Contents 1. Introduction
Wavelength tunable semiconductor lasers have wide applications in the future dense wavelength division multiplexed (DWDM) optical communication systems and sensing technology [1]. tunable lasers with a narrow linewidth will make them very suitable for applications in coherent optical communications [2] [3]. However, typical DFB and DBR based lasers are conventionally fabricated with buried gratings, which generally requires complex regrowth and high resolution processing. Recently, our group proposed a single mode laser platform by etching high-order surface grating (slots) into one side of laser cavity. Such a laser platform is regrowth free, integrable and can be fabricated by standard photolithography. we have demonstrated single mode lasers with threshold current about 32 MA and side-mode suppression-ratio (SMSR) of 50dB [4]. By integrating a semiconductor optical amplifier (SOA) and applying high-reflection (HR)/anti-reflection (AR) coating onto the facets, a 9 channel single mode laser array has been demonstrated with threshold ~19rnA and optical power >35mW for all channels [5]. Here, we further present 10 channels of such a laser array which exhibit a quasi-continuous tuning range ~31nm and linewidth ~2MHz for all channels.
