Noriaki Miyanaga

Dual beam laser grooving of CFRP by pulsed lasers

We have been investigating micromachining of CFRP by short laser pulses in order to minimize material damages and HAZ. The laser system used in this study was a Ti:Sapphire laser with pulsewidth of 100fs. For comparison, we also used 200ps stretched pulses from the Ti:Sapphire laser and output from a 200ns-pulsed fiber laser. In order to overcome slow processing speed by ultra-short pulses, we have proposed a novel dual beam grooving. In the first process, small-energy ultra-short pulses are used to cut the edges of the groove with multiple scanning. Secondly, high-energy long-pulses ablate the remained part with a single scanning. We used 1.3mm-thick uni-directional CFRP samples. Trenches with depth of 100µm and width of 50µm were machined by 200ps laser pulses. Then, 200ns fiber laser pulses were focused on one of the remained part in a single scanning. As a result, a groove with depth of 100u2005µm and width of 150u2005µm was formed without significant HAZ.We have been investigating micromachining of CFRP by short laser pulses in order to minimize material damages and HAZ. The laser system used in this study was a Ti:Sapphire laser with pulsewidth of 100fs. For comparison, we also used 200ps stretched pulses from the Ti:Sapphire laser and output from a 200ns-pulsed fiber laser. In order to overcome slow processing speed by ultra-short pulses, we have proposed a novel dual beam grooving. In the first process, small-energy ultra-short pulses are used to cut the edges of the groove with multiple scanning. Secondly, high-energy long-pulses ablate the remained part with a single scanning. We used 1.3mm-thick uni-directional CFRP samples. Trenches with depth of 100µm and width of 50µm were machined by 200ps laser pulses. Then, 200ns fiber laser pulses were focused on one of the remained part in a single scanning. As a result, a groove with depth of 100u2005µm and width of 150u2005µm was formed without significant HAZ.

Critical role of plasmacytoid dendritic cells in induction of oral tolerance

Background: Exposure to dietary constituents through the mucosal surface of the gastrointestinal tract generates oral tolerance that prevents deleterious T cell–mediated immunity. Although oral tolerance is an active process that involves emergence of CD4+ forkhead box p3 (Foxp3)+ regulatory T (Treg) cells in gut‐associated lymphoid tissues (GALTs) for suppression of effector T (Teff) cells, how antigen‐presenting cells initiate this process remains unclear. Objective: We sought to determine the role of plasmacytoid dendritic cells (pDCs), which are known as unconventional antigen‐presenting cells, in establishment of oral tolerance. Methods: GALT‐associated pDCs in wild‐type mice were examined for their ability to induce differentiation of CD4+ Teff cells and CD4+Foxp3+ Treg cells in vitro. Wild‐type and pDC‐ablated mice were fed oral antigen to compare their intestinal generation of CD4+Foxp3+ Treg cells and induction of oral tolerance to protect against Teff cell–mediated allergic inflammation. Results: GALT‐associated pDCs preferentially generate CD4+Foxp3+ Treg cells rather than CD4+ Teff cells, and such generation requires an autocrine loop of TGF‐&bgr; for its robust production. A deficiency of pDCs abrogates antigen‐specific de novo generation of CD4+Foxp3+ Treg cells occurring in GALT after antigenic feeding. Furthermore, the absence of pDCs impairs development of oral tolerance, which ameliorates the progression of delayed‐type hypersensitivity and systemic anaphylaxis, as well as allergic asthma, accompanied by an enhanced antigen‐specific CD4+ Teff cell response and antibody production. Conclusion: pDCs are required for establishing oral tolerance to prevent undesirable allergic responses, and they might serve a key role in maintaining gastrointestinal immune homeostasis.

Laser micromachining of CFRP by ultra-short pulse lasers

CFRP (Carbon Fiber-Reinforced Plastic) has attractive features like high-durability, high-strength and light-weight. We have been investigating micromachining of CFRP by ultra-short laser pulses in order to minimize material damages and HAZ. The laser system used in this study was a commercially available Ti:Sapphire laser (Spectra Physics, Hurricane). Various samples of CFRP were supplied by Japanese leading manufacturing companies. Optimizations of the laser parameters were investigated.CFRP (Carbon Fiber-Reinforced Plastic) has attractive features like high-durability, high-strength and light-weight. We have been investigating micromachining of CFRP by ultra-short laser pulses in order to minimize material damages and HAZ. The laser system used in this study was a commercially available Ti:Sapphire laser (Spectra Physics, Hurricane). Various samples of CFRP were supplied by Japanese leading manufacturing companies. Optimizations of the laser parameters were investigated.

Pivotal Role of IL-22 Binding Protein in the Epithelial Autoregulation of Interleukin-22 Signaling in the Control of Skin Inflammation

Disruption of skin homeostasis can lead to inflammatory cutaneous diseases resulting from the dysregulated interplay between epithelial keratinocytes and immune cells. Interleukin (IL)-22 signaling through membrane-bound IL-22 receptor 1 (IL-22R1) is crucial to maintain cutaneous epithelial integrity, and its malfunction mediates deleterious skin inflammation. While IL-22 binding protein (IL-22BP) binds IL-22 to suppress IL-22 signaling, how IL-22BP controls epithelial functionality to prevent skin inflammation remains unclear. Here, we describe the pivotal role of IL-22BP in mediating epithelial autoregulation of IL-22 signaling for the control of cutaneous pathogenesis. Unlike prominent expression of IL-22BP in dendritic cells in lymphoid tissues, epidermal keratinocytes predominantly expressed IL-22BP in the skin in the steady state, whereas its expression decreased during the development of psoriatic inflammation. Deficiency in IL-22BP aggravates psoriasiform dermatitis, accompanied by abnormal hyperproliferation of keratinocytes and excessive cutaneous inflammation as well as enhanced dermal infiltration of granulocytes and γδT cells. Furthermore, IL-22BP abrogates the functional alternations of keratinocytes upon stimulation with IL-22. On the other hand, treatment with IL-22BP alleviates the severity of cutaneous pathology and inflammation in psoriatic mice. Thus, the fine-tuning of IL-22 signaling through autocrine IL-22BP production in keratinocytes is instrumental in the maintenance of skin homeostasis.

Micromachining of thin CFRP with UV-PS laser pulses

We have been investigating micromachining of Carbon Fiber Reinforced Plastics (CFRP) with ultra-short pulse lasers in order to utilize the CFRP for various applications. The ultra-short laser pulses are advantageous to the micromachining of sub-mm thick CFRP because of the precise cutting quality with negligible HAZ. Considering the mechanical and thermal properties of carbon fibers, the CFRP has potentials to replace metals and would be useful for innovative devices in electronics industries. Especially, anisotropic pitch-type CF has high thermal conductivity (800W/mK), which is higher than copper. In order to characterize the laser processing quality of CFRPs, we tested UV-ps lasers to cut 250µm-thick CFRP sheets. Varying laser power, repetition rate and scanning speed, we observed SEM images of the samples. It was confirmed that the scanning speed of laser beams should be faster to avoid significant HAZ. Also PAN-based CFRPs were more vulnerable to thermal damages than Pitch-based CFRPs, while Pitch-based CFRPs required more laser energy to be ablated compared to the PAN-based CFRPs.We have been investigating micromachining of Carbon Fiber Reinforced Plastics (CFRP) with ultra-short pulse lasers in order to utilize the CFRP for various applications. The ultra-short laser pulses are advantageous to the micromachining of sub-mm thick CFRP because of the precise cutting quality with negligible HAZ. Considering the mechanical and thermal properties of carbon fibers, the CFRP has potentials to replace metals and would be useful for innovative devices in electronics industries. Especially, anisotropic pitch-type CF has high thermal conductivity (800W/mK), which is higher than copper. In order to characterize the laser processing quality of CFRPs, we tested UV-ps lasers to cut 250µm-thick CFRP sheets. Varying laser power, repetition rate and scanning speed, we observed SEM images of the samples. It was confirmed that the scanning speed of laser beams should be faster to avoid significant HAZ. Also PAN-based CFRPs were more vulnerable to thermal damages than Pitch-based CFRPs, while Pitch-ba...

Debris-free low-stress laser dicing for multi-layered MEMS wafers

We have developed a novel debris-free low-stress laser dicing technology for multi-layered MEMS wafers, which are generally consisted of glass and Si. Our technology combines two processes: dicing guide fabrication and wafer separation process. The first process is the internal transformation using a pulsed 1µm laser. The second process is non-contact separation by thermally-induced crack propagation using a CO2 laser or mechanical separation by bending stress. We tested several pulsed lasers with different pulsewidths, including a Nd:YVO4 laser and an Yb fiber laser for generating the internal transformation in silicon and/or glass. The internal transformed lines worked well as a guide of the separation. We found that the internal transformation only in Si layer was enough for dicing the glass/Si double-layered wafer. Also the thermal stress induced by the CO2 laser was quite effective to propagate the crack inside the glass layer without internal transformation. The double-layered wafer consisting of glass and silicon can be diced in low stress by our technology.We have developed a novel debris-free low-stress laser dicing technology for multi-layered MEMS wafers, which are generally consisted of glass and Si. Our technology combines two processes: dicing guide fabrication and wafer separation process. The first process is the internal transformation using a pulsed 1µm laser. The second process is non-contact separation by thermally-induced crack propagation using a CO2 laser or mechanical separation by bending stress. We tested several pulsed lasers with different pulsewidths, including a Nd:YVO4 laser and an Yb fiber laser for generating the internal transformation in silicon and/or glass. The internal transformed lines worked well as a guide of the separation. We found that the internal transformation only in Si layer was enough for dicing the glass/Si double-layered wafer. Also the thermal stress induced by the CO2 laser was quite effective to propagate the crack inside the glass layer without internal transformation. The double-layered wafer consisting of gl...

Generation and amplification of ultra-short-pulsed vacuum ultraviolet radiation

We have been developing an ultra-short-pulsed vacuum ultraviolet (VUV) laser system for advanced applications such as micro and precise processing and photochemical reactions. We propose and construct a new VUV laser system to generate output energy of sub-mJ with a pulse width of sub-picosecond at the wavelength of 126u2005nm. A VUV seed pulse was generated in Xe gas at the pressure of 1.2 Torr with high conversion efficiency as the 7th harmonics of a 882u2005nm Ti:Sapphire laser. The Ar2* amplification medium was generated in an optical-field-induced ionized Ar plasma pumped by another 800u2005nm Ti:Sapphire laser with an amplification factor of 400. VUV output at 1u2005µJ in the sub-picosecond pulse will be obtained at a repetition rate of 1u2005kHz, leading to an average power of 1u2005mW at 126u2005nm. It will be useful VUV coherent source for applications of precise and micro laser processing.We have been developing an ultra-short-pulsed vacuum ultraviolet (VUV) laser system for advanced applications such as micro and precise processing and photochemical reactions. We propose and construct a new VUV laser system to generate output energy of sub-mJ with a pulse width of sub-picosecond at the wavelength of 126u2005nm. A VUV seed pulse was generated in Xe gas at the pressure of 1.2 Torr with high conversion efficiency as the 7th harmonics of a 882u2005nm Ti:Sapphire laser. The Ar2* amplification medium was generated in an optical-field-induced ionized Ar plasma pumped by another 800u2005nm Ti:Sapphire laser with an amplification factor of 400. VUV output at 1u2005µJ in the sub-picosecond pulse will be obtained at a repetition rate of 1u2005kHz, leading to an average power of 1u2005mW at 126u2005nm. It will be useful VUV coherent source for applications of precise and micro laser processing.

Chirped Pulse Amplification System Using Nd-Doped Zig-Zag Glass Slab Pumped by Laser Diodes

We have developed a chirped pulse amplification system using Nd-doped zig-zag glass slab pumped by laser diodes as a pump source for the OPA. The output energy of 1 J with 4.1 nm bandwidth was obtained.

High Repetition and High Average Power Nd:YAG Laser for EUV Lithography

We have been developing a high repetition (5-100 kHz) and high power Nd: YAG laser system pumped by cw LDs. Average power of 4.6 kW was obtained at 28.8 kW of pumping power.

OFI vacuum ultraviolet rare-gas excimer amplifier for subpicosecond VUV pulse amplification

We evaluated amplification characteristics of the nanosecond vacuum ultraviolet argon excimer emission at 126 nm, whose kinetics was initiated by high-intensity femtosecond laser-produced electrons. Subpicosecond 126 nm emissions were produced simultaneously as a result of the nonlinear wavelength conversion, which will be amplified in the amplifier.