Advances in Optics http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Analyzing Density Operator in Thermal State for Complicated Time-Dependent Optical Systems Thu, 24 Jul 2014 14:05:03 +0000 http://www.hindawi.com/journals/ao/2014/141076/ Density operator of oscillatory optical systems with time-dependent parameters is analyzed. In this case, a system is described by a time-dependent Hamiltonian. Invariant operator theory is introduced in order to describe time-varying behavior of the system. Due to the time dependence of parameters, the frequency of oscillation, so-called a modified frequency of the system, is somewhat different from the natural frequency. In general, density operator of a time-dependent optical system is represented in terms of the modified frequency. We showed how to determine density operator of complicated time-dependent optical systems in thermal state. Usually, density operator description of quantum states is more general than the one described in terms of the state vector. Jeong Ryeol Choi, Ji Nny Song, and Yeontaek Choi Copyright © 2014 Jeong Ryeol Choi et al. All rights reserved. Submicron Surface Vibration Profiling Using Doppler Self-Mixing Techniques Wed, 23 Jul 2014 00:00:00 +0000 http://www.hindawi.com/journals/ao/2014/576380/ Doppler self-mixing laser probing techniques are often used for vibration measurement with very high accuracy. A novel optoelectronic probe solution is proposed, based on off-the-shelf components, with a direct reflection optical scheme for contactless characterization of the target’s movement. This probe was tested with two test bench apparatus that enhance its precision performance, with a linear actuator at low frequency (35 µm, 5–60 Hz), and its dynamics, with disc shaped transducers for small amplitude and high frequency (0.6 µm, 100–2500 Hz). The results, obtained from well-established signal processing methods for self-mixing Doppler signals, allowed the evaluation of vibration velocity and amplitudes with an average error of less than 10%. The impedance spectrum of piezoelectric (PZ) disc target revealed a maximum of impedance (around 1 kHz) for minimal Doppler shift. A bidimensional scan over the PZ disc surface allowed the categorization of the vibration mode (0, 1) and explained its deflection directions. The feasibility of a laser vibrometer based on self-mixing principles and supported by tailored electronics able to accurately measure submicron displacements was, thus, successfully demonstrated. Tânia Pereira, Mariana Sequeira, Pedro Vaz, Ana Tomé, Helena C. Pereira, Carlos Correia, and João Cardoso Copyright © 2014 Tânia Pereira et al. All rights reserved. Field Squeezing in a Quantum-Dot Molecule Jaynes-Cummings Model Thu, 03 Jul 2014 07:54:24 +0000 http://www.hindawi.com/journals/ao/2014/395836/ We investigate the field squeezing in a system composed of an initial coherent field interacting with two quantum dots coupled by electron tunneling. An approximate quantum-dot molecule Jaynes-Cummings model describing the system is given, and the effects of physical quantities, such as the temperature, phonon-electron interaction, mean photon number, field detuning, and tunneling-level detuning, are discussed in detail. Xu Chu, Xiaodong Ma, Ying Wang, Qingchun Zhou, and Yu Zhou Copyright © 2014 Xu Chu et al. All rights reserved. Hybrid Materials for Integrated Photonics Thu, 26 Jun 2014 10:53:35 +0000 http://www.hindawi.com/journals/ao/2014/891395/ In this review materials and technologies of the hybrid approach to integrated photonics (IP) are addressed. IP is nowadays a mature technology and is the most promising candidate to overcome the main limitations that electronics is facing due to the extreme level of integration it has achieved. IP will be based on silicon photonics in order to exploit the CMOS compatibility and the large infrastructures already available for the fabrication of devices. But silicon has severe limits especially concerning the development of active photonics: its low efficiency in photons emission and the limited capability to be used as modulator require finding suitable materials able to fulfill these fundamental tasks. Furthermore there is the need to define standardized processes to render these materials compatible with the CMOS process and to fully exploit their capabilities. This review describes the most promising materials and technological approaches that are either currently implemented or may be used in the coming future to develop next generations of hybrid IP devices. Paolo Bettotti Copyright © 2014 Paolo Bettotti. All rights reserved. Fiber-Wireless (FiWi) Broadband Access Networks in an Age of Convergence: Past, Present, and Future Sun, 22 Jun 2014 10:41:18 +0000 http://www.hindawi.com/journals/ao/2014/945364/ After describing the beginnings and state of the art of integrated fiber-wireless (FiWi) broadband access networks in great detail, we briefly review recent progress and point to various ongoing research activities, including the design of energy-efficient “green” FiWi access networks, advanced survivability techniques, and integration of wireless and fiber optic sensors, towards realizing adaptable, dependable, and ecoconscious future-proof broadband access networks based on both wireless and shared passive fiber media. Furthermore, we discuss service, application, business, and operation related aspects, which motivate access technology to move into a substantially different direction in the long run than continued capacity provisioning. Given that most 4G cellular mobile network researches so far have been focusing on the achievable performance gains in the wireless front-end only without looking into the details of backhaul implementations and possible backhaul bottlenecks, we identify open key research challenges for FiWi broadband access networks. We explore ways of how they can be deployed across relevant economic sectors other than telecommunications per se, taking major paradigm shifts such as the Third Industrial Revolution, Energy Internet, smart grid, and explosion of mobile data traffic in today’s cellular networks into account. Martin Maier Copyright © 2014 Martin Maier. All rights reserved.