Graphene-enabled adaptive infrared textiles

Interactive clothing requires sensing and display functionalities to be embedded on textiles. Despite the significant progress of electronic textiles, the integration of optoelectronic materials on fabrics remains as an outstanding challenge. In this Letter, using the electro-optical tunability of graphene, we report adaptive optical textiles with electrically controlled reflectivity and emissivity covering the infrared and near-infrared wavelengths. We achieve electro-optical modulation by reversible intercalation of ions into graphene layers laminated on fabrics. We demonstrate a new class of infrared textile devices including display, yarn, and stretchable devices using natural and synthetic textiles. To show the promise of our approach, we fabricated an active device directly onto a t-shirt, which enables long-wavelength infrared communication via modulation of the thermal radiation from the human body. The results presented here provide complementary technologies which could leverage the ubiquitous use of functional textiles

Fotolaidumo anizotropijos ir terahercinių impulsų generavimo puslaidininkiuose dinamika

The purpose of work presented in this thesis was to study the transient anisotropic photoconductivity in cubic semiconductors excited by femtosecond laser pulses and to investigate how this effect is manifested in emission of THz radiation from the semiconductor surface. The existing notion of the transient picosecond photoconductivity is far from complete in spite of the intensive study of this phenomenon. For example, the influence of the optical alignment of photocarriers over momenta on the transient photoconductivity has not been properly investigated. Meanwhile, as shown in this work the anisotropic momentum distribution of photocarriers can have a dramatic effect on the photocarrier dynamics during the first few hundred femtoseconds after photoexcitation. It has been shown in this work that the anisotropic transient photoconductivity in cubic semiconductors excited by femtosecond laser pulses is determined by photocarrier dynamics on a subpicosecond time scale and plays a significant role in THz emission from semiconductors. The study of this phenomenon gives us a better insight into ultrafast electronic processes which are of fundamental importance to the operation of high-speed semiconductor devices having a picosecond response time

Transient anisotropic photoconductivity and terahertz pulse generation from semiconductors

The purpose of work presented in this thesis was to study the transient anisotropic photoconductivity in cubic semiconductors excited by femtosecond laser pulses and to investigate how this effect is manifested in emission of THz radiation from the semiconductor surface. The existing notion of the transient picosecond photoconductivity is far from complete in spite of the intensive study of this phenomenon. For example, the influence of the optical alignment of photocarriers over momenta on the transient photoconductivity has not been properly investigated. Meanwhile, as shown in this work the anisotropic momentum distribution of photocarriers can have a dramatic effect on the photocarrier dynamics during the first few hundred femtoseconds after photoexcitation. It has been shown in this work that the anisotropic transient photoconductivity in cubic semiconductors excited by femtosecond laser pulses is determined by photocarrier dynamics on a subpicosecond time scale and plays a significant role in THz emission from semiconductors. The study of this phenomenon gives us a better insight into ultrafast electronic processes which are of fundamental importance to the operation of high-speed semiconductor devices having a picosecond response time

Video-speed Graphene Modulator Arrays for Terahertz Imaging Applications

Electrically tuneable high mobility charges on graphene yield an efficient electro-optical platform to control and manipulate terahertz (THz) waves. Real-world applications require a multiplex THz device with efficient modulation over a large active area. The trade-off between the efficient gating and switching speed, however, hinders the realization of these applications. Here, we demonstrate a large-format 256-pixel THz modulator which provides high-frame-rate reconfigurable transmission patterns. The time-domain and frequency-domain THz characterizations of graphene devices reveal the relaxation pathways of gate-induced charges and ion packing at graphene-electrolyte interface. The fundamental understanding of these limiting factors enables us to break the trade-off permitting switching frequencies up to 1 kHz. To show the promises of these devices, we demonstrate a single-pixel THz camera which allows spatial and spectroscopic imaging of large-area objects without any moving components. These results provide a significant advancement towards the achievement of non-invasive THz imaging systems using graphene-based platforms.Comment: 16 pages, 5 figure