Silicon and germanium mid-infrared optical modulators

Cao, W., Nedeljković, M., Littlejohns, C.G., Li, T., Zhou, Z., Gardes, F.Y., Thomson, D.J., Reed, G.T. and Mashanovich, G.Z. (2018) Silicon and germanium mid-infrared optical modulators. In IEEE Photonics Society Summer Topicals Meeting Series, SUM 2018. IEEE. pp. 209-210 . (doi:10.1109/PHOSST.2018.8456777).

Abstract

The mid-infrared wavelength region contains absorption fingerprints of numerous molecules and therefore is mostly considered for sensing applications [1]. However, due to a need for more spectral bandwidth for communications, and because modulation can be used to enhance signal to noise ratio in sensing applications, photonic modulator devices operating at mid infrared (MIR) wavelengths would be useful functional devices [2]. However, to date there have been few reported investigations of modulation in Si or Ge in the mid-infrared. SOI carrier injection modulators operating at up to 3 Gb/s with pre-emphasis at a wavelength of 2165 nm have been reported [3]. By using Ge rib waveguides with lateral p-i-n junctions, optical intensity modulation based on free-carrier absorption was demonstrated in Ge by injecting carriers through a Ge p-i-n junction at 1950 nm [4]. Also, thermo-optic modulation has been demonstrated in SOI at 3.8 μm [5], and in Ge-on-Si (GOS) and Ge-on-SOI (GOSOI) at ∼5.3 μm [6]. An all optical modulator based on free-carrier absorption has also been demonstrated in GOS with bandwidth of around 55 MHz across the 2-3.2 μm wavelength range [7]. In addition, two photon absorption (TPA) cross absorption modulation has been reported on the same platform and in the same wavelength range [8].

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Contributors

Author: W. Cao

Author: M. Nedeljković

Author: F.Y. Gardes

Author: G.Z. Mashanovich

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