Furukawa Electric Institute of Technology Ltd.

Budapest, Hungary

Furukawa Electric Institute of Technology Ltd.

Budapest, Hungary

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Szabo A.,H+ Technology | Varallyay Z.,Furukawa Electric Institute of Technology Ltd. | Rosales-Garcia A.,OFS Laboratories | Headley C.,OFS Laboratories
Optics InfoBase Conference Papers | Year: 2014

A fast method is introduced to model high power, continuous wave Yb-doped fiber lasers. Excellent agreement with measurements is obtained for up to 708W output power within 5 minutes of computation on a desktop computer. © 2014 OSA.


Sinko J.,University of Szeged | Dudas L.,University of Szeged | Gajdatsy G.,Furukawa Electric Institute of Technology Ltd. | Erdelyi M.,University of Szeged | And 3 more authors.
Optics Letters | Year: 2011

Line-scanning tomographic optical microscopy (LSTOM) requires precise rotation of the scanning line. We demonstrate a method that applies translation-invariant optical elements (polarizer and birefringent plate) to minimize the rotation error. An astigmatic line produced by means of a focused beam through a birefringent plate is used as line illumination. A comparative theoretical and experimental study is presented using an LSTOM system. © 2011 Optical Society of America.


Szabo A.,Budapest University of Technology and Economics | Varallyay Z.,Furukawa Electric Institute of Technology Ltd.
IEEE Photonics Technology Letters | Year: 2012

Based on a non-distributed numerical model including fiber birefringence and orthogonal mode coupling, we investigate the effects of saturable absorber (SA) parameters on the mode-locking of a realistic Erbium fiber ring laser. We compute the pulse evolution in the oscillator where the pulse properties are also affected by the intracavity polarization controller (PC). Simultaneous effect of the SA and PC parameters on the properties of the generated vector solitons are studied, and their stability against intracavity polarization perturbation at different SA parameter ranges is discussed. © 2006 IEEE.


Dems M.,Technical University of Lodz | Chung I.-S.,Technical University of Denmark | Nyakas P.,Furukawa Electric Institute of Technology Ltd. | Bischoff S.,Alight Technologies | And 2 more authors.
Optics Express | Year: 2010

We show comparison of four different numerical methods for simulating Photonic-Crystal (PC) VCSELs. We present the theoretical basis behind each method and analyze the differences by studying a benchmark VCSEL structure, where the PC structure penetrates all VCSEL layers, the entire top-mirror DBR, a fraction of the top-mirror DBR or just the VCSEL cavity. The different models are evaluated by comparing the predicted resonance wavelengths and threshold gains for different hole diameters and pitches of the PC. The agreement between the models is relatively good, except for one model, which corresponds to the effective index method. The simulation results elucidate the strength and weaknesses of the analyzed methods; and outline the limits of applicability of the different models. © 2010 Optical Society of America.


Varallyay Z.,Furukawa Electric Institute of Technology Ltd. | Arashitani Y.,Furukawa Electric Group | Varga G.,Budapest University of Technology and Economics
Optical Fiber Technology | Year: 2011

Coated and ribboned optical fibers are liable to external stress of the coating materials which may induce additional birefringence in the fiber glass. This residual stress in the coating may increase the polarization mode dispersion (PMD) of the fibers with a value well above allowed in modern, optical telecommunication systems. We report our numerical efforts on reducing the stress caused birefringence in fiber ribbons optimizing the geometry as well as the material parameters of the coating materials. We found that changing the cross-sectional geometry of the fiber ribbon such as edge shape or the ratio of primary and secondary coatings may lead to significant stress and constitutively PMD reduction in optical fibers. Changing the stiffness or the glass transition temperature (GTT) of the different components may also yield optimal conditions for stress reduction according to our finite element analyzes. © 2010 Elsevier B.V. All rights reserved.


Nyakas P.,Furukawa Electric Institute of Technology Ltd.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

We simulated the cold-cavity optical modes of coupled defect cavities in photonic crystal (PhC) vertical-cavity surface-emitting lasers (VCSELs). Holes were etched into the top distributed Bragg reflector of the COST benchmark structure in hexagonal pattern, leaving 2×1 or 2×2 positions intact. A lattice constant of 4 μm was selected, the hole diameter-to-lattice- constant ratio was varied from 0.5 to 0.7 outside the defect region and from 0.15 to 0.7 between the cavities. We used finite volume method to discretize the scalar Helmholtz equation, and finite element method to solve the vectorial Helmholtz equation, both in three dimensions. Prism elements were selected that fit the complicated contours of the PhC-VCSEL. In-phase and out-of-phase couplings were specified with different symmetry boundary conditions. The complex eigenvalues and optical field distributions were obtained with an in-house developed iterative algorithm. The real part of the eigenvalue determined the wavelength, its imaginary part was proportional to the cold-cavity modal loss. In-phase and out-of-phase coupled modes possessed almost equal properties when all holes had relatively large diameters, indicating uncoupled behavior. For a narrower hole between the defect cavities, the in-phase coupled mode exhibited slightly larger mode area than its out-of-phase counterpart due to its extending tails, but also showed considerably larger optical loss. This predicted out-of-phase operation. If one etched very small holes into the coupling region of the 2×2 PhC-VCSEL array, an additional lobe appeared between the holes, which resulted in enhanced overlap with the gain region. This confirmed in-phase operation. © 2010 SPIE.


Nyakas P.,Furukawa Electric Institute of Technology Ltd.
IEEE Photonics Technology Letters | Year: 2011

In this letter, the optical modes of a ring-defect photonic crystal vertical-cavity surface-emitting laser are calculated by the fully numerical solution of the scalar Helmholtz equation. We explain the experimentally observed higher order mode emission on the basis of optical loss discrimination. Special photonic crystal patterns that favor even higher order optical modes are designed and simulated. These modes are beyond the scope of previous simplified analysis. © 2011 IEEE.


Nyakas P.,Furukawa Electric Institute of Technology Ltd.
Journal of the Optical Society of America B: Optical Physics | Year: 2013

A new design is proposed to increase the single-mode current range of low threshold current, photonic crystal vertical-cavity surface-emitting lasers. Our method is based on the optical coupling between the usual central defect and six others of nearly identical sizes. The resulting honeycomb configuration aims to spread higher supermodes in transverse directions, and to reduce their overlap with a central current-injected region. Simultaneous confinement of the fundamental mode within the central cavity and the shift of higher modes toward outer trapping defects can lead to stable single-mode operation. Simulations confirm that either in-phase or out-of-phase coupled supermodes could be promoted by slightly modifying the areas of outer cavities, while thermal lensing always stabilizes the in-phase coupled supermodes. The single-mode current regime should be extended noticeably compared to the conventional single-defect lasers. © 2013 Optical Society of America.


Szilvasi T.,Budapest University of Technology and Economics | Veszpremi T.,Budapest University of Technology and Economics | Veszpremi T.,Furukawa Electric Institute of Technology Ltd.
Structural Chemistry | Year: 2015

We explored the possible reaction of three model carbenes and two model silylenes with white phosphorus leading to insertion, bis-adduct, and tris-adduct products. The energetics of the calculated mechanisms are in accordance with the experimental observations explaining key features like carbene–P4 ratio-dependent reactivity of carbonyl decorated bisamidocarbene and cyclic alkyl-amino carbene. The analysis of the bonding motif of C–P and Si–P bonds in the key intermediate revealed the importance of double-bond and donor–acceptor resonance structures. We found correlation between the σ-donor and π-acceptor strength of investigated carbenes and silylenes and their reactivity with white phosphorus. The combination of low σ-donor and high π-acceptor strength in N-heterocyclic silylene (NHSi) indicated the instability of the key intermediate, bis-adduct, and tris-adduct products and the stability of the insertion product, while high σ-donor and low π-acceptor strength of N-heterocyclic carbene (NHC) resulted in reversed stability order of the previous compounds explaining the different reaction of NHC and NHSi with white phosphorus. Donor-stabilized silylene (DSSi) has high σ-donor and low π-acceptor strength similar to NHC supporting their similar reactivity and the difference between NHSi and DSSi. © 2015 Springer Science+Business Media New York


Nyakas P.,Furukawa Electric Institute of Technology Ltd.
Proceedings of the International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD | Year: 2011

A fully numerical solution of the scalar Helmholtz equation is applied for the optical mode calculation of a ring-defect photonic crystal vertical-cavity surface-emitting laser. It is shown that the diameter of the central hole determines which mode starts lasing at the threshold current. This confirms the result of a previous experimental work. © 2011 IEEE.

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