| 1. |
- Ha Ryu, Jae, et al.
(författare)
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Beam stability of buried-heterostructure quantum cascade lasers employing HVPE regrowth
- 2021
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Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 29:2, s. 2819-2826
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of beam stability for mid-infrared (IR)-emitting quantum cascade lasers (QCLs) are important for applications that require the beam to travel through air to remote targets, such as free-space communication links. We report beam-quality measurement results of narrow-ridge, 4.6 mu m-emitting buried-heterostructure (BH) QCLs fabricated using ICP etching and HVPE regrowth. Beam-quality measurements under QCW operation exhibit M-2 < 1.2 up to 1 W for similar to 5 mu m-wide ridges. 5 mu m-wide devices display some small degree of centroid motion with increasing output power (< 0.125 mrad), which corresponds to a targeting error of similar to 1.25 cm over a distance of 100 m.
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| 2. |
- Roh, Kyung-Baeg, et al.
(författare)
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Proteolytic cascade for the activation of the insect toll pathway induced by the fungal cell wall component
- 2009
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 284:29, s. 19474-19481
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Tidskriftsartikel (refereegranskat)abstract
- The insect Toll signaling pathway is activated upon recognition of Gram-positive bacteria and fungi, resulting in the expression of antimicrobial peptides via NF-kappaB-like transcription factor. This activation is mediated by a serine protease cascade leading to the processing of Spätzle, which generates the functional ligand of the Toll receptor. Recently, we identified three serine proteases mediating Toll pathway activation induced by lysine-type peptidoglycan of Gram-positive bacteria. However, the identities of the downstream serine protease components of Gram-negative-binding protein 3 (GNBP3), a receptor for a major cell wall component beta-1,3-glucan of fungi, and their order of activation have not been characterized yet. Here, we identified three serine proteases that are required for Toll activation by beta-1,3-glucan in the larvae of a large beetle, Tenebrio molitor. The first one is a modular serine protease functioning immediately downstream of GNBP3 that proteolytically activates the second one, a Spätzle-processing enzyme-activating enzyme that in turn activates the third serine protease, a Spätzle-processing enzyme. The active form of Spätzle-processing enzyme then cleaves Spätzle into the processed Spätzle as Toll ligand. In addition, we show that injection of beta-1,3-glucan into Tenebrio larvae induces production of two antimicrobial peptides, Tenecin 1 and Tenecin 2, which are also inducible by injection of the active form of Spätzle-processing enzyme-activating enzyme or processed Spätzle. These results demonstrate a three-step proteolytic cascade essential for the Toll pathway activation by fungal beta-1,3-glucan in Tenebrio larvae, which is shared with lysine-type peptidoglycan-induced Toll pathway activation.
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| 3. |
- Ryu, Jae Ha, et al.
(författare)
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Reverse-Taper Mid-Infrared Quantum Cascade Lasers for Coherent Power Scaling
- 2022
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 14:3
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Tidskriftsartikel (refereegranskat)abstract
- We present a reverse-taper quantum cascade laser (QCL) emitting at 4.6 mu m, a novel-geometry device that can scale the output power while maintaining good beam quality. Buried-ridge waveguides with tapered and straight regions were formed by ICP etching and HVPE regrowth - the tapered region scales the output power, while the emitting facet is located at the narrow-end taper section, which provides mode filtering by suppressing high-order spatial modes. Beam profiles were observed under quasi-continuous-wave (QCW)/CW operation and beam quality (M-2) measurements along with beam-stability measurements were performed - a small degree of collimated-beam centroid movement (<0.46 mrad, peak-to-peak) was observed, along with M-2 values close to 1 up to similar to 1 W QCW power. Devices of shorter cavity lengths were also investigated, indicating that the output power scales with the core-region volume but results in a small increase in angular deviation.
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| 4. |
- Ryu, Jae Ha, et al.
(författare)
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Reverse-Taper Mid-IR Quantum Cascade Lasers for Coherent Power Scaling
- 2021
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Ingår i: 2021 27th International Semiconductor Laser Conference (ISLC). - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- Novel-geometry, 4.6 mu m-emitting BH QCLs were fabricated, where a tapered region scales the output power and, ahead of the emitting aperture, a narrow section provides mode filtering for suppressing high-order spatial modes. Beam-stability measurements indicate a small degree of collimated-beam centroid motion (< 0.25 mrad).
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| 5. |
- Strömberg, Axel, et al.
(författare)
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Semi-insulating InP:Fe growth by hydride vapor phase epitaxy for advanced buried heterostructure quantum cascade lasers
- 2023
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Ingår i: Novel In-Plane Semiconductor Lasers XXII. - : SPIE-Intl Soc Optical Eng.
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Konferensbidrag (refereegranskat)abstract
- Buried heterostructure quantum cascade lasers (BH-QCLs) operating at high temperature in mid-infrared (MIR) to THz spectral range are desired for chemical sensing and free-space optical communication (FOC). In this work, Fe doped semi-insulating InP (SI-InP) regrowth is demonstrated in a hydride vapor phase epitaxy (HVPE) reactor for advanced MIR and THz BH-QCLs grown by MBE and MOCVD. SI-InP regrowth is implemented in THz QCL pillar arrays and narrow width and reverse-taper MIR BH-QCLs for efficient heat dissipation. By exploiting SI-InP regrowth, the parasitic capacitance in MIR distributed feedback BH-QCL can be suppressed, which is exploited for high speed FOC application.
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