Micro/nano-structured amorphous carbon promises functional prospects in energy-saving, water purification, nonlinear optics, catalysis, sensors, and the internet of things, but there exist many challenges, especially in rapid synthesized nanostructured carbon materials towards performance improvement. Thereby, a transfer-free digital photochemical synthesis method is studied here via scalable single-step nanosecond laser processing. Controllable photon energy from a 1064nm wavelength nanosecond laser drives different degrees of carbonization on paper surfaces. The blended cellulose-lignin network is converted into a series of micro/nano-stacked porous carbon materials during fabrication. High-resolution transmission electron microscope showcases that lattice characteristics of synthesized carbon shift according to optical parameters. A comparison of material morphologies formed at different conditions can be found here. Nanosecond laser processing opens a new avenue for the rapid preparation of carbon nanomaterials on paper substrates with special textures and special microstructures, promising more carbon-based multifunctional devices.
Optical lithography or 3D printing operates on multi-dimensional movement at high resolution. Therefore, accurate position of both x-axis and y-axis deserves real-time measurement. Herein, we utilizes a half-external cavity orthogonal self-mixing laser interferometry for determining displacement of two independent targets. Synchronous detection of irrelevant displacements with nanometer accuracy (<10 nm) is realized here. Circularly polarized laser beam is optically-multiplexed into two polarization states for two additional external cavity. The laser system only needs a single-channel optical intensity to reflect the perpendicular displacement without reference path, which is conducive to simplify the acquisition channel and collimation.
The theoretical basis of self-mixing interference (SMI) employing a resonant phase modulator is explored to prove its tempting advantages. The adopted method induces a pure phase carrier without increasing system complexity. A simple time-domain signal process is used to estimate modulation depth and precisely track vibrating trail, which promises the flexibility of measuring ultrasonic vibration regardless of the constraint of the Bessel functions. The broad bandwidth, low speckle noise, compact, safe, and easy operating SMI system obtains the best resolution of a poor reflection environment. Numerical simulation discusses the spectrum broadening and errors due to multiple reflections. Experimental results agree with theory coherently and are compared with laser Doppler vibration meter showing a dynamical error better than 20 nm in ultrasonic vibration measurement.
An advanced sinusoidal phase-shifting technique and a time-domain phase demodulation method were used to improve the measurement accuracy and realize the real-time measurement speed of the laser self-mixing interferometer in a large range of displacement. An electro-optic crystal modulator (EOM) was used to realize the sinusoidal phase-shifting on the laser beam in the external cavity. The interference signal was demodulated using a time-domain phase demodulation method. The speed requirement could be met by combining the two together in a wide range of displacement measurement processes together with the real-time measurement requirement as an interferometer at the same time. It was experimentally verified that the displacement measurement precision of a sinusoidal phase-shifting laser self-mixing interferometer could reach less than 0.5 μm in the hundred mm large-scale displacement measuring process. In addition, the factors affecting the interferometer’s measurement speed in the real-time displacement measurement process is analyzed and the maximum speed of our system was obtained as well. Keywords: self-mixing interference; phase modulation; time-domain phase demodulation
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