Fig. 1. Schematic diagram of the super-resolution precision phase shift function of the digitally coding needle meta-chip. (a) Schematic of the meta-chip with 8 meta-structure units. (b) Schematic of a single needle meta-structure unit, whose detailed dimensions are described in Appendix A.1.

Fig. 2. Simulation results of a single needle meta-structure unit. (a) S21 parameter and (b) phase of a single meta-structure unit change as the diode switches between “0” and “1” states. (c)–(e) With or without the enhancing-branch, (c) the electric field strength, (d) the overall current distribution, and (e) the local current distribution of the diode are varied after switching between the “0” and “1” states.

Fig. 3. Nonlinear phase superposition of the needle meta-structure units. (a), (b) Charge stacking at the tips of the meta-structure allows the electric fields to couple with other meta-structures and affect the resonances. (c)–(f) The electric fields of the encoded four needle meta-structure units in the sequences “0000,” “0101,” “1100,” and “0110,” where the sequence “0000” serves as the reference. (g), (h) The amplitude and phase variations for the four coding sequences.

Fig. 4. Simulation with 256 coding sequences of the 8-unit digitally coding needle meta-chip. The simulated (a) phase shift and (b) S21 parameter of the 8-unit meta-chip. Phase modulation of over 180° was achieved at 213–227 GHz utilizing 256 coding sequences.

Fig. 5. Experiments with 256 coding sequences of the digitally coding needle meta-chip. (a) Experimental schematic of the packaged meta-chip. (b), (c) Photographs of the meta-chip. The experimental (d) phase shift and (e) S21 parameter for the 256 sequences of 8-unit meta-chip, which are well consistent with the simulation.

Fig. 6. Results of super-resolution precision coding phase shifts using the digitally coding needle meta-chip. (a)–(c) Phase shifts of (a) 11.25°, (b) 5.625°, and (c) 3° accuracy were achieved at 213.2 GHz. (d)–(f) Phase shifts of (d) 11.25°, (e) 5.625°, and (f) 3° accuracy were achieved at 220 GHz, with all mean absolute errors less than 0.623°. (g)–(i) Phase shifts of (g) 11.25°, (h) 5.625°, and (i) 3° accuracy at 226.7 GHz.

Fig. 7. Detailed information of the device. (a) Schematic of the layered composition of the GaAs Schottky diode. (b) Diode model for simulation. (c) Detailed dimensions of the needle meta-structure unit.

Fig. 8. Photos and schematic diagram of terahertz wave S21 parameter and phase measurement.