Institute of Post-LED Photonics, Tokushima University

KISHIKAWA Hiroki KISHIKAWA Hiroki
High-capacity optical communication by optical vortexKISHIKAWA Hiroki[Associate Professor]

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High-capacity optical communication by optical vortex

KISHIKAWA Hiroki[Associate Professor]

Division of Next-generation Photonics​ (Core Faculty)

2004 Toyohashi University of Technology, Faculty of Information and Computer Sciences, Graduated
2006 Toyohashi University of Technology, Graduate School of Information and Computer Sciences, Master Course, Graduated
2006-2009 Nomura Research Institute, Researcher
2012 Tokushima Univeresity, Graduate School of Advanced Technology and Science, Doctral Course, Graduated
2012-2015 Nippon Telegraph and Telephone Corporation, NTT Network Innovation Laboratory, Reseracher
2015- Tokushima University, Assistant Professor, Associate Professor (from 2018)
June 2021 Concurrently assigned to our institute

  • Medical Photonics
  • Visible
  • Infrared
  • Terahertz
  • Deep ultraviolet
  • Information Technology
  • Medical
  • Inspection
  • Light source / Sensing
  • etc.
  • Optical fiber communication
  • Optical free-space communication
  • Orbital angular momentum
  • Optical vortex
  • Multiplexing
Research Interests

Multiplexing technology is important for increasing the capacity of optical communications. The optical vortex, which is an optical beam with orbital angular momentum, is composed of optical beams with different orders of rotation direction that are orthogonal to each other, and it is attracting attention because it enables multiplexed communication by placing different data on each of them. Figure 1 shows the spiral phase front that characterize optical vortices.
    It is necessary to maintain the spiral phase structure as much as possible before reaching the receiver for multiplexed communication using optical vortices. In free-space optical wireless communication, the atmospheric refractive index fluctuates both spatially and temporally due to the effects of atmospheric flow, temperature, air pressure, etc. The phase of the passing optical vortex is distorted, making it difficult to maintain the spiral phase structure and determine which order is transmitted.
    In this research, we have been studying a method to evaluate and compensate for the effects of phase fluctuations caused by disturbances in the atmospheric propagation of optical vortices. Figure 2 shows the proposed method of compensation with high speed and high performance using a reference light. In the conventional method, a Gaussian beam, which is an ordinary laser beam, is used as the reference light, which limits the compensation performance. In this study, the compensation performance is improved by using an optical vortex as the reference light and also by introducing a spatial light modulator in the adaptive compensation section.