PSTD analysis of optical phase conjugation
Date Issued
2012
Date
2012
Author(s)
Huang, Yi-An
Abstract
In the thesis, we show the development of a simulation tool for optical phase conjugation (OPC) phenomenon. We use the pseudospectral time-domain (PSTD) algorithm to implement our OPC simulation. The PSTD simulation is computationally efficient and memory-economic, enabling accurate modeling of the OPC phenomenon of light penetration through large-scale turbid media.
In PSTD algorithm, however, we have a few problems to cope with, including the construction of a light source and an OPC mirror. To avoid the hard-source artificial reflection, a light source is implemented by soft sources. Also, the Gibbs’ phenomenon causes overshoots on the boundary of a soft source. Therefore, we broaden the width of the soft source to reduce the spatial frequency of the input signal. The overshoot noises are eliminated. With these problems solved, the PSTD simulation of OPC phenomenon is robust and error-controllable.
The PSTD simulation of OPC phenomenon is divided into two parts as the OPC experiment: the forward and playback scenarios. In the forward scenario, we record the phasor of light scattered by turbid media; in the playback scenario, we emit the recorded scattered light with its phase conjugated and Poynting vectors inverted. The phase-conjugated light penetrates through the turbid media and focus at the location of the original source.
By increasing the simulation scale, we can apply the OPC phenomenon to a macroscopic, biological tissue. To speed up the macroscopic simulation, we develop an PSTD simulation of OPC phenomenon with parallel computation, distributing the computation work and data to different CPUs and computer memories, respectively. The time consumption of the OPC simulation reduces as the number of CPUs increases.
We develop an efficient simulation technique to model the OPC phenomenon using the PSTD analysis. In the simulation, the phasors of light scattered by turbid media are recorded by the OPC mirror. With these phasors, the OPC mirror emits phase-conjugated light. The light penetrates through the turbid media and focuses at where it originated. As for future applications, our goal is to deliver light to arbitrary location within the turbid media by the OPC simulation. With the progressive tomography of a biological tissue, the development of a non-invasive OPC treatment is promising.
Subjects
pseudospectral time-domain (PSTD) algorithm
optical phase conjugation (OPC)
parallel computing technique
Type
thesis
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