不同張角下精確與常數振幅光學相位共軛於散射介質中波前回聚效果之模擬分析

Abstract

本研究以時域擬譜法（Pseudospectral Time-Domain Method, PSTD）模擬大尺度電磁波傳播行為，並結合光學相位共軛（Optical Phase Conjugation, OPC）技術探討散射介質中有限相位共軛鏡（Phase Conjugate Mirror, PCM）張角與振幅資訊對波前回聚焦品質之影響。研究比較精確振幅（Exact-Amplitude, EA）OPC與常數振幅（Constant-Amplitude, CA）OPC在不同散射體數量及不同PCM張角下之回聚焦表現，分析正向參考波前與逆向回聚波前之差異，以探討有限PCM張角與散射體數量對兩種OPC技術的影響。研究結果顯示，EAOPC整體仍具有較低重建誤差，但是隨著散射體數量增加，CAOPC與EAOPC之間差距逐漸縮小。進一步比較不同張角後發現，較大張角通常具有較理想回聚焦效果，但在CAOPC條件下，90° 張角能夠達到較佳的波形重建表現。因此，有限張角CAOPC可作為兼顧系統簡化與重建品質的設計參考，並為未來生醫光學中散射介質之波前控制與OPC系統應用提供基礎。

This study employs the pseudospectral time-domain (PSTD) method to simulate large-scale electromagnetic wave propagation and applies optical phase conjugation (OPC) to investigate the effects of finite phase conjugate mirror (PCM) angular span and amplitude information on wavefront refocusing in scattering media. Exact-amplitude (EA) OPC and constant-amplitude (CA) OPC are compared under different numbers of scatterers and different PCM angular spans. The differences between the forward reference wavefront and the backward refocused wavefront are analyzed to evaluate how the finite PCM angular span and the number of scatterers affect the refocusing performance of the two OPC approaches. The simulation results show that EAOPC generally yields lower reconstruction errors than CAOPC. However, as the number of scatterers increases, the performance gap between CAOPC and EAOPC gradually decreases. Further comparison among different angular spans indicates that larger angular spans generally provide better refocusing performance. Notably, under CAOPC conditions, the 90° angular span shows better waveform reconstruction performance. These findings suggest that finite-span CAOPC can serve as a design reference for balancing system simplification and reconstruction quality, and may provide a basis for future wavefront control in scattering media and OPC system applications in biomedical optics.