Far field resolution beyond the Abbe limit using photodiffraction

In this paper we show how a tightly focused pump beam can be used to alter the local refractive index of the sample. This local variation acts as a sc attering site, which enables resolution exceeding that of a conventional sc anning microscope to be obtained in the far field. The improvement in resol ution depends on a number of factors which are discussed in the paper, incl uding the optical configuration (confocal or non-confocal), the thermal pro perties of the sample, the 'strength' of the object and the duration of the heating pulse. Experimental results confirming the theoretical predictions are presented; these demonstrate more than 25% improvement in edge respons e compared with a conventional scanning system.