We report on advances in the fabrication of Josephson junctions, crucial devices in superconducting quantum circuits. In our previous work, we successfully fabricated these on 12-inch substrates using ArF immersion lithography. To enable future large-scale production, we are moving towards sputtering and dry etching techniques. After initial successful tests on a 4-inch substrate, we have now verified this process on 12-inch substrate fabrication equipment, marking significant progress despite the challenges we have faced.
Laser Ultrasonic Testing (LUT) is a noncontact and nondestructive method for inspecting internal and surface defects of materials. Ultrasonic waves are generated by pulsed lasers, reflected or scattered by defects, and detected by an optical interferometer through surface displacements. One of the most significant challenges of LUT is improving the sensitivity of the interferometer. In this paper, we report the development of a highly sensitive interferometer and its application in detecting minute defects within the internal structure and on the surface of metals. The interferometer utilizes a fiber-optic Sagnac configuration, which incorporates a loop of polarization-maintaining fiber components. We enhanced the sensitivity not only by amplifying the optical source power to increase the signal-to-shot-noise ratio, but also by eliminating stray light in the optical head to minimize beat noise. The resulting sensitivity, evaluated by noise-equivalent surface displacement, is 1.1×10−6 nm/ √ Hz, which is nearly half of the best sensitivity achieved by commercial industrial interferometers currently used for ultrasonic measurement. We successfully applied the interferometer to two specific cases: the detection of artificial line defects with a diameter of 100 μm engraved on the backside of a 10-mm-thick SS400 steel, and the detection of surface cracks with a width of 0.5 μm and depth of 10 μm. These results demonstrate the potential of our LUT system in detecting minute defects.
In recent years, the number of qubits in superconducting quantum computers has increased. It is anticipated that future attempts to realize fault-tolerant superconducting quantum computers will require an ability to fabricate large numbers of superconducting qubits uniformly on large-area substrates. Specifically, it is expected that technology will be developed to fabricate a large number of Josephson junctions on a 12-inch substrate in a short period with minimum dimensional variations in the superconducting quantum circuits. In this manuscript, we report on a technology that enables the uniform formation of resist patterns for Josephson junctions in large quantities on 12-inch substrates by replacing electron beam lithography with ArF immersion lithography.
Carbon nanotubes (CNTs) have been expected for applications in many future electronic devices. To fabricate CNT structures on substrates, several techniques such as spray coating, spin coating and vacuum filtration have been proposed so far. In this work, we report a very simple and efficient method to deposit CNTs on a glass substrate by only scanning a focused light in CNT dispersion. This fabrication technique can provides a bottom up method for the deposition of CNTs in arbitrary shape on the substrate.
We placed the dispersion of single-walled carbon nanotubes (SWCNTs) on a glass substrate. From the back side of the substrate, a laser (λ=975 nm; 100 mW) was focused on the interface between the substrate and the SWCNT dispersion by an oil immersion objective lens (Nikon 100X 1.25NA). Once the focal spot of the light is in focus on the substrate, it began to deposit SWCNTs around the spot (~1 um). Then, the linewidth of the deposition of SWCNTs was approximately 30um, and its electrical conductivity was 12.5 S/cm. We measured the Raman spectrums of the SWCNT dispersion and the deposited SWCNTs. Their G/D ratios were the same value, which indicated that any lattice defects were hardly occurred to SWCNTs in this process. Hence, this method can be useful application for fabrication processes of a variety of CNT devices. We have built the prototype of CNT field-effect transistors. In this presentation, we will show that a collimated light instead of the focused light can be applicable also.
Without moving parts, the snapshot imaging polarimeter utilizing Savart plates is capable of stable and fast measurements of spatiallly distributed Stokes parameters. To increase feasibility of the optical design, we propose modi cations that enable a wider eld-of view. By changing the Savar plates' con guration and improving the calibration procedure, the unwanted effects associated with the increase in the eld of view can be reduced. We carried out the veri cation experiments of the wide eld of view snapshot imaging polarimeter.
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