Volatile Ultrafast Switching at Multilevel Nonvolatile States of Phase Change Material for Active Flexible Terahertz Metadevices

Abstract

Phase change materials provide unique reconfigurable properties for photonic applications that mainly arise from their exotic characteristic to reversibly switch between the amorphous and crystalline nonvolatile phases. Optical pulse based reversible switching of nonvolatile phases is exploited in various nanophotonic devices. However, large area reversible switching is extremely challenging and has hindered its translation into a technologically significant terahertz spectral domain. Here, this limitation is circumvented by exploiting the semiconducting nature of germanium antimony telluride (GST) to achieve dynamic terahertz control at picosecond timescales. It is also shown that the ultrafast response can be actively altered by changing the crystallographic phase of GST. The ease of fabrication of phase change materials allows for the realization of a variable ultrafast terahertz modulator on a flexible platform. The rich properties of phase change materials combined with the diverse functionalities of metamaterials and all-optical ultrafast control enables an ideal platform for design of efficient terahertz communication devices, terahertz neuromorphic photonics, and smart sensor systems.

Reconfigurable terahertz metamaterials: From fundamental principles to advanced 6G applications

“…Microelectromechanical system (MEMS) technology enables micro/nanoscale mechanical manipulation, which is suitable for meta-atom construction in the THz region, bringing various applications in THz functional devices. The reconfigurable MEMS metamaterials can be further classified by their actuator mechanisms, such as piezoelectric ( Willatzen and Christensen, 2014 ; Amirkhan et al., 2020 ; Le et al., 2022 ), electrothermal ( Lee and Wu, 2005 ; Lee and Yeh, 2005 ; Lee, 2005 ; Lee, 2006 ; Lee, 2007 ; Pitchappa et al., 2017 ), and electrostatic ( Pitchappa et al., 2015a , 2015b , 2015c , 2016a , 2016c ; Shih et al., 2017 ) ( Pitchappa et al., 2021a , 2021b ), and so on ( Lee et al., 2005 ; Lee, 2005 ; Yeh et al., 2006 ). Combining with metamaterial resonator designs, the deformed structures can effectively modify the electromagnetic field distribution inside the resonators.…”

“…Therefore, reconfigurable metadevices are more competitive, especially when dealing with complicated systems, where programmable design can benefit signal processing algorithms for a large amount of data, providing opportunities for the assistance of artificial intelligence for healthcare, environmental monitoring, reconfigurable intelligence surface for wireless communication systems, and Internet of Things applications.

Figure 1 A roadmap of the development of reconfigurable THz metamaterials in the past 10 years, and metamaterials-enabled THz functional devices Reprinted from ref ( Tao et al., 2011 ; Grant et al., 2013 ; Liu et al., 2017 ; Belacel et al., 2017 ; Park et al., 2013 ; Lee et al., 2015 ; Tenggara et al., 2017 ; Zhou et al, 2021c ; Zhu et al., 2011 ; Zhu et al., 2012 ; Li et al., 2013 ; Ma et al., 2014 ; Pitchappa et al., 2015a , 2016c ; Zhang et al., 2017 ; Zhao et al., 2018 ; Cong et al., 2019 ; Pitchappa et al., 2020 , 2021b ) with permission, Copyright@2011 Optical Society of America, Copyright@2013 Wiley-VCH, Copyright@2017 Spring Nature, Copyright@2017 Spring Nature, Copyright@2013 American Chemical Society, Copyright@2015 Spring Nature, Copyright@2017 IOP Publishing, Copyright@2021 Elsevier, Copyright@2011 Wiley-VCH, Copyright@2012 Spring Nature, Copyright@2013 AIP Publishing, Copyright@2014 Spring Nature, Copyright@2015 Optical Society of America, Copyright@2016 Wiley-VCH, Copyright@2017 Spring Nature, Copyright@2018 Optical Society of America, Copyright@2019 AAAS, Copyright@2020 Wiley-VCH, Copyright@2021 Wiley-VCH.

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“… Reprinted from ref ( Tao et al., 2011 ; Grant et al., 2013 ; Liu et al., 2017 ; Belacel et al., 2017 ; Park et al., 2013 ; Lee et al., 2015 ; Tenggara et al., 2017 ; Zhou et al, 2021c ; Zhu et al., 2011 ; Zhu et al., 2012 ; Li et al., 2013 ; Ma et al., 2014 ; Pitchappa et al., 2015a , 2016c ; Zhang et al., 2017 ; Zhao et al., 2018 ; Cong et al., 2019 ; Pitchappa et al., 2020 , 2021b ) with permission, Copyright@2011 Optical Society of America, Copyright@2013 Wiley-VCH, Copyright@2017 Spring Nature, Copyright@2017 Spring Nature, Copyright@2013 American Chemical Society, Copyright@2015 Spring Nature, Copyright@2017 IOP Publishing, Copyright@2021 Elsevier, Copyright@2011 Wiley-VCH, Copyright@2012 Spring Nature, Copyright@2013 AIP Publishing, Copyright@2014 Spring Nature, Copyright@2015 Optical Society of America, Copyright@2016 Wiley-VCH, Copyright@2017 Spring Nature, Copyright@2018 Optical Society of America, Copyright@2019 AAAS, Copyright@2020 Wiley-VCH, Copyright@2021 Wiley-VCH. …”

“…In this year, Pitchappa et al. proposed a flexible metadevice integrated with phase change materials, where picosecond-level time delay was demonstrated for the reconfiguration process ( Pitchappa et al., 2021b ).…”

Multilevel Switching in Phase‐Change Photonic Memory Devices

“…[ 65 ] In addition, the delay in the optical switching observed during the multishot laser pulses has been overcome with the help of single‐shot laser pulses. [ 66 ] To achieve ultrafast switching, a single‐shot picosecond laser pulse has been irradiated for the multilevel SET and RESET process. [ 51,61 ] Furthermore, single‐shot programming has also demonstrated better thermal stability during the multilevel switching compared with the multishot accumulative programming technique.…”