Professor of Physics
| Office Phone: | (503) 725 - 3818 |
| Office: | Room 406 Science Building 2 |
| E-Mail: | <hopl@pdx.edu> |
then...
and
now...
| Pui-Tak (Peter) Leung Professor of Physics
|
|
|
|
||||||
|
then... |
and |
now... |
On Research: when research cannot be measured with "the shock from a discovery"; "the excitement from a breakthrough"; "the realization of an imaginative idea"...; you measure it with money!
On Teaching: you can only become a successful teacher when you feel more joy in bringing up others than in bringing up yourself!
On Doing Physics: if I can survive in a Physics Department only by not doing physics, I'd rather become a patent officer!
We are at present the only
research group in theoretical
physics among the regular faculty in the department.
It is of
interest to recall a survey conducted by the magazine “Physics World”
at the
turn of the new century (http://physicsworld.com/cws/article/print/851)
for the nomination of the greatest physicists ever lived. Among the top 10 greatest ones, only
Well, we are still in the game, doing (and enjoying) theoretical research in the following three areas: atomic, optical, and “surface” physics, with the last area to include boundaries of nanostructures. In fact, our latest efforts have been focused on the optical properties of metallic nanostructures. Thus we have divided into the following research engagements:
Plasmonics: we
have been studying the possibly novel optical
properties of metallic nanoparticles and nanoshells. These
properties originated mainly from the
localized collective excitation of the free electrons at the particle
surfaces
(surface plasmon excitation). These
excitations can lead to very strong local evanescent fields which can
be
applied to various spectroscopy and sensor technologies.
Our interest is mainly in the possible
quantum effect on these excitations as the metallic structure gets to
ultra-small sizes (below ~ 10 nm). While
such dimensions are small enough for one to start worrying about
possible
quantum effects, they still require huge amount of computation starting
with the
Schrodinger equation for the system. To
compromise, we have adopted a phenomenological approach using the
formulations
from nonlocal optics. We have also
applied our results to study possible novel spectroscopic features such
as
those from surface enhanced Raman scattering (SERS) from metallic
nanoshells. Our work is in collaboration
with people at the
Other novel optical phenomena at metallic surfaces have also been studied from time to time. One interesting discovery from our recent study is the possibility of observing very large backward lateral displacement of the incident beam (known as negative Goos-Hanchen shift) at a vacuum-metal interface. Possible application of this displacement to optical sensing was also explored.
Another collaboration took place in 1991 with the IBM (Almaden) group in the study of the laser cleaning technique of contaminated surfaces. In this technique, a liquid layer (microns thick) is deposited on the surface and exploded by the fast heating of an excimer laser pulse (~20 ns). This project has since been completed by the IBM group, although we still keep our interest alive on the study of optothermal effects from the interaction of a solid surface with a laser pulse.
Atomic
Physics: Besides optical and
surface
physics, we have also engaged recently in the study of energy
deposition of
fast particles in matter. For this, we have applied previous
results
worked out in relativistic quantum mechanics concerning atomic sum
rules. This
represents a continuation of work in an area I first studied as a
graduate
student.
Most of the publications below appeared in journals from the following societies/publishers :
American Chemical Society
Optical
Society of America
American Physical Society
American Insitute of Physics
Institute of Physics
Elsevier
For my publications in Physical Review and Physical Review Letters,
please click here
For more details, see my complete c.v.
Graduate
students supervised at PSU
Link to an essay written in memory
of
my mother (in Chinese)
Selected Publications
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Refereed Journals (since joining PSU, 1988
- )
J. H. Huang, R. Chang, P. T. Leung and D. P. Tsai, 2008 “ Nonlinear dispersion relation for
H. Y. Xie, P.
T. Leung, and D. P. Tsai, 2008 " General proof of optical reciprocity for
nonlocal electrodynamics " J. Phys. A (in press). pdf
H. Y. Xie, P.
T. Leung, and D. P. Tsai, 2008
" General validity of reciprocity in quantum mechanics"
Phys.
Rev. A (in press). pdf
C. W. Chen, H.-P. Chiang,
P. T. Leung, and D. P. Tsai, 2008 " Temperature dependence of
enhanced optical absorption and Raman spectroscopy
from metallic nanoparticles " Solid State Commun 148:
413-416. pdf
Z. E. Goude and P. T. Leung, 2007 " Surface Enhanced Raman
Scattering from
Metallic Nanoshells with Nonlocal Dielectric Response" Solid
State Commun 143: 416-420. pdf
C. W. Chen, C. H. Lin, H. P. Chiang, Y. -C. Liu, P. T. Leung and
W. S. Tse, 2007
"Temperature Dependence of the Sensitivity of a Long-Range Surface
Plasmon Optical
Sensor" Applied Phys A 89: 377-380. pdf
C.-W. Chen, W.-C. Lin, L.-S. Liao, Z.-H. Lin, H.-P. Chiang, P.
T. Leung, E. Sijercic
and W. S. Tse, 2007 "Optical Temperature Sensing Based on the
Goos-Hanchen Effect"
Applied Optics 46: 5347-5351. pdf
P. T. Leung, C..W. Chen and H.-P. Chiang, 2007
"Large negative Goos-Hanchen shift at
metal surfaces" Optics Commun 276: 206-208. pdf. Experimental observation had
verified this
effect two months after our paper appeared. See experimental verification
H.P. Chiang, C. W. Chen, J. J. Wu, H. L. Li, T. Y. Lin , E. J.
Sanchez and P. T. Leung, 2007
"Effects of temperature on the surface plasmon
resonance at a metal-semiconductor interface"
Thin Solid Films 515: 6953-6961. pdf
H. Sinky and P. T. Leung, 2006 " Relativistic
corrections to a generalized sum rule"
Phys. Rev. A 74: 034703. pdf
Leung P. T., Ni G. J., 2006 "
On the singularities of the electrostatic and magnetostatic dipole
fields"
Eur. J. Phys. 27: N1-N3. pdf
R. Chang and P. T. Leung, 2006
" Nonlocal effects on the optical and molecular interactions with
metallic nanoshells" Phys. Rev. B
73: 125438; ibid 75:079901(E). pdf
H. P. Chiang, J. L. Lin, R. Chang, Z. W. Chen
and P. T. Leung, 2005 " High resolution angular
measurement using
surface-plasmon-resonance heterodyne
interferometry at optimal incident wavelengths "
Proc. SPIE vol. 6002, 600218: 1-10. pdf
R. Chang and P. T. Leung, 2005 "
Theoretical study of nonloal effects in the optical response of
metallic nanoshells"
Proc. SPIE vol. 6002, 60020V: 1-10. pdf
Chiang H. P., Lin J. L., R. Chang, Su S. Y.
and
Leung P. T., 2005 " High resolution angular measurement
using
surface-plasmon-resonance via phase interrogation
at optimal incident wavelengths " Opt. Lett. 30:
2727-2729. pdf
Chang R, Chiang H. P., Leung P. T.,
Tsai
D. P. and Tse W. S., 2005 " Nonlocal effects in the
optical
response of composite
materials with metallic nanoparticles "
Solid State Commun. 133: 315-320; ibid.
137: 343. pdf
Chiang H. P., Yeh H. T., Chen C. M., Wu J. C.,
Su S. Y., Chang R., Wu Y. J., Tsai D. P., Jen S. U., and
Leung P. T., 2004" Surface plasmon
resonance monitoring of temperature via phase measurement" Optics
Commun.
241: 409-418. pdf
Leung P. T. 2004 " A note on the 'system-free' expressions of Maxwell's equations " Eur. J. Phys. 25: N1-N4. pdf
Chang R., Chiang H. P., Leung P. T.,
and
Tse W. S. 2003 " Nonlocal electrodynamic effects in the optical
excitation
of the surface plasmon resonance " Optics
Commun. 225: 353-361. pdf
Chiang H. P., Wang Y. C., and Leung P. T. 2003
" Effect of temperature on the incident angle-dependence of
the sensitivity for surface plasmon resonance spectroscopy " Thin
Solid Films, 425: 135-138. pdf
Hider M. H. and Leung P. T. 2002
" Nonlocal electrodynamic modeling of fluorescence characteristics for
molecules in a spherical cavity " Phys.
Rev. B, 66: 195106. pdf
Chiang H. P., La Rosa A. H., Leung P. T.,
Li K. P., and Tse W. S. 2002 " Optical spectroscopy
for
single-molecules near
a microstructure at varying substrate temperatures " Optics
Commun. 205: 343-350. pdf
Hartman R. L. and Leung P. T. 2001. " Dynamical theory for
modeling dipole-dipole interactions in
a microcavity: The Green dyadic approach " Phys. Rev. B,
64: 193308. pdf
Chiang H. P., Wang Y. C., Leung P. T. and Tse W. S. 2001
." A theoretical model for the temperature-
dependent sensitivity of the optical sensor
based on surface plasmon resonance " Optics Commun.
188: 283-289. pdf
Chang R., Leung P. T., Lin S. H. and Tse W. S. 2000.
" Surface-enhanced Raman scattering at cryogenic substrate
temperatures"
Phys. Rev. B 62:
5168-5173. pdf
Hartman R. L., Leung P. T. and Cohen S. M. 2000. "
Molecular fluorescence in the vicinity of a gradient-index
medium " J. Opt. Soc. Am. A 17: 933-936. pdf
Chiang H. P., Leung P. T. and Tse W. S. 2000. "
Remarks
on the substrate-temperature dependence of surface-enhanced Raman
scattering " J. Phys. Chem. B 104: 2348-2350. pdf
Leung, P. T. 1999. "Addendum : ‘Bethe stopping-power
theory for heavy target atoms’ " Phys. Rev. A
60: 2562-2564; 63: 069902 (E). pdf
Cohen S. M. and Leung P. T. 1999. " Comment on
'Relativistic correction of the generalized oscillator strength sum
rule " Phys. Rev. A 59: 4847. pdf
Hartman, R. L., Cohen S. M. and Leung P. T. 1999.
" A note on the Green dyadic calculation of the decay rates for
admolecules at multiple planar interfaces. " J. Chem. Phys.
110: 2189-2194. pdf
Cohen S. M. and Leung P. T. 1998. "
General
formulation of the semirelativistic approach to atomic sum rules. "
Phys. Rev. A 57: 4994-4997. pdf
Chiang H. P., Leung P. T. and Tse W. S. 1998. " The
surface plasmon enhancement effect on adsorbed molecules at elevated
temperatures. " J. Chem. Phys. 108: 2659-2660. pdf
Blacke W. L. and Leung P. T. 1997. " Molecular
fluorescence at a rough surface : the orientation effects. "
Phys. Rev. B 56: 12625-12631. pdf
Leung, P.T. 1997. " Emission frequency of
single molecules at a metallic aperture: the applicability of the image
theory. "
Optics Commun. 136: 360-364; 139: 336 (E). pdf
Chiang, H.P., Leung, P. T. and Tse, W.S. 1997.
“ Optical properties of composite materials at high temperatures ”
Solid State Commun. 101: 45-50. pdf
Leung, P.T. and Tse, W.S. 1995. " Non-local
electrodynamic effect on the enhancement factor for surface enhanced
Raman scattering. " Solid State Commun. 95:
39-44. pdf
Xiong, T., Leung, P. T. and George, T. F. 1995. “
Modeling of decay rates for molecules at an island surface ” J.
Chin. Chem. Soc. 42 : 249-254. pdf
Leung, P. T. and George, T. F. 1995 " Molecular
Fluorescence Spectroscopy in the Vicinity of a Microstructure." J.
de Chim. Phys. (France) 92: 226-247. pdf
Leung, P. T. 1995. " Magnetic monopole and Poynting's
theorem " Euro. J. Phys. 16: 43-44. pdf
Leung, P. T., Pollard-Knight, D., Malan, G. P. and
Finlan, M. F. 1994. " Modeling of particle-Enhancement
Sensitivity of the Surface-Plasmon-Resonance Biosensor. " Sensors
and Actuators B 22:175-180. pdf
Pliska, M. J., Sanzhez, E. D., Leung, P. T. and George, T.
F. 1994. " Effect of Particle-Clustering on Decay Rates of
Admolecules at the Interface of a Composite Material Substrate. " Solid
State Common. 89: 397-401. pdf
Do, N., Klees, L., Tam, A. C., Leung, P. T. and Leung, W. P. 1993.
" Photodeflection Probing of the Explosion of a Liquid Film in Contact
with a Solid Heated by Pulsed Excimer Laser Irradiation. " J.
App. Phys. 74:1534-1538. pdf
Park, H. K., Xu, X., Grigoropoulos, C. P., Do, N., Klees, L.,
Leung, P. T. and Tam, A. C. 1993. " Transient optical
transmission measurement in excimer-laser irradiation of amorphous
silicon films " J. Heat Transfer 115: 178-183. pdf
Leung, P. T. and Hider, M. H. 1993. " Nonlocal
Electrodynamic Modeling of Frequency Shifts of Molecules at Rough Metal
Surfaces." J. Chem. Phys. 98:5019-5022. pdf
Bodegom E. and Leung, P. T. 1993. " A surprising twist to a
simple capacitor problem " Euro. J. Phys. 14:
57-58. pdf
Yavas, O., Do, N., Tam, A. C., Leung, P. T., Leung, W. P.,
Park, H. K., Grigoropoulos, C. P., Boneberg, J and Leiderer, P. 1993.
" Temperature dependence of optical
properties for amorphous silicon at wavelengths of 632.8 and 752
namometer " Opt. Lett. 18: 540-542. pdf
Tam, A. C., Do, N, Klees, L., Leung, P. T. and Leung, W. P. 1992.
" Explosion of a liquid film in contact with a pulse-heated solid
surface detected by the probe-beam deflection method " Opt. Lett.
17: 1809-1811. pdf
Leung, P. T., Do, N., Klees, L., Leung, W. P., Tong, F., Lam,
L., Zapka, W. and Tam, A. C. " Transmission Studies of
Explosive Vaporization of a Transparent Liquid Film on an Opaque Solid
Surface Induced by Excimer-Laser-Pulsed Irradiation." 1992 J.
Appl. Phys.72: 2256-2263. pdf
Park, H. K., Xu, X, Grigoropoulos, C. P., Do, N, Klees, L, Leung,
P. T., and Tam, A C. 1992. " Temporal profile of
optical transmission probe for pulsed-laser heating of amorphous
silicon films " App. Phys. Lett. 61: 749-751. pdf
Do, N., Klees, L, Leung, P. T., Tong, F, Leung, W. P.
and Tam, A. C. 1992. " Temperature dependence of optical
constants for amorphous silicon " App. Phys. Lett. 60:
2186-2188. pdf
Hider M. H. and Leung, P. T. 1991. " Frequency shifts of
molecules at rough metal surfaces " Phys. Rev. B 44:
3262-3265. pdf
Leung, P. T. 1989. " Bethe stopping power theory for
heavy target atoms " Phys. Rev. A 40: 5417-5419. pdf
For experimental evidence, see experiment
(1) experiment (2)
Leung, P. T., Kim, Y. S. and George, T. F. 1989 "
Photochemistry at corrugated thin metal films : a
phenomenological
approach " SPIE Conference Proceeding 1056:
139-146. pdf
Leung, P. T., Kim, Y. S. and George, T. F. 1989 "
Photoabsorption of molecules at corrugated thin metal films."
J. Chem. Phys. 90: 7472-7477. pdf
Leung, P. T., Kim, Y. S. and George, T. F. 1989 "
Decay
of molecules at corrugated thin metal films "
Phys. Rev. B 39: 9888-9893. pdf
Leung, P. T. and George, T. F. 1989 " Molecular
spectroscopy at corrugated metal surfaces " Spectroscopy 4:
35-41. pdf