• Title, Summary, Keyword: Cavity resonator

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The Study of Near-field Scanning Microwave Microscope for the Nondestructive Detection System (비파괴 측정을 위한 근접장 마이크로파 현미경 연구)

  • Kim, Joo-Young;Kim, Song-Hui;Yoo, Hyun-Jun;Yang, Jong-Il;Yoo, Hyung-Keun;Yu, Kyong-Son;Kim, Seung-Wan;Lee, Kie-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.5
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    • pp.508-517
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    • 2004
  • We described a near-field scanning microwave microscope which uses a high-quality dielectric resonator with a tunable screw. The operating frequency is f=4.5 5GHz. The probe tip is mounted in a cylindrical resonant cavity coupled to a dielectric resonator We developed a hybrid tip combining a reduced length of the tapered part with a small apex. In order to understand the function of the probe, we fabricated three different tips using a conventional chemical etching technique and observed three different NSMM images for patterened Cr films on glass substrates. We measured the reflection coefficient of different metal thin film samples with the same thickness of 300m and compared with theoretical impedance respectly. By tuning the tunable screw coming through the top cover, we could improve sensitivity, signal-to-noise ratio, and spatial resolution to better than $1{\mu}m$. To demonstrate the ability of local microwave characterization, the surface resistance of metallic thin films has been mapped.

Development of TEM Coil for Animal Experiments at 3T MRI System

  • Chu, Myung-Ja;Choe, Bo-Young;Kim, Kyung-Nam;Chung, Sung-Taek;Oh, Chang-Hyun;Lee, Hyoung-Koo;Suh, Tae-Suk
    • Proceedings of the KSMRM Conference
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    • pp.78-78
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    • 2002
  • Purpose: The purpose of this study is to describe a distributed circuit approach to high frequency volume coil design illustrated with specific coils built accordingly and results obtained from animal studies at 3.0 tesla. Method: All experiments were conducted on 3T MRI system (Medinus Co., Ltd. Korea). The tuned TEM resonator measures 15cm outer diameter. by 10cm inside diameter by 30cm in length. The inside diameter and length were determined by animals body or head size (eg. rats or small dogs, etc.) while the outer diameter was chosen for compactness with some sacrifice of the optimal coil Q predicted for a larger cavity. A spin echo sequence with a TR/TE/flip angle=500/12.4ms/$75^{\circ}$was used to check image qualities with phantom. The breed of rat which used for animal images was Sprague-dawley(SD) and was anesthetic using ketamin hydrochloride 75mg/kg.

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Development of a Mid-infrared CW Optical Parametric Oscillator Based on Fan-out Grating MgO:PPLN Pumped at 1064 nm

  • Bae, In-Ho;Lim, Sun Do;Yoo, Jae-Keun;Lee, Dong-Hoon;Kim, Seung Kwan
    • Current Optics and Photonics
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    • v.3 no.1
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    • pp.33-39
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    • 2019
  • We report development of a frequency-stabilized mid-infrared continuous-wave (cw) optical parametric oscillator (OPO) based on a fan-out grating MgO:PPLN crystal pumped at 1064 nm. The OPO resonator was designed as a pump-enhanced standing-wave cavity that resonates to the pump and signal beams. To realize stable operation of the OPO, we applied a modified Pound-Drever-Hall technique, which is a well-known method for powerful laser frequency stabilization. Tuning a poling period of the fan-out grating of the crystal allows wavelength-tunable OPO outputs from 1510 nm to 1852 nm and from 2500 nm to 3600 nm for signal and idler beams, respectively. At the idler wavelengths of 2500 nm, 3000 nm and 3500 nm, we achieved more than 50 mW of output powers at a pumping power of 1.1 W. The long-term stability of the OPO was confirmed by recording the power and wavelength variations of the idler for an hour.

Construction and Characterization of Travelling Wave Type Single Mode Fiber Laser Using a Fiber Grating (광섬유격자를 이용하는 진행파형 단일모드 광섬유레이저의 제작과 특성 측성)

  • 김택중;박희갑;이동한
    • Korean Journal of Optics and Photonics
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    • v.6 no.4
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    • pp.296-301
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    • 1995
  • A single-mode erbium-doped fiber laser is constructed by using a intracore fiber Bragg grating and a unidirectional fiber loop mirror. The laser cavity is designed in such a way that the laser beam forms a travelling wave in the gain medium by placing the erbium-doped fiber inside the unidirectional loop and that the wavelength-selective feedback is made from the outside of the loop by a fiber grating with 0.2 nm reflection linewidth. An additional fiber ring resonator is constructed and used as an optical spectrum analyzer to observe the variation of the laser mode spectra. As the result, relatively stable single mode, single polarization output is observed for the most of the time except some mode hoppings in minute scale due to enviommental temperature variations. tions.

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Single Longitudinal Mode Operation of a Pulsed Dye Laser Injection-seeded with a CW Ring Dye Laser (인젝션 록킹 방법에 의한 펄스 색소레이저의 단일 종모우드 발진)

  • 김재완;공홍진;한재원;박승남
    • Korean Journal of Optics and Photonics
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    • v.5 no.1
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    • pp.84-89
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    • 1994
  • A tunable pulsed dye laser was operated in a single longitudinal mode by injection locking with a cw ring dye laser. A doubled Nd:YAG laser was used as the pumping source. Phase sensitive detection technique was applied to maintain the required match between the master laser frequency and the slave resonator cavity length. The fluctuation of the center frequency of the pulsed laser was < 10 MHz, and the pulse duration (FWHM) was 6 ns. The linewidth measured by scanning confocal interferometer was 130 MHz. When pumped by 50 mJ of the doubled Nd:YAG laser, the output energy of the pulsed dye laser was 2 mJ and the peak power was 330 kW. 30 kW.

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Acoustic test of the payload fairing of Korea satellite launch vehicle (소형 위성 발사체의 페이로드 페어링부에 대한 음향 가진 시험)

  • Park, S.H.;Seo, S.H.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.220-223
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    • 2007
  • Acoustic test of the payload fairing of Korea satellite launch vehicle was conducted to verify the performance of acoustic protection system installed inside the payload fairing. This paper briefly introduces the acoustic test procedures and its results. Overall 148 dB acoustic loads were exerted on the payload fairing structures which mated with the upper stage structure of the launch vehicle. In order to verify the increase of insertion loss by the acoustic protection system, two kinds of test were performed. One is conducted with acoustic protection system and the other without acoustic protection system. Internal acoustic loads as well as external ones were measured and the measured insertion losses were compared with the requirement. The results showed that the acoustic protection system increases the insertion loss by more than 6 dB above 125 Hz. They also indicated that some design modification of Helmholtz resonator array is required to increase the insertion loss at a cavity resonant frequency.

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Equivalent Circuit Analysis of a Rectangular Waveguide Probe with H-type Small Aperture (H-형태 소형 개구를 갖는 도파관 탐침의 등가회로 해석)

  • Ko, Ji-Hwan;Cho, Young-Ki
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.12
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    • pp.1300-1305
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    • 2014
  • Equivalent circuits for the waveguide probe with H-shaped small aperture, as a key ingredient of near field microwave microscope, is described along with a working principle of the probe. Small rectangular or circular aperture in comparison with the wavelength behaves like the inductive element. So adding the ridged structure (corresponding to capacitive component) to the small aperture allows the transmission resonance to occur. For verification, we represents the equivalent circuit descriptions for the two types, ridged aperture and cavity types. The values of obtained by use of the equivalent circuit approaches are compared with those obtained by use of the available numerical software. The results are also experimentally verified.

Analysis of Fiber-grating External-cavity Laser Diode Using Large-signal Time-domain Model (대신호 시영역 모델을 이용한 광섬유 격자 외부 공진 레이저 다이오드의 해석)

  • Kim, Jae-Seong;Chung, Youngchul;Cho, Ho Sung
    • Korean Journal of Optics and Photonics
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    • v.23 no.5
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    • pp.227-232
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    • 2012
  • A large-signal time-domain model is implemented to analyze an FG-LD (Fiber Grating Laser Diode) in which a reflective laser diode is hybrid-integrated with a fiber Bragg grating (FBG). When the length of the externally integrated resonator is 8 mm, in which the effective FBG length of 2.1 mm is included, a static frequency chirp of 0.44 GHz and a dynamic frequency chirp of 6.4 GHz are observed. In addition, it is also observed that the eye of the 10Gbps NRZ signal is well open. The FG-LD is expected to be a cost-effective solution for a 10Gbps-class single wavelength laser covering a span of 50 km range.

A femtosecond Cr:LiSAF laser pumped by semiconductor lasers (반도체 레이저 여기 펨토초 Cr:LiSAF 레이저)

  • 박종대
    • Korean Journal of Optics and Photonics
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    • v.11 no.5
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    • pp.360-364
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    • 2000
  • We demonstrate self-starting passIve mode locking of a Cr:LiSAF laser, using a SCIDlconduclor Saturable Absorber Mirror (SESAM), Two high-power red semiconductor lasers (Coherent S-67-500C-100-H) of wavelength 667 nm and maximum power of 500 mW were used as pump lasers, The cavity has 10 cm radius-ai-curvature folding minors, two SF 10 prisms, a 99% reflectivity output coupler and a SESAM at dIe focus of a 10 cm radIus-at-curvature mirror. We used the laser crystal in BrewsterBrewster shape with 1 5% $Cr^{+3}$ ion concentration and the length of 6 mm, An X-shaped resonator was used to compensate the astigmatism induced by tile crystal. The structure of the SESAM cOllSists of 30 pmr of $AlAs/Al_{0.15}Ga_{0.85}As$ layer, wi1l1 a 10 nm GaAs quantum well situated in the topmost layer Output spectra were centeled at 833 nm, with 4 nm spectral bandwidth and pulse width was measured to be 220 fs, Output power of 3 mW is obtained at a pump power of 800 mW. 00 mW.

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