An Introduction to Quantum Optics

3Diffraction and Propagation

3.1 Diffraction

To demonstrate the minimum-width diffraction pattern, we need a spatially coherent radiation source such as that in Figure 2.1 with either ψ(x₀) = ψ₀ or ψ(x₀) = k_x0x₀. A laser beam with TEM₀₀ mode is definitely a better choice. Before the invention of the laser, optical collimators were widely used to simulate such a source. A collimator consists of a pin hole, or a line aperture (1D), and a lens system, as shown in Figure 3.1. The pin hole is placed at the principal focus of the lens system and is illuminated by a discharged light tube. The use of the pin hole is to simulate a point radiation source. The lens system introduces appropriate phase delays to the spherical wavefront originating from ...