• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.352-352
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• 2010

일반적인 근접장 현미경은 광섬유 팁 (tip) 끝에 수십 nm 크기의 구멍을 이용하여 근접장을 발생시키거나 측정한다. 근접장은 전파되는 빛보다 미세한 구조의 정보를 반영하게 되는데 수십 나노미터의 구멍대신 FRET (fluorescence resonance energy transfer)이라는 현상을 근접장 현미경에 적용하고자 한다. 10 nm 이내의 거리에서 상호작용을 하는 이 현상을 이용하여 광학적 분해능을 향상시킬 수 있다. FRET 현상의 도우너(donor)로서는 양자점을 사용하였으며 억셉터(acceptor) 로서는 Cy5 염료를 사용하였다. 팁으로는 광섬유를 에칭한 팁에 Cy5 염료를 코팅한 팁과 광섬유의 코어(core) 부근에 양자점이 포함된 광 폴리머를 응고시켜서 만들어진 팁을 사용하였다. 팁에 위치한 도우너와 시료로 사용되는 억셉터를 FRET 상호 작용 거리 내로 접근시키기 위하여 tuning fork를 이용한 shear force control을 사용하였다. 한 점에서의 접근 과정에서 FRET의 현상의 특징으로서 도우너인 양자점의 형광이 약해지고 Cy5의 형광이 강해지는 것을 측정하였다. 또한, 양자점을 Cy5 염료에 근접시켰을 때 발광 생존시간 (lifetime)이 짧아지는 것을 관찰하여 FRET 현상을 재확인 하였다.

• Korean Journal of Optics and Photonics
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• v.25 no.4
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• pp.200-206
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• 2014

In this paper, using the value theoretically calculated to emit multidirectionally a beam coming into an optical fiber with diameter of $125{\mu}m$, we modeled and produced a cone-shaped structure at the distal end of the fiber. A numerical simulation was performed for an optical fiber tip in which all incident beams were totally reflected and emitted toward the side, as well as for an optical fiber tip from which the beams could be emitted forward and sideways simultaneously. We produced multidirectional-firing optical fiber tips based on the simulation result and model. Laser fabrication of the optical fiber was done by processing a cone-shaped structure at the distal end of an optical fiber with diameter of $125{\mu}m$ using a femtosecond pulsed laser and polishing the processed surface with a $CO_2$ laser. We also conducted an analysis to compare experimental and simulation results.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.871-876
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• 2019

We fabricated concave optical fiber tips using hydrofluoric acid solution and photothermal effect induced by $1.55{\mu}m$ wavelength laser applied to an optical fiber. The radius of curvature of the concave optical fiber tips fabricated with different applied laser power, etching time, and concentration of hydrofluoric acid was measured with an optical microscope. Then, we analyzed how the radius of curvature changes for those three variables. In addition, the reliability of the measurement method using a microscope was verified through a free spectral range(FSR) and a scanning electron microscope(SEM). Through this paper, the radius of curvature can be adjusted by the variables of the fabrication process of concave optical fiber tips; thus, it is overcoming the limitations of conventional optical fiber etching methods using hydrofluoric acid solutions.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.267-272
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• 1999

We attached a fiber tip on the branch of a quartz crystal oscillator in order to make a feedback control system for near field optical microscope. The electrical impedance of the quartz crystal oscillator depends on the distance between the surface of the sample and the tip caused by the surface damping. Using this method, we can directly monitor the distance between the sample and the tip without inserting extra beam which might give extra optical noise. We characterize the XY scanning resolution and the amplitude of the vibrating tip and the Z-dependent decay of the evanescent wave.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.5
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• pp.731-736
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• 2017

In this paper, we report the fabrication of concave surface fiber tips for optical resonators. It was confirmed that the radius of curvature on fiber end can be controlled by introducing the hydrofluoric acid solution and the wavelength of $1.55{\mu}m$ laser which is absorbed well in the etchant to induce the photothermal effect. Using the microscope images, we observed the proposed concave fiber tip fabrication method is effective to make the controllable concave tips. We also observed changes in the size of the beam emitted from the tips with the various radius of curvature using the beam profiler. The authors believe that the proposed method will be applied to resonators for optical communications.

• Laser Solutions
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• v.18 no.3
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• pp.14-19
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• 2015

A helical fabricating method using $CO_2$ laser was utilized for producing cone-shaped structure on a silica substrate. Output power and the number of scanning radiation were modified in order to control the structure. The experiment shows that the depth and width of cone-shape were increased with higher output power of the laser and the number of scanning. We demonstrate fabrication of multidirectional side-firing optical fiber with diameter of 440 um using the $CO_2$ laser fabrication technique.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.10
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• pp.1017-1022
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• 2013

Currently, various optical fiber tips are used to deliver laser beam for endoscopic surgery. In this paper, we demonstrated multidirectional (forward and side) firing optical fiber tip using a femtosecond micromachining and $CO_2$ laser polishing technology. We controlled the edge width of optical fiber tip, by modulating the condition of $CO_2$ laser, to regulate the amount of side and forward emission. The distal end of the optical fiber with core/clad diameter of $400/440{\mu}m$ was microstructured with cone shape by using a femtosecond laser. And then the microstructured optical fiber tip was polished by $CO_2$ laser beam result in smoothing and specular reflection at the surface of the cone structure. Finally, we operated the LightTools simulation and good agreement was generally found between the proposed model and experimental simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1058-1061
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• 2004

미세 소자를 관측, 가공 및 분석하기 위해 사용되는 기존 광학현미경은 빛으로 물체를 관측하므로 대물렌즈 (Object lens)에서의 회절한계 때문에 분해능의 있으므로 매우 뽀족한 탐침(Probe)을 시료의 표면에 근접시킨 후 표면을 주사하여 이미지를 얻는 방법이 개발되어 최근에는 Optical Fiber를 이용하여 fiber 끝단을 nano-scale 정도로 첨예화시키는 기술이 개발되었다. 이러한 광섬유 탐침은 구경의 직경이 작을수록 높은 분해능을 얻을 수 있으므로 광섬유 탐침의 제작 공정 확립은 매우 중요하다. 그 중에서 대표적인 방법이 $CO_2$ 레이저를 이용하여 가열한 후 인장 하는 방법 (Heating and Pulling)이 있다. 그래서 본 연구에서는 $CO_2$ 레이저를 이용하여 100nm 정도의 팁 반경을 갖는 뽀족한 탐침을 제작하고자 한다.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.147-148
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• 2009

We have fabricated a down tapered polymer tip on optical fiber end-face by a guided UV light. One side of fiber was aligned with a mercury-xenon lamp and another was put into UV curable polymer. A shape of tip was controlled by adjusting an irradiance of lamp and time of exposure. A bending effect also affects the result. Optical characteristic was achieved preliminarily with solution of minute particles.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.260-261
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• 2002

For Near-field Scanning Optical Microscopy measurements, the fiber tip is glued on the side of one of the tuning fork prongs vertically to its extended direction. Higher Q-factor is attainable in this geometry than in the arrangement with the fiber tip parallel to the prong. A simple mechanical design is applied to hold the fiber tip above the gluing point. The overall tuning fork-fiber tip assembly gives another advantage of the flexible Q-factor enhancement. With this treatment, Q-factor higher than 3000 is easily achievable. As an operating instance, a grating is scanned for its one dimensional topographical image.