In this situation, if the mirrors are of very low optical loss, nearly all of the light supplied to the
interferometer is reflected back towards the laser. In other words the laser is not properly impedance
matched to the interferometer. The impedance matching can be improved by placing another mirror of
correctly chosen transmission – a power recycling mirror – between the laser and the interferometer so that
a resonant cavity is formed between this mirror and the rest of the interferometer; in the case of perfect
impedance matching, no light is reflected back towards the laser [131, 278]. There is then a power build-up
inside the interferometer as shown in Figure 10. This can be high enough to create the required
kilowatts of laser light at the beamsplitter, starting from an input laser light of only about
10 W.
To be more precise, if the main optical power losses are those associated with the test mass mirrors –
taken to be A per reflection – the intensity inside the whole system considered as one large cavity is
increased by a factor given by , where the number of bounces, or light storage time, is
optimised for signals of timescale
and the other symbols have their usual meaning. Then:
http://www.livingreviews.org/lrr-2011-5 |
Living Rev. Relativity 14, (2011), 5
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