Abstract

We experimentally demonstrate a THz integrated circuit with a pixel-array-based orbital-angular-momentum (OAM) mode converter for the generation and multiplexing of multiple data-carrying OAM beams. The integrated device consists of (i) two coupling spikes, which serve as inputs and can couple THz signals from hollow metallic waveguides to the device; (ii) two mode expansion structures, which expand the mode profiles from the waveguide inputs to match the OAM mode converter; and (iii) a 3.6 × 3.6 mm² pixel-array-based OAM mode converter, which vertically emits and multiplexes two free-space THz data-carrying OAM beams with different mode orders. The generated OAM order depends on the corresponding input port. Two different designs of the integrated OAM emitters show the generation and multiplexing of (a) OAM +1 and –1, and (b) OAM +1 and –2 at the center frequency of ∼ 0.317 THz. Crosstalk lower than –15 dB between the OAM modes can be achieved. Specifically, the OAM +1/–1 emitter has a 3-dB power bandwidth of ∼15 GHz. Using the OAM +1/–1 emitter for a free-space link at a 0.317-THz carrier frequency, we experimentally demonstrate 20-Gbit/s quadrature-phase-shift-keying (QPSK) transmission by multiplexing OAM +1 and –1. Compared to a single-beam transmission, the multiplexed link induces a ∼1-dB signal-to-noise ratio (SNR) penalty at the bit error rate (BER) of 3.8×10⁻³.

Demonstration of generating a 100 Gbit/s orbital-angular-momentum beam with a tunable mode order over a range of wavelengths using an integrated broadband pixel-array structure

Hao Song, Huibin Zhou, Kaiheng Zou, Runzhou Zhang, Kai Pang, Haoqian Song, Amir Minoofar, Xinzhou Su, Nanzhe Hu, Cong Liu, Robert Bock, Shlomo Zach, Moshe Tur, and Alan E. Willner
Opt. Lett. 46(19) 4765-4768 (2021)

“Hiding” a low-intensity 50 Gbit/s QPSK free-space OAM beam using an orthogonal coaxial high-intensity 50 Gbit/s QPSK beam

Haoqian Song, Ahmed Almaiman, Hao Song, Zhe Zhao, Runzhou Zhang, Kai Pang, Cong Liu, Long Li, Karapet Manukyan, Shlomo Zach, Nadav Cohen, Moshe Tur, and Alan E. Willner
Appl. Opt. 59(24) 7448-7454 (2020)

Orbital angular momentum vector modes (de)multiplexer based on multimode micro-ring

Shimao Li, Zhichao Nong, Xiong Wu, Wen Yu, Mingbo He, Charalambos Klitis, Yuntao Zhu, Shengqian Gao, Jie Liu, Zhaohui Li, Liu Liu, Marc Sorel, Siyuan Yu, and Xinlun Cai
Opt. Express 26(23) 29895-29905 (2018)

Free-space coherent optical communication with orbital angular, momentum multiplexing/demultiplexing using a hybrid 3D photonic integrated circuit

Binbin Guan, Ryan P. Scott, Chuan Qin, Nicolas K. Fontaine, Tiehui Su, Carlo Ferrari, Mark Cappuzzo, Fred Klemens, Bob Keller, Mark Earnshaw, and S. J. B. Yoo
Opt. Express 22(1) 145-156 (2014)

Turbulence mitigation of four mode-division-multiplexed QPSK channels in a pilot-assisted self-coherent free-space optical link using a photodetector array and DSP-based channel demultiplexing

Huibin Zhou, Hao Song, Xinzhou Su, Yuxiang Duan, Kaiheng Zou, Runzhou Zhang, Moshe Tur, and Alan E. Willner
Opt. Lett. 49(5) 1209-1212 (2024)