Spiral amplifiers in a-Al2O3:Er on a silicon chip with 20 dB internal net gain

S. A. Vázquez-Córdova; E. H. Bernhardi; Ke. Wörhoff; J. L. Herek; S. M. García-Blanco; M. Pollnau

doi:10.1117/12.2077503

27 February 2015 Spiral amplifiers in a-Al₂O₃:Er on a silicon chip with 20 dB internal net gain

S. A. Vázquez-Córdova, E. H. Bernhardi, Ke. Wörhoff, J. L. Herek, S. M. García-Blanco, M. Pollnau

Proceedings Volume 9365, Integrated Optics: Devices, Materials, and Technologies XIX; 93650M (2015) https://doi.org/10.1117/12.2077503
Event: SPIE OPTO, 2015, San Francisco, California, United States

Abstract

Spiral-waveguide amplifiers in erbium-doped amorphous aluminum oxide are fabricated by RF reactive co-sputtering of 1-μm-thick layers onto a thermally-oxidized silicon wafer and chlorine-based reactive ion etching. The samples are overgrown by a SiO₂ cladding. Spirals with several lengths ranging from 13 cm to 42 cm and four different erbium concentrations between 0.5−3.0×10²⁰ cm^-3 are experimentally characterized. A maximum internal net gain of 20 dB in the small-signal-gain regime is measured at the peak emission wavelength of 1532 nm for two sample configurations with waveguide lengths of 13 cm and 24 cm and erbium concentrations of 2×10²⁰ cm^-3 and 1×10²⁰ cm^-3, respectively. The obtained gain improves previous results by van den Hoven et al. in this host material by a factor of 9. Gain saturation as a result of increasing signal power is investigated. Positive net gain is measured in the saturated-gain regime up to ~100 μW of signal power, but extension to the mW regime seems feasible. The experimental results are compared to a rate-equation model that takes into account migration-accelerated energy-transfer upconversion (ETU) and a fast quenching process affecting a fraction of the erbium ions. Without these two detrimental processes, several tens of dB/cm of internal net gain per unit length would be achievable. Whereas ETU limits the gain per unit length to 8 dB/cm, the fast quenching process further reduces it to 2 dB/cm. The fast quenching process strongly deteriorates the amplifier performance of the Al₂O₃:Er³⁺ waveguide amplifiers. This effect is accentuated for concentrations higher than 2×10²⁰ cm^-3.

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S. A. Vázquez-Córdova, E. H. Bernhardi, Ke. Wörhoff, J. L. Herek, S. M. García-Blanco, and M. Pollnau "Spiral amplifiers in a-Al₂O₃:Er on a silicon chip with 20 dB internal net gain", Proc. SPIE 9365, Integrated Optics: Devices, Materials, and Technologies XIX, 93650M (27 February 2015); https://doi.org/10.1117/12.2077503

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