Simulation and optimization of a polymer directional coupler electro-optic switch with push–pull electrodes

Design of integrated 1×2, 1×4 low driving voltage polymer electro-optic switches based on Y-fed directional couplers

“…Compared to the directional coupler electro-optic switch with push-pull electrodes reported in our previous paper [17], the Y-fed directional coupler electro-optic switch designed in this paper shows several differences as follows. First, when both of the two kinds of switches have the same waveguide structure with identical parameters, the length of the Y-fed switch is shorter than that of the directional coupler switch due to the effects caused by the Y-junction splitter, for which the lengths are l/2 1/2 and l, respectively, and l is the coupling length for the directional coupler switch.…”

“…Second, we define K Y and K D as the coupling coefficients, respectively, and define G Y y and G D y as the electro-optic overlap integrals, respectively, where the subscripts or superscripts of Y and D represent the Y-fed coupler switch and directional coupler switch, respectively. In view of the following considerations: (1) the switching voltages U Y s and U D s of the two switches should satisfy ðU Y s , G Y y Þ ¼ 2K Y and ðU D s , G D y Þ ¼ 3 1=2 K D , respectively, and the relations between , U s and À y can also be seen from Equation (5); (2) the difference between the voltages applied on the two coplanar electrodes is 2U for the Y-fed coupler in this paper, while it is U for the directional coupler switch reported in [17], which results in different electric field distribution E y and different electro-optic overlap integral À y for the two switches; (3) since the value of 2 is the difference between the effective propagation constants of the two waveguides which are obtained by the effective index method, there are no fixed formulas of U Y s and U D s , which can be seen from Section 2 in this paper and Section 2.3 in our previous paper [17]; and according to the values of G Y y , G D y , K Y and K D calculated in terms of our theory, the switching voltage U Y s of the Y-fed switch is lower than U D s of our previously reported directional coupler switch. Two kinds of integrated 1 Â 2 and 1 Â 4 electrooptic switches based on Y-fed directional couplers have been designed and optimized by using the coupled mode theory, electro-optic modulation theory, conformal transforming method and image method.…”

Analysis and optimum design of a polymer Y-fed coupler electro-optic switch using double-section reversed electrodes

“…In the design, we choose the coupling gap d ¼ 2.5 mm, the relative coupling length L 0 ¼ 2375 mm, and the electro-optic coupling region length L ¼ 4389 mm, which is determined by Equations (23) and (24) for m ¼ 1. Based on our previous analysis results [9][10][11], to get the minimum switching voltage, the electrode width W and electrode gap G should be taken as the core width a and coupling gap d, respectively. Thus, we take W ¼ a ¼ 4.0 mm, Figure 4 shows the relations between the switching voltage U s and the gap G 0 between the two electrode sections.…”

“…Additionally, besides selecting appropriate polymer materials, the selection and optimization of electrode structure and waveguide structure are also key steps in the design of such switches for the purpose of getting low switching voltage and fast response speed [9,10]. Compared to the conventional directional coupler structure, which was used to fabricate an electrooptic switch with the switching voltage of about 2.14 V. In our previous paper [9], the Y-fed coupler waveguide structure reveals some advantages, and has been employed in our previous reported integrated 1 Â 2 and 1 Â 4 electro-optic switches exhibiting much lower branch-driving voltages of þ0.891 and À0.891 V [11].…”

“…Compared to the conventional directional coupler structure, which was used to fabricate an electrooptic switch with the switching voltage of about 2.14 V. In our previous paper [9], the Y-fed coupler waveguide structure reveals some advantages, and has been employed in our previous reported integrated 1 Â 2 and 1 Â 4 electro-optic switches exhibiting much lower branch-driving voltages of þ0.891 and À0.891 V [11]. Compared to the switches using single-section electrode structure in [9][10][11], the switch based on the conventional directional coupler structure using multisection reversed electrodes also shows some superior characteristics [12]. Therefore, in view of the above considerations, in order to further reduce the switching voltage and to further minimize the size of the device, a packaged 1 Â 2 polymer electro-optic switch with double-section reversed electrode based on Y-fed coupler structure is designed in this paper, and a unique formulization technique is also especially presented for simulating the switch.…”