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 Mach-Zehnder. Assume that arms of the modulator are 1.5cm long and it is configured as push-pull.

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 EO polymer is given in [[2]]. Assume that.

(1)  First design the polymer waveguide as an infinite slab waveguide. (Determine d1 and d3.)

  1. Make sure that the waveguide is single mode.
  2. 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.

  1. Calculate the change in the bulk index of refraction of the core.
  2. Calculate the change in the effective index of the mode (use the effective index method).
  3. Calculate the total phase change.
  4. 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.