Fig. 1: Low-loss multi-bit electrically driven photonic random-access memory (P-RAM) on-chip.

a 3D schematic of a planarized waveguide with a 30 nm GSSe layer on top of the waveguide and multiple parallel double-sided tungsten–titanium microheaters. b Detailed optical image of GSSe on waveguide with discrete double-sided heaters (c) Zoom-in detailed image of in (b). Discrete double-sided heaters are arranged along the waveguide over the GSSe film. d Detailed optical image of GSSe strip array with single-sided heaters for measurement of high-order bit memory. e Experimentally obtained (ellipsometry) optical properties of GSSe film. Absorption coefficient contrast (imaginary part of the refractive indices of amorphous and crystalline alloys) of GSSe for crystalline and amorphous states at 1550 nm. The GSSe shows a strong unity ∆k, while simultaneously showing a small, induced loss at the amorphous state. f Normalized electric field mode profile of hybrid Si-GSSe waveguide for TE and TM mode with 0.54 dB/µm absorption coefficient between amorphous and crystalline state. The effective refractive index of k in the amorphous state is \({-2.18\times 10}^{-5}\) which leads to an exceedingly small unit of passive absorption of the memory. g 2D cross-section schematic of the lateral thermoelectric switching configuration to optimize the heater resistance for max heating efficiency with minimum optical scattering. h Cross-section SEM image of the device