Linear Optical Modulators for Prospective Communications at the 2 {\mu}m Waveband

TL;DR

This paper introduces the first linear optical modulator at 2 μm, achieving high spurious free dynamic range and bandwidth, crucial for advanced communication applications like 5G and coherent transmission.

Contribution

It develops the first 2 μm ring-assisted Mach-Zehnder modulator demonstrating high linearity and bandwidth, addressing a key gap in silicon photonics for this waveband.

Findings

Spurious free dynamic range up to 95 dB.Hz^2/3

Bandwidth exceeding 17.5 GHz

Modulation efficiency from 0.70 to 1.25 V.cm

Abstract

The 2 {\mu}m waveband is an area that could have significant technological consequences, with applications ranging from spectroscopy, LIDAR and free-space communications. The development of the thulium-doped fiber amplifier, hollow-core photonic bandgap fiber and 2 {\mu}m GaSb-based diode lasers has highlighted the ability of the waveband in alleviating the fiber capacity crisis in the incumbent communication infrastructure. The above has initiated vibrant development in the silicon photonic-space at 2 {\mu}m, where the area is capable of enabling highly-integrated photonic circuits, and potentially at low-cost and high-volumes. However, as of now, modulator linearity at 2 {\mu}m has not been addressed. The metric, as characterized by spurious free dynamic range is imperative for numerous applications such as RF photonic links for 5G and digital analog transmission in coherent communications. The development of linear optical modulators will be crucial in bringing these applications to the 2 {\mu}m. In view of that, this work is the first to address modulator linearity at the 2 {\mu}m, where the ring-assisted Mach-Zehnder modulator is developed, indicating spurious free dynamic range as high as 95 dB.Hz^2/3. It is found that that modulator spurious free dynamic range has a strong dependence on modulator bias voltage where it impacts the linearity of the transfer function in which the input RF signal is applied upon. The demonstrated modulator indicates favorable performance within silicon photonic modulators developed at 2 {\mu}m with bandwidth exceeding 17.5 GHz and modulation efficiency ranging from 0.70 to 1.25 V.cm.