KEYWORDS: Polarization, Laser processing, Spatial light modulators, Laser systems engineering, Digital Light Processing, Internet of things, Holography, Phase shift keying, Optical signal processing, Manufacturing
The arbitrary dynamic control of both amplitude and polarization distributions is attracting strong interest in laser processing field to manage the quality and to collect valuable polarization characteristics of processing materials in smart manufacturing. We present a holographic method to generate arbitrary polarization state of multiple beams by synchronizing two phase-only liquid crystal spatial light modulators (SLMs) with imaging feedback system for hologram designing of each polarization state. This research work will help to accelerate the use of liquid crystal SLMs for high-throughput and optimized additive manufacturing.
We developed an ultra-precise retardation-measurement system based on optical-heterodyne interferometry with a 3σ repeatability of λ/360, 000 for zero retardation, where the frequency shift for the optical-heterodyne interferometry was generated by a rotating half-waveplate, and both polarizations for the retardation measurement were always exactly on a common path. Using this system, the direction of the c-axis of a sapphire window was determined by analyzing the incidence-angle dependence of the retardation. The possible resolution of the c-axis direction of the sapphire window was estimated to be 0.9 arcmin from the retardation-measurement repeatability. This c-axis determination method will be applicable to, for example, high-precision sapphire-mirror production/evaluation for gravitational-wave detection.
We developed a liquid-crystal spatial light modulator having a 30 mm active area and a multilayered dielectric mirror for industrial infrared lasers to establish an innovative manufacturing and fabrication technique in the smart-manufacturing post-pandemic era. The reconstruction of computer-generated holograms was achieved to demonstrate the concept of this device in the IR region. The incident phase performance characteristics of this device under high-power laser irradiation were obtained using a 1030 nm ultrashort pulse laser. The work presented here will accelerate the use of liquid-crystal SLMs in high-precision laser processing of the process-resistant materials and high-throughput processing for additive manufacturing.
In this study, we developed a liquid-crystal spatial light modulator with high laser power capacity for industrial ultrafast pulse lasers to demonstrate innovative manufacturing and fabrication techniques using a cyber-physical system. The incident phase performance characteristic of this device was obtained with a 60 W, 1035 nm ultrafast laser. This research work will help to accelerate the use of liquid crystal spatial light modulators for high-precision laser processing of resistant materials and high-throughput for additive manufacturing.
We developed a liquid-crystal-on-silicon (LCOS) spatial light modulator (SLM) for phase-only modulation. The SLM
was designed mainly for wavefront control in adaptive optics, optical manipulation, laser processing, etc. A dielectric
multilayer mirror was incorporated into the device to enhance the reflectivity. The number of pixels was 792 x 612 and
their size was 20 x 20 microns square. The range of the phase modulation exceeded one wavelength, and the light-utilization
efficiency for monochromatic light was approximately 90%. The silicon backplane of the SLM was
mechanically weak and its surface was not flat. The poor flatness degraded the output wavefront from the SLM. The
device was driven by electronics composed of a digital-visual-interface (DVI) receiver, a field programmable gate array,
and 12-bit digital-to-analog converters (DACs). The converted analog voltage signals from the DACs were transmitted to
the pixels of the SLM and created phase changes. The driver had several kinds of control modes for the device,
according to the level of flatness compensation. In one of the modes, the driver received 12-bit data and transferred them
directly to the DACs. This 12-bit control mode enabled highly flexible control of the device characteristics. In the
presentation, we report details of the device and experimental results on compensation of distortion in the output
wavefront from the device.
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