Superresolving linear optical imaging in the far field

CQT Online Talks – Series: Colloquium

Speaker: Alexander Lvovsky, University of Oxford
Abstract: The resolution of optical imaging devices is ultimately limited by the diffraction of light. To circumvent this limit, modern superresolution microscopy techniques employ active interaction with the object by exploiting its optical nonlinearities, nonclassical properties of the illumination beam, or near field probing. These techniques are therefore not applicable whenever such interaction is not possible, for example, in astronomy or noninvasive biological imaging. Far field, linear optical superresolution techniques based on passive analysis of light coming from the object would cover these gaps.

We present the first proof-of-principle demonstration of such a technique for 2D imaging. It works by accessing information about spatial correlations of the image optical field and, hence, about the object itself via measuring projections onto Hermite-Gaussian transverse spatial modes. With a basis of 21 spatial modes in both transverse dimensions, we perform two-dimensional imaging with twofold resolution enhancement beyond the diffraction limit.

Additionally, we determine the ultimate quantum limit in estimating the precision of reconstructing a distribution of a set of coherent and incoherent light sources in terms of the quantum Fisher information. We show that Hermite-Gaussian microscopy and several related techniques are capable of approaching this limit and significantly surpass direct imaging. This theory is an important step towards taking QISR from toy examples to real imaging scenarios.