Feng Hu

The realization of long focal depth with a linear varied-area zone plate

Abstract We report a linear varied-area zone plate, in which arbitrary long focal depth can be achieved by properly adjusting the corresponding parameters. Meanwhile, the lateral focal spot and side lobes can be kept very small. Numeral simulations are carried out to verify the performance of our zone plate through Fresnel–Kirchhoff diffraction theory, and the results are in good accord with the experimental verifications. The influences of our zone plate’s parameters to the intensity distribution in focal region are discussed in detail. Comparisons are made with the behaviour of a linear varied-line-space grating, and we find that the behaviour of our novel zone plate along optical axis is just like a reverse transformation of the focusing behaviour of a linear varied-line-space grating.

Photon counting statistics of a single molecule under pump–probe fields

We consider the photon statistical properties emitted from a two-level quantum system under pump–probe driving. The line shapes and Mandels Q parameters are studied for a single quantum system based on the generating function method developed recently. The control of photon emission from a single quantum system driven simultaneously by a driven field and a tunable probe field is investigated. Our theoretical results and the experimental results are in good agreement.