Efficient 52 µm wavelength fiber-to-chip grating couplers for the Ge-on-Si and Ge-on-SOI mid-infrared waveguide platform

Abstract

Abstract:We present the design, fabrication and characterization of efficient fiber-to-chip grating couplers on a Germanium-on-Silicon (Ge-on-Si) and Germanium-on-silicon-on-insulator (Ge-on-SOI) platform in the 5 µm wavelength range. The best grating couplers on Ge-on-Si and Ge-on-SOI have simulated coupling efficiencies of -4 dB (40%) with a 3 dB bandwidth of 180 nm and -1.5 dB (70%) with a 3 dB bandwidth of 200 nm, respectively. Experimentally, we show a maximum efficiency of -5 dB (32%) and a 3 dB bandwidth of 100 nm for Ge-on-Si grating couplers, and a -4 dB (40%) efficiency with a 3 dB bandwidth of 180 nm for Ge-on-SOI couplers. References and links 1. P.A. Werle, "Review of recent advances in semiconductor laser based gas monitors", Spectrochim. Acta Mol.

III-V-on-silicon Photonic Integrated Circuits for Spectroscopic Sensing in the Mid-Infrared

“…Beyond 4 µm wavelength we propose the use of germanium on silicon-on-insulator waveguide circuits. We demonstrate high efficiency grating couplers [7], thermooptic heaters [8] and widely tunable Vernier ring resonator filters [9] on this platform in the 5 µm wavelength range. Such circuits can then be integrated with III-V semiconductor quantum cascade or interband cascade gain chips to realize miniaturized widely tunable lasers.…”

Mid-infrared Vernier racetrack resonator tunable filter implemented on a germanium on SOI waveguide platform [Invited]

“…The grating coupler structures used to characterize the PIC by interfacing with a single mode InF fiber [25] at 5.3 µm wavelength, are etched 1 µm deep, have a grating period of 1.45 µm and a grating duty cycle of 0.8 (duty cycle being the ratio of the width of the unetched part and the period). 30 periods were implemented to have a good coupling efficiency to the InF fiber with a mode field diameter of 18 µm [17]. The fiber is tilted 5 degrees off-normal.…”

“…The Si device layer in the SOI substrate of the Ge-on-SOI platform is thick enough to prevent overlap of the Ge waveguide mode with the underlaying oxide, hence the mode does not incur losses from the highly absorptive oxide at 5 µm wavelength. The fabrication of devices on this platform can also take advantage of the additional SiO 2 layer to under-etch parts of the PIC, such as to further improve the efficiency of thermo-optic phase shifters and diffractive grating couplers [17].…”

Design and Performance of Diamond‐Based Mid‐Infrared Sensor

“…Current MIR ATR units comprise silicon and germanium. [9][10][11][12][13] This indicates that we will compare and analyze these three base materials of Si, Ge, and diamond to find appropriate materials.…”