Abstracts of Vol. 12, No 2
and 12(2)first_page.pdf
files, full text
169
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Rare-earth-doped high-power fiber lasers generating in
near infrared range
J. Swiderski, A. Zajac, M. Skorczakowski, Z. Jankiewicz, and P.
Konieczny
In this paper, high power double-clad fibre lasers are presented. We have built two experimental laser set-ups based on neodymium- and ytterbium-doped active media. A Yb3+-silica fiber laser has been cladding pumped at 937 nm by a InGaAs semiconductor laser diode and generated 4 W cw output power with slope efficiency of 73 ±3%. However, Nd3+-doped fiber laser generated over 10 W cw output power with a slope efficiency of 63%. As a result of the experiment, we have elaborated very efficient coherent sources of laser radiation that can be used in many industrial applications.
Keywords: fiber laser, double clad fiber, diode pumping laser.
175
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New electrolyte for electrochromic devices
M. Kucharski, T. Lukaszewicz, and P. Mrozek
The paper presents the results of the research on a new
polymer-gel electrolyte for electrochromic devices. In the
performed studies, various electrolytes were used. They all
contained an ionic conductor, a matrix of polymer gel and organic
solvent or mixture of polar organic solvents. The electrolyte
which had the best properties contained 8% LiCF3SO3
as an ionic conductor, a matrix consisting of two polymers: 10%
PMMA, 6% PEO, and a mixture of the following two polar organic
solvents: 38% propylene carbonate and 38% ethylene carbonate. The
high conductivity (s = 4.8 mS/cm),
which provides easy deposition in layers, gives stability
(resistance) in time and high transmittance value of radiation in
the visible region makes the electrolyte very useful for
electrochromic devices. A seven-layer electrochromic device with
this new gel electrolyte was assembled according to the following
formula: glass1/ITO/WO3/electrolyte/BP/ITO/glass2,
where ITO was an indium-tin film oxide, WO3 was an
electrochemically deposited tungsten oxide film and BP an
electrochemically deposited film of prussian blue. The density of
the current flowing through the unit and the transmittance at the
wavelength l = 550 nm are given in the
paper as a function of sinusoidal voltage. The transmittance
varies from 70–50% (coloured) to 25–10% (for fully
bleached) in the range of visible radiation and the colouration
efficiency is high (above 100 cm2/C). These results
are considerably better than those reported in the other similar
studies.
Keywords: gel-electrolyte, conductivity, lithium salt, based polymer, polar organic solvent, electrochromic devices, colouration efficiency.
181
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Electric properties of ionic metal alkanoate smectics with
different dyes
G. Klimusheva, A. Koval'chuk, A. Sadovenko, S. Bugaychuk, T.
Mirnaya, and A. Ishchenko
The comparison analysis of electric properties of dye-doped ionic lyotropic liquid crystals before and after applying dc voltage was studied experimentally. The contributions both of the electrode – liquid crystal boundary layers and of electrochemical processes to electric effects are estimated.
Keywords: low frequency dielectric spectroscopy, ionic lyotropic liquid crystals, electric properties, electrochemical processes.
187
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Modelling of dynamic performance of semiconductor lasers
under subthreshold biasing
P. Krehlik and L. Sliwczynski
The problem of turn-on delay induced by the subthreshold bias of the semiconductor laser in the burst-mode fiber optic transmitters is discussed. An easy to use method of estimation of the turn-on delay is proposed and experimentally verified. The Simulink model of the laser is proposed, allowing to simulate the data pattern distortions in fiber optic communication systems. Presented considerations may be useful for high-speed burst-mode system designers.
Keywords: semiconductor laser, subthreshold biasing, burst-mode transmitters.
193
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Three methods for photon migration measurements in pulp
J. Saarela, M. Tormanen and R. Myllyla
This paper gives an overview of three promising optical techniques for conducting laser pulses time-of-flight measurements in pulp. The oscilloscope method and time-of-flight lidar method are especially good for fast in-line measurements while a streak camera is superior in the laboratory.
Keywords: time of flight, lidar, streak camera, oscilloscope, pulp measurements.
199
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Crystal growth of the oxide fiber single crystal for
optical applications
D.H. Yoon
Recently, certain materials have attracted attention for a new generation of high speed, efficient, multi-functional optical devices. Among these materials, small-diameter and long-length bulk crystals are of considerable interest for miniaturization and high efficiency. In particular, rod or fiber-like micro-single crystals have already received attention as attractive materials for a variety of electro-optical application, such as second harmonic generation (SHG), micro-laser sources or optical memory arrangements because of their extended interaction length and high optical intensity.
Keywords: optical application, micro-pulling down method, oxide crystals, crystal growth.
213-
12(2)213.PDF file
Two-layer responsivity modelling of HgCdTe photoconductive
detectors
R.K. Bhan and V. Dhar
This paper presents a simple two-layer responsivity model of n-HgCdTe photoconductive detectors by including the contribution of shunt resistance arising due to the accumulation layer at the surface. It is shown that in general responsivity of a proper two-layer model is higher than quasi two-layer model that is reported in literature and used by many workers.
Keywords: Hg CdTe photoconductive detectors, two-layer responsity model, shunt resistance.
221-
12(2)221.PDF file
Optical detectors for focal plane arrays
A. Rogalski
The paper presents progress in optical detector technologies during the past 25 years. Classification of two types of detectors (photon detectors and thermal detectors) is done on the basis of their principle of operation. The overview of optical material systems and detectors is presented. Also recent progress in different technologies is described. Discussion is focused mainly on current and the most rapidly developing focal plane arrays using: CdZnTe detectors, AlGaN photodiodes, visible CCD and CMOS imaging systems, HgCdTe heterostructure photodiodes, quantum well AlGaAs/GaAs photoresistors, and thermal detectors. The outlook for near-future trends in IR technologies is also presented.
Keywords: photon detectors, thermal detectors, optical detectors, focal plane arrays, milti-colour detectors.
247-
12(2)247.PDF file
Infrared-to-visible upconversion in erbium fluoride
(ZBLAN:Er3+) optical fiber: competition between the parasitic 850
nm fluorescence and the green laser emission at 544 nm
F. Kaczmarek and J. Karolczak
The role of 850-nm fluorescence, amplification, and laser emission in ZBLAN:Er3+ optical fiber was first investigated by Whitley et al. [1,2] and Allain et al. [3]. In the case of a green upconversion fiber laser at 544 nm, the 850-nm fluorescence is a parasitic component, so it should be minimized or eliminated. Two pumping wavelengths are usually applied to excite the green upconversion laser: 970 nm or 800 nm. It has been already observed that 800-nm pumping favours, to some extend, the 850-parasitic emission, and the 970-nm one makes this emission negligible [1–3]. We have studied the role of 800-nm pumping in more detail and observed a dependence of the pumping wavelength ~800 nm on the intensity of the 850-nm parasitic fluorescence.
Keywords: infrared-to-visible upconversion and lasers.
249-
12(2)249.PDF file
Time-resolved optical spectroscopy and imaging of breast
P. Taroni, A. Pifferi, A. Torricelli, and R. Cubeddu
A fully automated system for time-resolved reflectance and transmittance spectroscopy from 610 to 1010 nm was developed and applied to the optical (absorption and scattering) characterization of breast tissue in vivo. From absorption spectra, information is derived on tissue content of oxy-, deoxyhemoglobin, water and lipids, while scattering spectra provide knowledge on tissue structure. A portable system for breast imaging at four wavelengths (683, 785, 912, and 975 nm) was also developed and is being tested in clinics for the detection and characterization of breast lesions (optical mammography).
Keywords: absorption, optical mammography photon migration, reflectance, scattering, time-resolved imaging, time-resolved spectroscopy, tissue, transmittance.