Reduction of Wavelength Dependence of Coupling Characteristics Using Si Optical Waveguide Curved Directional Coupler

Abstract

Directional couplers are widely used as one of the key components of optical integrated circuits. However, the coupling efficiency of the conventional directional coupler is highly sensitive to wavelength. This sensitivity degrades the characteristics of devices that contain directional couplers for wavelength division multiplexing transmission. A curved directional coupler has been proposed using silica optical waveguide as one of the coupler which realize wavelength insensitive, small footprint and tolerant to fabrication. In this paper, we theoretically investigated this curved coupler using Si wire waveguide and got results that the curved coupler whose bending radius of 21 μm and coupling length of 7.40 μm can reduce the wavelength dependence and achieve about a sevenfold enhancement of operational bandwidth in the transmittance variation range of −3 ± 0.1 dB compared with conventional directional coupler.

Surrogate‐assisted design optimization of photonic directional couplers

“…The initial vector of parameters is based on Morino et al . . The lower/upper bounds of the design space are defined based on engineering experience and to ensure sufficient flexibility of the structure geometry.…”

Fast Optimization of Integrated Photonic Components Using Response Correction and Local Approximation Surrogates

“…Consider an integrated photonic 2 × 2 directional coupler based on a design of Morino et al (2014). The structure is a four-port device with two waveguide cores arranged parallel in proximity with each other.…”

“…It should be noted that high difference in refractive indexes of the coupler allows for strong confinement of the light beam within the core waveguides. Therefore, the former may be constructed using low radius bends without considerable losses, and, thus, allowing for the utilization of the structure with highly integrated devices (Morino et al 2014;Tsuchizawa et al 2005;Yamada et al 2005). Geometry of the discussed integrated coupler including its visualization, top-and cross-view, as well as detailed dimensions, are shown in Fig.…”

“…It should be noted that β is set as a variable to minimize the influence of the feed lines bending losses on a circuit operation (Hill et al 2003). In a contrary to (Morino et al 2014), where theoretical studies on a coupler have been performed using its two-dimensional representation, we have performed the design using a fully threedimensional electromagnetic model. Optimization of a structure in such a setting is considerably more challenging than in the two-dimensional one, because evaluation of a reliable model is very time consuming.…”

“…The possibility of realizing photonic components on a silicon substrate with a silica cladding allows for their integration with conventional electrical circuits (Kaminow 2008). Furthermore, owing to high refractive index contrast, low losses can be achieved within the waveguide, as well as compact designs (Morino et al 2014;Littlejohns et al 2011). One of the simplest, yet fundamental types, of integrated photonic components are directional couplers.…”