Ultrafast Three-Dimensional Serial Time-Encoded Imaging With High Vertical Resolution

A three-dimensional (3-D) serial time-encoded imaging system with a high vertical resolution based on microwave phase or frequency detection is proposed and experimentally demonstrated. A regular serial time-encoded imaging system can perform ultrafast two-dimensional imaging in which the reflectivity of a sample surface is represented by the intensity change of a microwave waveform. By adding one reference channel to form a Mach-Zehnder interferometer structure, the depth information of the sample surface is encoded as the microwave phase or frequency change, thus, 3-D imaging is implementable by extracting the phase or frequency information. In the proposed approach, the intensity and phase or frequency information are extracted based on Hilbert transform from the microwave waveform. The approach is experimentally evaluated. The imaging of a silicon chip as a sample is performed. A vertical resolution better than 130 nm and a depth measurement range greater than 2 mm are demonstrated.