Optical phase modulation based on PZT piezoelectric ceramics

With the production technology and the continuous expansion of applications, PZT piezoelectric ceramics have been widely entered into people's vision, and their popularity is also rising.

PZT piezoelectric ceramics have the inverse piezoelectric effect, that is, the micro displacement of the corresponding voltage signal can be generated under the applied voltage signal, and it has the characteristics of high resolution and micro-second response speed, which meets the accuracy of optical phase modulation. PZT piezoelectric ceramic phase shifter is also the main component of various interferometers, and its accuracy of piezo ceramic disc will directly affect the measurement accuracy of the interferometer.

  According to the difference of interference optical path, the number and types of PZT piezoelectric ceramics used are different, generally can be divided into single and multi-branch, and according to different usage scenarios of customers, the core will provide a variety of phase modulation / phase shifted piezoelectric ceramic solution. When optical fiber is used as the propagation medium of light, such as fiber differential interferometer, tunable fiber laser, etc., the phase of light will change with the propagation length. For example, when an optical fiber is wound on a PZT piezoelectric ceramic, when a voltage signal is applied, the piezoelectric ceramic is slightly deformed, thereby changing the length and refractive index of the optical fiber wound on the piezoelectric ceramic. When the piezo ceramic cylinder pipe undergoes periodic micro-deformation, the fiber length changes periodically, and the phase of the propagating light also changes periodically. For this scenario, the types of optional PZT piezoelectric ceramics are very diverse, affected by many factors such as size, delay time, and adjustment methods.

Piezoelectric fiber stretcher

For this situation, fiber stretch expander can be used, which has two versions, both with fiber winding groove, the fiber can be directly wound in the groove, and the length of the wound fiber can reach 100 meters the above. Its displacement range is large, and the radial displacement can reach 80μm, which can greatly reduce the driving voltage and still produce a large displacement. For example, at 10V, the radial displacement can still reach more than 5μm.

Hollow piezoelectric ceramic stack

Another way is to use a hollow piezoelectric ceramic stack, which deforms along the length and has a through hole in the center. Through the periodic elongation deformation of the piezoelectric ceramic, the length of light propagation can be periodically changed, thereby changing the phase of light. This kind of piezoelectric ceramic can produce displacement >1.5μm under 15V voltage, and basically eliminate the negative effects caused by the voltage signal.

piezo ceramics piezoelectric transducer has a dimensional tolerance of ±0.01mm and a flatness of up to ±5μm, which is very suitable for phase modulation of fiber optics and can guarantee the accuracy of interferometers.

The frequency and amplitude of the output light intensity of the fiber interferometer have a linear relationship with the frequency and magnitude of the voltage signal applied to the PZT piezoelectric ceramic. An interferometer using a hollow piezoelectric ceramic optical phase modulator has very high sensitivity and is very suitable for monitoring vibration sources in the external environment, as well as monitoring the vibration frequency and amplitude of the vibration source.

Tube shape piezoelectric ceramic tube

Another way is to use piezoelectric ceramic tubes/rings. It produces expansion and contraction movements in the radial direction. Under the action of the periodic voltage signal, the piezoelectric ceramic tube produces a periodic expansion movement, which causes the length and refractive index of the optical fiber wound on the outer diameter surface to change periodically, thereby periodically changing the phase of the transmitted light.

Piezoelectric phase shifters are used in large-diameter interferometers. The principle is the same, and large-diameter interferometers are also mentioned here. For the large diameter horizontal horizontal optical path of the Fizeau interferometer, the reflector it uses is generally a heavier spherical lens, and its measurement process is by adjusting the position of the reflector. It is difficult for a single PZT piezoelectric ceramic to meet the requirements, so generally multiple PZT piezoelectric ceramics are used internally, evenly distributed around a concentric circle.

Large-diameter interferometers generally have larger loaded lenses and require larger central through holes. For this application requirement, the core can custom design PZT piezoelectric phase shifters according to the structure of the interferometer, such as P77 series piezoelectric phase shifters. It has a bearing capacity of up to 15kg when placed upright, 5kg when placed horizontally, and 10kg when placed upside down, and the central clear aperture can be arbitrarily selected from φ36 to φ260mm, and can be customized for larger apertures and larger loads. At present, the stroke of the standard product is 6μm, 20μm, 50μm, etc. This kind of piezoelectric phase shifter is very suitable for laser interferometer, used to detect the flatness of lenses, etc.