The Technology
Silicon Integrated electro-optical (EO) modulators are essential for insertion the information into the optical channel in high-speed optical communication technology. Further applications are optical sensors and guiding high frequency microwave signals by optical wave carriers. Device footprint, driven voltage, modulation depth (Extinction Ratio/ER) and modulation speed (modulation Band Width / BW) are the main measures of the component quality performance.
There are 2 technologies for modulators – Mach-Zehnder Interferometer (MZI), which suffers from large length and the necessity of velocity matching between the electrical driven waves to optical carrier wave, and it’s alternative – microring modulators. However, microring modulators with the required modulation depth and bandwidth for today’s evolving optical communication could not be realized using resonance shifting configuration. Also, modulation is not linear enough to be used in analog modulators. In addition, in current microring modulators, the modulation depth is limited and the cavity optical energy gradually decays with the modulation duration and couples into the output straight waveguide.
The new EO Microring Modulator based on coupling strength altering method. It has two different optical inputs (two straight waveguides), when the amount of optical energy coupled from each one into the ring (coupling strength) could be controlled separately – modulating the two inputs simultaneously by appropriate electrical signals, the required response is obtained at specific output waveguide.
Advantages
- Allows continuous modulation (without distortions due to “memory effect” of the resonator)
- Allows linear wide bandwidth modulation – fast and effective analog modulation
- Significantly higher modulation bandwidth
- No optical energy decay
- The extinction Ratio which is not limited in principle by the Q-factor of the cavity
Applications and Opportunities
- On-chip photonics
- Optical communication
- Optical sensing
- Extremely wide RF modulation frequency range (for example for radar electronic warfare, remote antennas)
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