The main objective of this project is the investigation of super continuum (SC) generation and spectral transformation of ultra short pulses in photonic-crystal fibres (PCFs) and tapered fibres, search for the methods to control these phenomena, and the development of practical photonic solutions and components based on enhanced nonlinear-optical processes in PCFs and tapered fibres. Experimental and theoretical investigations will be focused on super continuum generation in PCF starting with nanojoule and subnanojoule femtosecond pulses, including pulses of 800--900-nm Ti: sapphire laser radiation, 1.2--1.3 micrometer Cr: forsterite laser radiation, and broadly frequency-tuneable radiation of femtosecond optical parametric amplifiers. Strategies to enhance four-wave mixing and solution self-frequency shifting effects in PCFs and tapered fibres will be developed, allowing highly efficient PCF and tapered-fibre frequency converters for ultra short laser pulses to be created. Frequency-metrology applications will include the creation of PCF and tapered-fibre-based frequency chains. Spectroscopic experiments will include elastic and inelastic light scattering of PCF-generated SC in the atmosphere and the detection of trace gases and aerosols. Special attention will be given to the development of new advanced theoretical and time-saving numerical methods of modelling light propagation in PCFs. The proposed research combines theoretical, numerical and experimental investigations. The main objectives of the proposed research thus include (i) investigation of SC generation in PCFs, including analysis of the physical mechanisms behind SC generation, and characterisation of SC properties; (ii) development of methods to control SC generation using polarisation and phase sensitivity of SC generation; (iii) the use of PCFs and tapered fibres for efficient spectral transformation and frequency conversion of ultrashort laser pulses, including anti-Stokes frequency conversion, third-harmonic generation, and soliton self-frequency shifting; (iv) application of SC generation in PCFs and tapered fibres for frequency metrology, spectroscopic studies and development of PCF and tapered-fibre frequency converters. The complementary expertise of the teams involved in the project covers all the aspects of the proposed research, including fibre design and fabrication, theoretical modelling of short-pulse propagation and nonlinear-optical phenomena in PCFs and tapered fibres, as well as experimental investigations using advanced femtosecond laser facilities and pulse-characterisation equipment. Research teams involved in the project have a long-term collaboration with each other, documented by scientific publications in highly ranked journals. The project will include all the phases of investigations from the design of microstructure and photonic-crystal fibres through their fabrication, characterisation, and testing to the experimental work and real-life applications.