THz Metamaterial Characterization Using THz-TDS

The purpose of this chapter is to familiarize the reader with metamaterials and describe terahertz (THz) spectroscopy within metamaterials research. The introduction provides key background information on metamaterials, describes their history and their unique properties. These properties include negative refraction, backwards phase propagation, and the reversed Doppler Effect. The history and theory of metamaterials are discussed, starting with Veselago’s negative index materials work and Pendry’s publications on physical realization of metamaterials. The next sections cover measurement and analyses of THz metamaterials. THz Time-domain spectroscopy (THz-TDS) will be the key measurement tool used to describe the THz metamaterial measurement process. Sample transmission data from a metamaterial THz-TDS measurement is analyzed to give a better understanding of the different frequency characteristics of metamaterials. The measurement and analysis sections are followed by a section on the fabrication process of metamaterials. After familiarizing the reader with THz metamaterial measurement and fabrication techniques, the final section will provide a review of various methods by which metamaterials are made active and/or tunable. Several novel concepts were demonstrated in recent years to achieve such metamaterials, including photoconductivity, high electron mobility transistor (HEMT), microelectromechanical systems (MEMS), and phase change material (PCM)-based metamaterial structures

THz Metamaterial Characterization Using THz-TDS

The purpose of this chapter is to familiarize the reader with metamaterials and describe terahertz (THz) spectroscopy within metamaterials research. The introduction provides key background information on metamaterials, describes their history and their unique properties. These properties include negative refraction, backwards phase propagation, and the reversed Doppler Effect. The history and theory of metamaterials are discussed, starting with Veselago’s negative index materials work and Pendry’s publications on physical realization of metamaterials. The next sections cover measurement and analyses of THz metamaterials. THz Time-domain spectroscopy (THz-TDS) will be the key measurement tool used to describe the THz metamaterial measurement process. Sample transmission data from a metamaterial THz-TDS measurement is analyzed to give a better understanding of the different frequency characteristics of metamaterials. The measurement and analysis sections are followed by a section on the fabrication process of metamaterials. After familiarizing the reader with THz metamaterial measurement and fabrication techniques, the final section will provide a review of various methods by which metamaterials are made active and/or tunable. Several novel concepts were demonstrated in recent years to achieve such metamaterials, including photoconductivity, high electron mobility transistor (HEMT), microelectromechanical systems (MEMS), and phase change material (PCM)-based metamaterial structures

Graphene Photonics and Optoelectronics

The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential to be in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultra-wide-band tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light emitting devices, to touch screens, photodetectors and ultrafast lasers. Here we review the state of the art in this emerging field.Comment: Review Nature Photonics, in pres

3-D Printed Plug and Play Prototyping for Low-cost Sub-THz Subsystems

Polymer-based additive manufacturing using 3-D printing for upper-millimeter-wave ( ca. 100 to 300 GHz) frequency applications is now emerging. Building on our previous work, with metal-pipe rectangular waveguides and free-space quasi-optical components, this paper brings the two media together at G-band (140 to 220 GHz), by demonstrating a compact multi-channel front-end subsystem. Here, the proof-of-concept demonstrator integrates eight different types of 3-D printed components (30 individual components in total). In addition, the housing for two test platforms and the subsystem are all 3-D printed as single pieces, to support plug and play development; offering effortless component assembly and alignment. We introduce bespoke free-space TRM calibration and measurement schemes with our quasi-optical test platforms. Equal power splitting plays a critical role in our multi-channel application. Here, we introduce a broadband 3-D printed quasi-optical beamsplitter for upper-millimeter-wave applications. Our quantitative and/or qualitative performance evaluations for individual components and the complete integrated subsystem, demonstrate the potential for using consumer-level desktop 3-D printing technologies at such high frequencies. This work opens-up new opportunities for low-cost, rapid prototyping and small-batch production of complete millimeter-wave front-end subsystems

3D printed waveguides: A revolution in low volume manufacturing for the 21st century

3D printing is a disruptive technology, offering the inherent capabilities for creating truly arbitrary 3D structures, with low manufacturing costs associated with low volume production runs. This paper provides an overv iew of the current progress in 3D printing of metal - pipe rectangular waveguide (MPRWG) components, from 10 GHz to 1 THz, at Imperial College London. First, measurements performed at the UK National Physical Laboratory demonstrate that 3D printed MPRWG perf ormance is comparable to standard commercial waveguides at X - band and W - band. Then, a fully 3D printed X - band dielectric flap tuneable phase shifter and W - band 6th - order inductive iris bandpass filter are demonstrated experimentally. Finally, an optically - controlled 500 GHz IQ vector modulator will also be presented; packaged laser diodes and high resistivity silicon implants are integrated within a hybrid 3D printed split - block module, representing a paradigm shift in additive manufacturing for realizing t uneable THz applications

Tunable terahertz photodetector using ferroelectric-integrated graphene plasmonics for portable spectrometer

Terahertz (THz) detector has great potential for use in imaging, spectroscopy, and communications due to its fascinating interactions between radiation and matter. However, current THz detection devices have limitations in sensitivity, operating frequency range, and bulky footprint. While recent ferroelectric-integrated graphene plasmonic devices show promise in overcoming these limitations, they are not yet extended to the THz range. Here, we propose a wavelength-sensitive terahertz detector that uses a single layer graphene integrated onto the ferroelectric thin film with patterned polarization domains. This device works at room temperature, with high responsivity and detectivity by coupling graphene plasmons with THz frequencies through spatial modulation of carrier behaviors using ferroelectric polarization, without requiring additional local electrodes. By reconfiguring an interweaving squared ferroelectric domain array with alternating upward and downward polarizations to highly confine graphene surface plasmon polaritons, our device achieves an ultrahigh responsivity of 1717 A W-1 and a normalized detectivity of 1.07*10^13 Jones at a resonance frequency of 6.30 THz and a 0.3 V bias voltage. We also show that the device makes possible for spectrum reconstruction application of portable spectrometer combining the mathematical algorithms.Comment: 17 pages, 5 figure

Design and fabrication of ultrathin nanophotonic devices based on metasurfaces

Wydział FizykiOd kilkuset lat badania natury światła fascynuje naukowców na całym świecie. W XVII wieku, holenderski astronom i matematyk, Willebrord Snellius zdefiniował pojęcie refrakcji światła, które później od jego nazwiska zostało nazwane prawem Snella. Prawo to wciąż jest szeroko stosowane, a jego uogólnienie w roku 2011 zaproponował prof. Capasso z Uniwersytetu Harvarda. Uogólnione prawo Snella pozwala na rozwijanie technik kontroli frontów falowych wykorzystując powierzchnie zmieniające ich fazę w transmisji lub w odbiciu, zwane metapowierzchniami. Uogólnione prawo Snella jest zgodne z zasadą Fermata a wytwarza się je przy użyciu bardzo małych struktur mogących arbitralnie modyfikować amplitudę, fazę, polaryzację fali światła. Mechanizm odpowiedzialny za to zjawisko można dostosować do konkretnych zakresów długości fali i jest szczególnie dobrze sprawdzone dla światła z zakresu widzialnego. W pracy doktorskiej przedstawiłem koncepcję wykorzystania metapowierzchni do projektowania kilku urządzeń nanofotonicznych. Zaprojektowałem w pełni dielektryczne filtry koloru na bazie krzemu, które efektywnie działają dla fal przechodzących i odbitych. Rozszerzyłem te badania również o projekt dynamicznych i przestrajalnych filtrów kolorów kontrolując polaryzację światła przy wykorzystaniu ciekłych kryształów. Następnie zaproponowałem koncepcję urządzenia wykorzystujące zjawisko impedancji powierzchniowej do sterowania transmisją i umożliwiając prowadzenie fal w płaszczyźnie falowodu kryształu fotonicznego.Light is one of the most fascinating research areas of science since the past few centuries and this century no exception. In 17th, Snell's law was introduced by Willebrord Snellius a Dutch astronomer and mathematician, which explain the properties of refraction and reflection of light. In 2011, prof. Capasso group from Harvard University generalized the Snell's law and introduce a new way to modify the wave-front of the wave using phase varying surfaces. The modified Snell's law follows the Fermat principle for the phase changing surfaces. This phase changing surface can be created using tiny nanostructures to arbitrarily modified the amplitude, phase, polarization of the wave, commonly known as metasurfaces. The concept is scalable to arbitrary wavelength range and very well followed especially in the visible range. In this thesis, I used the concept of metasurfaces to design and fabricate the different nanophotonics devices. I design and fabricate the Si-based all-dielectric color filters which can be used in transmission and reflection mode. The color filter design presented in this thesis is very efficient due to the all dielectric material approach. I also extended the research to design dynamically tunable color filters with the aid of source polarisation and liquid crystal. Furthermore, I also proposed the surface impedance approach to control the in-plane transmission within the photonic crystal waveguide

Fiber-Drawn Metamaterial for THz Waveguiding and Imaging

In this paper, we review the work of our group in fabricating metamaterials for terahertz (THz) applications by fiber drawing. We discuss the fabrication technique and the structures that can be obtained before focusing on two particular applications of terahertz metamaterials, i.e., waveguiding and sub-diffraction imaging. We show the experimental demonstration of THz radiation guidance through hollow core waveguides with metamaterial cladding, where substantial improvements were realized compared to conventional hollow core waveguides, such as reduction of size, greater flexibility, increased single-mode operating regime, and guiding due to magnetic and electric resonances. We also report recent and new experimental work on near- and far-field THz imaging using wire array metamaterials that are capable of resolving features as small as λ/28