Fourier Domain Mode Locked laser is a novel fast frequency swept source used in Optical Coherence Tomography. The laser has a unidirectional all-fiber ring cavity that incorporates a semiconductor optical amplifier, a tunable Fabry-Perot filter and a fiber delay forming the cavity of up to 20km long. Our numerical modeling based on a set of delay differentiation equations is in excellent agreement with the experimental results that employed real-time intensity and phase characterisation techniques. We show that FDML lasers display a sequence of bifurcations that can co-exist within a sweep and lead, in particular, to the formation of Nozaki-Bekki holes.
Multiple reference optical coherence tomography (MR-OCT) applies a unique low-cost solution to enhance the scanning depth of standard time domain OCT by inserting an partial mirror into the reference arm of the interferometric system. This novel approach achieves multiple reflections for different layers and depths of an sample with minimal effort of engineering and provides an excellent platform for low-cost OCT systems based on well understood production methods for micro-mechanical systems such as CD/DVD pick-up systems. The direct integration of a superluminescent light-emitting diode (SLED) is a preferable solution to reduce the form- factor of an MR-OCT system. Such direct integration exposes the light source to environmental conditions that can increase fluctuations in heat dissipation and vibrations and affect the noise characteristics of the output spectrum. This work describes the impact of relative intensity noise (RIN) on the quality of the interference signal of MR-OCT related to a variety of environmental conditions, such as temperature.
A novel, time-resolved interferometric technique is presented allowing the reconstruction of the complex electric field output of a fast frequency swept laser in a single-shot measurement. The power of the technique is demonstrated by examining a short cavity swept source designed for optical coherence tomography applications, with a spectral bandwidth of 18 THz. This novel analysis of the complete electric field reveals the modal structure and modal evolution of the device as well as providing a time-resolved real-time characterization of the optical spectrum, linewidth and coherence properties of a dynamic rapidly swept laser.
We analyse the dynamical behaviour of a Fourier domain mode locked laser experimentally and theoretically. Heterodyne measurements of laser dynamics allows some insight into the frequency behaviour of the laser which coupled with theoretical arguments from previous work allow for a clear interpretation of the observations. Direct simulations using a delay differential equation model in full FDML mode display excellent agreement with the experimental results.
An experimental and theoretical analysis of the dynamics of a Fourier domain mode locked laser, currently one of the fastest swept source lasers applied in optical coherence tomography, is performed. A novel time- resolved technique to measure the laser output electric field allows access to the phase dynamics of the laser and thus the coherence properties. A delay-differential equation model for the laser is used to analyse the system theoretically and via direct simulation. Numerical simulations of the laser output are in excellent agreement with experimentally measured data.
We analyse the dynamical behaviour of a short cavity OCT swept-source laser experimentally and theoretically. Mode-hopping, sliding frequency mode-locking and chaos are all observed during the laser sweep period. Hetero- dyne measurements of laser dynamics allows some insight into the behaviour of the laser, while interferometric techniques allow the full phase reconstruction of the laser electric field. A delay differential equation enables modelling of the laser output, and laser parameters can be altered to provide optimisation conditions for future laser designs.