Regular Papers|2 Article(s)
Mid-infrared 2 × 2 electro-optical switching by silicon and germanium three-waveguide and four-waveguide directional couplers using free-carrier injection
Richard Soref
New designs are proposed for 2×2 electro-optical switching in the 1.3–12 μm wavelength range. Directional couplers are analyzed using a two-dimensional effective-index approximation. It is shown that three or four side-coupled Si or Ge channel waveguides can provide complete crossbar broad-spectrum switching when the central waveguides are injected with electrons and holes to modify the waveguides’ core index by an amount Δn+iΔk. The four-waveguide device is found to have a required active length L that is 50% shorter than L for the three-waveguide switch. A rule of ΔβL>28 for 3w and ΔβL>14 for 4w is deduced to promise insertion loss 1.5 dB and crosstalk ?15 dB at the bar state. At an injection of ΔNe=ΔNh=5×1017 cm?3, the predicted L decreased from ~2 to ~0.5 mm as λ increased from 1.32 to 12 μm. Because of Ge’s large Δk, the Ge bar loss is high in 4w but is acceptable in 3w.
Photonics Research
  • Publication Date: Jul. 01, 2014
  • Vol. 2, Issue 5, 05000102 (2014)