In this article, we generalize fractional operators (differential and integral) in the unit disk. These operators are generalized the Srivastava--Owa operators. Geometric properties are studied and the advantages of these operators are discussed. As an application, we impose a method, involving a memory formalism of the Beer--Lambert equation based on a new generalized fractional differential operator. We give solutions in terms of the multi-index Mittag--Leffler function. In addition, we sanctify the out come from a stochastic standpoint. We utilize the generalized Wright function to obtain the analytic formula of solutions.