Enhancing the Sensing Capability for An Optical Feedback Interferometer

The lasers diodes (LD) experiencing external optical feedback are known to demonstrate complex dynamics, which may give rise to negative effect on the LD performance, e.g., degrading the modulation response characteristics, enhancing laser intensity noise, etc. Meanwhile, such external optical feedback effect in an LD also enables many applications, e.g., a class of laser interferometry, termed optical feedback interferometry (OFI) or self-mixing interferometry (SMI). As a promising non-contact sensing technology, OFI has attracted intensive research in recent decades due to the merits of minimum part-count scheme, low cost in implementation and ease in optical alignment. In general, the LD operates at a steady state if undergoing a weak level optical feedback from the target. Various OFI-based sensing applications have been reported for such weak optical feedback scenario, including measurement of displacement, velocity, vibration, laser related parameters, thickness, mechanical resonance, etc. Recently, OFI based sensing has been extended to other areas, such as imaging, material parameters measurement, near-field microscopy, chaotic radar, acoustic detection, biomedical applications etc. With the increase of the optical feedback level, an LD will leave the steady state and enter other operational states such as period-one (P1) oscillation, multiperiodic oscillation and chaos, and rich dynamics can then be observed. In recent years, LD dynamics have been investigated and found their various potential applications in optical communications, defence and security, and detection. In this thesis, we focus on enhancing the sensing capability of the OFI system through proposal of new physical configurations and investigation on the LD dynamic.