• ETRI Journal
• /
• 제25권3호
• /
• pp.149-155
• /
• 2003

A self-pulsating multisection distributed-feedback laser diode (DFB LD) can potentially realize all-optical clock extraction. This device generally consists of three sections, two DFB sections and one waveguide section. The most important variable in this device is detuning, which is the relative spectral position between the stop bands of two DFB sections. We fabricated a novel structure in which two gratings were located one over and one under the active layers. Each grating structure was independently defined in processing so that detuning, which is the prerequisite for self-pulsation, could be easily controlled. Observing various self-pulsating phenomena in these devices under several detuning conditions, we characterized the phenomena as dispersive Q-switching, mode beating, and self-mode-locking.

• 센서학회지
• /
• 제20권1호
• /
• pp.46-52
• /
• 2011

In this paper, the swept source-optical coherence tomography system using frequency domain mode locked(FDML) laser has realized. The FDML swept source laser showed 55.03 kHz sweeping speed, 125 nm sweeping range, and 9 mW output optical power, which are the superiority of FDML laser compared to previous swept source lasers. Also, through the cross-sectional image captured at 5 frames per second for a mirror, a 1 mm-thickness glass plate, and a thumb bottom, the performance of the system has demonstrated.

• Bulletin of the Korean Chemical Society
• /
• 제31권8호
• /
• pp.2293-2298
• /
• 2010

Focused electrospray (FES) deposition method is presented for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. FES ion optics consists of two cylindrical focusing electrodes capped with a truncated conical electrode through which an electrospray emitter passes along the cylindrical axis. A spray of charged droplets is focused onto a sample well on a MALDI target plate under atmospheric pressure. The shape and size distributions of matrix crystals are visualized by scanning electron microscope and the mass spectra are obtained by time-of-flight mass spectrometry. Angiotensin II, bradykinin, and substance P are used as test samples, while $\alpha$-cyano-4-hydroxycinnamic acid and dihydroxybenzoic acid are employed as matrices. FES of a sample/matrix mixture produces fine crystal grains on a 1-3 mm spot and reproducibly yields the mass spectra with little shot-to-shot and spot-to-spot variations. Although FES greatly stabilizes the signals, the space charge due to matrix ions limits the detection sensitivity of peptides. To avoid the space charge problem, we adopted a dual FES/FES mode, which separately deposits matrix and sample by FES in sequence. The dual FES/FES mode reaches the detection sensitivity of 0.88 amol, enabling ultrasensitive of peptides by homogeneously depositing matrix and sample under atmospheric pressure.

• 한국연소학회지
• /
• 제19권1호
• /
• pp.29-38
• /
• 2014

This paper described an experimental investigations of combustion instability mode in a lean premixed dual swirl combustor for micro-gasturbine system. When such the instability occurs, a strong coupling between pressure oscillations and unsteady heat release excites a self-sustained acoustic wave which results in a loud, annoyed sound and may also lead a structural damage to the combustion chamber. The detailed period of flame behavior and heat release in combustion instability mode have been examined with high speed OH and CH-PLIF system and $CH^*$ chemiluminescence measurement, flame tomography with operated at 10 kHz and 6 kHz each. Experiment results suggest that unstable flame behavior has a specific frequency with 200 Hz and this frequency is accords with about 1/2 sub-harmonic of combustor resonance frequency, not fundamental frequency. This is very interesting phenomenon that have not reported yet from other previous works. Therefore, when a thermo-acoustic instability with Rayleigh criterion occurs, the fact that the period of heat release and flame behavior are different each other was proposed for the first time through this work.

• 한국광학회지
• /
• 제18권1호
• /
• pp.56-65
• /
• 2007

이득 분산이 두 개의 복소 결합 DFB 영역과 위상조정 영역으로 구성되는 다중 영역 복소 결합 DFB 레이저에서 발진하는 두 모드의 비팅에 의한 self-pulsation (SP) 주파수와 출력 파워의 변조지수에 미치는 영향에 대하여 살펴보았다. 능동 영역의 이득이 최대가 되는 파장을 두 DFB 영역의 발진 모드의 파장 중심 또는 브래그 파장 중심에 위치시킨 경우가 특정 DFB 영역의 발진 모드의 파장 또는 브래그 파장에 위치시킨 경우에 비하여 두 DFB 영역의 브래그 파장 차이, ${\Dalta}{\lambda}_{B}$, 증가에 따른 두 발진 모드가 받는 이득 차이가 적게 발생하여 최대 SP 주파수가 크고, 변조지수 특성도 좋음을 볼 수 있었다. 또한 능동 영역의 이득이 최대가 되는 파장을 두 DFB 영역의 브래그 파장 중심에 위치시키는 경우가 발진 모드의 파장 중심에 위치시키는 경우에 비하여 더 큰 최대 SP 주파수를 얻을 수 있었고 변조지수 특성도 더 우수함을 볼 수 있었다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.357-360
• /
• 2002

Nowadays, the improvement and development of Multi-media, information and communication technology are rapidly processed. And many products, for example, digital camera, digital camcorder, and PDA, are used for them. They need large data storage capacity and small size, light storage system. Due to that, many studies and researches in data storage system have been carried out. Especially, micro drive system was presented by IBM.(1) However, its system is expensive and uneasy to be portable. In ODD technologies, 1 inch drive system is not yet or in processing status.(2) If to be possible and to be come up, it is cheap than HDD system and easy to transfer information. In this paper, a miniaturized actuator(about linch) is designed and tested for ODD system. Specially, it is adapted for NFR(Near-field Recoding) system using SIL(Solid Immersion Lens). It is the dual-servo actuator which consists of a coarse actuator and fine actuator. Its actuating force generation method is VCM(Voice Ceil Motor). The fine actuator has 4-wire suspensions and bobbin wrapped by coil and includes focusing motion as well as tracking motion. The coarse actuator has an actuating coil and V-grooved guide mechanism. Also, the characteristics of the designed actuator is estimated by sine-swept mode and LDV(Laser Doppler Vibro-meter).

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 춘계학술대회 논문집
• /
• pp.732-737
• /
• 2005

Distal 3D Real Object Duplication System(RODS) consists of 3D Scanner and Solid Freeform Fabrication System(SFFS). It is a device to make three-dimensional objects directly from the drawing or the scanning data. In this research, we developed an office type SFFS based on Three Dimensional Printing Process and a industrial SFFS using Dual Laser. An office type SFFS applied sliding mode control with sliding perturbation observer(SMCSPO) algorithm for control of this system. And we measured process variables about droplet diameter measurement and powder bed formation etc. through experiments. Also, in order to develop more elaborate and speedy system for large objects than existing SLS process, this study applies a new Selective Multi-Laser Sintering(SMLS) process and 3-axis dynamic Focusing Scanner for scanning large area instead of the existing $f\theta$ lens. In this process, the temperature has a great influence on sintering of the polymer. Also the laser parameters are considered like that laser beam power, scan speed, scan spacing. Now, this study is in progress to eveluate the effect of experimental parameters on the sintering process.

• 한국항공우주학회지
• /
• 제35권9호
• /
• pp.799-804
• /
• 2007

액체추진제 추력기 연소실의 인젝터로부터 발생하는 분무 거동을 파악하기 위하여 광학계측 기법을 사용한다. 실험에 사용된 인젝터는 지름이 0.406 mm이며 중심축으로부터 30 의 경사각을 이루는 8 개의 노즐 구멍으로 구성된다. 분무생성의 초기조건과 분무발달에 따른 미립화 과정을 분석하기 위해, 이중모드 위상도플러속도계(DPDA)로 측정된 액적의 속도 및 입경 등의 변이 거동을 제시하고 Nd:Yag 레이저평면광에 의해 획득된 순간평면이미지와 함께 고찰한다. 분무액적의 초기 분사속도에 근거한 Re 수와 We 수 등의 무차원 변수를 도출하여 인젝터 발생 분무의 미립화 및 난류성질 등에 대한 분무유동 양식의 범주를 결정한다. 이러한 분무분열에 대한 정성적, 정량적 결과는 향후 새로운 추력기 개발에 확실한 설계 기반을 제공할 것이다.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2003년도 하계학술발표회
• /
• pp.88-89
• /
• 2003

현대 시대에 광통신 시스템은 안정적이고 높은 단일 모드를 갖는 광원을 필요로 한다. 이 조건을 만족하는 λ／4 phase shifted DFB는 높은 단일모드 생성을 보였으나 high spatial hole burning문제점을 가지고 있다. λ／4 phase shift를 사용하지 않은 dual-pitch grating DFB가 소개되었지만 제작상의 어려움을 가지고 있다. 또 다른 구조인 selection-free tapered stripe DFB lasers가 제안되었는데 제작이 간단하면서도 높은 단일모드 생성을 보였다. (중략)

• 한국정밀공학회지
• /
• 제18권8호
• /
• pp.174-181
• /
• 2001

Nowadays, the improvement and development of Multi-media and information & communication technology is rapidly processed. They need large data storage capacity. So that, many studies and researches in data storage have been carried out. According to them, the data storage capacity has been increased. But the limitation of storage capacity is happened for several problems. One of them is spot & pit size in optical and magnetic data storage and another is the resolution of actuators. The problems in spot & pit size are covered by new data storage methods-- for examples, AFM(Atomic Force Microscopy), MO(Magneto-optical) system, and NFR(Near-Field decoding) system etc. But the resolution limit of an actuator was not developed and doesn\`t follow up the development of spot & pit size. Because of them, we should improve a resolution of an actuator. Especially, in this paper an actuator if studied and designed for NFR (in using SIL(Solid Immersion Lens) system. It is a dual stage actuator, which consists of a Fine actuator and a Coarse actuator. and should desire 100nm accuracy. Its actuating force generation method is VCM(Voice Coil Motor). The Fine actuator is composed of 4-leaf springs and a bobbin wrapped by coil. The Coarse actuator has Coils and 3-Roller bearings. Also, The Characteristics of designed actuator for NFR system is estimated by Sine-Swept mode and LDV(Laser Doppler Vibro-meter).