Towards low-loss waveguides in SOI and Ge-on-SOI for mid-IR sensing

Abstract

Silicon-on-insulator is an attractive choice for developing mid-infrared photonic integrated circuits. It benefits from mature fabrication technologies and integration with on-chip electronics. We report the development of SOI channel and rib waveguides for mid-infrared wavelengths centered at 3.7 μm. Propagation loss of ∼1.44 dB/cm and ∼1.2 dB/cm has been measured for TE and TM polarizations in channel waveguides, respectively. Similarly, propagation loss of ∼1.39 dB/cm and ∼2.82 dB/cm has been measured for TE and TM polarized light in rib waveguides. The propagation loss is consistent with the measurements obtained using a different characterization setup and for the same waveguide structures on a different chip. Given the tightly confined single-mode in our 400 nm thick Si core, this propagation loss is among the lowest losses reported in literature. We also report the development of Ge-on-SOI strip waveguides for mid-infrared wavelengths centered at 3.7 μm. Minimum propagation loss of ∼8 dB/cm has been measured which commensurate with that required for high power midinfrared sensing. Ge-on-SOI waveguides provide an opportunity to realize monolithically integrated circuit with on-chip light source and photodetector.

Recent Progress on Two-Dimensional Materials

“…The reverse rectification ratio of WSe2/PtS2 is over 10 8 . Compared to conventional semiconductors-based backward diodes, vdW tunneling diodes exhibit a higher rectification ratio and show great potential in high-speed and low-power devices 806,807 . On the other hand, Wu et al designed a unilateral depletion structure based on AsP and MoS2.…”

High coupling efficiency 2D metasurface integrated with strip waveguide in SOI for mid‐IR wavelengths

“…Strip waveguide of width 1.2 μm and height 400 nm has been employed. Firstly, this waveguide design has enabled us to achieve propagation loss of 1.4 dB/cm for TE polarised light at 3.7 μm wavelength [25]. Secondly, the waveguide structure is consistent with that of the unit cells to achieve the entire 2D metasurface integrated with waveguide in a single etch.…”

“…In this paper, we present the design of 2D metasurface integrated with a strip waveguide to couple off-chip, out-of-plane, 3.8 μm wavelength into on-chip, in-plane waveguide [24]. Metasurface and strip waveguide integration have been achieved using 400 nm thick SOI material system, which we have previously employed to demonstrate low-loss waveguides for the 3.8 μm wavelength [25]. The maximum coupling efficiency achieved is 98% for the designed 2D meta-surface integrated with strip waveguide.…”

Integrated photonic materials for the mid‐infrared

“…Most development in SOI photonics is concentrated largely for the telecommunication band, with a recent surge for mid‐IR applications. While previous studies on SOI showed the low propagation losses of ~1.44 dB/cm for TE and ~1.2 dB/cm for TM polarization mode at λ = 3.7 μm in channel waveguides, 33 0.6‐1.5 dB/cm for λ = 3.39‐3.73 μm for TE/TM polarization mode in rib waveguides, 20 and 1.4 dB/cm at λ = 3.8 μm in slot waveguides 34 . But as mentioned above, SiO 2 has high material absorption loss in the 2.6 and 2.9 μm range with losses increasing to unacceptably large values above λ = 3.8 μm, 10 making a traditional SOI platform unsuitable at wavelengths beyond 3.8 μm.…”