Optical Parametric Oscillators

1.         Novel, High-power, Nonlinear Optical Sources and Applications

The arrival of new nonlinear materials, structured with a periodic variation in non-linearity, has had a dramatic effect on nonlinear optical devices. This project, drawing on the fabrication capabilities for these materials at the ORC (e.g. periodically-poled lithium niobate, PPLN) explores some of the exciting new device possibilities. Particular emphasis will be given to optical parametric oscillator (OPO) devices, operating in the ultrashort pulse regime (~100fs). These provide excellent power handling capabilities and extremely wide tuning ranges and hence offer major opportunities for numerous scientific applications. This research will involve important device developments, both in power-scaling of these devices (to ~100W average power) so as to extend the range of applications, and in the introduction of a new generation of high-power fibre lasers to serve as pumps for the OPO. The convergence of these two important technologies, fibre lasers and periodic nonlinear materials, is seen as a major area of future development and exploitation.

2.         Intelligent Light Sources

The area of 'Intelligent Light Sources' explores the use of adaptive self-optimisation of laser light sources. It is expected that some form of adaptive control will become a feature of many future light sources. Here we examine the use of a spatial light modulator, controlled via a computer using a genetic algorithm, to make the performance characteristics of a laser light source evolve towards the optimal characteristics for a given application.  This technique will be used to control the spatial beam characteristics and temporal/spectral characteristics, and is currently applied to two applications, a. Adaptive control of high-power, femtosecond-pulse propagation in optical fibres and, b. Adaptive control of vibrational molecular dynamics using an intelligent, mid-infrared pulse generator.

3.        Coherent Control

Optimally shaped femtosecond light pulses offer the prospect of an experimental means of promoting conformational switching in large molecules. Such conformational change is one of the most important areas of current research in protein chemistry. The importance ranges from the role in the functioning of signaling proteins, to the harmful effect of prion proteins. In this project we will apply an intelligent mid-IR femtosecond optical parametric oscillator to optimally exciting specific local molecular vibrations in order to drive large-scale collective motions of whole domains (conformational change). We will exploit the fact that high-fidelity, pulse-shaping schemes already exist for wavelengths ranging from the visible to the near-IR, and will use this to control the shape of pulses at longer wavelengths via parametric frequency conversion. This will be accomplished by high-fidelity transfer of pulse shapes from the near-IR pump to the mid-IR idler of a synchronously pumped optical parametric oscillator. In addition, we will implement ‘closed-loop’, adaptive control of the idler pulse shape using a learning algorithm.

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Copyright University of Southampton 2006