Pulse-shaping assisted nonlinear optical signal generation in fibres

Abstract

This thesis investigates pulse-shaping assisted nonlinear optical signal generation in fibers. A linear pulse shaping stage is included in nonlinear fibre optic systems to achieve flexible and precise control over the characteristics of the output signal. The nonlinear generation of broadband spectra with desired characteristics is demonstrated as a first application of this technique. The key feature is that the linear filtering stage is placed prior to the nonlinear broadening stage in the system. A numerical simulation procedure is established to find the appropriate transfer functions of the programmable pulse shaper based on the backward propagation in a fibre. Consequently, an adaptive pulse shaping system exploiting evolutionary algorithms is built and employed to facilitate automatic convergence to the desired spectrum. The nonlinear generation of ultra-fast broadband spectra with different bandwidths is demonstrated. Additionally, the generation of broadband spectra with symmetric and linear edges exhibiting slopes of different steepness is also presented.

As a second application of this technique, the linear filtering stage is incorporated into the cavity of a passively mode-locked erbium-doped fibre ring laser (EFRL). The aim here is to achieve flexible and precise control over the temporal waveforms of the laser pulses. In order to find the appropriate laser configuration which allows for the manipulation of the characteristics of the laser pulses through intra-cavity spectral filtering, both all anomalous dispersion and all-normal dispersion cavities are numerically studied. The influence of intra-cavity amplitude filtering and net dispersion on the characteristics of laser pulses in a passively mode-locked dispersion-managed (DM) EFRL is experimentally demonstrated.

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Identifiers

ORCID for P. Petropoulos: orcid.org/0000-0002-1576-8034

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