An objective scanning optical microscope technique to inspect the surfaces of optical components for imperfections (ranging from sub-micrometre to several micrometres in size) would replace the subjective methods currently in use by human quality controllers. Some laboratory microscope systems have been developed but they are too expensive and complex to be used on production lines. The atomic force microscope, with its image analysis software, has proved to be ideal for characterizing scratches and digs which, it is hoped, will assist the development of simpler optical microscope systems. The atomic force microscope images are repeated by the scanning electron microscope micrographs and both have their particular merits. The Form Talysurf was found to have insufficient resolution for the smallest unacceptable scratches and digs but could measure the waviness and form of large components.

The chaotic dynamics of a DFB laser are studied ex-5 perimentally under a combination of short and long feedbacks. 6 Chaos bandwidth enhancement is demonstrated using a hybrid 7 III-V/Si DFB laser with a large relaxation oscillation frequency 8 (ROF) of 14 GHz. The impact of short feedback on the ROF is Q1 9 studied and an increase of 2 GHz is observed. Under long feed-10 back, the route to chaos of the device and its dependence on the 11 short feedback dynamics are studied. The short feedback allows 12 tuning the chaotic dynamics obtained under long feedback, and the 13 increase of the ROF translates into an enhancement of the chaos 14 bandwidth to above 16 GHz. This configuration can allow gener-15 ation of wideband chaos using a single laser source in a photonic 16 integrated circuit. 17 Index Terms-III-V materials, nonlinear dynamics, optical feed-18 back, silicon photonics, secure communications. 19 I. INTRODUCTION 20 S ILICON photonics offer tight integration of a variety of 21 active and passive optical and electrical components, and 22 gained so much interest in the last decade that it is now con-23 sidered one of the most promising technology for optical appli-24 cations [1], [2]. Building on the mature fabrication techniques 25 first developed for microelectronics allows creating photonic 26 integrated circuits (PICs) with a high density of optical compo-27 nents, in high volumes and at low costs. Academic and industrial 28 efforts led to the development of novel technical solutions for 29 a variety of domains including sensing, measurement instru-30 mentation, optical signal processing and telecommunications 31

The high-speed dynamics of a hybrid distributed feedback semiconductor laser heterogeneously integrated onto silicon is experimentally investigated in the presence of external optical feedback. The laser fabrication relies on a proper modal engineering in which light is generated in the III-V material and stored in the low-loss silicon region in order to substantially enhance the quality factor of the cavity resonator. In this work, the hybrid laser is found to be insensitive to parasitic reflections leading to a 10 Gbps floor-free transmission with a power penalty no greater than 1.5 dB at room temperature. As a conclusion, owing to the large quality factor, a high coherence collapse level is unveiled in such laser indicating its vast potential to serve as an alternative solution for the development of isolator-free applications in future photonics integrated circuits. A qualitative interpretation is also provided by linking the standard feedback equations to the quality factor of the resonator.