Fig. 1: Device configuration and working mechanism.
From: Broadband nonlinear modulation of incoherent light using a transparent optoelectronic neuron array
a A photo of the finished transparent optoelectronic neuron array (marked by the red box, polarizers not included). The 100 × 100-pixel array covers 1 cm × 1 cm area. b Diagram of an array with all neurons connected to the common Vdd and GND electrodes. A globally wired metal electrode (black lines in Fig. 1b and gold wires in microscope images in Fig. 2b) is fabricated with lithography and applies Vdd to all pixels in parallel, as also illustrated in Fig. 1c. Each neuron responds independently to the local illumination intensity (rendered as pink to dark brown input patterns) to provide the corresponding nonlinear transmissions. c The equivalent circuit of the neuron pixels sharing common Vdd and GND. The red arrows represent the local incident light. d Self-amplitude modulation of light in the TPT-LC optoelectronic neuron array. Under low light illumination (left pixel), the TPT is highly resistive, most voltage drop occurs on the TPT. Thus, the voltage drop and electrical field across the LC are small (blue thin dashed line represents a weak field). The LC is unperturbed and remains transmissive. The equivalent circuit is shown on the left side, where the TPT is highly resistive and highlighted in red. At high input optical power, the TPT becomes conductive (marked in green in the equivalent circuit on the right side), so most voltage drops across the LC layer (thick solid line represents a strong field), shutting off the optical transmission. e Schematic illustration of a single-pixel structure disassembled by layers. The light is incident from the bottom, passing through the first polarizer (P1) and then through a glass substrate and a TPT made with MoS2 VDWTF. An SU-8 insulating layer isolates an ITO electrode from the TPT channel. The ITO electrode is only locally connected to a single TPT and isolated from nearby pixels. The liquid molecules are anisotropic, rendered as ellipsoids. The molecules gradually rotate their 3D orientations to form a spiral pattern, rotating the incident light’s polarization. A polyvinyl alcohol (PVA) alignment layer controls the LC molecule orientation at the PVA-LC interface. Another orthogonal alignment layer is on top of the LC layer, so the LC molecules gradually twist in the cell. Electrical current flows through the TPT to the ITO layer in the middle, then to the top ITO layer, which is grounded. The LC cell also works as an optically inactive resistor.
