Supporting information: NEMS-tunable dielectric chiral metasurfaces
Hyounghan Kwon
1, 2
and Andrei Faraon
1, 2,
∗
1
T. J. Watson Laboratory of Applied Physics and Kavli Nanoscience Institute,
California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
2
Department of Electrical Engineering, California Institute of Technology,
1200 E. California Blvd., Pasadena, CA 91125, USA
∗
Corresponding author: A.F.: faraon@caltech.edu
1
Figure
2
푝
(nm)
푤
(nm)
푔
1
(nm)
푔
2
(nm)
푤
푝
(nm)
푙
푝
(nm)
Figure 3b 1400 505 165 225
53
275
Figure 3c 1400 520 150 210
70
270
Table S1 Measured design parameters of the devices used in Figs. 3b and 3c.
The definitions of the
design parameters are shown in Fig.
1b
.
2
푝
: Period for a pair of the nanostructures.
푤
: Width of the nano
structure.
푔
1
: Gap between the silicon bars having voltage difference.
푔
2
: Gap between the silicon bars
having same voltage.
푤
푝
: Perturbated width.
푙
푝
: Perturbated length.
2
Figure S1 Schematic illustration of the experimental setup.
Red lines represent the paths of the light.
Pol. of the objective lens are aligned to 45
◦
. To achieve the reflection spectra of
푅
퐿,퐿
and
푅
푅,푅
, the QWP2
is mounted on the rotation stage and aligned to 0
◦
and 90
◦
. To achieve the plane-wave illumination
condition, the L2 is used as an illumination lens and a tube lens. The L2 and the objective lens are aligned
such that the beam after the objective lens is collimated on-axis. As the sample is always aligned with the
fixed objective lens, illumination angle in the experiments is set to 0 degree. Pol.: linear polarizer. BS:
beamsplitter. PBS: polarizing beamsplitter. L: lens. PD: photodetector. M: mirror. QWP: quarter
waveplate. HWP: half waveplate. Obj.: microscope objective lens. SWIR camera: short-wave infrared
camera.
3
Figure S2 Numerical investigation on fabrication errors. a
-
c
The simulated reflection spectra of
푅
퐿,퐿
and
푅
푅,푅
for different values of
푙
푝
. Other parameters are the same as the parameters noted in Fig.
2
in the
main text. Top: Schematic illustration of the nanostructures constituting the metasurface. The values of
푙
푝
are shown in the illustration. Bottom: Calculated reflection spectra of
푅
퐿,퐿
and
푅
푅,푅
. The spectra of
푅
퐿,퐿
and
푅
푅,푅
are plotted in dashed and solid lines, respectively.
Figure S3 Measured reflection spectra with electrical biases. a
and
b
Measured reflection spectra of
푅
퐿,퐿
and
푅
푅,푅
under different external biases. The devices exploited in Figs.
3b
and
3c
are measured and
plotted in
a
and
b
, respectively. The spectra of
푅
퐿,퐿
and
푅
푅,푅
are plotted in dashed and solid lines,
respectively. The applied bias for each color is shown in legends. The spectra of CD,
|
푅
퐿,퐿
−
푅
푅,푅
|
, are
calculated from
a
and
b
and plotted in Fig.
4a
and
4b
in the main text.
4