Abstract
In this article, a method for indium phosphide (InP) electro-optic modulator (EOM) optimization is introduced. The method can be used for the design and analysis of an EOM based on the Mach-Zehnder interferometer (MZI) design. This design is based on the division of the input optical signal into two optical paths and then, after processing, it combines the light into a single waveguide. The symmetry of the structure can provide state-of-the-art EOM characteristics with a push-pull control signal. Using a traveling wave electrode (TWE) design as a starting point, the authors varied the heterostructure design and optical waveguide parameters to obtain the optimal values of initial optical loss, evenness of the initial optical loss in the operating wavelength range, and the extinction ratio and length of the modulator arm. The key features of the proposed optimization method include the following: all independent input parameters are linked into a single system, where the relationship between the electrical and optical parameters of the modulator is realized; all physically realizable combinations of the input parameters are available for analysis; and EOM optimization is possible for one target parameter or for a group of target parameters. The results of the EOM optimization using the described method are presented.
Highlights
Electro-optic modulators (EOMs) are widely used for the phase or intensity modulation of light waves in digital and analog fiber-optic systems
We considered the optimization of an EOM by exploiting the traveling wave electrode electrode (TWE) design and the push–pull principle
The EOM can be characterized by more than ten parameters, we only considered the following four parameters, which are of primary importance for the performance and cost of the device: Active length of the EOM arm, defined as the total length of all internal sections larm ; Minimal optical loss Lmin, defined as the ratio of optical power in the output to the optical power in the input in the open EOM state; Maximal difference in the values of Lmin in the optical operating wavelength range ∆Lmin ; Extinction ratio re, defined as the ratio of the optical power in the output in the open EOM state to the optical power in the output in the closed EOM state
Summary
Electro-optic modulators (EOMs) are widely used for the phase or intensity modulation of light waves in digital and analog fiber-optic systems. For the purpose of high-speed modulation, lithium niobate [4], organic materials [5], and compound semiconductor systems [6] are used. Modulators based on compound semiconductor systems can control light wave propagation using two physical effects: change in permittivity (EOM) [8] or change in the light absorption coefficient (electro-absorption modulators (EAMs) [9] in optical waveguide media under the conditions of an applied alternating electric field. EOMs may be preferable due to their all-purpose nature: both the phase and the intensity can be controlled effectively. EOMs exhibit a high extinction ratio and a Symmetry 2020, 12, 1920; doi:10.3390/sym12111920 www.mdpi.com/journal/symmetry
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