定义：
调制激光光束相位的装置。

相位调制器是可以控制激光光束相位的光学调制器。 
常用的相位调制器类型为基于普克尔斯盒的电光调制器和液晶调制器，还可以利用热致光纤折射率变化或者长度变化，或者通过拉伸改变长度。在集成光学领域中用到各种相位调制器，其中调制的光在波导中传播。 
相位调制器的重要性质包括： 

• 相位调制的大小（决定了调制指数和边带的相对功率） 
• 需要的驱动电压 
• 调制带宽（调制频率范围），电光调制器为GHz量级，采用热效应或者液晶材料的器件则远小于该值 
• 器件的工作带宽 
• 器件孔径，限制了调制光束的光束半径 
• 器件的外部尺寸 

对于不同类型的相位调制器来说，这些性质差别很大。因此，不同的实际应用情况下需要采用不同的相位调制器。 

应用 
相位调制器应用的例子包括： 

• 在单频激光器的激光器谐振腔中的相位调制器可以用于波长调谐，或者激光器的主动锁模（FM锁模） 
• 对光束的相位调制如果具有适中的调制强度，可以用在激光频率稳定机制中，例如，采用Pound-Drever-Hall方法 
• 在很多采用干涉仪进行光谱测量装置中需要使用相位调制器，通常使用周期性的驱动信号 
• 有些测量需要采用频率梳，是将单频光束入射到相位调制器中得到的。这种情况下，相位调制通常需要很强，这样可以得到很多边带。 
• 在光纤通信系统的数据发射器中，相位调制器可以用来解码透射的信息。例如，采用相移键控方法。

Definition: devices for manipulating the phase of a laser beam

More general terms: optical modulators

A phase modulator is an optical modulator which can be used to control the optical phase of a laser beam.

Frequently used types of phase modulators are electro-optic modulators based on Pockels cells, and liquid crystal modulators, but it is also possible e.g. to exploit thermally induced refractive index changes or length changes e.g. of an optical fiber, or induce length changes by stretching. Various kinds of phase modulators are used within the area of integrated optics, where the modulated light propagates in waveguides.

Important properties of phase modulators are:

• the amount of phase modulation which can be achieved (determining the possible modulation index and relative power in optical sidebands)
• the required drive voltage (see the article on Pockels cell drivers)
• the modulation bandwidth (range of modulation frequencies), which can e.g. be many gigahertz for electro-optic modulators, and far less for devices based on thermal effects or using liquid crystal materials
• the optical bandwidth in which the device can be used
• the device aperture, limiting the beam radius of the modulated beam
• the outer dimensions of the device

For different types of phase modulators, such properties vary in huge ranges. Therefore, different kinds of phase modulators are appropriate for different applications.

Phase Modulators with Spatial Control

A special class of phase modulators can not only modulate the optical phase of a beam as a whole, but apply controlled phase changes with a more or less substantial spatial resolution. Such devices are needed in particular for adaptive optics. More clear terms for such devices are spatial light modulator and wavefront modulator.

Applications

Some examples of applications of phase modulators are:

• A phase modulator within a laser resonator of a single-frequency laser can be used for wavelength tuning, or for active mode locking (FM mode locking) of a laser.
• A phase modulation of a beam with moderate modulation strength is often used in laser frequency stabilization schemes, e.g. with the Pound–Drever–Hall method.
• Various kinds of interferometers and setups for spectroscopic measurements require phase modulators, often with a periodic drive signal.
• Some optical metrology applications require frequency combs, generated by sending a single-frequency beam into a phase modulator. In that case, the phase modulation often needs to be strong in order to obtain a large number of optical sidebands.
• In data transmitters of optical fiber communication systems, phase modulators can be used for encoding the transmitted information. An example is the method of phase shift keying.