The role of thin film of lithium niobate in electro-optic modulator

The role of thin film of lithium niobate in electro-optic modulator
From the beginning of the industry to the present, the capacity of single-fiber communication has increased by millions of times, and a small number of cutting-edge research has exceeded tens of millions of times. Lithium niobate played a great role in the middle of our industry. In the early days of optical fiber communication, the modulation of the optical signal was directly tuned on the laser. This mode of modulation is acceptable in low bandwidth or short distance applications. For high-speed modulation and long distance applications, there will be insufficient bandwidth and the transmission channel is too expensive to meet the long distance applications.
In the middle of optical fiber communication, the signal modulation is faster and faster to meet the increase of communication capacity, and the optical signal modulation mode begins to separate, and different modulation modes are used in short-distance networking and long-distance trunk networking. Low-cost direct modulation is used in short-distance networking, and a separate “electro-optic modulator” is used in long-distance trunk networking, which is separated from the laser.
Electro-optic modulator uses Machzender interference structure to modulate signal, light is electromagnetic wave, electromagnetic wave stable interference needs stable control frequency, phase and polarization. We often mention a word, called interference fringes, light and dark fringes, bright is the area where electromagnetic interference is enhanced, dark is the area where electromagnetic interference causes energy to weaken. Mahzender interference is a kind of interferometer with special structure, which is the interference effect controlled by controlling the phase of the same beam after splitting the beam. In other words, the interference result can be controlled by controlling the interference phase.
Lithium niobate this material is used in optical fiber communication, that is, it can use the voltage level (electrical signal) to control the phase of the light, to achieve the modulation of the light signal, which is the relationship between the electro-optical modulator and lithium niobate. Our modulator is called an electro-optic modulator, which needs to consider both the integrity of the electrical signal and the modulation quality of the optical signal. The electrical signal capacity of indium phosphide and silicon photonics is better than that of lithium niobate, and the optical signal capacity is slightly weaker but can also be used, which creates a new way to seize the market opportunity.
In addition to their excellent electrical properties, indium phosphide and silicon photonics have the advantages of miniaturization and integration that lithium niobate does not have. Indium phosphide is smaller than lithium niobate and has a higher integration degree, and silicon photons are smaller than indium phosphide and have a higher integration degree. The head of lithium niobate as a modulator is twice as long as indium phosphide, and it can only be a modulator and cannot integrate other functions.
At present, the electro-optical modulator has entered the era of 100 billion symbol rate, (128G is 128 billion), and lithium niobate has once again put on the battle to participate in the competition, and hopes to lead this era in the near future, taking the lead in entering the 250 billion symbol rate market. For lithium niobate to recapture this market, it is necessary to analyze what indium phosphide and silicon photons have, but lithium niobate does not. That’s electrical capability, high integration, miniaturization.
The change of lithium niobate lies in three angles, the first Angle is how to improve electrical capability, the second Angle is how to improve integration, and the third Angle is how to miniaturize. The solution to these three technical angles requires only one action, that is, to thin film the lithium niobate material, take out a very thin layer of lithium niobate material as an optical waveguide, you can redesign the electrode, improve the electrical capacity, improve the bandwidth and modulation efficiency of the electrical signal. Improve electrical ability. This film can also be attached to the silicon wafer, to achieve mixed integration, lithium niobate as a modulator, the rest of the silicon photon integration, silicon photon miniaturization ability is obvious to all, lithium niobate film and silicon light mixed integration, improve integration, naturally achieved miniaturization.
In the near future, the electro-optical modulator is about to enter the era of 200 billion symbol rate, the optical disadvantage of indium phosphide and silicon photons is becoming more and more obvious, and the optical advantage of lithium niobate is becoming more and more prominent, and the lithium niobate thin film improves the disadvantage of this material as a modulator, and the industry focuses on this “thin film lithium niobate”,that is, the thin film lithium niobate modulator. This is the role of thin film lithium niobate in the field of electro-optical modulators.