The Universe is dominated by a mysterious component that we call
as Dark Energy, which is believed to be the cause of the accelerated
expansion of the Universe. The idea of cosmological constant as Dark
Energy is unsettling and a large number of exotic theories for the same
have been proposed. While the precise nature of Dark Energy is unknown, it
is clear that it must affect how the large-scale-structure grows with
cosmic time. Gravitational lensing provides a direct way to measure the
matter distribution in the Universe. By measuring the statistical
properties of the distribution in cosmic time slices, gravitational
lensing can enable us to understand the properties of the dark energy. The
strange behaviour of the Universe at large scales may also be attributed
to our ignorance about the correct theory of gravity on those scales.
Large surveys such as the Kilo-Degree Survey (KiDS), Dark Energy Survey
(DES), Hyper-Suprime Cam (HSC) survey and future surveys such as the Large
Sky Synoptic Telescope (LSST), Wide-Field Infra-Red Space Telescope
(WFIRST) and Euclid attempt to make extremely precise measurements of the
Dark Energy parameters and look for deviations from the general theory of
relativity. In this talk, after a short overview about the theory of
gravitational lensing, I will show the results on the Dark Energy equation
of state parameters from the current surveys and present the forecasts for
future missions. Estimates of the cosmological parameters obtained from
lensing are in mild tension with those obtained from CMB experiments
(Planck Collaboration) and I will briefly discuss the attempts made to
alleviate this tension.