Stabilized Mode-Locked Tapered Monolithic Laser Diode with 200pJ Pulse Energy for Space Metrology Applications

Abstract

European Space Agency (ESA) considers Mode-Locked Semi-Conductor Laser (MLSCL) technology as a promising candidate for applications in precision optical metrology spaceborne systems such as High Accuracy Absolute Long Distance Measurement (HAALDM). Very challenging performance requirements should be met for these applications: pulse duration 20MHz, average optical output power > 200 mW, pulse energy > 200pJ, high spatial beam quality (M2 < 2.5) in addition to the space application requirements on launch vibrations, volume, weight, power consumption and efficiency. Previously, we have realized two types of passively mode-locked (ML) multiple section edge emitting lasers to address these challenging targets: (i) very long (13.5mm) monolithic tapered laser [1], and (ii) inverse bow-tie external cavity (EC) laser [2]. Both lasers are designed using the model from [3] and produce mode-locked pulses of 70–90pJ energy without amplifier stages. In this communication we report on the design, fabrication and testing of a novel monolithic tapered laser achieving pulse energy up to 200pJ from a solitary chip (Fig.1, panel (a)). While the epitaxial structure is the same as reported in [2] the tapered laser structure has now different cavity sections: two absorber sections, a tuning section and a gain section. The last one consists of the linear and the tapered waveguide parts and comprises beam spoilers in between the two parts.