The article "A low-fabrication-temperature, high-gain chip-scale waveguide amplifier" by Bo Wang and Peiqi Zhou, PhD students of the Center, was recently published in the journal SCIENCE CHINA Information Sciences.

In this study, researchers in this group have realized CMOS process-compatible high-gain silicon-based rare-earth-doped waveguide amplifiers by using a hybrid thin film of silicon-bismuth oxide and erbium-ytterbate as the gain medium. Erbium ions are present in the gain material in the form of compound cations and are thus not limited by the solid solubility of the parent material, increasing the concentration by one to two orders of magnitude. At the same time, by introducing bismuth oxide, the annealing temperature required for crystallization of the material is greatly reduced, and erbium ions can be activated by annealing at 600°C to achieve strong photoluminescence, which in turn realizes the compatibility of silicon-based rare-earth doped waveguide amplifiers with CMOS processes.

Fig. 1 Photoluminescence (PL) spectra of bismuth oxide and erbium-ytterbium silicate hybrid thin films at different annealing temperatures and doping ratios

A silicon-based rare-earth doped waveguide amplifier prepared using a hybrid thin film of silicon-bismuth oxide and erbium ytterbates can theoretically achieve up to 23 dB of on-chip gain, much higher than that of other silicon-based rare-earth doped waveguide amplifiers, under the conditions of 300 mW pump optical power, 1 μW signal optical power, and a waveguide length of 3.3 mm. Thus, waveguide amplifiers based on hybrid materials of bismuth oxide and erbium ytterbates on silicon have significant application prospects and offer the possibility of large-scale integration of future on-chip optoelectronic devices.

Fig. 2 (a) On-chip waveguide amplifier structure; (b) and (c) gain-transmission curves at different concentration ratios, pump optical power, and signal optical power

The above work was supported by the National Natural Science Foundation of China (NSFC) program.

Link to the paper: http://engine.scichina.com/doi/10.1007/s11432-021-3360-0