Abstract

Al₂O₃:Er³⁺ is an established material for integrated amplifier applications, offering several advantages such as low background losses, a broad emission spectrum, and a relatively high refractive index of 1.65, which enables the fabrication of small optical waveguide structures [1]. Our growth method allows for straightforward deposition on silicon wafers [2] and direct integration with silicon photonic circuits [3]. Net gain over a bandwidth of 80 nm (1500-1580 nm) and with a peak value of 2.0 dB/cm at 1533 nm was measured in our waveguide amplifiers [4]. By fitting the gain measurements with a simple Er³⁺ rate-equation model described in [4] one can extract values for the coefficient W_ETU of energy-transfer upconversion (ETU) between neighboring Er³⁺ ions, which has a detrimental influence on the amplifier performance. In the model, unlike other authors [5], we have discarded the excited-state absorption (ESA) process ⁴I_13/2→⁴I_9/2, because our direct ESA measurements show that this process lies outside the gain bandwidth. In further experiments we prove the existence of an additional ETU process (⁴I_13/2, ⁴I_11/2)→(⁴I_15/2, ⁴F_9/2), whose influence on gain, however, turned out to be small.

© 2011 Optical Society of America