Doing the Work: Linyou Cao, Majid Esfandyarpour, Erik C. Garnett, Soo-Jin Pengyu Fan Soo-Jin Kim, Dianmin Lin, Juhyung Kang, Jung Hyun Park, Isabell Thomann. Speaking: Mark Brongersma @ Stanford University Funding: AFOSR, DOE EFRC, Samsung Semiconductor Nanowire Nanophotonics and Optoelectronics Thank you: Mike McGehee group (Stanford) Yi Cui group (Stanford) Pieter Kik (CREOL) Nader Engheta (Upenn) Erez Hasman (Technion) Reflection Absorption/Emission Transmission P <<
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Doing the Work: Linyou Cao, Majid Esfandyarpour, Erik C. Garnett, Soo-JinPengyu Fan Soo-Jin Kim, Dianmin Lin, Juhyung Kang, Jung Hyun Park, Isabell Thomann.
Speaking: Mark Brongersma @ Stanford University
Funding: AFOSR, DOE EFRC, Samsung
Semiconductor Nanowire Nanophotonics and Optoelectronics
Thank you: Mike McGehee group (Stanford) Yi Cui group (Stanford)Pieter Kik (CREOL)Nader Engheta (Upenn)Erez Hasman (Technion)
Reflection Absorption/Emission Transmission
P <<
Optoelectronic Devices are Everywhere…
Flexible displaySamsung
LasersSolar cells, SunPower
Image sensors
Most Optoelectronic Devices Rely on Planar Device Technologies
1908 Gustav Mie: Light scattering from a dielectric sphere
1947 L. Lewin Medium with spheresL. Lewin, Inst. Electr. Eng. III Radio Commun. Eng. 94, 65–68. 1947,
Gustav Mie, Ann. Phys. 25, 377–445 (1908)
1980 Long, McAllister, and Shen Dielectric Resonator AntennasS. A. Long, M. W. McAllister, and L. C. Shen, "The Resonant Cylindrical Dielectric Cavity Antenna," IEEE Transactions on Antennas and Propagation, 31, 406, 1983.
Engineering optical resonance frequency with size
Beneficial Properties of Resonant Semiconductor Nanostructures
Effective light concentration to the deep subwavelength scales
|E|2
x
y
E
d =100nm
d
d
SiO2 (n = 1.45)
Air
g = 10 nm
= 550 nm
Si
Engineering optical resonance frequency with shape
Cao, Brongersma et al., Nano Lett., 2649, 10, 2010.
Experimentally measured intensity profile of Bessel beam
y
x
Semiconductors offer: low optical loss, facile integration with electronics, easy patterning, .. New opportunities to construct low-loss gradient metasurface optical elements
Experiment on DGMOE Axicon based on Si nanobeams
Enhancing Light Absorption in a Ge Metafilm on Metal Substrate
SEM image of fabricated sample Optical reflection image A 50-nm-thick Ge film is patterned into a metafilm consisting of many subwavelength Ge beams
Patterning the Ge film at subwavelength scale enhances the broadband light absorption
Soo Jin Kim et al., Nature Communications 6, 7591 (2015).
Power flow ( = 800 nm)
The flow light (Poynting vector) shows an antenna effect that ‘funnels’ light into the beams
Optical, Mie-like resonances in the Ge beams are at the origin of the strong light absorption
The continuous film look grey and patterned Ge film look black !
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Absorptivity ( 1 – Reflectivity)
Reflection measurement from Ge nanobeams on Au
Example: Array with 60 nm beams illuminated 800 nm, TM polarized light Strong absorption is observed at the nanobeam resonance wavelength
Individu
al beam
Soo Jin Kim et al., Nature Communications 6, 7591 (2015).
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Wavelength (nm)
Absorptivity ( 1 – Reflectivity)
w = 60 nm
Tuning of the absorption spectrum by changing the beam width
Resonance wavelength is tunable with the beam width Reflection spectra Ge metafilms with constant duty cycle of 1:3 (beam width : period) First-order effective medium theory predicts that optical properties are independent of period
εeff = fGe εGe + (1‐fGe)εairFor TM polarization:
30 45 60
w = 30 nmw = 45 nm
Soo Jin Kim et al., Nature Communications 6, 7591 (2015).
Broadband Absorption Can be Achieved with Big and Small Beams
Just 120 nm beams Just 30 nm beams 120 nm and 30 nm beam
800 nm
Experiment simulation
Metafilms with wide (120 nm) and narrow (30 nm) beams were created SEM images of the subwavelength nanobeam arrays
Reflection measurements show strong absorption at resonance wavelength beams
Sample with wide and narrow beams show strong absorption at short and long