Coincidence Time Measurement of Pulsed Lasers & "Useful" Applications
Members
Tan Wen Yi, Kim Mu Young
Abstract
Given two paths through a which a pulsed laser propagates, one might be interested in ensuring that the pulses coincide on the same spatial point at exactly the same time. One possible situation where such a coincidence may be useful is in the driving of Raman transitions via a pulsed laser. We intend to perform such a coincidence time measurement using commonly-available metals. By choosing a material with a work function on the order of the energies of two 355nm photons, the detection of a photocurrent through a metal would then indicate that both laser pulses arrived at the metal at approximately the same time. The project first aims to find such a metal and design a set-up to perform this experiment; after which, we intend to measure the timing resolution such a method is limited to. If time permits, we then intend to try to use this method to perhaps characterise the density/surface smoothness and other possible features of the metal object used.
Theory
Photoelectric Effect
The photoelectric effect is a simple yet revolutionary phenomena, being one of the first experiments to show the quantisation of energy. A typical set-up goes as the following:
Every metal surface has a characteristic feature known as the work function () which describes the amount of energy required for an electron to be ejected from its crystal structure into the continuum. If one provides such a metal surface with energy more than that of the work function, the electrons that are emitted are characterised by a simple equation: