Download Design Project 4: Modulator

Electro-Optic Modulator using Polymer
An electro-optic modulator requires an electric field to be applied to a nonlinear optical
material such as an electro-optic polymer. In order to attain a large applied electric field
without requiring a huge voltage, metallic electrodes are applied above and below the
polymer (see Figure 1). Assume that the nonlinear optical polymer that is used as the
core has a refractive index of n=1.55 and it is surrounded by a cladding material that has
a refractive index of n=1.52. Use a wavelength is λ=1550nm. In this project you will
design a polymer electro-optic modulator. The modulator is configured as MachZehnder. Assume that arms of the modulator are 1.5cm long and it is configured as pushpull.
gold electrode
w
d2
d1
d3
EO polymer
cladding
material
d3
gold electrode
Figure 1
Use PMMA doped with DR1 as the EO polymer. And choose a UV cured optical cement
from Norland as the cladding. Assume that the EO polymer has a refractive index of
npolymer=1.55 and use an r33 from [1]. The linear electro-optic coefficient matrix for an
1
EO polymer is given in [2]. Assume that r13  r33 .
2
(1) First design the polymer waveguide as an infinite slab waveguide. (Determine d1 and
d3.)
a. Make sure that the waveguide is single mode.
b. The cladding layer has to be thick enough such that 99% of the mode power is
contained in the core and cladding. Do this analysis as a symmetric slab
waveguide.
(2) Now use the effective index method to analyze the waveguide and determine the
ridge width and thickness (d2 and w). Make sure that the waveguide is still single
mode. Make sure that the ridge width is practical to fabricate (larger than 5 μm).
(3) Calculate the Vπ of the modulator.
a. Calculate the change in the bulk index of refraction of the core.
b. Calculate the change in the effective index of the mode (use the effective
index method).
c. Calculate the total phase change.
d. Calculate the required voltage.
Be sure to show plots of the various calculations not just a calculated number.
1 A. Nahata, C. Wu, and J. Yardley, “Electrooptic characterization of organic media,”
IEEE Trans. on Instrum. And Meas., vol. 41, pp. 128-131, Feb. 1992.
2 E. Tomme, P. Van Daele, R. Baets, and P. Lagasse, “Integrated optic devices based on
nonlinear optical polymer,” IEEE J. of Quant. Electron., vol. 27, pp. 778-787, Mar. 1991.