MSci (4th year) Project Proposal Form
Project Code:
Project title:
PLAS-Smith-2
An "Optical Fuse" for use in High Power Laser Experiments.
Supervisor: Prof Roland A Smith
Assessor:
Prof John Tisch
Telephone: 47866
Telephone:
47701
E-mail:
E-mail:
[email protected]
[email protected]
Research Group: PLAS
Research Group: QOLS
Project Summary:
The Plasma Physics and QOLS research groups operate UK’s largest university based laser called
“Cerberus”. This is a multi-beam system that produces high-power laser pulses that are used in
laboratory astrophysics and high energy density plasma experiments. In order to monitor and optimise
the performance of the laser system, a broad range of diagnostics are needed to measure laser energy,
focal spot size, beam pointing and pulse duration. For sub-ns beams it is impossible to use a simple
photodiode and fast oscilloscope to measure the pulse duration, such technologies are many orders of
magnitude too slow. Instead an indirect non-linear optical technique such as autocorrelation [1], FROG
[2] or Grenouille [3] is used. With this type of indirect measurement, some computer post processing of
the output of the measurement system is required to recover a laser pulse shape and duration. However
these systems cannot capture the “contrast” of the laser system (the ratio of the smallest to the largest
intensity components) spread over many nanoseconds. This is a critical parameter for large laser
systems, a 10E-11 pre-pulse several nanoseconds before the main pulse can completely change the
dynamics of an experiment.
The aim of this project will be to build and characterise a high-dynamic-range laser contrast diagnostic
for Cerberus using an array of filtered silicon photodiodes. Unfortunately a diode sensitive enough to
detect a low level pre-pulse can also be destroyed by the main laser pulse and so a key part of this
project will be to develop an “optical fuse” based protection system based on a highly non-linear process
that can shut off the laser light just before the arrival of the main laser pulse. This is likely to use a
combination plasma break down and Kerr lensing in a liquid cell, as the liquid can "repair" itself after
each high power laser shot. We will investigate a range of interesting liquids, including highly non-linear
materials such as C60 buckyballs dissolved in an organic solvent.
How to contact supervisor for further info:
Please Email [email protected] to arrange a meeting
Suggested reading (relevant references):
[1] http://en.wikipedia.org/wiki/Optical_autocorrelation
[2] http://www.physics.gatech.edu/frog/OPN/OPN.html
[3] http://www.swampoptics.com/tutorials_GRENOUILLE.htm
Is the project eligible for students on the MSci
Physics with Theoretical Physics Degree ?
NO
How many pairs of students
could you accommodate ?
ONE...
Imperial College of Science, Technology, and Medicine
Experimental component:
70
%
Computational component:
20
%
Theoretical component:
10
%
Would you also consider supervising an MSc
student over the summer (2015) on this project ?
YES