δ ob constant depending on the object objectIncident electric field About the resonance P E scat resonant nonresonant P E scat ε ： ResonanceP ： largeE scat ： large

The merit of using electronic resonance Greater advantage of resonance about smaller object! Object CuCl particle hw t = [eV] R=100nm R=50nm

The size dependence of its maximum value in the energy range 0 ~ 4 eV. 100nm → No difference 10nm → 10 4 times lager Handling smaller object Resonance light

Heat problem AbsorptionHeat problem R=50nm 〈I〉〈I〉 〈 II 〉 〈 III 〉, ・・・ Scattering Prevent the heat problem ・・・ Absorption

Size selective manipulation Quantum size effect -Discrete energy levels -Energy shift depends on the size Energy level

Future Application to nanotechnology. Particular particles Propagating plane wave Image

Summary When the size is less than 100nm, the use of electronic resonance has the merit. The exerted acceleration increases as the size decreases. The peak position of the force sensitively varies with the size change. Nanoscale size selection nanotechnology

Optical tweezer Glass sphere (dielectric particle) lens Force laser Force~ pN R>>λ μm

Gradient Force Uniform electric field sloping electric field － － － cancel each other － － － E E total force In the sloping electric field, the power works.

Quantum size effect Discrete energy levels Energy shift depends on the size dot size Size changeEnergy gap change AtomSemiconductor nanoparticle (quantum dot)

Quantum dot laser ・ Laser wavelength depends on the dot size. ・ Low threshold. ・ Stable property at high temperature. threshold ：しきい値 Useful property ↑ The same size dots are needed.

Maxwell stress tensor method Lorentz Force (of N charges) G(t) is the summation of momenta