Silicon Photonic Modulator Linearity and Optimization for Microwave Photonic Links

We experimentally demonstrate the influence of the DC Kerr effect in silicon photonic Mach-Zehnder modulators (MZMs) and the ability to optimize the combined effects of plasma-dispersion and DC Kerr to achieve linear transfer characteristics and thus demonstrate suitability for microwave photonic links and digital modulation formats such as multilevel pulse amplitude modulation. PN and PiN doped modulators were fabricated through AIM Photonics. Intermodulation distortion products are demonstrated to have reverse bias and MZM bias dependencies advantageous for highly linear operation. The spurious-free dynamic range, gain, and noise figure are optimized by choice of phase modulator reverse bias and MZM bias point yielding analog links with spurious-free dynamic ranges greater than 100 dB·Hz
^2/3
. The silicon modulators demonstrate link spurious-free dynamic ranges on par with a commercial lithium niobate modulator. Furthermore, we show that simulations including the DC Kerr effect can reliably predict device performance although direct prediction of analog link metrics remains challenging, and final tuning of the device operating conditions is required to achieve optimum performance.