Application Cases

Experiment Title: Dual-Channel Pulse Coherent Synthesis System and Active Phase Control System

Testing Equipment: Voltage Amplifier, Photodetector, Low Pass Filter, PZT, etc.

Figure 1: Schematic Diagram of the Active Phase Control System

Experiment Process:

The HC detector in the system consists of a wave plate, a PBS, and two photodetectors. The photodetectors are placed at the s-polarized and p-polarized ends of the PBS to detect the intensity signals. The differential amplifier extracts the error signal containing the phase information of the optical path difference from these intensity signals. This error signal is filtered by a low pass filter and then fed back through a PI2D phase control circuit. The feedback signal is amplified by a voltage amplifier to drive and control the PZT. The structural diagram of the active phase control system is shown in Figure 1. The PZT used in the system has a control precision of 0.28μm/V, can withstand a maximum voltage of 150V, and has a maximum elongation of 42μm. By adjusting the bias voltage of the phase control circuit, the phase difference between the two pulses can be fine-tuned. When external environmental changes or noise disturbances affect the optical path difference, the phase difference detected by the HC polarization detector changes. The feedback signal then adjusts the driving voltage of the PZT to compensate for the phase of the optical path difference.

Figure 2: Power Fluctuations Measured by the Detector at the Zero Optical Path Difference Position Before and After Locking

In the experiment, the power changes of the synthesized light before and after synthesis were first measured at a position where the optical path difference was close to zero. By fine-tuning the bias voltage of the control circuit, the system's synthesis efficiency was maximized. At this point, it was considered that the optical path difference was zero, and the phase locking effect is shown in Figure 2. When verifying the performance of the phase locking system, the output power of the amplifier was relatively low, so there was no need to activate the water cooling system for heat dissipation. The influence of external environmental disturbances on the system was relatively small.

Experimental Results:

Figure 3: Relationship Between Optical Path Difference and System Synthesis Efficiency in the Locked State

To verify the performance of the phase locking system, a certain optical path difference was generated by adjusting the position of the electric delay line. Figure 3 describes the changes in system synthesis efficiency under different optical path differences.

When the optical path difference was within 10μm, the system synthesis efficiency was basically maintained above 90%. When the optical path difference increased to 25μm, the system synthesis efficiency dropped to 80%. Since the system output power was relatively low at this time, the decrease in synthesis efficiency was mainly due to the optical path mismatch. At the same time, the movement of the electric fiber delay line would have a certain impact on the system coupling, thereby affecting the quality of the output light spot. Therefore, spatial light field position mismatch would also lead to some loss of synthesis efficiency. When the optical path difference exceeded 60μm, the system synthesis efficiency dropped to 60%. At this point, the optical path difference mismatch was the main factor leading to the decrease in synthesis efficiency, and the impact of spatial light field mismatch on system synthesis efficiency was relatively small. When the optical path difference exceeded 80μm, the actuator could no longer compensate the optical path difference between the two amplifiers within the coherent length range. The active phase control system could not compensate for the optical path difference, and the system could hardly achieve coherent output of the synthesized light. At this point, the optical path difference had exceeded the control range of the phase control system. Therefore, the control range of the active phase control system is approximately ±20μm. Within this range, the phase control system can optimize the synthesis efficiency. Beyond this range, the system can still achieve a certain degree of phase control, but the synthesis efficiency will decrease and complete phase compensation cannot be achieved. Based on this phase control system, compensatory control of the electric delay line can achieve phase locking over a wider compensation range.

Voltage Amplifier Recommendation: ATA-2088

Figure: Specifications of the ATA-2088 High Voltage Amplifier

This material is compiled and released by Aigtek Antai Electronics. For more case studies and product details, please continue to follow us. Xi'an Aigtek Antai Electronics has become a widely recognized supplier of instruments and equipment with a broad product line and considerable scale in the industry. Sample machines are available for free trial.