| 1. |
- Aghamiri, Seyed Mohammadreza, et al.
(author)
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Effect of gamma irradiation on the light polarization variation of PMMA polymer
- 2008
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In: Optics Communications. - : Elseevier. - 0030-4018 .- 1873-0310. ; 281:3, s. 356-359
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Journal article (peer-reviewed)abstract
- Analyzing the effect of ionized gamma irradiation on the optical parameters of materials is a solution for finding newer techniques in the field of detector and dosimeter systems. A PMMA (polymethylmethacrylate) polymer was radiated from a 60Co source with a power of 1800 C and a constant dose rate of 1.44 kGy/h in three steps of 5, 25 and 61.2 kGy. The ionized gamma irradiation affected the refractive index of polymer and therefore it changes the polarization of the incident light. The difference in the polarization phase shift of the polymer depended on the dose it had been irradiated with.
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| 2. |
- Anderson, Dan, 1943, et al.
(author)
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Interaction between two partially incoherent soliton stripes
- 2008
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In: Optics Communications. - : Elsevier BV. - 0030-4018. ; 281:14, s. 3919-3923
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Journal article (peer-reviewed)abstract
- A detailed analysis is made of the mutual interaction of two, initially well separated, partially incoherent solitons in a nonlinear Kerr medium. Explicit expressions are obtained describing the influence of partial incoherence on the subsequent dynamics of the solitons. In particular it is shown that as the degree of incoherence increases, the character of the interaction may change between attractive and repulsive behavior (or vice versa). Furthermore, it is found that this dependence is not always monotonous. © 2008 Elsevier B.V. All rights reserved.
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| 3. |
- Bjurshagen, Stefan, et al.
(author)
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Quasi-three-level Nd:YAG laser under diode pumping directly into the emitting level
- 2006
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In: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 261:1, s. 109-113
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Journal article (peer-reviewed)abstract
- We present theoretical and experimental investigations on ground-state direct pumping at 869 nm into the emitting level F-4(3/2) of end-pumped quasi-three-level Nd:YAG lasers operating at 946 nm. We have demonstrated, what we believe is for the first time, a Nd:YAG laser at 946 nm directly pumped by diodes and obtained 1.6 W of output power.
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| 4. |
- Bogdanski, Jan, et al.
(author)
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Multiuser quantum key distribution over telecom fiber networks
- 2009
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In: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 282:2, s. 258-262
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Journal article (peer-reviewed)abstract
- We report five-user quantum key distribution (QKD) over switched fiber networks in both star and tree configurations, using the BB84-protocol [1] with phase encoding. Both setups implement polarization insensitive phase modulators, necessary for birefringent single mode fiber (SMF) networks. In both configurations we have achieved transmission distances between 25 km and 50 km with quantum bit error rates between 1.24% and 5.56% for the mean photon number l ¼ 0:1. The measurements have showed feasibility of multiuser QKD over switched fiber networks, using standard fiber telecom components.
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| 5. |
- Bogdanski, Jan, et al.
(author)
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Sagnac quantum key distribution over telecom fiber networks
- 2009
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In: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 282:6, s. 1231-1236
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Journal article (peer-reviewed)abstract
- We present a new concept for compensation of single mode fiber (SMF) birefringence effects in a Sagnac quantum key distribution (QKD) setup, based on a polarization control system and a polarization insensitive phase modulator. Our experimental data show stable (in regards to birefringence drift) QKD over 1550 nm SMF telecom networks in Sagnac configuration, using the BB84-protocol [C.H. Bennett, G. Brassard, in: Proceedings of the IEEE International Conference on Computers, Systems, and Signal Processing, Institute of Electrical and Electronic Engineers, New York, 1984, p. 175] with phase encoding. The achieved total Sagnac transmission loop distances were between 100 km and 150 km with quantum bit error rates (QBER) between 5.84% and 9.79% for the mean-photon-number l = 0.1. The distances were much longer and rates much higher than in any other published Sagnac QKD experiments. We also show an example of our one-decoy state protocol implementations (for the 45 km distance between Alice and Bob, corresponding to the 130 km total Sagnac loop length), providing an unconditional QKD security. The measurement results have showed feasibility of QKD over telecom fiber networks in Sagnac configuration, using standard fiber telecom components.
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| 6. |
- Cai, Yangjian, et al.
(author)
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Analytical formula for a decentered elliptical Gaussian beam propagating in a turbulent atmosphere
- 2007
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In: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 271:2, s. 509-516
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Journal article (peer-reviewed)abstract
- Analytical formulas for the average intensity and decentered parameter of a decentered elliptical Gaussian beam (DEGB) propagating in a turbulent atmosphere are derived in a tensor form. The propagation properties of a DEGB in a turbulent atmosphere are investigated in detail, and found to be different from that in free space. Furthermore, as an application example, we investigate the propagation of a decentered elliptical flat-topped beam (DEFB) by expressing its electric field as a finite sum of DEGBs in a turbulent atmosphere. The properties of a DEGB or a DEFB in a turbulent atmosphere are closely related with the beam's parameters and the structure constant of the turbulent atmosphere.
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| 7. |
- Cai, Yangjian, et al.
(author)
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Propagation of a hollow Gaussian beam through a paraxial misaligned optical system
- 2006
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In: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 265:2, s. 607-615
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Journal article (peer-reviewed)abstract
- Based on the generalized diffraction integral formula for treating the propagation of a laser beam through a paraxial misaligned optical system in the cylindrical coordinate system, we obtain an analytical formula for a hollow Gaussian beam passing through a paraxial misaligned optical system. Furthermore, we also obtain the approximate analytical formula for a hollow Gaussian beam passing through a paraxial circularly apertured misaligned optical system by expanding the hard aperture function into a finite sum of complex Gaussian functions. As a numerical example, the propagation properties a hollow Gaussian beam through a misaligned thin lens are studied numerically.
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| 8. |
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| 9. |
- Dai, Daoxin, et al.
(author)
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Reduction of multimode effects in an SOI-based etched diffraction grating demultiplexer
- 2005
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In: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 247:4-6, s. 281-290
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Journal article (peer-reviewed)abstract
- Multimode effects in the free propagation region (FPR) of a silicon-on-insulator (SOI)-based etched diffraction grating (EDG) demultiplexer are analyzed. In a conventional design, the power coupled to the higher order modes is considerable, which introduces a significant excess loss and crosstalk. It is shown that the multimode effects in an SOI EDG demultiplexer are much more detrimental than in an arrayed waveguide grating demultiplexer. Several methods for reducing the multimode effects are discussed. In particular, a laterally tapered structure between the FPR and the input/output waveguides is proposed as a simple and effective method for reducing the power coupled to the higher order modes and consequently reducing the multimode effects. The taper width is optimized to minimize the crosstalk.
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| 10. |
- Dai, Daoxin, et al.
(author)
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Three-dimensional hybrid modeling based on a beam propagation method and a diffraction formula for an AWG demultiplexer
- 2007
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In: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 270:2, s. 195-202
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Journal article (peer-reviewed)abstract
- An efficient and accurate three-dimensional (3D) hybrid modeling, which combines a 3D beam propagation method (BPM) and the two-dimensional (2D) Kirchhoff-Huygens diffraction formula, is developed to simulate the field propagation in an arrayed waveguide grating (AWG) dernultiplexer. The 2D Kirchhoff-Huygens diffraction formula is used for the simulation of the light propagation in the free propagation regions (FPRs). A 3D BPM in a polar coordinate system is used to simulate the light propagation in the transition region between the input FPR and the arrayed waveguides so that the coupling coefficients for the arrayed waveguides are calculated conveniently and accurately. For the simulation in the transition region between the arrayed waveguides and the output FPR, only the central arrayed waveguide and several adjacent ones are needed in the computational window of a standard BPM and thus the computation efficiency is improved. Finally, a flat-top AWG is designed and fabricated to verify the reliability of the present simulation method. The calculated and measured spectral responses are in a good agreement.
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