Application Cases

Experiment Title: Laboratory Coherent Beam Combination Experiment of Fiber Laser Phased Array

Testing Equipment: High Voltage Amplifier, Fiber Laser, Position Sensitive Detector, etc.

Experiment Process:

Figure 1: Schematic Diagram of the Fiber Laser Phased Array System

In the experiment, the voltage control signal output by the SPGD algorithm is sent to the high voltage amplifiers of the PZT-PC and AFOC via the acquisition card to compensate and correct the piston and tilt phase errors in real time. The system algorithm iteration rate can meet the real-time correction demand of dynamic phase errors in the hundreds of Hz range in a laboratory environment, with the phase-locking control iteration rate at 9.8kHz and the tilt control iteration rate at 1kHz. When driving the AFOC, the control voltage output by the algorithm controller is amplified a hundredfold by the high voltage amplifier (HVA) to generate sufficient thrust.

Experimental Results:

Figure 2: Normalized Performance Index Variation Curve

The performance index and far-field long-exposure images of the synthesized beam were collected for 5 seconds in open-loop state, phase-locking control state only, and closed-loop state with both phase-locking and tilt control running simultaneously, and then analyzed. The 15-second normalized performance index curve collected by PD is shown in Figure 2. When the piston and tilt phase errors are not corrected and the system is in open-loop state, the average value (Ave) of the normalized performance index is 0.0182, and the mean square error (MSE) in the open-loop state is 0.0162. Both of these indicators are dimensionless data. A higher Ave indicates better synthesized beam quality, while a higher MSE indicates more noticeable fluctuation in the spot intensity. After 36ms, the system converges through phase-locking control (the convergence time of the SPGD algorithm is defined as the time required for the normalized objective function to reach 90% of the stable value). When the piston phase error is corrected and the system is in phase-locking state, the Ave value increases from 0.0182 to 0.335, and the MSE decreases from 0.0162 to 0.0021, indicating that phase-locking control can enhance the effect of partial coherent combination. After 670ms, both piston and tilt phase errors are corrected, and the Ave value further increases to 0.994. Due to the slight vibration of the fiber end face in the AFOC during tilt control in closed-loop, the MSE slightly rises to 0.0034. Comparing the normalized performance index intensity in these three states, it can be seen that only by correcting both piston and tilt phase errors simultaneously can the energy density in the pinhole reach the highest value in the experiment, achieving efficient coherent combination.

Figure 3: Normalized Long-Exposure Images of Far-Field Spots (a) Open-loop; (b) Phase-Locking Control Only; (c) Closed-Loop

The 5-second long-exposure images of the synthesized beam in the far-field are shown in Figure 3. The corresponding PIB can be obtained by calculating the ratio of the intensity of the main lobe pixels of the synthesized beam to the intensity of all pixels in the far-field image. Figure 3(a) shows the long-exposure image without phase-locking and tilt control in the open-loop state. It can be seen from the figure that there is almost no interference pattern on the camera surface, and the far-field spot is incoherent. At the same time, the energy concentration of the synthesized beam is very low, with an average PIB of only 0.08. Figure 3(b) shows the long-exposure image of the far-field spot when only phase-locking control is executed. It can be seen that partial coherent combination effect appears on the camera target surface, and four side lobes appear around the main lobe of the synthesized beam. At this stage, the average PIB of the synthesized beam is 0.26, which is 0.18 higher than that in the open-loop state. Figure 3(c) is the long-exposure image of the far-field spot after the closed-loop. When the closed-loop state is stable, it can be seen that there are seven clear spots in the far-field. At this time, the intensity of the main lobe of the synthesized beam is significantly higher than the other two states, with an average PIB of 0.49, which is the highest level in the experiment.

High Voltage Amplifier Recommendation: ATA-7020

Figure: Specifications of the ATA-7020 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.