Many promising functional optical devices that exploit saturable absorption in graphene have been theoretically studied and experimentally demonstrated. Early works on graphene SA demonstrated practical applications that ranged from fiber-based mode-locked and Q-switched pulsed lasers to solid-state lasers and pulse shaping. Almost all demonstrations of fiber-based mode-locked lasers confirm ultrafast pulse generation, with graphene operating as a passive self-amplitude modulator placed inside the fiber laser’s cavity and hosted between two standard fiber connectors, as shown in Fig. 1. Alternatively, graphene’s SA has been exploited in fiber-based arrangements using either the evanescent optical field interaction with a gated graphene layer or wrapping graphene around a microfiber for all-optical modulation attributed to SA.

Focusing on SA-enabled components for lasing modules, GRAINS will exploit devices borrowed from the fiber-laser world, transforming, and incorporating them into integrated photonic platforms, as conceptually illustrated in Fig. 2. In the latter figure a Si-photonic pulsed source is envisaged in a Fabry-Perot type standing-wave resonator; the gain medium is a dye-doped organic material cladding, while graphene is placed on top of the right Bragg reflector acting as the Saturable Absorber Mirror (GSAM).

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Fig. 1: Fiber laser where a graphene flake housed between two connectors is used to passively mode-lock the fiber cavity. 
(Click on image to enlarge)

Fig. 2: Concept of a Si-photonic pulsed source implemented with a Fabry-Perot type standing-wave resonator; the gain medium is a dye-doped organic material cladding, while graphene is placed on top of the right Bragg reflector. 
(Click on image to enlarge)