We demonstrate tunable, polarization-dependent, dual-color plasmonic filters based upon arrays of asymmetric cross-shaped nano-apertures. Acting as individual color emitting nano-pixels, each aperture can selectively transmit one of 2 colors, switched by controlling the polarization of white-light incident on the rear of each pixel. By tuning the dimensions of the pixels we build a polarization sensitive color palette at resolutions far beyond the diffraction limit. Using this switchable color palette we are able to generate complex optical surfaces encoded with dual color and information states; allowing us to embed two color images within the same unit area, using the same set of nanoapertures. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Clark, Alasdair W.

Cooper, Jonathan M.

Heydari, Esmaeil

Li, Zhibo

English

Enlighten: Publications

 
 
 
 
 
Heydari, E., Li, Z., Cooper, J. M., and Clark, A. W. (2016) Polarization switchable two-
color plasmonic nano-pixels for creating optical surfaces encoded with dual information 
states. Proceedings of the SPIE: The International Society for Optical Engineering, 9756, 
975619. (doi:10.1117/12.2209103) 
 
Copyright 2016 Society of Photo Optical Instrumentation Engineers. One print or 
electronic copy may be made for personal use only. Systematic reproduction and 
distribution, duplication of any material in this paper for a fee or for commercial 
purposes, or modification of the content of the paper are prohibited. 
 
http://eprints.gla.ac.uk/129062/ 
     
 
 
 
 
 
 
Deposited on: 14 October 2016 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Enlighten – Research publications by members of the University of Glasgow 
http://eprints.gla.ac.uk 
Polarization switchable two-color plasmonic nano-pixels for creating 
optical surfaces encoded with dual information states 
Esmaeil Heydari, Zhibo Li, Jonathan M. Cooper, Alasdair W. Clark*  
Biomedical Engineering Research Division, School of Engineering, University of Glasgow, UK 
G128LT 
*Alasdair.clark@glasgow.ac.uk; phone +44 141 330 3216; 
www.gla.ac.uk/schools/engineering/staff/alasdairclark/ 
ABSTRACT 
We demonstrate tunable, polarization-dependent, dual-color plasmonic filters based upon arrays of asymmetric cross-
shaped nano-apertures. Acting as individual color emitting nano-pixels, each aperture can selectively transmit one of 2 
colors, switched by controlling the polarization of white-light incident on the rear of each pixel. By tuning the 
dimensions of the pixels we build a polarization sensitive color palette at resolutions far beyond the diffraction limit. 
Using this switchable color palette we are able to generate complex optical surfaces encoded with dual color and 
information states; allowing us to embed two color images within the same unit area, using the same set of nano-
apertures.  
Keywords: nano-pixels, cavity-apertures, plasmonics, metasurfaces, color filter, color printing, nano holes, optical 
surfaces 
1. INTRODUCTION 
Color filters are a vital elements of modern digital imaging and display systems, allowing white-light to be broken into 
component parts for the purpose of recording or projecting information. Although conventionally constructed from 
polymers embedded with organic dyes, there has been increased interest as of late towards the development of filters 
which rely on the plasmonic resonances of engineered metallic nanostructures to provide more environmentally robust 
color filtering solutions1-5 (whereas filters based on organic dyes are susceptible to degradation over time, plasmonic 
filters offer long-term stability). Furthermore, plasmonic filters can perform over length scales of >100 nm, making them 
ideal for miniaturized, compact optical imaging solutions where space is at a premium. Effective color filtering has been 
demonstrated using both positive nanostructures 6-12 and ‘negative’ nanostructures (apertures through a metallic thin-
film). 13-14 These filtering solutions have thus far been shown applicable to color separation in CMOS image sensors, 15, 16 
to full-color image reproduction (‘printing’) with pixel sizes beyond the diffraction limit 3, 4, 17, and to ultra-high 
resolution optical data storage. 18 As a result, this technology has the potential to compete with conventional color 
filtering techniques (which employ dyes, liquid crystals and quantum dots) in the near future.19, 20 
Typically, color filters, whether they be conventional or plasmonic, are tuned to operate efficiently at a single 
wavelength. We have recently demonstrated that by using cross-shaped nano-apertures in an aluminum thin-film it is 
possible to encode a single aperture with dual color selectivity.21 Each aperture in this case acts as a plasmonic nano-
pixel capable of emitting one of two colors chosen by controlling the polarization of white-light incident on the rear of 
the pixel. By altering the length of the ‘arms’ of each cross, as well as the spacing between individual crosses in an array, 
it is possible to tune the plasmon band of the structures across the visible spectrum and create a polarization sensitive 
color palette. We now demonstrate that by careful arrangement of differently colored nanopixels in an array format we 
can generate full-color micro-scale images. Significantly, the ability to embed two colors within each pixel allows us to 
generate image arrays encoded with dual information states (i.e. the polarization sensitive array can display two distinct 
images using the same set of pixels). These new pixel technology holds the potential to improve upon current plasmonic 
pixel examples by enabling smaller, more versatile filter sets for imaging applications (where a single array can function 
at two selectable filtering regimes within the same unit area, rather than building two separate arrays), while also having 
potential applications in display technologies, image ‘printing’, storage, anti-counterfeiting, and biosensing. 
 
 
 
Photonic and Phononic Properties of Engineered Nanostructures VI, edited by Ali Adibi, Shawn-Yu Lin, Axel Scherer, 
Proc. of SPIE Vol. 9756, 975619 · © 2016 SPIE · CCC code: 0277-786X/16/$18 · doi: 10.1117/12.2209103
Proc. of SPIE Vol. 9756  975619-1
Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx
Glass
b)
e)d)
GlassGlass
Glass .....m.111/ E
0
Glass
2. METHODS 
 
 
 
Figure 1. Schematic of the fabrication process a) Deposition of a 100nm Al layer onto a glass substrate b) Deposition of a 
220nm ZEP520A ebeam resist layer c) Patterning of the cross-shaped pixels via Ebeam lithography, followed by 
development d) SiCl4 dry-etching of the exposed Al areas, followed by removal of the ZEP520A mask e) & f) White light 
excitation of the sample at different polarizations showing single pixels can transmit 2 different colors. 
Figure 1 shows a schematic of the fabrication steps taken to produce the dual color nano-pixels using nano-scale cavity 
apertures defined in a thin-film of aluminum. Al was chosen as our filter metal due to the flexibility of its plasmon 
resonance band (which can be tuned over a wide spectral range from deep UV to NIR), its low-cost, and its compatibility 
with current CMOS manufacturing processes. Initially, a 100nm Al layer was deposited onto a 500 µm Pyrex glass 
substrate. Spun onto the Al layer was a 220nm layer of ZEP520A, a positive electron-beam resist. A Vistec VB6 UHR 
EWF electron-beam lithography tool was used to pattern the pixel geometries into the resist. After development of the 
exposed resist, an Oxford instruments System 100 RIE tool was used to etch the electron-beam-defined pattern through 
the Al layer using SiCl4. After excess resist removal a 150nm SiO2 layer was deposited onto the sample using an Oxford 
instruments Plasmalab 80+ PECVD tool. The SiO2 layer prevents excess oxidation of the Al taking place and also acts to 
increase transmission through the apertures. 
 
 
 
  
 
 
 
Proc. of SPIE Vol. 9756  975619-2
Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx
Lx=140nm Lx=140n m Lx=140nm Lx=140nm
p=250nm p=280nm p=310nm p=340nm
3. RESULTS AND DISCUSSION 
 
Figure 2 shows bright-field images of a selection of color nano-pixel arrays when illuminated from the rear using light 
polarized along the x-axis (Figure 2a) and the y-axis (Figure 2b). The color displayed by each pixel array is dictated by 
the length of the aperture’s ‘arms’, as well as the spacing between each aperture in the array. 21 As is the case for nano-
scale slit apertures, the selection rules for light transmission through these cross-shaped apertures dictates that the 
electric-field of the exciting light must be perpendicular to the arm through which light propagates.  As a result, the color 
transmitted through the x-axis arm of the cross is dictated by the length of the x-axis arm, and the period of the y-axis 
arm (and vice-versa). To demonstrate color tuning possible using these selection rules, a polarization dependent color 
palette was created (Figure 2). The x-axis arm length was held steady at 140 nm while the length of the y-axis arm was 
varied from 140 – 200 nm in 20 nm increments (rows moving from top to bottom in Figure 2). The period of the arrays 
(in both the x and y-axes) was varied from 250 – 340 nm in 30 nm increments (columns moving left to right in Figure 2).  
Figure 2a was illuminated with light polarized along the y-axis. As a result, the colors we see transmitted by the arrays in 
this case are a result of light propagation through the x-axis arm of each cross-shaped pixel. Since the x-axis arm is being 
held steady at 140 nm, we see that each column transmits a different color. The color variation from column to column is 
due to the change in array period alone. As the inter-aperture distance increases we see a distinct red-shift in the light 
transmitted by those arrays (moving from blue at a period of 250 nm to green at 340 nm.)  
In the case of Figure 2b, the light incident on the rear of the palette was polarized along the x-axis. As a result, Figure 2b 
shows the transmission of color through the y-axis arms of the cross-shaped pixels. Since we are altering both the y-axis 
arm length and the period of the apertures, each of the 16 arrays exhibit a different color. As was the case for the 
transmission of light through the shorter, x-axis arm, the colors transmitted through the y-axis arm red-shifts with 
increasing period. Furthermore, since we are altering the length of the transmission arm in this case, we also see a red 
shift, at constant period, as the arm length is increased from 140 – 200 nm. Using a combination of these parameters it is 
possible to tune these pixels across the entire visible spectrum.  
 
 
Figure 2. Nano-pixel color palette based on Al nano-apertures a) it shows the situation when the sample excited with a x-
polarized white light b) the arm length and period of each nano-pixel array in x and y direction has been shown. c) it shows 
the situation when the sample is excited with a y-polarized white light. 
 
Figure 3 illustrates an application of these new, polarization selective dual-color nano-pixels; a nanopatterned surface 
encoded with two different micro-scale images. In this case, a polarization dependent, color micro-display has been 
Proc. of SPIE Vol. 9756  975619-3
Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx
E
I
100µm
created that displays a different image at each illumination state. The pixels have been arranged such that their color 
output contributes to these different images at each polarization. Note that we are not using different pixels to each of the 
2 images seen in Figure 3; the same pixels are used in each image and engineered to perform a different color function at 
each polarization. Significantly, this allows us to encode 2 information states into the same unit area using the same 
nano-pixels. As a result, in addition to high-resolution color image reproduction, this technology may prove useful for 
applications in high-density optical storage, and color filtering for image recording in miniaturized consumer devices 
(where a single pixel could function at two wavelengths, thus reducing the number and size of filtering elements 
required). 
 
 
Figure 3. A polarization-dependent micro-display consisting of sub-wavelength plasmonic nano-pixels. a) An image of the 
University of Glasgow coat of arms, displayed when the array is illuminated with white-light polarized along the x-axis. b) 
When the illuminating white-light is polarized along the y-axis, the same pixels display the letters BME (to represent 
Glasgow’s Bio Medical Engineering Research Division). 
 
4. CONCLUSION 
We have demonstrated a new dual-color plasmonic nano-pixel that can be used to create micro-scale image displays with 
polarization sensitive outputs. Using these sub-wavelength nano-pixels it is possible to create optical metasurfaces 
encoded with dual information states.  
 
 
Proc. of SPIE Vol. 9756  975619-4
Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx
ACKNOWLEDGMENTS 
The work was supported by the Royal Academy of Engineering (grant number 10216/103). The authors also wish to 
acknowledge China Scholarship Council (CSC) and the ERC Advanced Grant, Bio-Phononics (340117) for supporting 
this work. The authors also thank all the staff working in the James Watt Nanofabrication Centre (JWNC) at the 
University of Glasgow for their support. 
 
REFERENCES 
[1] Barnes, W. L., Dereux, A. and Ebbesen, T. W., "Surface plasmon subwavelength optics," Nature 424, 824-830 
(2003). 
[2] Knight, M. W., Liu, L., Wang, Y., Brown, L., Mukherjee, S., King, N. S., Everitt, H. O., Nordlander, P. and 
Halas, N. J., "Aluminum plasmonic nanoantennas," Nano Lett. 12, 6000-6004 (2012). 
[3] Kumar, K., Duan, H., Hegde, R. S., Koh, S. C. W., Wei, J. N. and Yang, J. K. W., "Printing colour at the optical 
diffraction limit," Nat. Nanotechnol. 7, 557-561 (2012). 
[4] Gu, Y. , Zhang, L., Yang, Joel K. W., Yeo, S. P. and Q. C.-W., "Color generation via subwavelength plasmonic 
nanostructures," Nanoscale 7, 6409-6419 (2015). 
[5] Tan, S. J., Zhang, L., Zhu, D., Goh, X. M., Wang, Y. M., Kumar, K., Qiu, C.-W. and Yang, J. K. W., 
"Plasmonic color palettes for photorealistic printing with aluminum nanostructures," Nano Lett. 14(7), 4023-
4029 (2014). 
[6] Ellenbogen, T., Seo, K. and Crozier, K. B., "Chromatic plasmonic polarizers for active visible color filtering 
and polarimetry, " Nano Lett. 12(2), 1026-1031 (2012). 
[7] Franklin, D., Chen, Y., Vazquez-Guardado, A., Modak, S., Boroumand, J., Xu, D., Wu, S.-T. and Chanda, D. 
"Polarization independent actively tunable colour generation on imprinted plasmonic surfaces," Nat. Commun. 
6, 7337 (2015). 
[8] Shrestha, V. R., Lee, S.-S., Kim, E.-S. and Cho, D.-Y., "Aluminum plasmonics based highly transmissive 
polarization-independent subtractive color filters exploiting a nanopatch array," Nano Lett. 14(11), 6672-6678 
(2014). 
[9] Goh, X. M., Zheng, Y., Tan, S. J., Zhang, L., Kumar, K., Qiu, C.-W. & Yang, J. K. W., "Three-dimensional 
plasmonic stereoscopic prints in full colour," Nat. Commun 5, 5361 (2014). 
[10] Olsona, J., Manjavacasb, A., Liub, L., Chang, W.-S., Foerster, B., King, N. S., Knight, M. W., Nordlander, P., 
Halas, N. J., and Link, S., "Vivid, full-color aluminum plasmonic pixels," PNAS 111(40), 14348-14353 (2014). 
[11] Roberts A. S., Pors, A., Albrektsen, O. and Bozhevolnyi, S. I., "Subwavelength plasmonic color printing 
protected for ambient use," Nano Lett. 14(2), 783-787 (2014). 
[12] Clark, A. W. and Cooper, J. M., "Plasmon shaping by using protein nanoarrays and molecular lithography to 
engineer structural color," Angew. Chem. 124(15), 3622-3626 (2012) 
[13] Chen, Q. and Cumming D. R. S., "High transmission and low color cross-talk plasmonic color filters using 
triangular-lattice hole arrays in aluminum films," Opt. Express 18, 14056-14062 (2010).  
[14]  Inoue, D., Miura, A., Nomura, T., Fujikawa, H., Sato, K., Ikeda, N., Tsuya, D., Sugimoto, Y., Koide, Y., 
"Polarization independent visible color filter comprising an aluminum film with surface plasmon enhanced 
transmission through a subwavelength array of holes," Appl. Phys. Lett. 98, 093113 (2011). 
[15] Yokogawa, S., Burgos, S. P. and Atwater, H. A., "Plasmonic color filters for CMOS image sensor applications," 
Nano Lett. 12(8), 4349-4354 (2012). 
[16] Burgos, S. P., Yokogawa, S. and Atwater, H. A., "Color imaging via nearest neighbor hole coupling in 
plasmonic color filters integrated onto a complementary metal-oxide semiconductor image sensor," ACS Nano 
7(11), 10038-10047 (2013). 
[17] Dean, N., "Colouring at the nanoscale," Nat. Nanotechnol. 10, 15-16 (2015). 
[18] Zijlstra, P., Chon, J. W. M. and Gu, M., "Five-dimensional optical recording mediated by surface plasmons in 
gold nanorods," Nature 459, 410-413 (2009). 
[19] Clausen, J. S., Højlund-Nielsen, E., Christiansen, A. B., Yazdi, S., Grajower, M., Taha, H., Levy, U., 
Kristensen, A. and Mortensen, N. A., "Plasmonic metasurfaces for coloration of plastic consumer products," 
Nano Lett. 14(8), 4499-4504 (2014). 
Proc. of SPIE Vol. 9756  975619-5
Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx
[20] Huang, Y.-W., Chen, W. T., Tsai, W.-Y., Wu, P. C., Wang, C.-M., Sun, G. and Tsai, D. P., "Aluminum 
plasmonic multicolor meta-hologram," Nano Lett. 15(5), 3122-3127 (2015). 
[21] Li, Zhibo, Clark, A. W. and Cooper, J. M., "Dual color plasmonic pixels create a polarization controlled nano 
color palette," ACS Nano, 10.1021/acsnano.5b05411 (2016). 
 
 
Proc. of SPIE Vol. 9756  975619-6
Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx


Polarization switchable two-color plasmonic nano-pixels for creating optical surfaces encoded with dual information states

Enlighten

     Heydari, E., Li, Z., Cooper, J. M., and Clark, A. W. (2016) Polarization switchable two-color plasmonic nano-pixels for creating optical surfaces encoded with dual information states. Proceedings of the SPIE: The International Society for Optical Engineering, 9756, 975619. (doi:10.1117/12.2209103)  Copyright 2016 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.  http://eprints.gla.ac.uk/129062/            Deposited on: 14 October 2016                       Enlighten – Research publications by members of the University of Glasgow http://eprints.gla.ac.uk Polarization switchable two-color plasmonic nano-pixels for creating optical surfaces encoded with dual information states Esmaeil Heydari, Zhibo Li, Jonathan M. Cooper, Alasdair W. Clark*  Biomedical Engineering Research Division, School of Engineering, University of Glasgow, UK G128LT *Alasdair.clark@glasgow.ac.uk; phone +44 141 330 3216; www.gla.ac.uk/schools/engineering/staff/alasdairclark/ ABSTRACT We demonstrate tunable, polarization-dependent, dual-color plasmonic filters based upon arrays of asymmetric cross-shaped nano-apertures. Acting as individual color emitting nano-pixels, each aperture can selectively transmit one of 2 colors, switched by controlling the polarization of white-light incident on the rear of each pixel. By tuning the dimensions of the pixels we build a polarization sensitive color palette at resolutions far beyond the diffraction limit. Using this switchable color palette we are able to generate complex optical surfaces encoded with dual color and information states; allowing us to embed two color images within the same unit area, using the same set of nano-apertures.  Keywords: nano-pixels, cavity-apertures, plasmonics, metasurfaces, color filter, color printing, nano holes, optical surfaces 1. INTRODUCTION Color filters are a vital elements of modern digital imaging and display systems, allowing white-light to be broken into component parts for the purpose of recording or projecting information. Although conventionally constructed from polymers embedded with organic dyes, there has been increased interest as of late towards the development of filters which rely on the plasmonic resonances of engineered metallic nanostructures to provide more environmentally robust color filtering solutions1-5 (whereas filters based on organic dyes are susceptible to degradation over time, plasmonic filters offer long-term stability). Furthermore, plasmonic filters can perform over length scales of >100 nm, making them ideal for miniaturized, compact optical imaging solutions where space is at a premium. Effective color filtering has been demonstrated using both positive nanostructures 6-12 and ‘negative’ nanostructures (apertures through a metallic thin-film). 13-14 These filtering solutions have thus far been shown applicable to color separation in CMOS image sensors, 15, 16 to full-color image reproduction (‘printing’) with pixel sizes beyond the diffraction limit 3, 4, 17, and to ultra-high resolution optical data storage. 18 As a result, this technology has the potential to compete with conventional color filtering techniques (which employ dyes, liquid crystals and quantum dots) in the near future.19, 20 Typically, color filters, whether they be conventional or plasmonic, are tuned to operate efficiently at a single wavelength. We have recently demonstrated that by using cross-shaped nano-apertures in an aluminum thin-film it is possible to encode a single aperture with dual color selectivity.21 Each aperture in this case acts as a plasmonic nano-pixel capable of emitting one of two colors chosen by controlling the polarization of white-light incident on the rear of the pixel. By altering the length of the ‘arms’ of each cross, as well as the spacing between individual crosses in an array, it is possible to tune the plasmon band of the structures across the visible spectrum and create a polarization sensitive color palette. We now demonstrate that by careful arrangement of differently colored nanopixels in an array format we can generate full-color micro-scale images. Significantly, the ability to embed two colors within each pixel allows us to generate image arrays encoded with dual information states (i.e. the polarization sensitive array can display two distinct images using the same set of pixels). These new pixel technology holds the potential to improve upon current plasmonic pixel examples by enabling smaller, more versatile filter sets for imaging applications (where a single array can function at two selectable filtering regimes within the same unit area, rather than building two separate arrays), while also having potential applications in display technologies, image ‘printing’, storage, anti-counterfeiting, and biosensing.    Photonic and Phononic Properties of Engineered Nanostructures VI, edited by Ali Adibi, Shawn-Yu Lin, Axel Scherer, Proc. of SPIE Vol. 9756, 975619 · © 2016 SPIE · CCC code: 0277-786X/16/$18 · doi: 10.1117/12.2209103Proc. of SPIE Vol. 9756  975619-1Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspxGlassb)e)d)GlassGlassGlass .....m.111/ E0Glass2. METHODS    Figure 1. Schematic of the fabrication process a) Deposition of a 100nm Al layer onto a glass substrate b) Deposition of a 220nm ZEP520A ebeam resist layer c) Patterning of the cross-shaped pixels via Ebeam lithography, followed by development d) SiCl4 dry-etching of the exposed Al areas, followed by removal of the ZEP520A mask e) & f) White light excitation of the sample at different polarizations showing single pixels can transmit 2 different colors. Figure 1 shows a schematic of the fabrication steps taken to produce the dual color nano-pixels using nano-scale cavity apertures defined in a thin-film of aluminum. Al was chosen as our filter metal due to the flexibility of its plasmon resonance band (which can be tuned over a wide spectral range from deep UV to NIR), its low-cost, and its compatibility with current CMOS manufacturing processes. Initially, a 100nm Al layer was deposited onto a 500 µm Pyrex glass substrate. Spun onto the Al layer was a 220nm layer of ZEP520A, a positive electron-beam resist. A Vistec VB6 UHR EWF electron-beam lithography tool was used to pattern the pixel geometries into the resist. After development of the exposed resist, an Oxford instruments System 100 RIE tool was used to etch the electron-beam-defined pattern through the Al layer using SiCl4. After excess resist removal a 150nm SiO2 layer was deposited onto the sample using an Oxford instruments Plasmalab 80+ PECVD tool. The SiO2 layer prevents excess oxidation of the Al taking place and also acts to increase transmission through the apertures.         Proc. of SPIE Vol. 9756  975619-2Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspxLx=140nm Lx=140n m Lx=140nm Lx=140nmp=250nm p=280nm p=310nm p=340nm3. RESULTS AND DISCUSSION  Figure 2 shows bright-field images of a selection of color nano-pixel arrays when illuminated from the rear using light polarized along the x-axis (Figure 2a) and the y-axis (Figure 2b). The color displayed by each pixel array is dictated by the length of the aperture’s ‘arms’, as well as the spacing between each aperture in the array. 21 As is the case for nano-scale slit apertures, the selection rules for light transmission through these cross-shaped apertures dictates that the electric-field of the exciting light must be perpendicular to the arm through which light propagates.  As a result, the color transmitted through the x-axis arm of the cross is dictated by the length of the x-axis arm, and the period of the y-axis arm (and vice-versa). To demonstrate color tuning possible using these selection rules, a polarization dependent color palette was created (Figure 2). The x-axis arm length was held steady at 140 nm while the length of the y-axis arm was varied from 140 – 200 nm in 20 nm increments (rows moving from top to bottom in Figure 2). The period of the arrays (in both the x and y-axes) was varied from 250 – 340 nm in 30 nm increments (columns moving left to right in Figure 2).  Figure 2a was illuminated with light polarized along the y-axis. As a result, the colors we see transmitted by the arrays in this case are a result of light propagation through the x-axis arm of each cross-shaped pixel. Since the x-axis arm is being held steady at 140 nm, we see that each column transmits a different color. The color variation from column to column is due to the change in array period alone. As the inter-aperture distance increases we see a distinct red-shift in the light transmitted by those arrays (moving from blue at a period of 250 nm to green at 340 nm.)  In the case of Figure 2b, the light incident on the rear of the palette was polarized along the x-axis. As a result, Figure 2b shows the transmission of color through the y-axis arms of the cross-shaped pixels. Since we are altering both the y-axis arm length and the period of the apertures, each of the 16 arrays exhibit a different color. As was the case for the transmission of light through the shorter, x-axis arm, the colors transmitted through the y-axis arm red-shifts with increasing period. Furthermore, since we are altering the length of the transmission arm in this case, we also see a red shift, at constant period, as the arm length is increased from 140 – 200 nm. Using a combination of these parameters it is possible to tune these pixels across the entire visible spectrum.    Figure 2. Nano-pixel color palette based on Al nano-apertures a) it shows the situation when the sample excited with a x-polarized white light b) the arm length and period of each nano-pixel array in x and y direction has been shown. c) it shows the situation when the sample is excited with a y-polarized white light.  Figure 3 illustrates an application of these new, polarization selective dual-color nano-pixels; a nanopatterned surface encoded with two different micro-scale images. In this case, a polarization dependent, color micro-display has been Proc. of SPIE Vol. 9756  975619-3Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspxEI100µmcreated that displays a different image at each illumination state. The pixels have been arranged such that their color output contributes to these different images at each polarization. Note that we are not using different pixels to each of the 2 images seen in Figure 3; the same pixels are used in each image and engineered to perform a different color function at each polarization. Significantly, this allows us to encode 2 information states into the same unit area using the same nano-pixels. As a result, in addition to high-resolution color image reproduction, this technology may prove useful for applications in high-density optical storage, and color filtering for image recording in miniaturized consumer devices (where a single pixel could function at two wavelengths, thus reducing the number and size of filtering elements required).   Figure 3. A polarization-dependent micro-display consisting of sub-wavelength plasmonic nano-pixels. a) An image of the University of Glasgow coat of arms, displayed when the array is illuminated with white-light polarized along the x-axis. b) When the illuminating white-light is polarized along the y-axis, the same pixels display the letters BME (to represent Glasgow’s Bio Medical Engineering Research Division).  4. CONCLUSION We have demonstrated a new dual-color plasmonic nano-pixel that can be used to create micro-scale image displays with polarization sensitive outputs. Using these sub-wavelength nano-pixels it is possible to create optical metasurfaces encoded with dual information states.    Proc. of SPIE Vol. 9756  975619-4Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspxACKNOWLEDGMENTS The work was supported by the Royal Academy of Engineering (grant number 10216/103). The authors also wish to acknowledge China Scholarship Council (CSC) and the ERC Advanced Grant, Bio-Phononics (340117) for supporting this work. The authors also thank all the staff working in the James Watt Nanofabrication Centre (JWNC) at the University of Glasgow for their support.  REFERENCES [1] Barnes, W. L., Dereux, A. and Ebbesen, T. W., "Surface plasmon subwavelength optics," Nature 424, 824-830 (2003). [2] Knight, M. W., Liu, L., Wang, Y., Brown, L., Mukherjee, S., King, N. S., Everitt, H. O., Nordlander, P. and Halas, N. J., "Aluminum plasmonic nanoantennas," Nano Lett. 12, 6000-6004 (2012). [3] Kumar, K., Duan, H., Hegde, R. S., Koh, S. C. W., Wei, J. N. and Yang, J. K. W., "Printing colour at the optical diffraction limit," Nat. Nanotechnol. 7, 557-561 (2012). [4] Gu, Y. , Zhang, L., Yang, Joel K. W., Yeo, S. P. and Q. C.-W., "Color generation via subwavelength plasmonic nanostructures," Nanoscale 7, 6409-6419 (2015). [5] Tan, S. J., Zhang, L., Zhu, D., Goh, X. M., Wang, Y. M., Kumar, K., Qiu, C.-W. and Yang, J. K. W., "Plasmonic color palettes for photorealistic printing with aluminum nanostructures," Nano Lett. 14(7), 4023-4029 (2014). [6] Ellenbogen, T., Seo, K. and Crozier, K. B., "Chromatic plasmonic polarizers for active visible color filtering and polarimetry, " Nano Lett. 12(2), 1026-1031 (2012). [7] Franklin, D., Chen, Y., Vazquez-Guardado, A., Modak, S., Boroumand, J., Xu, D., Wu, S.-T. and Chanda, D. "Polarization independent actively tunable colour generation on imprinted plasmonic surfaces," Nat. Commun. 6, 7337 (2015). [8] Shrestha, V. R., Lee, S.-S., Kim, E.-S. and Cho, D.-Y., "Aluminum plasmonics based highly transmissive polarization-independent subtractive color filters exploiting a nanopatch array," Nano Lett. 14(11), 6672-6678 (2014). [9] Goh, X. M., Zheng, Y., Tan, S. J., Zhang, L., Kumar, K., Qiu, C.-W. & Yang, J. K. W., "Three-dimensional plasmonic stereoscopic prints in full colour," Nat. Commun 5, 5361 (2014). [10] Olsona, J., Manjavacasb, A., Liub, L., Chang, W.-S., Foerster, B., King, N. S., Knight, M. W., Nordlander, P., Halas, N. J., and Link, S., "Vivid, full-color aluminum plasmonic pixels," PNAS 111(40), 14348-14353 (2014). [11] Roberts A. S., Pors, A., Albrektsen, O. and Bozhevolnyi, S. I., "Subwavelength plasmonic color printing protected for ambient use," Nano Lett. 14(2), 783-787 (2014). [12] Clark, A. W. and Cooper, J. M., "Plasmon shaping by using protein nanoarrays and molecular lithography to engineer structural color," Angew. Chem. 124(15), 3622-3626 (2012) [13] Chen, Q. and Cumming D. R. S., "High transmission and low color cross-talk plasmonic color filters using triangular-lattice hole arrays in aluminum films," Opt. Express 18, 14056-14062 (2010).  [14]  Inoue, D., Miura, A., Nomura, T., Fujikawa, H., Sato, K., Ikeda, N., Tsuya, D., Sugimoto, Y., Koide, Y., "Polarization independent visible color filter comprising an aluminum film with surface plasmon enhanced transmission through a subwavelength array of holes," Appl. Phys. Lett. 98, 093113 (2011). [15] Yokogawa, S., Burgos, S. P. and Atwater, H. A., "Plasmonic color filters for CMOS image sensor applications," Nano Lett. 12(8), 4349-4354 (2012). [16] Burgos, S. P., Yokogawa, S. and Atwater, H. A., "Color imaging via nearest neighbor hole coupling in plasmonic color filters integrated onto a complementary metal-oxide semiconductor image sensor," ACS Nano 7(11), 10038-10047 (2013). [17] Dean, N., "Colouring at the nanoscale," Nat. Nanotechnol. 10, 15-16 (2015). [18] Zijlstra, P., Chon, J. W. M. and Gu, M., "Five-dimensional optical recording mediated by surface plasmons in gold nanorods," Nature 459, 410-413 (2009). [19] Clausen, J. S., Højlund-Nielsen, E., Christiansen, A. B., Yazdi, S., Grajower, M., Taha, H., Levy, U., Kristensen, A. and Mortensen, N. A., "Plasmonic metasurfaces for coloration of plastic consumer products," Nano Lett. 14(8), 4499-4504 (2014). Proc. of SPIE Vol. 9756  975619-5Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx[20] Huang, Y.-W., Chen, W. T., Tsai, W.-Y., Wu, P. C., Wang, C.-M., Sun, G. and Tsai, D. P., "Aluminum plasmonic multicolor meta-hologram," Nano Lett. 15(5), 3122-3127 (2015). [21] Li, Zhibo, Clark, A. W. and Cooper, J. M., "Dual color plasmonic pixels create a polarization controlled nano color palette," ACS Nano, 10.1021/acsnano.5b05411 (2016).   Proc. of SPIE Vol. 9756  975619-6Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/14/2016 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx

http://eprints.gla.ac.uk/129062/1/129062.pdf

Polarization switchable two-color plasmonic nano-pixels for creating optical surfaces encoded with dual information states

Abstract

Similar works

Full text

Available Versions

Enlighten: Publications

Enlighten