We propose a spatial mode generation technology using spatial cross modulation (SCM) for mode division multiplexing (MDM). The most well-known method for generating arbitrary complex amplitude fields is to display an off-axis computer-generated hologram (CGH) on a spatial light modulator (SLM). However, in this method, a desired complex amplitude field is obtained with first order diffraction light. This critically lowers the light utilization efficiency. On the other hand, in the SCM, the desired complex field is provided with zeroth order diffraction light. For this reason, our technology can generate spatial modes with large light utilization efficiency in addition to high accuracy. In this study, first, a numerical simulation was performed to verify that the SCM is applicable for spatial mode generation. Next, we made a comparison from two view points of the coupling efficiency and the light utilization between our technology and the technology using an off-axis amplitude hologram as a representative complex amplitude generation method. The simulation results showed that our technology can achieve considerably high light utilization efficiency while maintaining the enough coupling efficiency comparable to the technology using an off-axis amplitude hologram. Finally, we performed an experiment on spatial modes generation using the SCM. Experimental results showed that our technology has the great potential to realize the spatial mode generation with high accuracy.
We performed an experiment on a 3D display by employing spatial cross modulation (SCM) using a random diffuser and phase-only spatial light modulator (SLM). In our experiment, a 3D object, which is constructed using four 2D images acquired from different spatial positions, is generated and the encoded 3D object is then displayed on the SLM. The different object images are observed when the image sensor is moved to different spatial positions. The experimental results revealed that the SCM method allows the generation of arbitrarily complex amplitude fields with high diffraction efficiency and with almost no speckle noise.
We proposed a new technology for tomographic imaging based on beam diffusion and wavefront reconstruction through digital phase conjugation (DPC). The principle of this technology is highly unique and completely different from that of well-known optical coherence tomography (OCT) because it does not utilize the coherence property of light. In our experiment, it was shown that the depth resolution of smaller than 5μm is obtained when using the objective lens with NA of 0.42. In addition, we achieved the extraction of the information from a specific specimen among several specimens arranged along optical axis.
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