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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. 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)
Effects of polarization on stimulated Brillouin scattering in a birefringent optical fiber
Daisy Williams, Xiaoyi Bao, and Liang Chen
The most general model of elliptical birefringence in an optical fiber has been developed for a steady-state and transient stimulated Brillouin scattering interaction. The impact of the elliptical birefringence is to induce a Brillouin frequency shift and distort the Brillouin spectrum—which varies with different light polarizations and pulsewidths. The model investigates the effects of birefringence and the corresponding evolution of spectral distortion effects along the fiber, providing a valuable prediction tool for distributed sensing applications. The most general model of elliptical birefringence in an optical fiber has been developed for a steady-state and transient stimulated Brillouin scattering interaction. The impact of the elliptical birefringence is to induce a Brillouin frequency shift and distort the Brillouin spectrum—which varies with different light polarizations and pulsewidths. The model investigates the effects of birefringence and the corresponding evolution of spectral distortion effects along the fiber, providing a valuable prediction tool for distributed sensing applications.
Photonics Research
- Publication Date: Jul. 31, 2014
- Vol. 2, Issue 5, 05000126 (2014)
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