For higher-density integration and acceleration of operating speed in Si ICs, 3D integration of wafers and/or dies is essential. Fabrication of current 3D ICs relies on 3D assembly which electrically connects stacked chips to form a single circuit. A key technology for the 3D assembly is TSVs which are vertical electrical connections passing completely through silicon chips to electrically connect vertically assembled Si ICs. Typical TSVs have wide features, with diameters of a range from several microns to 50 μm and depths up to 500 μm with aspect ratios up to 15 depending on the application and integration scheme. In this work, we present high-throughput, taper-free TSVs fabrication using femtosecond Bessel beams operated at different wavelengths from 400 nm to 2.4 μm. Furthermore, special phase filters are designed to suppress the damages induced by the side-lobes of Bessel beams for high-quality TSVs fabrication. Our technique can be potentially used for 3D assembly in manufacture of 3D silicon integrated circuits.
According to specific configurations, three-dimensional (3D) patterning involves both 3D bioimaging and laser
micromachining. Recent advances in bioimaging have witnessed strong interests in the exploration of novel microscopy
methods capable of dynamic imaging of living organisms with high resolution, and large field of view (FOV). For most,
applications of bioimaging should be limited by the tradeoff between the speed, resolution, and FOV in common
techniques, e.g., confocal laser scanning microscopy and two-photon microscopy. However, a recently proposed
temporal focusing (TF) technique, based on spatio/temporal shaping of femtosecond laser pulses, enables depth-resolved
bioimaging in a wide-field illumination. This lecture firstly provides a glimpse into the state-of-the-art progress of
temporal focusing for bioimaging applications. Then we reveal a bizarre point spread function (PSF) of the temporal
focusing system, both experimentally and theoretically. It can be expected that this newly emerged technique will
exhibited new advances in not only 3D nonlinear bioimaging but also femtosecond laser micromachining in the future.
Hydrophilic photopolymers with AA as the monomer are versatile materials for use as holographic recording media. It has demonstrated a possibility to improve the refractive index modulation by doping inorganic nanoparticles into the polymer matrix. But the agglomerate effect of inorganic nanoparticles always deteriorate the holographic storage characteristics of the inorganic nanoparticle dispersed photopolymer compound materials. monodisperse hydrophilic gold nanoparticles are fabricated by the method of sodium citrate reduction, and then were dispersed into the PVA/AA photopolymer. Our results indicate that citrate ions coated on the surface of gold nanoparticles can effectively prevent the agglomerate effect, so that the gold nanoparticles can uniformly dispersed in the sol-gel photopolymer. The permanent refractive index grating can be formed owing to a spatial distribution of the effective refractive index with periodically distributed nanoparticles and polymerized monomers during the holographic recording. Furthermore, the citrate ion modified gold nanoparticles and polymer chain can induce the formation of hydrogen bonds which can prevent the material from distortion and at the same time improve the stability of the material by the coordination effect of carboxylate. Therefore, the incorporation of gold nanoparticles leads to a significantly improvement in the holographic properties of the materials, so that the volume shrinkage during the holographic exposure can be well suppressed. Additionally, there exists the optimum concentration of gold nanoparticles, at which the maximum diffraction efficiency can be as high as 90% and the volume shrinkage can be reduced to 0.8%.
In this work, a nanoscale surface-enhanced Raman scattering (SERS) substrate is fabricated by fs laser reduction and
deposition. The conductive silver microstructures are also deposited in fs laser irradiated area on the glass surfaces.
Based on this approach, we integrate the microelectronic circuit and micro-Raman substrate into a microfluidic chamber
and form a prototype of Raman biochip for biosensing. Enhancement of Raman signal and control of temperature of the
sensor are both achieved. This technique provides a great potential for integrating microelectronics and micro-Raman
sensors on a single glass chip.
Femtosecond laser micromachining has emerged as a promising technique for creating three dimensional (3D)
microstructures. As an essential building block for microfluidics, homogeneous microfluidic channel with high aspectratio
is indispensable for lab-on-a-chip (LOC) applications. Fused silica is considered to be an excellent substrate
material for LOC applications due to its low thermal expansion coefficient, low autofluorescence, and exceptional
transmittance over a wide spectral range. Microfluidic channels can be directly fabricated inside fused silica by
femtosecond laser direct writing followed by a subsequent wet chemical etching. However, the fabricated channels
usually display a tapered feature and highly elliptical cross-section with limited length (usually <5 mm) and poor inner
surface smoothness, which would hamper their applications. Herein, we demonstrate direct fabrication of homogeneous
microfluidic channels embedded in fused silica by femtosecond laser direct writing, followed by wet chemical etching
and glass drawing. With these procedures, the homogeneity of the fabricated channels has become excellent. Namely, the
taper of the microchannels is greatly reduced while their cross-sectional shape becomes circular after the drawing. In
addition, an inner surface smoothness of ~0.2 nm can be realized by this method. Finally, the glass drawing method can
lead to centimeters long microfluidic channels with an aspect ratio as high as ~1,000. We expect that these microfluidic
channels will have important applications in optofluidics in the future.
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