In der vorliegenden Arbeit werden ZnO-Mikronadeln bezüglich ihrer Anwendbarkeit als Mikroresonatoren untersucht. Dabei stehen Kavitätsmoden im Fokus der Untersuchungen, die sich nur senkrecht zur Nadelachse ausbreiten, sprich innerhalb der hexagonalen Nadelquerschnittsfläche. Folglich wird der Einfluss der Gestalt der Querschnittsfläche auf Resonatoreigenschaften wie Propagation, Form, Direktionalität und Qualität der Kavitätsmoden sowohl theoretisch simuliert als auch experimentell nachgewiesen. Die dabei beobachteten hohen Qualitätsfaktoren von Flüstergalerie-Moden ermöglichen es darüberhinaus, Wechselwirkungseffekte zwischen Kavität und Mode zu beobachten. Der erste Teil der Arbeit beschäftigt sich mit der regulären, polygonalen Resonatorform und deren Einfluss auf die Dimensionalität von Kavitätsmoden sowie deren mögliche Wechselwirkung mit dem elektronischen System des Resonators. Beispielhaft wird ein hexagonaler Resonator zur Veranschaulichung gewählt, wie er durch ZnO-Mikronadeln gegeben ist, undmittels Finite-Difference-Time-Domain (FDTD)-Simulationen sowie winkelaufgelöster Photolumineszenz (PL)-Spektroskopie untersucht. Die aufgenommenen PL-Spektren können unter Zuhilfenahme photonischer Dispersionskurven von ein- und zwei-dimensionalen Kavitätsmoden reproduziert werden. Basierend auf diesen Ergebnissen wird der Einfluß der Resonatorecken auf die Lichtauskopplung diskutiert und mittels winkelaufgelöster, anregungsabhängiger und temperaturabhängier PL-Spektroskopie nachgewiesen. Desweiteren wird auf die Wechselwirkung zwischen dem Resonator und den Kavitätsmoden eingegangen, imSpeziellen auf die starke Kopplung zwischen Flüstergalerie-Moden und freien Exzitonen imResonatormaterial. Bereits erschienende Publikationen zu diesemThema werden präsentiert und kritisch hinterfragt. Dabei wird ein Leitfaden aufgestellt, der eine Evaluierung möglicher Polaritonen-Phänomene ermöglicht. Um Wechselwirkungen dieser Art auch in den hier untersuchtenMikronadeln nachzuweisen, werden Hochanregungs-PL-Messungen durchgeführt. Dabei werden Messungen in der Mitte der Nadel sowie in der Nähe ihrer Ecken getätigt, um spezielle Polaritonen-Propagationseffekte beobachten zu können. Im zweiten Teil der Arbeit wird der Einfluß von irregulären und inhomogenen Resonatorformen auf die Bildung von Flüstergalerie-Moden diskutiert. Dafür werden elongierte Teile der Nadeln, die durch laterale Auswüchse entstehen, winkelaufgelöst bezüglich einer gerichteten Auskopplung von Kavitätsmoden vermessen und verzerrte Mikronadeln, wie sie beim Biegen entstehen, bezüglich der entstehenden Deformationseffekte und deren Einfluss auf die Kavitätsmoden mittels hochaufgelöster Mikro-PL untersucht. Die experimentellen Ergebnisse zu irregulären Resonatoren können durch FDTD-Simulationen bestätigt werden. Desweiteren wurden Mikronadel- und Nanonadel-Quantengraben-Heterostrukturen hergestellt und deren Lumineszenzeigenschaften diskutiert. Dabei wird speziell auf die Homogenität der Quantengrabenemission eingegangen und Strategien zur Realisierung einer starken Kopplung zwischen Flüstergalerie-Moden und Quantengraben-Exzitonen aufgestellt. Diese Strategien werden experimentell umgesetzt und deren Ergebnisse anhand von Kathodolumineszenzmessungen vorgestellt.

The increasing demand for high performance communications systems and signal processing is constantly driving researchers to develop novel devices in both the microwave and optical domains. The possibility of using high temperature superconductors (HTS) as a platform for ultra-fast, ultra-high sensitive optoelectronic and microwave photonic devices has been explored. This report introduces a cryogenic microwave photonic probe station, designed and built to characterize HTS microwave photonic devices. A methodology is presented to design coplanar waveguide transmission lines using HTS. The transmission line is then modified to include a meander line structure to serve the optoelectronic function. The device is characterized in several different operating domains, as an optically tunable microwave resonator, an optically tunable delay line, and finally as a photodetector. A planar HTS weak leak structure is investigated with the measurements of the I-V characteristics. Moreover, this device is proposed as the next generation platform to fabricate ultra-fast and ultra-high sensitive photodetectors using HTS.

One of the key advances in photonic technology in recent decades was the development of a new type of diode lasers emitting in the visible and infrared region. These vertical cavity surface-emitting lasers (VCSELs) emerged from a laboratory curiosity in 1977 [13] to an object of industrial mass production [14] and are currently used in many applications. The applications include communication, printing, and absorption spectroscopy [15]. Their rise in credibility has largely been motivated by the rapid evolution of their performance, the more sweeping recognition of their compatibility with low-cost wafer-scale fabrication, and their possible formation into specific arrays with no change in the fabrication procedure. Various applications such as advanced chemical sensors and high-density optical storage require coherent and small-size ultraviolet-emitting devices (below 400nm). Therefore, to extend the VCSEL emission to the ultraviolet (UV) region, intensive efforts have been made in the VCSEL technology. However, the achievement of such UV VCSEL is very challenging because of the various limitations and issues. The issues noticeably include the carrier injection, optical confinement, and highly reflective distributed Bragg reflectors (DBR) structures with a broad bandwidth operating in the UV region [16]. In this context, motivated by the reported large refractive index induced by boron incorporation [7], we propose to introduce the boron-based material systems (BAlGaN) as an innovative solution to address some of the encountered difficulties. The objective of the proposed research is to investigate and optimize new wide-bandgap BAlGaN material systems and illustrate their incorporation into the building blocks of vertical cavity surface-emitting laser structures for operation in the UV spectral range (<400nm). Toward this goal, we have focused our research activities in three main directions. The first direction is devoted to the simulation of DBRs reflectivity by taking into consideration the experimental refractive indexes. Once the materials needed in the different components of the VCSEL are well defined, the second direction lies in the achievement of growth conditions optimization and characterization of the new wide-bandgap BAlGaN material systems. The study has led to the structural and morphological quality improvement of (B,Al,Ga)N materials. Unique optical properties of the BGaN and BAlN materials were also demonstrated. Upon demonstrating the materials' promising optical characteristics, the final direction consists of the epitaxial growth and characterization of the highly reflective DBRs and active region of the UV VCSEL structure.

No description available.

No description available.

Orthogonal Frequency Division Multiplexing (OFDM) is a suitable solution due to its many advantages known in wireless communications. On the other hand, optical communications is also used as a backbone to transmit and receive large data rates with economical and good performance. Recently, fiber optical communication and OFDM method are combined to obtain both advantages in a communication link. Coherent optical OFDM (CO-OFDM) has recently been proposed against the chromatic dispersion effect in electrical domain. According to the ITU-T standards there are 111 channels (C and L bands) can be used (191.4 to 185.9 THz) at 50 GHz spacing. Thanks to Wavelength Division Multiplexing, even we use only one RF carrier, we can reach 1.7 Tb/s (111*16 Gb/s) using only one optical cable and utilizing C and L bands. In this research, CO-OFDM technique is modeled and simulated by designing a Monte Carlo simulation. In this simulation, dispersion, data rate, SNR-BER and BER-Distance variations are calculated and results are given in graphical forms. These graphics show the performance of the CO-OFDM system in 5, 8 and 16 Gb/s at different distances for one RF carrier and one optical carrier. It is also shown that how to get 64 Gb/s data rate using the same structure with one optical carrier.

The increasing demand for high performance communications systems and signal processing is constantly driving researchers to develop novel devices in both the microwave and optical domains. The possibility of using high temperature superconductors (HTS) as a platform for ultra-fast, ultra-high sensitive optoelectronic and microwave photonic devices has been explored. This report introduces a cryogenic microwave photonic probe station, designed and built to characterize HTS microwave photonic devices. A methodology is presented to design coplanar waveguide transmission lines using HTS. The transmission line is then modified to include a meander line structure to serve the optoelectronic function. The device is characterized in several different operating domains, as an optically tunable microwave resonator, an optically tunable delay line, and finally as a photodetector. A planar HTS weak leak structure is investigated with the measurements of the I-V characteristics. Moreover, this device is proposed as the next generation platform to fabricate ultra-fast and ultra-high sensitive photodetectors using HTS.

No description available.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Triplet; rigidly linked polychromophores; intramolecular energy transfer. Includes bibliographical references (p. 83-87).

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Electrical and Computer Engineering." Includes bibliographical references (p. 256-264).