Control amplitude and phase of light by plasmonic
meta-hologram with T-shaped nano-cavity
Wei Song (宋 伟), Shanguang Zheng (郑闪光), Yanan Fu (付亚男),
Changjun Min (闵长俊)*, Yuquan Zhang (张聿全), Zhenwei Xie (谢振威),
and Xiaocong Yuan (袁小聪)**
Nanophotonics Research Center, Shenzhen Key Laboratory of Micro-Scale Optical Information Technology,
Shenzhen University, Shenzhen 518060, China
*Corresponding author: cjmin@szu.edu.cn; **corresponding author: xcyuan@szu.edu.cn
Received January 16, 2019; accepted March 13, 2019; posted online May 31, 2019
Controlling both amplitude and phase of light in the subwavelength scale is a challenge for traditional optical
devices. Here, we propose and numerically investigate a novel plasmonic meta-hologram, demonstrating broad-
band manipulation of both phase and amplitude in the subwavelength scale. In the meta-hologram, phase modu-
lation is achieved by the detour phase distribution of unit cells, and amplitude is continuously modulated by a
T-shaped nano-cavity with tunable plasmonic resonance. Compared to phase-only holograms, such a meta-
hologram could reconstruct three-dimensional (3D) images with higher signal-to-noise ratio and better image
quality, thus offering great potential in applications such as 3D displays, optical communications, and beam
shaping.
OCIS codes: 240.6680, 160.3918, 090.2890.
doi: 10.3788/COL201917.062402.
Holography is a very powerful technology for recording and
reconstructing three-dimensional (3D) optical information
of the target object in free space and is widely used in
various optical fields, including 3D imaging, optical storage,
optical communication, and others
[1–3]
. Traditional holo-
graphic imaging technology is generally achieved by
common optical devices, such as a spatial light modulator
or digital micromirror device. These devices have pixel sizes
much larger than the working wavelength and, thus, suffer
from drawbacks, such as low spatial resolution, narrow
viewing angle, large device size, and unnecessary twin
image
[3]
. Besides, these devices could only modulate a single
parameter of light (amplitude, phase, or polarization),
while the simultaneous control of multiple parameters of
light for holography is still a challenge.
Recently, thanks to the rapid development of nano-
fabrication techniques, a variety of subwavelength optical
devices have been proposed and studied, showing advan-
tages of ultra-compact size and novel functions for optical
modulation, which offer great potential in breaking
through the limitation of traditional devices for 3D holo-
graphic imaging
[4–6]
. As a new type of subwavelength de-
vices, the metasurface has attracted enormous interest
for the fantastic capability of tailoring the wavefront of
light at the nanoscale by engineering the optical resonance
or geometric orientation
[7–9]
of optical scatterers (or optical
antennas)
[10]
, such as metallic nanorods
[11]
and V-shaped
nano-antennas
[12]
. Numerous metasurfaces have been
proposed to realize the arbitrary phase profile of light
from the visible to terahe rtz wave bands
[13]
and, conse-
quently, contribute to diverse applications, including
ultrathin meta-lens
[14,15]
, orbital angular momentum
modulation
[16–18]
, photonic spin Hall effect detection
[19]
,
active-controlled devices
[20]
, and chiral-dependent multi-
functional devices
[21,22]
. Metasurface-based hologram
devices (called meta-holograms) have also been investi-
gated in recent years
[5,11,21–23]
. However, many previous
meta-holograms were designed for pure phase modulation
rather than complex amplitude modulation and, thus,
had to work with a phase retrieval algorithm
[5,23]
that is
time-consuming and could degrade the performance of
3D holographic imaging
[24]
. Attempts have been made to
manipulate both the amplitude and phase of light in recent
years, but some previous works are limited by the only two-
or four-level amplitude modulation capability
[25,26]
.
In our previous works, we proposed a phase-only meta-
hologram based on a plasmonic nano-slits array
[27]
and then
achieved complex amplitude modulation by inserting multi-
ple nano-slits in each unit cell of the meta-hologram
[28]
.
However, such an amplitude modulation method suffers
from the limited number of nano-slits and the discrete ad-
justment of amplitude. Besides, the coupling effect between
adjacent nano-slits could influence the accuracy in ampli-
tude and phase manipulation.
In this Letter, we propose and numerically study a new
plasmonic meta-hologram based on a T-shaped nano-
cavity and detour phase, showing advantages of continu-
ous amplitude and phase modulation for 3D holographic
imaging. In the T-shaped nano-cavity, the amplitude of
transmitted light is strongly dependent on the resonance
of surface plasmon polaritons (SPPs) inside the cavity;
hence, we can modify the cavity structure to control the
resonance as well as the transmittance amplitude. Our re-
sults show that the amplitude can either be enhanced or
suppressed by adjusting the cavity structure parameters
for continuous amplitude modulation. To realize a phase
COL 17(6), 062402(2019) CHINESE OPTICS LETTERS June 2019
1671-7694/2019/062402(6) 062402-1 © 2019 Chinese Optics Letters