Voltage-controlled wavelength conversion by terahertz electro-optic modulation in double quantum wells

An undoped double quantum well (DQW) was driven with a terahertz (THz) electric field of frequency \omega_{THz} polarized in the growth direction, while simultaneously illuminated with a near-infrared (NIR) laser at frequency \omega_{NIR}. The intensity of NIR upconverted sidebands \omega_{sideband}=\omega_{NIR} + \omega_{THz} was maximized when a dc voltage applied in the growth direction tuned the excitonic states into resonance with both the THz and NIR fields. There was no detectable upconversion far from resonance. The results demonstrate the possibility of using gated DQW devices for all-optical wavelength shifting between optical communication channels separated by up to a few THz.Comment: 3 pages, 6 figures. Figures 5 and 6 are JPEG files, figures/fig5.jpg and fig6.jp

Spin-based quantum gating with semiconductor quantum dots by bichromatic radiation method

A potential scheme is proposed for realizing a two-qubit quantum gate in semiconductor quantum dots. Information is encoded in the spin degrees of freedom of one excess conduction electron of each quantum dot. We propose to use two lasers, radiation two neighboring QDs, and tuned to blue detuning with respect to the resonant frequencies of individual excitons. The two-qubit phase gate can be achieved by means of both Pauli-blocking effect and dipole-dipole coupling between intermediate excitonic states.Comment: Europhysics Letters 66 (2004) 1

Nonlinear electromagnetic response of graphene: Frequency multiplication and the self-consistent-field effects

Graphene is a recently discovered carbon based material with unique physical properties. This is a monolayer of graphite, and the two-dimensional electrons and holes in it are described by the effective Dirac equation with a vanishing effective mass. As a consequence, electromagnetic response of graphene is predicted to be strongly non-linear. We develop a quasi-classical kinetic theory of the non-linear electromagnetic response of graphene, taking into account the self-consistent-field effects. Response of the system to both harmonic and pulse excitation is considered. The frequency multiplication effect, resulting from the non-linearity of the electromagnetic response, is studied under realistic experimental conditions. The frequency up-conversion efficiency is analysed as a function of the applied electric field and parameters of the samples. Possible applications of graphene in terahertz electronics are discussed.Comment: 14 pages, 7 figures, invited paper written for a special issue of JPCM "Terahertz emitters

Growth and optical properties of self-assembled InGaAs Quantum Posts

We demonstrate a method to grow height controlled, dislocation-free InGaAs quantum posts (QPs) on GaAs by molecular beam epitaxy (MBE) which is confirmed by structural investigations. The optical properties are compared to realistic 8-band k.p calculations of the electronic structure which fully account for strain and the structural properties of the QP. Using QPs embedded in n-i-p junctions we find wide range tunability of the interband spectrum and giant static dipole moments.Comment: Proccedings paper for MSS-13, 7 pages, 4 figure

Implementasi Teknologi NFC Untuk Akses Pintu Masuk Dan Keluar

Keamanan dalam akses membuka pintu sebuah ruangan merupakan faktor yang sangat mempengaruhi akan pentingnya peranan kunci yang dapat memberikan keamanan pada ruangan. Kunci sangat dibutuhkan dalam suatu keamanan sebagai pengaman yang digunakan untuk membuka pintu ruangan. Pintu merupakan salah satu akses masuk dan keluar ruangan yang membutuhkan tingkat keamanan tinggi untuk mencegah tingkat pencurian dan kehilangan ketika ditinggal oleh pemiliknya, dan juga mencegah apabila kunci di duplikat banyak cara yang dilakukan untuk memenuhi kebutuhan tersebut. Dalam penelitian ini memanfaatkan teknologi NFC ( Near Field Communication ) untuk akses pintu masuk dan keluar merupakan solusi untuk mengatasi masalah keamanan ruangan. Karena tag NFC memiliki id yang tidak dapat diduplikat beda dengan kunci pada umumnya. Sistem ini dibuat menggunakan mikrokontroler Arduino, NFC reader, selenoid doorlock untuk membuka pintu, dan LCD Untuk menampilkan nama dan id pengguna, Esp8266 untuk menghubungkan Arduino dengan server. Untuk menyimpan data log NFC via web server, dengan nama domain Ahmadsadiknfcskripsi.com. Dengan adanya penggunaan NFC di pintu masuk diharapkan orang yang masuk dan keluar ruangan dapat di - identifikasi terlebih dahulu sebelum diperbolehkan masuk atau keluar ruangan. Penelitian ini menghasilkan aplikasi sistem akses pintu masuk dan keluar menggunakan NFC yang bisa mengetahui waktu user masuk dan keluar ruangan,dan siapa saja yang memiliki hak untuk masuk dalam sebuah ruangan

Monitored Energy Use Patterns in Low-Income Housing in a Hot and Humid Climate

The Florida Solar Energy Center (FSEC) is metering energy use in two Habitat for Humanity developments. The objective is to understand how energy is used in low income housing and how it can be effectively reduced. The ten "control homes" come from a conventional housing project built by in 1993 Habitat for Humanity in Homestead, Florida. Another ten "experimental homes" have been recruited from the 190 home Jordan Commons development in the same vicinity. These houses, which are soon to be metered, are designed to be energy efficient with high SEER air conditioners, reflective roofing, solar water heaters and energy efficient lighting and appliances.' The instrumentation was installed in the control homes in July of 1994 with a year of 15-minute data now collected on all sites. Data are obtained on seven electrical end-uses (air conditioning, heating, hot water, dryer, range, refrigerator, washer/freezer) as well as total. Weather conditions are also monitored as well as interior comfort conditions (temperature and humidity) and hot water consumption and window ventilation status. The field data allow unique insight into how energy is used in low income housing in a hot and humid climate

Combined CG-HDG Method for Elliptic Problems: Performance Model

We combine continuous and discontinuous Galerkin methods in the setting of a model diffusion problem. Starting from a hybrid discontinuous formulation, we replace element interiors by more general subsets of the computational domain - groups of elements that support a piecewise-polynomial continuous expansion. This step allows us to identify a~new weak formulation of Dirichlet boundary condition in the continuous framework. We examine the expected performance of a Galerkin solver that would use continuous Galerkin method with weak Dirichlet boundary conditions in each mesh partition and connect partitions weakly using trace variable as in HDG method