Form 1

2017 Report Form for Collaboration withResearch Center for Biomedical Engineering

Year/month/date

2018/03/142042

NumberTo Chairman, Board of Directors, Research Center for Biomedical Engineering

ApplicantAffiliation Tokyo Institute of Technology, School of Materials and Chemical T
echnology, Department of Materials Science and Engineering
Title Professor
Name Junko Morikawa
Address 2-12-1, S8-29, Ookayama, Meguro-ku, 152-8550, Tokyo
Phone 3-5734-2497
Fax 3-5734-2497
E-mailmorikawa.j.aa@m.titech.ac.jp
Report Form for Collaboration ResearchResearch Theme

Development of infrared sensor based on 3D photonic crystal

Research Area1. Biomaterials
2. Bioengineering
3. Functional molecules
4 . Chemistry/Electrical Engineering/Mechanical Engineering/Materials Science○Research Period

From:1/6/2017

To: 31/3/2018

Applicant Organization
Name
Junko Morikawa

Department

TitleRole

Tokyo Institute of Technology, School ofMaterials and Chemical Technology,
Department of Materials Science andEngineering
Centre of Microphotonics, Swinburne
University of Technology, Melbourne,
Australia
Universitat Politecnica de Catalunya (UPC),
Fisica i Enginyeria Nuclear, Barcelona, Spain

Professor

LeaderProfessor

Participant

Professor

Participant

Mangirdas Malinauskas

Laser Research Center, Vilnius University,
LithuaniaResearcherParticipant

Kamen Kanev

Research Institute of Electronics, Shizuoka
University

Professor

Participant

Arturas Vailionis

Stanford Nano Shared Facilities (SNSF),
Geballe Laboratory for Advanced Materials

Staff scientist

Participant

Saulius Juodkazis

Kestutis Staliunas

(GLAM)
Vygantas Mizeikis

Research Institute of Electronics, Shizuoka
University

Collaboration Partners
Research Centerin

Professor

Participant,coordinator

theResearch Results (Including Purpose, Results, Figures, etc.)
The purpose of this project is development of micro-scale thermal sensors capable of uncooled operation at room
temperature offers considerable advantages in cost and operational convenience, higher reliability, reduced power
consumption, smaller size and weight, as well as multispectral response capability. Traditional IR detectors
exploit either electronic response of narrow-gap semiconductors, or bolometric response of IR absorbing
materials. However, fabrication of semiconductor-based IR detectors often requires advanced semiconductor
growth and micro-/nano-fabrication techniques, while their high -sensitivity operation requires external cooling.
Traditional bolometric detectors have large size and considerable thermal mass, which limits their response speed.
Rapid development of micro-total analysis systems (µTAS), Micro-Opto-Electro-Mechanical Systems (MOEMS)
and microfluidic systems demands super-compact, high-sensitivity uncooled IR detectors that can be easily
integrated into these systems. In addition to high performance, very low cost and expendability is required for IRdetectors. This project pursues practical realization of a novel IR detector concept based on the optical response of
3D nanostructured dielectrics (Nature Photonics 6, 195 (2012)). In particular, structural color of natural photonic
crystal (PhC) structures existing in blue scales of Morpho butterfly wing, visible as bright blue coloration and thereflection peak centered near the wavelength λ ≈ 450nm, can be modified in the presence of IR radiation. The
reflectivity modification mechanism is associated with thermal expansion of the periodic lattice or refractive index
modification upon heating due to absorption of IR radiation by the PhC (Nature Photonics 6, 195 (2012)). The
proposed research is aimed at realization of micro-scale infra-red (IR) sensing devices based on the above
principle. Replication of this behavior in artificially fabricated 3D PhCs is the main goal of this research. It is amajor challenge, because it requires fabrication of 3D periodic structures with lattice periods much shorter than
1µm. This challenge is being tackled by using an advanced 3D laser micro-/nano-fabrication technique called
Direct Laser Writing (DLW) for the fabrication of artificial photonic crystal structures exhibiting structural color
effect. At the present stage of studies, the structural color was mainly pursued, while modification of the structural
color by IR radiation, and clarification of its mechanism (presumably, thermal dilation of the photonic crystal
lattice, will be addressed during the subsequent stages of research.

Fig. 1 Experimental procedure for fabrication of 3D PhC structures exhibiting structural color.

The main results achieved during this joint-research effort as well as some experimental details are summarized
below. Figure 1 outlines the experimental procedure for the fabrication of photonic crystal structures inphotoresist ZS2080, which involves (left to right) exposure of photoresist by spatial scan of a tightly focusedfemtosecond laser beam which draws a 3D woodpile structure with high spatial resolution, development of theexposed 3D pattern in a liquid development, and drying the sample in a super-critical CO 2 chamber. Figure 2
shows detailed schematic image of the 3D woodpile architecture realized in this work. To tune the structural color
region into a visible spectral range, lattice period a xy was decreased to less than 1µm, while diameter of individual
photoresist rods composing the structure was close to 200nm.

Fig. 2 Schematic explanation of a 3Dwoodpile PhC architecture, (a) perspective view, (b,c) top and side views,and explanation of parameters.
In order to obtain pure and spatially uniform structural color it was necessary to avoid non-uniform deformationof the PhC structures which mainly develop in samples rigidly attached to a glass substrate, since top part of thesamples is allowed to shrink, whereas bottom remains fixed at the original size. Shrinkage in photoresist can not
be eliminated, however, by fabricating encage structures floating above the substrate it was possible to achieve
uniform shrinkage as explained schematically and by Scanning Electron Microscopy (SEM) pictures in Fig. 3.

Fig. 3 The advantage of encaged PhC structures, (a,b) schematic explanation, (c) SEM image illustrating
non-uniform shrinkage of a PhC sample directly attached to the glass substrate, (d) uniform shrinkage of anencaged PhC sample which is not attached to the substrate .
Figure 4 shows optical microscopy image of a single substrate containing multiple encaged PhC structures withdifferent structural parameters (lattice period a xy was set directly during the sample design, while diameter ofindividual photoresist rods was controlled indirectly by changing average writing laser power during the DLW).
As can be seen from the Figure, most structures exhibit structural color. Moreover, systematic variation of thePhC lattice parameters leads to color change in the entire visible spectral range from blue to deep-red.

Fig. 4 Optical microscopy images of the fabricated PhC samples exhibiting structural color, and control of thecolor via PhC lattice parameters.
The apparent color correlates well with experimental reflectance spectra of the structures. This is illustrated by thespectra of structures 1 to 5 (Fig. 4) shown in Fig. 5. Increase in the lattice period leads to red-shift of the mainreflectance peak in a broad spectral range from 500 to 600 nm. Such red shift is consistent with so-called
Maxwell’s scaling behavior characteristic to dielectric photonic crystals. Similar shift can be also observed when
the writing laser power increases, leading to ticker dielectric rods composing the woodpile, and larger dielectricfilling fraction, as is seen in samples i to iv in Fig. 4.

Fig. 5 Experimental reflectivity spectra of several fabricated PhC samples from Fig. 4.
Altogether this data illustrates that 3D PhC structures exhibiting structural color were successfully realized, andcolor of the samples is controllable via PhC lattice parameters. Hence, the fabricated samples can be used as
artificial equivalents of Morpho butterfly wing scales, and their sensitivity to the presence of IR irradiation as wellas other environmental factors can be investigated. This will be done during continuation of these studies.

List of Publications Related to the Collaboration Research[1]. Faniayeu, S.Khakhomov, I.Semchenko, V. Mizeikis, Highly transparent twist polarizer metasurface,Appl. Phys. Lett. 111, 111108 (2017).
[2]. Faniayeu, V. Mizeikis, Vertical split-ring resonator perfect absorber metamaterial for IR frequencies
realized via femtosecond direct laser writing, Appl. Phys. Expr. 10 (2017).
List of Presentations ( Conference, Meeting, etc)[1]. V. Mizeikis, Direct laser writing of electromagnetic metasurfaces for infra-red frequency range (Invited),
SPIE Photonics West 2018, San Francisco CA, Jan. 27-Feb. 1 (2018)[2]. V. Mizeikis, Z. Hayran, H. Kurt, D. gailevicius, M. Malinauskas, S. Juodkazias, K. Staliunas, Fabrication of
optical field concentrators based on 3D chirped photonic crystals by direct laser writing technique, Meta 2017,Incheon, Korea, July 25-28 (2017).
List of Awards
None

Research plan for the next year (from April 1, 2018 to March 31, 2019), if the collaboration research is continued.
Prior consent from the collaboration partner in the Research Center is necessary.
The main goals of research proposed for the next year are outlined below:
I. Obtaining experimental evidence that structural color of the fabricated photonic crystals is indeed sensitive toIR radiation. This will be done using experimental setup shown in Fig. 6 (see discussion below). To ensure
successful outcome of these studies, several preparatory steps will be needed:
1) Thermal response of natural Morpho butterfly wings will be investigated theoretically and experimentally inorder to obtain benchmarks for the performance of our samples;2) 3D woodpile PhCs will be designed theoretically using Finite-Difference Time-Domain (FDTD) simulation
aiming for the brightest and most pure structural color (as required for monitoring).
3) Suitability of SZ2080 photoresist as well as similar other photoresist will be re-examoned, taking into accountthe need for strong absorption at IR wavelengths, low absorption at visible wavelengths, and significant valuesof coefficient of thermal expansion (CTE).
After these steps, encaged woodpile PhC samples will be fabricated for experimental tests in the presence of IRradiation. Samples with relatively large footprint size ≈ (50x50)µm2 and bright structural color will be preparedand investigated as shown schematically in Fig. 6. For this purpose experimental setup shown in the Fig 6.
which allows monitoring of the structural color (intensity and spectrum) in the presence or absence of IR radiation

derived from a broadband (globar) source will be assembled. If necessary, numerical modeling, fabrication, andexperimental characterization will be iterated several times in order to obtain artificial PhC structures exhibiting
IR sensitivity levels similar to those exhibited by the natural Morpho butterfly wing scales.
All participants will be involved in the planning and realization of the proposed experiments as well asinterpretation of the obtained data. To promote collaboration between the teams participating in these activities,
joint research seminar(s) will be held.

Fig. 6 Experimental characterization of thermal sensitivity of PhC structures, and isolation of the PhC structurefrom substrate.
II. Finding other possible application areas for 3D PhC structures fabricated using the DLW approach. In thisrespect, applications of artificial structural color materials realized by other techniques will be analyzed aiming todetermine which of them are viable using DLW based approach. The requirements for wide range of applications
are summarized in Fig. 7.

Fig. 7 Summary of requirements and application areas for structural color materials.