We show that gravitational lensing can provide a direct method to probe the nature of dark energy at astrophysical scales .
For lensing system as an isolated astrophysical object , we derive the dark energy contribution to gravitational potential as a repulsive power-law term , containing a generic equation of state parameter w .
We find that it generates w -dependent and position-dependent modification to the conventional light orbital equation of w = -1 .
With post-Newtonian approximation , we compute its direct effect for an isolated lensing system at astrophysical scales and find that the dark energy force can deflect the path of incident light rays .
We demonstrate that the dark-energy-induced deflection angle \Delta \alpha _ { \text { DE } } \propto M ^ { ( 1 + \frac { 1 } { 3 w } ) } ( with 1 + \frac { 1 } { 3 w } > 0 ) , which increases with the lensing mass M and consistently approaches zero in the limit M \to 0 .
This effect is distinctive because dark energy tends to diffuse the rays and generates concave lensing effect . This is in contrast to the conventional convex lensing effect caused by both visible and dark matter .
Measuring such concave lensing effect can directly probe the existence and nature of dark energy .
We estimate this effect and show that the current gravitational lensing experiments are sensitive to the direct probe of dark energy at astrophysical scales .
For the special case w = -1 , our independent study favors the previous works that the cosmological constant can affect light bending , but our predictions qualitatively and quantitatively differ from the literature , including our consistent realization of \Delta \alpha _ { \text { DE } } \to 0 ( under M \to 0 ) at the leading order .