Watt-Class CMOS-Compatible Power Amplifier

Watt-level optical amplifiers have various applications such as laser detection and ranging, modelocked lasers, frequency combs and laser surgery. However, power amplifiers are usually limited to solid-state and fibre-based technologies, as in integrated photonics the very property of tight mode confinement becomes an impediment to high power applications due to small optical mode cross-section, and thus limiting powers to a few 10s of milliwatt range at best [1]. Semiconductor based slab coupled waveguide amplifiers [2] can allow for large mode area thus high power; the integration, however, has proven to be challenging. Rare earth doped chip-scale amplifier recently reached signal level > 100 mW, however, that is at the expense of a complex fabrication process [3]. The situation is even worse beyond telecom wavelength window, in the mid-infrared, where only a few mWs of amplified signal has so far been achieved [4]. Here, we demonstrate for the first time a CMOS compatible watt-scale power amplifier with signal amplification up to >0.9 W in a compact footprint of 3.6mm ² in the eye safe window. The signal power reaches a level enjoyed by commercial bench top fiber amplifiers [5].