DAC-less PAM-4 generation in the O-band using a silicon Mach-Zehnder modulator

Recent Progress in Silicon-Based Slow-Light Electro-Optic Modulators

As an important optoelectronic integration platform, silicon photonics has achieved significant progress in recent years, demonstrating the advantages on low power consumption, low cost, and complementary metal–oxide–semiconductor (CMOS) compatibility. Among the different silicon photonics devices, the silicon electro-optic modulator is a key active component to implement the conversion of electric signal to optical signal. However, conventional silicon Mach–Zehnder modulators and silicon micro-ring modulators both have their own limitations, which will limit their use in future systems. For example, the conventional silicon Mach–Zehnder modulators are hindered by large footprint, while the silicon micro-ring modulators have narrow optical bandwidth and high temperature sensitivity. Therefore, developing a new structure for silicon modulators to improve the performance is a crucial research direction in silicon photonics. Meanwhile, slow-light effect is an important physical phenomenon that can reduce the group velocity of light. Applying slow-light effect on silicon modulators through photonics crystal and waveguide grating structures is an attractive research point, especially in the aspect of reducing the device footprint. In this paper, we review the recent progress of silicon-based slow-light electro-optic modulators towards future communication requirements. Beginning from the principle of slow-light effect, we summarize the research of silicon photonic crystal modulators and silicon waveguide grating modulators in detail. Simultaneously, the experimental results of representative silicon slow-light modulators are compared and analyzed. Finally, we discuss the existing challenges and development directions of silicon-based slow-light electro-optic modulators for the practical applications.

Analysis of a SiGe Mach-Zehnder modulator for 400G data communication

In this paper, the performance of a silicon (Si) Mach-Zehnder modulator (MZM) is enhanced by implanting germanium (Ge) on Si, forming a graded Si-Ge (SiGe) core. A process simulation study is done, and the effect of substrate temperature, implantation energy, and pre-amorphization on the Ge composition and developed in-plane stress is observed. The dependence of active dopant concentration and defect-cluster formation on the annealing conditions is discussed. A comparison of the process simulated SiGe phase shifter with a Si phase shifter shows 2.27× higher phase shift at -5V for 1550 nm wavelength of operation. A dual-arm drive with quadrature operation is investigated for both SiGe and Si MZMs. A traveling-wave electrode is used to enhance the modulation bandwidth. The SiGe MZM achieves better performance in terms of modulation bandwidth, modulation speed, fiber transmission length, energy per bit, and dispersion tolerance compared to the Si MZM. The dual-arm driven SiGe MZM can achieve 62 Gbps error-free 2 km fiber transmission with energy per bit of 1.92 pJ/bit and 3 dB bandwidth of 62.8 GHz at -2.5V bias using 3V_pp on-off keying modulation.