Terahertz pulse shaping using diffractive networks

We present a diffractive network, trained for pulse engineering to shape input pulses into desired optical waveforms. The synthesis of square-pulses with various widths was experimentally demonstrated with 3D-fabricated passive diffractive layers that control both the amplitude and phase profile of the input terahertz pulse across a wide range of frequencies. Pulse-width tunability was also demonstrated by altering the layer-to-layer distances of a diffractive network. Furthermore, the modularity of this framework was demonstrated by replacing part of an already-trained network with newly-trained layers to tune the width of the output terahertz pulse, presenting a Lego-like physical transfer learning approach.