The bidirectional eigenmode propagation (BEP) combines the advantages of the transfer-matrix method for propagation and the mode-matching method (satisfying Maxwell's boundary conditions) at longitudinal large discontinuities for forward and backward travelling eigenvalues including discretized radiation modes. The calculated examples include a grating-assisted codirectional coupler for which 20% radiation losses have been found, and a cleaved waveguide facet with 39% reflected intensity and recapture of radiation modes due to a taperlike structure. The BEP is applicable to various types of optical passive (directional coupler, butt-coupling, taper) and active (DBR-, DFB-, and VCSE-laser, detector) devices with large refractive index differences
Some key results of a benchmark test, initiated in 1992 by the Working Group 2 of COST Project 240 at a modelling workshop in Teupitz, Germany, are presented. A great number of BPM algorithms, such as the FTBPM, various types of FDBPMs, wide angle approximations and adaptive FE-BPM are compared. The quasi-analytic character of the benchmark tests gains a deeper insight into the absolute accuracy
In a monolithic heterodyne polarization diversity receiver, mode splitters which effectively separate the TE and TM polarization of the optical wave are required. For this purpose, a directional coupler which utilizes a metal cladding on one of its branches to separate both polarizations was investigated. The polarization splitters can act in two distinct modes of operation, depending on the degree of lateral confinement of the optical rib waveguide before an asymmetric coupler. For weak confinement, the metallized waveguide is guiding for TE- but nonguiding for TM-polarization, and negligible TM-crosstalk results
The copropagation of two waves in an ultralong semiconductor optical amplifier (SOA) is considered in theory and experiment. One wave is a modulated signal, whereas the other one is unmodulated (continuous wave). The theory bases on a comprehensive traveling-wave model and predicts an exponential improvement of the signal extinction ratio (ER) of the modulated signal, caused by the presence of the unmodulated signal. Conditions for achieving this two-wave competition (TWC) effect are as follows. The SOA is operated under saturation, both waves are copolarized, they have comparable gain and their spectral correlation is between certain limits. The TWC effect is due to nondegenerate four-wave mixing (FWM) in the saturated part of a long SOA and is expected to have a high-speed potential. In order to check the theoretical predictions, 4-mm-long SOAs are developed and experimentally investigated under the given conditions. The measured ER improves by 1.3 dB for a 5-GHz sinusoidal signal, which compares well with the 2 dB theoretically predicted for this configuration. FWM is identified also experimentally as the basic mechanism. Variation of wavelength detuning, pump current, modulation frequency and ER of the injected signal are used to determine optimum conditions for the given device
TE to TM converters with constant 45 degrees operation are a key component in OEICs for coherent optical system applications. A passive TE/TM-mode converter with a laterally tilted rib waveguide fabricated on a stepped substrate is proposed and investigated. The conversion effect has been simulated using scalar and vectorial two-dimensional finite difference methods. The device fabricated on (001)-InP/GaInAsP yields 45 degrees conversion with two subsequent elements of half the TE/TM-beatlength at an excess loss of 3 dB
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.