a design of a semiconductor saturable absorber that offers a convenient and reliable way to control / decrease the recovery time of the absorption . the absorption recovery time is controlled during the epitaxial growth by using lattice - mismatched layer to induce dislocations , and implicitly non - radiative recombination centers within the nonlinear absorbing region . these lattice reformation layer are interposed between the distributed bragg reflector and the nonlinear absorption region , containing quantum - wells , quantum - dots or bulk semiconductor material . the thickness and composition of the lattice reformation layer is an instrumental to control the amount of non - radiative recombination centers used to trap the optically excited carriers generated in the absorption region .