Electromechanically reconfigurable optical nano-kirigami

Kirigami, with facile and automated fashion of three-dimensional (3D) transformations, offers an unconventional approach for realizing cutting-edge optical nano-electromechanical systems. Here, we demonstrate an on-chip and electromechanically reconfigurable nano-kirigami with optical functionalities. The nano-electromechanical system is built on an Au/SiO2/Si substrate and operated via attractive electrostatic forces between the top gold nanostructure and bottom silicon substrate. Large-range nano-kirigami like 3D deformations are clearly observed and reversibly engineered, with scalable pitch size down to 0.975 μm. Broadband nonresonant and narrowband resonant optical reconfigurations are achieved at visible and near-infrared wavelengths, respectively, with a high modulation contrast up to 494%. On-chip modulation of optical helicity is further demonstrated in submicron nano-kirigami at near-infrared wavelengths. Such small-size and high-contrast reconfigurable optical nano-kirigami provides advanced methodologies and platforms for versatile on-chip manipulation of light at nanoscale.

1. To show the response time of reconfigurable nano-kirigami/origami, the authors should add some figures about vertical displacement versus time when applying external voltages, simulation results is fine. 2. Could the authors provide more physical explanations for the reflection change induced by shape transformation illustrated in figure 3(a). Since the incident light is not blocked totally, how about the transmission and absorption?
Dear Reviewers, Thank you very much for reviewing our manuscript during the COVID-19 pandemic, which has caused a very difficult time to all of us. We are very pleased to see the supportive comments that "the work is innovative in terms of nanofabrication", "the manuscript is significant and novel" and "the electromechanical based nano-kirigami can realize fast and accurate optical reconfiguration". We also appreciate the reviewers' valuable suggestions for further improvements. As a result, we have considered the remarks and made all necessary changes to fully address the comments. The followings are the responses to the comments.
Reviewer #1: Comment 1: This manuscript presents the experimental investigation of the electromechanical actuation of optical nano-kirigami structures. The electrical tuning of the reflection spectrum and of the circular dichroism are demonstrated. While the work is innovative in terms of nanofabrication, I find the results in terms of optical functionality and especially their interpretation too thin to deserve publication in Nature Communications. The achieved modulation of the reflection spectrum (Fig. 3) is very limited, especially given the high voltages employed, and not competitive with other approaches. No attempt is made to interpret the observed features with electromagnetic simulations.
Response 1: Thank the reviewer very much for the positive comments on our nanofabrication results and sorry for the confusions in interpretations. In the revised manuscript, we have addressed the reviewer's concerns from four aspects.
(I) First, the significance of the functionality in this work has been clarified. In the field of spatial light modulations, the reduction of pixel size (p) and the enhancement of modulation rate (f) are highly challenging, such as the widely commercialized liquid crystal spatial light modulators (LC-SLMs, with f max =1 kHz) and digital micromirror devices (DMDs, with f max =40 kHz and p min =5 μm) summarized recently in Ref. [Light: Science & Applications 8, 110 (2019)].
Moreover, optical elements with smaller pixels may lead to the manipulation of more complex polarization states, such as the recently reported full-Stokes polarization imaging [Science 365, 43 (2019)]. In this aspect, the optical nano-kirigami is promising with its small pixels [p min =2.5 μm (Fig. 3c), 1.5 μm (Fig. 3f) and 0.975 μm (Fig. 4b)] and fast modulation [f max =200 kHz (Supplementary Fig. S8d)]. Meanwhile, the nano-kirigami design, as a new means, holds potentials for further development and improvement. For example, the modulation contrast can reach 494% by utilizing the sensitivity of the optical resonance at specific wavelength in Fig. 4b and the theoretical modulation frequency can be over 10 MHz (Supplementary Fig. S8c). To clarify this information, revisions have been made in [Lines 288-291, Page 13], as "Such flexibility is very desirable for the realization of high-speed spatial light modulations (SLM) with submicron pixels, which is promising since the pitch size and modulation speed of commercial DMD chips are limited to 5 μm and 40 kHz 50 , respectively." (II) Second, with the prototypes demonstrated in this work, the operation voltage (V) can be further reduced through two ways. As illustrated in the new Fig. 1c Supplementary Fig.   S8c., where decreases from 12 to 9 MHz for the spirals when V increases from 10 to 64 v.
To address this comment, a description has been added in Page 9], as "It  c.

Reviewer #3
Comment 1: Recently, kirigami/origami provides new platforms for versatile advanced 3D microfabrication/nanofabrication. In the manuscript titled 'Electromechanically reconfigurable optical nano-kirigami', the authors report series of on-chip CMOS-compatible optical nano-kirigami, which can realize reversible optical helicity and high contrast optical modulation. The contribution of this work to the optical community can be summarized as follows: 1. The proposed nano-kirigami is on-chip, CMOS-compatible and integrable, which may yield device level applications. 2. The electromechanical based nano-kirigami can realize fast and accurate optical reconfiguration. I recommend it be published in Nature communication after addressing some of my comments.
Response 1: Thank the reviewer very much for the positive comments on our manuscript.    Looking good! Reviewer #3 (Remarks to the Author): All my conccerns have been addressed in the revised manuscript. Now I would like to recommend the paper for publication.