Highly-reflective facet-coated multi-wavelength DFB laser array with exact wavelength spacings.

ABSTRACT

A distributed feedback (DFB) laser array of twenty wavelengths with highly reflective and anti-reflective (HR-AR) coated facets is both theoretically analyzed and experimentally validated. While the HR facet coating enhances high wall-plug efficiency, it inadvertently introduces a random facet grating phase, thereby compromising the lasing wavelength's predictability and the stability of the single-longitudinal-mode (SLM). In this study, two key advancements are introduced first, the precisely spaced wavelength is achieved with an error of within ±0.2 nm using the reconstruction-equivalent-chirp (REC) technique; second, the random grating phase on the HR-coated facet is compensated by a controllable distributed phase shift through a two-section laser structure. The SLM stability can be improved while the wavelength can be continuously tuned to the standard wavelength grid. The overall chip size is compact with an area of 4000 × 500 µm2. The proposed laser array has a light power intensity above 13 dBm per wavelength, a high side mode suppression ratio above 50 dB, and low relative intensity noise under -160 dB/Hz. These attributes make it apt for deployment in DWDM-based optical communication systems and as a light source for optical I/O.