# Sixty-Nine-Element Voice Coil Deformable Mirror for Visible Light Communication
## 5 Conclusions  
The VCDM has many merits, such as hysteresis free, low voltage, large phase stroke, and so on. However, traditional VCDM has many limitations and factors that hinder its use in visible-light communication systems. In the paper, to design a compact VCDM with high properties, the analytical expressions based on electromagnetic theory are given systematically, which include its parameters such as force, efficiency, and frequency, they guide the design and reasonable optimization of the compact VCDM. The thin mirror of the VCDM is made of polyimide and is coated with a thin layer of evaporated aluminum in order to make it optically reflective. The struts of micro VCAs are installed in the spring fixing plate, and the springs provide micro VCAs with axial stiffness. This structure makes it possible for the VCDM to have a higher operating bandwidth. Based on the multiparameter analysis and finite element analysis using ANSYS, a well-optimized VCDM is obtained with a micro VCA of a diameter of 2 mm and efficiency of 0.032 N/W\({}^{1/2}\). The maximum current of a micro VCA is 0.06 A, which makes the VCDM has excellent thermal stability. The temperature difference of the thin mirror is less than 0.4 degrees Celsius at the maximum current of 0.06 A, and the thermal deformation of the thin mirror is only 12.36 nm. The first resonance frequency of the 69-element compact VCDM is 2045 Hz which is more than three times that of the DM69-25. High wavefront fitting precision with a relatively low coupling coefficient of about 25% and large phase stroke is also demonstrated in the paper. The fitting results of Zernike aberrations show that the wavefront fitting precision of the compact VCDM has increased by 13% compared with a traditional VCDM. The VLC scenario was established, and the results proved that the compact VCDM can improve  
Figure 16: Application of VCDM in VLC system.  
Figure 17: Comparison of coupling coefficients before and after aberration correction.  
the coupling efficiency. The above results indicate that the compact VCDM can satisfy the requirements of optical communication systems. The design and optimization method are also valuable for the design of other kinds of DMs. Our design decreases the development cost and obtains a compact VCDM with high electro-optical performance.  
Conceptualization, Y.H. and L.H.; methodology, Y.H. and L.J.; software, L.J.; validation, Y.H., L.H. and L.J.; formal analysis, X.X.; investigation, L.J.; resources, Q.H.; data curation, J.W. and L.Y.; writing--original draft preparation, L.J.; writing--review and editing, L.H.; visualization, L.J.; supervision, Y.H.; project administration, L.H.; funding acquisition, L.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (No. 61475152, No. 62205127) and the Fund for Key Laboratory of Electro-Optical Countermeasures Test & Evaluation Technology (GKCP2021001).  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors declare no conflict of interest.