Preface

The new emerging field of photonics has significantly attracted the interest of many societies, professionals and researchers around the world. The great importance of this field is due to its applicability and possible utilization in almost all scientific and industrial areas. One can say that photonics is currently at the forefront of science and technology, both on a basic and an advanced level.

The scientific revolution in fiber optic communication, nanotechnology, materials fabrication and optical diagnostic techniques made these technologies some of the leading photonic technologies of the era. These vast technological developments with wide promising applications made photonics the field of choice for further advancement of human life.

The comprehensive applicability of photonics technology appeares in the following areas:


The advanced research in photonics is still very extensive and hence lot of research problems related to integrated photonics and photonic material fabrications are still under investigation and may give amazing results in the future. The advanced research in photonics has no limitations, it may be linked to all fields of Science and Engineering. Therefore, every application or technique employing photons in some way can be considered a branch of photonics. Consequentially, photonics is usually defined as the technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon.

This book contains 16 chapters presenting quite diverse research topics in photonics. An attempt has been made to provide researchers in this field with a comprehensive reference point for advanced research in various topics related to photonics, such as

#### XII Preface

integrated photonics, with many remarkable works to pave the way for further innovations in the future.

This book is divided into three general sections: integrated photonics, photonic materials, and photonic applications. The section dealing with integrated photonics presents information on integrated photonics in silicon and germanium, experimental engineering of photonic quantum entanglement, photonic band gap and utilizing photonic quantum angular momentum for information processing. The photonic materials section concentrates on the analysis related to new lead fluoride nanophotonic materials, Fianite in photonics, hybrid polyfluorene for optoelectronic devices materials and plasmonics for green technologies. The last section contains information on lightwave analysis in some applications, high resolution photonic spectroscopy, photonic imaging, time resolved photonic devices, near field optical microscopy and LIDAR atmospheric sensing.

> **Dr. Mohamed Fadhali**  Department of Physics, Faculty of Science Ibb University, Ibb Yemen

**Part 1** 

**Integrated Photonics** 

**0**

**1**

**Germanium-on-Silicon for Integrated**

To meet the unprecedented demands for data transmission speed and bandwidth silicon integrated photonics that can generate, modulate, process and detect light signals is being developed. Integrated silicon photonics that can be built using existing CMOS fabrication facilities offers the tantalizing prospect of a scalable and cost-efficient solution to replace electrical interconnects. Silicon, together with commonly used dielectric materials in CMOS processes such as silicon dioxide, is a great material system for optical confinement and wave transmission in near infrared range. However, silicon is not a good choice for active photonic devices due to its transparency in such wavelength range. Germanium and GeSi alloy, the materials that have long been adopted to improve the performance of silicon transistors in many ways, have been showing their potential as the building blocks of such active integrated optical devices. This chapter discusses the research of using germanium and GeSi for silicon-integrated photodetection and light source in the contexts of material physics and

This introduction section briefly introduces the background of integrated silicon photonics and some germanium properties which are important for photonic applications. Next section focuses on waveguide-integrated germanium photodetectors which can readily be integrated with silicon waveguide on mature silicon or silicon-on-insulator (SOI) platform. The physics and design considerations of these devices are presented with details. The fabrication processes of these devices are also discussed with some extent. Next section includes a newly developed field that using germanium for light sources in silicon photonics applications such as light-emitting-diodes (LEDs) and lasers. There has been a few breakthroughs in this topic including the author's work of epitaxial germanium LEDs and optically pumped lasers operating at room temperature. The physics of this unusual concept of using indirect band gap material for light emission is discussed in details and some important results are presented.

Silicon integrated circuits (ICs) had been developed in an extraordinary pace for almost four decades before 2005. It is known as Moore's law that the number of transistors in an integrated circuit doubles roughly every eighteen months (Moore, 1965). The scalability is the main reason of the tremendous success of many silicon IC based technologies (Haensch et al., 2006), such as silicon complimentary metal oxide semiconductor (Si-CMOS) technology.

**1. Introduction**

growth, device design and fabrication.

**1.1 Integrated silicon photonics**

**Silicon Photonics**

*Massachusetts Institute of Technology*

Xiaochen Sun

*USA*
