Push-pull fused vertical coupler switch

Abstract

Abstract-A single-electrode push-pull fused vertical coupler (FVC) switch using macroscopic crystal inversion symmetry is demonstrated. The anisotropic linear electrooptic effect in a zincblende crystal is used to achieve optical switching under 12-V reverse bias for a 6.9-mm-long FVC whose two guiding layers have different crystal symmetries. No switching is observed for the identical structure in which the two guiding layers have the same crystal symmetry.Index Terms-Electrooptic effects, optical directional couplers, optical switches, water bonding.are very attractive candidates to make optical waveguide switches and narrowband filters because of their very short coupling length and the feasibility of integration with other optoelectronic devices. Generally, switching is achieved by introducing a phase mismatch between two waveguides through the electrooptic effect. In a push-pull operation, the introduction of positive and negative phase shifts in the two waveguides of the coupler reduces the driving voltage and chirping for switching. It is well known that the linear electrooptic effect is anisotropic [4], [5] in zinc-blende crystal structures. When the applied electric field is perpendicular to the (001) surface, it gives a positive index change for the TE-polarized light propagating along [110] direction and a negative index change for the light propagating along the [110] direction. In conventional epitaxial vertical couplers, the upper and lower waveguides have the same crystal orientation [see Fig. 1(b)]. Consequently push-pull operation requires the signs of the electric fields in the upper and lower waveguides to be opposite. This requires presence of a third electrode between waveguides and application of positive and negative biases to the upper and lower waveguides. The fabrication is difficult in conventional vertical couplers. Since the electrooptic effect is anisotropic, if one of the waveguides in the vertical couplers is along the [110] orientation and the other one along the [110] orientation [see Fig. 1(a)], then under an applied bias, the index changes in two waveguides have different signs. This simplifies the electrode fabrication and only requires one electrode for push-pull operation. In this letter, a vertical coupler

Ultra Short Two-Section Vertical Directional Coupler Switches with High Extinction Ratios

“…With appropriate doping profile and material composition or orientation, one can control the change in the refractive index of different regions. For example Liu et al 5) have recently demonstrated push-pull operation for a vertical coupler switch with a use of a single electrode. This takes advantage of the anisotropic electrooptic effect in zinc-blende semiconductors.…”

3-D photonic circuit technology

“…Initially, an InP-InGaAsP vertical coupler switch that required a 12-V reverse bias for a 6.9-mm-long device was fabricated [16]. It was shown that switching at 12 V reverse bias for a 6.9-mm-long device could be achieved with a single electrode only when the crystal symmetry was inverted during fusion to achieve a push-pull configuration [14]. The cleaved facets and crystal orientations of the two configurations are shown in Fig.…”

“…Four-port devices were cascaded to make devices for more than two channels [12], [13]. Push-pull configuration optical switches [14] and devices of more than two layers [15] were also fabricated.…”

A Novel Vertical Directional Coupler Switch with Switching Operation-Induced, Extinction Ratio-Adjusted, and Extinction Ratio-Enhanced Sections

“…By manipulating the appropriate doping profile, material composition, or orientation we can control the change in the refractive index of different regions to produce the asymmetric structure. For example, Liu et al recently demonstrated a push-pull operation for a vertical coupler switch with a single electrode [9]. Their operation took advan-…”