Constructing a Laser - John M. Thomas & David Phillips's 1987 Christmas Lectures 4/6

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How do you amplify light with the stimulated emission of radiation? In this lecture, David Phillips shows us step by step how to construct a laser. Watch all the lectures in this series here: https://www.youtube.com/playlist?list=PLbnrZHfNEDZw7s3y3S1IsaEmka5MWlaq9 Watch our newest Christmas lectures here: https://www.youtube.com/playlist?list=PLbnrZHfNEDZyQJZLPMjwEoOLdkFBLU2m1 This lecture was filmed at the Ri on Tuesday 29th December 1987. -- How easy is it to assemble a laser? We shall answer this question by reconstructing what Maiman did in 1960 in California, where the laser was first demonstrated. A photographer’s flash tube, along with a good-quality rod of aluminium oxide doped with chromium is one of the key components of the so-called ruby laser. But there are many other types of systems, chemical and physical, which can be induced to ‘lase’. The requirement for ‘lasing action’ – the creation of a ‘population inversion’ of excited states – will be illustrated, and the stimulation of these excited states to give up their energy in the form of light emission demonstrated. Thus laser light emerges from a cavity as a narrow, exceptionally intense and parallel beam that can be put to many uses. There are lasers that operate in the ultra-violet, visible or infrared regions of the spectrum and a few of their properties will be demonstrated. Some lasers can be made to produce ultra-short pulses of light, others extraordinarily ‘pure’ colours. The polarisations of laser

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