1. Polarization Converter Design 2015-12-15 Paper Review Woojin Jo Si Photonics 2015-02 1

2.  For two modes in a waveguide with two different refractive indices (n1 and n2),  The modes will accumulate different phase after the propagation of a certain length (L) due to the difference in the effective indices (neff).  If the propagation length is long enough to accumulate a phase difference of pi, then L becomes Polarization Conversion Background Woojin Jo YONSEI Mixed Signal IC Lab. 2

3.  For the polarization converter, the FDE solver can be used to identify the regions where mode-crossings occur.  Run a number of FDE simulations, varying the waveguide width.  At each step, the n eff are subtracted by the n eff of the slab.  Choose in/output taper width parameter from FDE result.  Run EME simulation to findout light propagation in this device.  Choose adequate the length of this device from EME results. Simulation Process Woojin Jo YONSEI Mixed Signal IC Lab. 3

4.  Make simple waveguide structure.  Run a number of FDE simulations, varying the waveguide width from 0.5um to 3um.  Calculate the difference between n eff of the slab and n eff of the ridge. Simulation Setup Woojin Jo YONSEI Mixed Signal IC Lab. 4

5. FDE Analysis Results Woojin Jo YONSEI Mixed Signal IC Lab. 5  TE1: changes n eff of TE1 mode from 0.28 to 0.06.  Mode crossing occurs at 0.9um  Input Waveguide width= 1.5um  Output Waveguide width= 0.8um

6. Simulation Setup Woojin Jo YONSEI Mixed Signal IC Lab. 6  The device includes the input and output ridge waveguides, connected by a taper with 1.5um and 0.8um as the waveguide input and output respectively.  Track 3 modes: (TE0, TE1, TM0) at 1.5um, (TE0, TM0, TE1) at 0.8um  We will scan the length of this taper and track how efficiently the TE1 mode can be converted into the fundamental TM mode.

7. EME Analysis Setup Woojin Jo YONSEI Mixed Signal IC Lab. 7

8. EME Analysis Results Woojin Jo YONSEI Mixed Signal IC Lab. 8 S42: TE1->TE0 S52: TE1->TM0 S62: TE1->TE1 At L=250um The TE1 mode is almost completely transferred to the TM0 mode.