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What is an Optical Phase Modulator?
An optical phase modulator is a photonic device that changes the phase of an optical signal in response to an applied electrical or optical control signal, without directly changing its optical power. Phase modulation is widely used in optical communications, sensing, interferometry, and quantum photonics.
Electro-optic phase modulators commonly use materials such as lithium niobate (LiNbO₃) to achieve fast and precise control of the optical phase.
HOW an Optical Phase Modulator Works
An optical phase modulator works by changing the optical path experienced by light, causing its phase to shift according to the applied control signal. In electro-optic modulators, this is typically achieved by changing the material's refractive index.
Electrical signal applied
A voltage is applied to the modulator electrodes, generating an electric field in the electro-optic material.
Refractive index change
The electric field modifies the refractive index, changing the optical phase accumulated as the light propagates through the device.
Phase modulation
The resulting phase shift follows the applied electrical signal, allowing precise encoding or control of the optical wave.
