Single mode fiber laser를 이용한 micro wire joining에 관한 연구

박관우(K. W. Park),나석주(S. J. Na) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월

In the electronic, medical, aerospace and automobile industries, many products and parts are manufactured by joining. Recently, as these get smaller, micro joining is becoming more and more important. In this study, micro wire-to-micro wire parallel joining was performed using single mode fiber laser. Maximum power of the fiber laser is 100 W. The CCD(Charge-Coupled Device, CCD) camera to observe the specimen was made up. The objective was applied to micro joining system to make a small spot size of laser beam. In order to control the target position, micro-multi-axis-stage was set up. This paper presents results for the single mode fiber laser joining of micro wires.

싱글모드 파이버 레이저를 이용한 SUS304와 Ti 이종재료의 용접속도에 따른 용접특성

이수진,카타야먀 세이지,김종도,Lee, Su-Jin,Katayama, Seiji,Kim, Jong-Do 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.5

The joining of Ti and SUS304 dissimilar metals is one of the effective measures to save rare metal. But Ti and SUS304 have differences in materials properties, and Ti and Fe intermetallic compounds such as TiFe and $TiFe_2$ are easily formed in weld fusion zone between Ti and SUS304. Nevertheless, in this study, full penetration lap dissimilar welding of Ti and SUS304 using single-mode fiber laser with ultra-high welding speed was tried, and it was found out that ultra-high welding speed could control the generation of intermetallic compound. To recognize the formation of intermetallic phase in the weld fusion zone and the compound zone of interface weld area were observed and analyzed using energy dispersive X-ray spectroscopy (EDX). And it was confirmed that the ultra-high welding speed could reduce amount of intermetallic compounds, but the intermetallic compounds were existed in the weld fusion zone under the all conditions.

싱글모드 파이버 레이저를 이용한 SUS304와 Cu의 고속 겹치기 용접에서 접합부 및 인장시험 파단부의 특성에 관한 연구

이수진,김종도,카타야마 세이지,Lee, Su-Jin,Kim, Jong-Do,Katayama, Seiji 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.6

To develop and understand dissimilar metals joining of Stainless steel and Copper, ultra-high speed laser lap welding was studied using single mode fiber laser in this study. SUS304 and Cu have large differences in materials properties, and Cu and Fe have no intermetallic compounds by typical binary phase of Cu and Fe system. In this study, ultra-high speed lap welds of SUS304 and Cu dissimilar metals using single-mode fiber laser was generated, and weldability of the weld fusion zone was evaluated using a tensile shear test. To understand the phenomenon of tensile shear load, weld fusion zone of interface weld area and fracture parts after tensile shear test were observed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis system. And it was confirmed that Cu was easily melting and penetrating in the grain boundaries of SUS304 because of low melting temperature. And high thermal conductivity of copper occurred dissipate heat energy rapidly. These properties cause the solidification cracking in weld zone.

단일모드 광섬유 집광기를 이용한 Hong-Ou-Mandel 간섭 가시도 향상

한성욱,김헌오,서주연,김명훈 한국물리학회 2018 New Physics: Sae Mulli Vol.68 No.12

우리는 Hong-Ou-Mandel 간섭 실험에서 95% 간섭가시도를 획득했다. 지난 연구에서 56% 가시도를 획득한 것에 비하면 획기적으로 가시도가 개선되었다. 우리는 제1형 자발적 매개 하향 변환 목적으로 제작된 $\beta$-Barium Borate 단결정에 405 nm 단일모드 연속 발진 레이저를 주사하여 만들어진 쌍둥이 광자쌍을 표준적인 Hong-Ou-Mandel 간섭광학계를 거치게 한 후 다이오드 기반 단일광자 계수기와 자체적으로 제작한 동시계수기에 의해 간섭신호를 측정했다. 지난 연구와 이번 연구의 가장 큰 차이점은 광자를 집광하는데 단일모드 광섬유를 사용했다는 점이다. 단일모드 광섬유는 중심부 크기가 매우 작기 때문에 광결정에서 발생하는 여러 서로 다른 모드 광자 사이의 우연한 동시계수를 억제시키는 공간 필터 역할을 함으로써 가시도가 개선된 것으로 보인다. We achieved 95% visibility in the Hong-Ou-Mandel interference experiment while we achieved only 56% visibility in a previous report. We used a 120 mW 405 nm single-mode continuous wave laser, a 5-mm-thick type-1 $\beta$-barium borate single crystal, standard Hong-Ou-Mandel interferometer optics, two avalanche photodiode single-photon counters, and a homemade coincidence counting unit. The photon collection unit was the key difference between the present study and the previous study. In the present experiment, we used single-mode optical fibers for photon collection, which suppressed accidental coincidence between-different mode photons by acting as a spatial filter because of its core size being much smaller than a multi-mode fiber.

Single-walled carbon nanotubes on side polished fiber as a universal saturable absorber for various laser output states

Ko, J.,Jeong, H.,Choi, S.Y.,Rotermund, F.,Yeom, D.I.,Kim, B.Y. Elsevier 2017 CURRENT APPLIED PHYSICS Vol.17 No.1

<P>We demonstrated four different laser operational states in the same passive fiber ring laser cavity by controlling solely the polarization state in a saturable absorber. The demonstrated laser operational states were continuous wave, mode-locking, Q-switching, and Q-switched mode-locking. The saturable absorber was fabricated by spin-coating a single-walled carbon nanotubes (SWCNT)/polymer composite on a side polished fiber providing enhanced nonlinear interaction with the SWCNT. The wide tuning range of the saturable absorber allows the simple means to generate different forms of laser output from a single laser cavity. (C) 2016 Elsevier B. V. All rights reserved.</P>

Single-walled carbon nanotubes on side polished fiber as a universal saturable absorber for various laser output states

고재권,정환성,최선영,Fabian Rotermund,염동일,김병윤 한국물리학회 2017 Current Applied Physics Vol.17 No.1

We demonstrated four different laser operational states in the same passive fiber ring laser cavity by controlling solely the polarization state in a saturable absorber. The demonstrated laser operational states were continuous wave, mode-locking, Q-switching, and Q-switched mode-locking. The saturable absorber was fabricated by spin-coating a single-walled carbon nanotubes (SWCNT)/polymer composite on a side polished fiber providing enhanced nonlinear interaction with the SWCNT. The wide tuning range of the saturable absorber allows the simple means to generate different forms of laser output from a single laser cavity.

싱글모드 파이버 레이저를 이용한 Cu 와 Ni의 고속도 이종재료 용접부의 기계적 특성

이수진,김종도,Lee, Su-Jin,Kim, Jong-Do 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.3

As the industrial technology has been developed, a dissimilar welding has been received huge attention in various engineering fields. To understand the mechanical properties and possibility of applications of dissimilar metals joining, the laser welding of Cu and Ni dissimilar metals was studied in this paper. Cu and Ni have differences in materials properties, and Cu and Ni make no intermetallic compounds according to typical binary phase of Cu and Ni system. In this study, lap welds of Cu and Ni dissimilar metals using single-mode fiber laser with high welding speed were tried, and mechanical properties of the welds zone were evaluated using a Vickers hardness test and a tensile shear test. To recognize the relation between hardness and tensile shear load, weld fusion zone of interface weld area were observed. And it was confirmed that the ultra-high welding speed could make good weld beads and higher hardness parts had higher tensile shear load under the all conditions.

Multi-kilowatt Single-mode Ytterbium-doped Large-core Fiber Laser

정윤찬,Johan Nilsson,David N. Payne,Alexander J. Boyland,Jayanta K. Sahu,정승환 한국광학회 2009 Current Optics and Photonics Vol.13 No.4

We have demonstrated a highly efficient cladding-pumped ytterbium-doped fiber laser, generating >2.1 kW of continuous-wave output power at 1.1 μm with 74% slope efficiency with respect to launched pump power. The beam quality factor (M2) was better than 1.2. The maximum output power was only limited by available pump power, showing no evidence of roll-over even at the highest output power. We present data on how the beam quality depends on the fiber parameter, based on our current and past fiber laser developments. We also discuss the ultimate power-capability of our fiber in terms of thermal management, Raman nonlinear scattering, and material damage, and estimate it to 10 kW.

단일 결정립 내의 국소 레이저 조사를 이용한 일방향응고 및 단결정 초내열합금의 응고균열 억제 용접기술

이성진,김경민,강희신,서성문,박원아,천은준 대한용접접합학회 2023 대한용접·접합학회지 Vol.41 No.4

In this study, possibility of solidification crack-free welding of directionally solidified CM247LC and single crystal CMSX-4 superalloys was metallurgically investigated using single-mode fiber laser scanning. The key metallurgical factors of solidification cracking have been identified as the formation of highly misoriented solidification grain boundaries (low level of epitaxial growth behavior) at the fusion zone that affects the repulsive force between two adjacent dendrites and dendrite coalescence undercooling at the terminal stage of weld solidification. In particular, under extremely low heat input and ultra-high-speed laser beam scan conditions (welding speed: 1,000 mm/s, heat input: 2 J/mm, and energy density: 65 J/mm2), an effective fusion zone could be achieved within a single directionally solidified grain of CM247LC alloy owing to the characteristics of single-mode fiber laser. The fusion zone successfully showed a 99.9% of epitaxial growth achievement ratio (that is, low fraction of highly misoriented solidification grain boundaries at the fusion zone) without solidification cracking. Based on these results on CM247LC alloy, solidification crack-free welds could be successfully achieved using quadruple-pass and square-type weld geometries.

Hot Cracking Characteristics During Single-Mode Fiber and Green Laser Welding Processes in Lithium-Ion Battery Pack Manufacturing

Jae-Hyeon Park,Myung-Jin Kim,Hee-Shin Kang,박원아,천은준 대한용접접합학회 2023 대한용접·접합학회지 Vol.41 No.5

Solidification cracking during lithium-ion battery packaging was metallurgically investigated, specifically for Cu-steel dissimilar materials. To this end, single-mode fiber and green lasers were employed under heat input conditions ranging from 1.3 to 8.0 J/mm. For both laser welds, solidification cracking was concentrated in the steel region of the fusion zone, particularly in the locally Cu-depleted region, regardless of the welding condition. Modified self-restraint tests were performed for overlapping dissimilar material combinations to elucidate the mechanism of solidification cracking. Analysis of the solidification cracking surface revealed that approximately 15–30 mass% Cu existed on the surface. Cu was highly enriched with a droplet shape, formed during solidification within the miscibility gap. By calculating the non-equilibrium weld mushy zone range based on the diffusion-controlled Scheil’s model, the solidification cracking in the Cu-depleted region was estimated at 453 K. It was strongly affected by the severe segregation of Cu (95.7 mass%) in the residual liquid at the terminal stage of the solidification path. Therefore, from a welding metallurgical perspective, homogeneous Cu distribution and minimization of Cu segregation within the fusion zone are essential for suppressing or minimizing the solidification cracking susceptibility of Cu–steel dissimilar laser welding.