Entity

Time filter

Source Type


Swiderski J.,Military University of Technology
Progress in Quantum Electronics | Year: 2014

Mid-infrared (mid-IR) supercontinuum (SC) sources have recently gained much interest, as a key technology for such applications as spectral molecular fingerprinting, laser surgery, and infrared counter measures. However, one of the challenges facing this technology is how to obtain high power and broadband light covering a spectral band of at least 2-5 μm, especially with a very efficient output power distribution towards the mid-IR region. This directly affects their usage in the practical applications mentioned above. Typically, an SC is generated by pumping a piece of nonlinear fibre with high-intensity femtosecond pulses provided by mode-locked lasers. Although this approach can lead to wide continuum generation, the output power is limited only to the milliWatt level. Therefore, to achieve high-power SC light, other laser systems need to be employed as pump sources. This paper briefly reviews SC sources, restricted to those with an average output power of over 0.4 W and simultaneously with a long-wavelength edge of the continuum spectrum of over 2.4 μm. Firstly, the concepts of SC generation, including the nonlinear phenomena governing this process and the most relevant mid-IR fibre materials, are presented. Following this study, a review of the main results on SC generation in silica and soft-glass fibres, also including my experimental results, is presented. Emphasis is given to high-power SC generation with the use of different pump schemes, providing an efficient power distribution towards longer wavelengths. Some discussion and prospective predictions are proposed at the end of the paper. © 2014 Elsevier Ltd. All rights reserved.


Rogalski A.,Military University of Technology
Progress in Quantum Electronics | Year: 2012

Development of focal plane arrays started in seventies last century and has revolutionized imaging systems in the next decades. This paper presents progress in optical detector technology of focal plane arrays during the past twenty years. At the beginning of paper, emphasises are given on integrated detector assembly and cooling requirements of different types of detectors. Next, the classification of two types of detectors (photon detectors and thermal detectors) is done on the basis of their principle of operation. This topic is followed by general overview of focal plane array architectures. The main subject of paper is concentrated on describing of material systems and detectors operated in different spectral ranges. Special attention is given on recent progress in their detector technologies. Discussion is focused mainly on current and the most rapidly developing focal plane arrays including: CdZnTe detectors, AlGaN photodiodes, visible CCD and CMOS imaging systems, HgCdTe heterostructure photodiodes, quantum well AlGaAs/GaAs photoresistors, and thermal detectors. Emphasis is also given on far-infrared and sub-millimetre wave detector arrays. Finally, the outlook for near-future trends in optical detector technologies is presented. © 2012 Elsevier Ltd.


Rogalski A.,Military University of Technology
Infrared Physics and Technology | Year: 2011

In the paper, fundamental and technological issues associated with the development and exploitation of the most advanced infrared detector technologies are discussed. In this class of detectors both photon and thermal detectors are considered. Special attention is directed to HgCdTe ternary alloys on silicon, type-II superlattices, uncooled thermal bolometers, and novel uncooled micromechanical cantilever detectors. Despite serious competition from alternative technologies and slower progress than expected, HgCdTe is unlikely to be seriously challenged for high-performance applications, applications requiring multispectral capability and fast response. However, the nonuniformity is a serious problem in the case of LWIR and VLWIR HgCdTe detectors. In this context, it is predicted that type-II superlattice system seems to be an alternative to HgCdTe in long wavelength spectral region. In well established uncooled imaging, microbolometer arrays are clearly the most used technology. Present state-of-the-art microbolometers are based on polycrystalline or amorphous materials, typically vanadium oxide (VOx) or amorphous silicon (α-Si), with only modest temperature sensitivity and noise properties. Basic efforts today are mainly focused on pixel reduction and performance enhancement. Attractive alternatives consist of low-resistance α-SiGe monocrystalline SiGe quantum wells or quantum dots. In spite of successful commercialization of uncooled microbolometers, the infrared community is still searching for a platform for thermal imagers that combine affordability, convenience of operation, and excellent performance. Recent advances in MEMS systems have lead to the development of uncooled IR detectors operating as micromechanical thermal detectors. Between them the most important are biomaterial microcantilevers. © 2010 Elsevier Ltd. All rights reserved.


Sizov F.,Ukrainian Academy of Sciences | Rogalski A.,Military University of Technology
Progress in Quantum Electronics | Year: 2010

Terahertz (THz) detectors play an increasing role in different areas of human activities (e.g., security, biological, drugs and explosions detection, imaging, astronomy applications, etc.). In the paper, issues associated with the development and exploitation of THz radiation detectors are discussed. The basic physical phenomena and the recent progress in both direct and heterodyne detectors are described. More details concern Schottky barrier diodes, pair braking detectors, hot electron mixers and field-effect transistor detectors, where links between THz devices and modern technologies such as micromachining are underlined. Also the operational conditions of THz detectors and their upper performance limits are reviewed. © 2010 Published by Elsevier Ltd.


Janiszewski J.,Military University of Technology
International Journal of Solids and Structures | Year: 2012

Experimental studies on ductility of selected metals differing mechanical properties under strain rates between 4 × 10 3 and 2 × 10 4 s -1 are presented in this work. The electromagnetic expanding ring experiment was used as the primary tool for examining the ductility behaviour of metals. Through a use of the Phantom v12 digital high-speed camera and specialised TEMA Automotive software, rings expansion velocities were determined with satisfactory accuracy for all ring tests. In this paper, the experimental observations on cold-rolled copper Cu-ETP, aluminium alloy Al 7075, barrel steel and tungsten heavy alloy are reported. Ductility of studied materials was estimated by measuring changes in cross-sectional areas in the uniform strain portions of the recovered ring fragments. In a similar way the metals ductility was defined at the conventional tensile test condition. Moreover, results of analogue investigation for static and dynamic loading at the temperature of about -40 °C were described. The experimental observations mainly revealed the different ductility behaviour of metals tested at applied dynamic loadings; Cu-ETP and barrel steel demonstrated an increase in ductility, whereas aluminium alloy Al 7075 and tungsten heavy alloy were characterised by lower ductility in comparison to static loading. These results appear to be partially in contrast with the observations reported recently by some other investigators. © 2012 Elsevier Ltd. All rights reserved.

Discover hidden collaborations