A5083087149- Advanced Fiber Laser Technologies
- Advanced Fiber Optic Sensors
- Advanced Measurement and Metrology Techniques
- Photonic and Optical Devices
- Mechanical and Optical Resonators
- Photonic Crystal and Fiber Optics
- Advanced Optical Sensing Technologies
- Laser-Matter Interactions and Applications
- Solid State Laser Technologies
- Semiconductor Lasers and Optical Devices
- Optical Network Technologies
- Scientific Measurement and Uncertainty Evaluation
- Surface Roughness and Optical Measurements
- Advanced Frequency and Time Standards
- Thin-Film Transistor Technologies
- Retinal Diseases and Treatments
- Ocular Diseases and Behçet’s Syndrome
- Optical Coatings and Gratings
- Advanced Optical Network Technologies
- Ergonomics and Musculoskeletal Disorders
- Retinal and Optic Conditions
- Spectroscopy and Laser Applications
- Helicobacter pylori-related gastroenterology studies
- Advanced Sensor Technologies Research
- Occupational Health and Safety in Workplaces
Korea Research Institute of Standards and Science
2020-2025
Korea University of Science and Technology
2023-2025
University of California, Los Angeles
2019-2025
Kyung Hee University
2024
Dongguk University
2024
Yonsei University
2024
National University of Defense Technology
2024
University of California System
2022
Korea Advanced Institute of Science and Technology
2002-2020
St. Vincent's Hospital
2018
Laser interferometry serves a fundamental role in science and technology, assisting precision metrology dimensional length measurement. During the past decade, laser frequency combs - coherent optical-microwave ruler over broad spectral range with traceability to time-frequency standards have contributed pivotal roles ever-growing demands measurement precision. Here we report spectrally-resolved via soliton microcomb, nanometric-scale Spectral provides information on optical time-of-flight...
Abstract We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse payload designed to meet space-use requirements, undergone through ground qualification tests and finally launched into low-earth orbit early 2013. Test results obtained during one-year mission lifetime confirmed stable mode-locking all way although radiation induced attenuation (RIA) gain caused 8.6% reduction output power. This...
A multi-wavelength interferometer utilizing the frequency comb of a femtosecond laser as wavelength ruler is tested for its capability ultra-precision positioning machine axis control. The uses four different wavelengths phase-locked to and then determines absolute position through multi-channel scheme detecting interference phases in parallel so enable fast, precise stable measurements continuously over few meters axis-travel. Test results show that proposed proves itself potential...
Abstract A prototype laser distance interferometer is demonstrated by incorporating the frequency comb of a femtosecond for mass-production optoelectronic devices such as flat panel displays and solar cell devices. This comb-referenced uses four different wavelengths simultaneously to enable absolute measurement with capability comprehensive evaluation stability uncertainty. The result reveals that reaches 3.4 nm 3.8 m at 1.0 s averaging, which further reduces 0.57 100 averaging fractional...
We revisit the method of synthetic wavelength interferometry (SWI) for absolute measurement long distances using radio-frequency harmonics pulse repetition rate a mode-locked femtosecond laser. Our intention here is to extend nonambiguity range (NAR) SWI coarse virtual synthesized by shifting rate. The proposed concept NAR extension experimentally verified measuring ∼13-m distance with repeatability 9.5 μm (root-mean-square). precision estimated be 31.2 in comparison an incremental He–Ne...
The spectral domain interferometer (SDI) has been widely used in dimensional metrology. Depending on the nature of SDI, both wider bandwidth and narrower linewidth light source are paradoxically required to achieve better resolution longer measurable distances. From this perspective, a broadband frequency comb with repetition rate high enough be spectrally resolved can an ideal for SDIs. In paper, we propose implement electro-optic realize comb-mode SDI. proposed was designed optically...
Abstract Multilayer thin-film structures are widely used for many different types of devices in the semiconductor, display, and battery manufacturing industries. In such devices, thickness each layer should be strictly controlled to meet desired performance requirements. Various measurement techniques have been utilized take measurements, but verification these measurements continues rely on simple comparisons. this study, an uncertainty evaluation a multilayer structure, four-layer sample...
Over the last two decades, frequency combs have brought breakthroughs in length metrology with traceability to standards. In particular, frequency-comb-based spectral interferometry is regarded as a promising technology for next-generation However, achieve this, nanometer-level precision inherent laser interferometer required. Here, we report distance measurements by sub-nm close standard quantum limit. The measurement was confirmed 0.67 nm at an averaging time of 25 us. sensitivity found be...
A two-color scheme of heterodyne laser interferometer is devised for distance measurements with the capability real-time compensation refractive index ambient air. fundamental wavelength 1555 nm and its second harmonic 777.5 are generated, stabilization to frequency comb a femtosecond laser, provide fractional stability order 3.0 × 10(-12) at 1 s averaging. Achieved uncertainty 10(-8) in measuring distances 2.5 m without sensing air adverse environmental conditions.
Femtosecond lasers allow for simultaneous detection of multiple absorption lines a specimen over broad spectral range infrared or visible light with single spectroscopic measurement. Here, we present an 8-THz bandwidth, 0.5-GHz resolution scheme Fourier-transform spectroscopy using Er-doped fiber femtosecond laser. A resolving power 1.6 × 10(4) about 1560-nm center wavelength is achieved by sweeping the pulse repetition rate source on Mach-Zehnder interferometer configured to capture...
Abstract We report a multi-channel optical frequency synthesizer developed to generate extremely stable continuous-wave lasers directly out of the comb an Er-doped fiber oscillator. Being stabilized high-finesse cavity with fractional stability 3.8 × 10 −15 at 0.1 s, comb-rooted produces multiple frequencies ultra-narrow linewidth 1.0 Hz 1 s concurrently output power tens mW per each channel. Diode-based stimulated emission by injection locking is key mechanism that allows modes sprout up...
We demonstrate a full C-band wavelength-tunable mode-locked fiber laser with repetition rate of 250 MHz, representing the highest for tunable lasers thus far to best our knowledge. The polarization-maintaining fiber-based Fabry-Perot cavity enables fundamental MHz semiconductor saturable absorber mirror as mode-locker. observed stable and single soliton mode-locking state wide tunability center wavelength from 1505 1561 nm by adjusting incident angle bandpass filter inside cavity....
Abstract Over the last two decades, frequency combs have brought breakthroughs in length metrology with traceability to standards. In particular, frequency‐comb‐based spectral interferometry is regarded as a promising technology for next‐generation However, achieve this, nanometer‐level precision inherent laser interferometer required. Here, distance measurements are reported by sub‐nm close standard quantum limit. The measurement confirmed 0.67 nm at an average time of 25 µs. sensitivity...
In this study, an optical system for simultaneous measurement of physical thickness, group refractive index, bow, and warp a large silicon wafer is first proposed based on reflection-type spectral-domain interferometer. Such key parameters are determined by combining four different path differences (OPDs) measured at each sampling point throughout two-axis sample scanning within area 250 mm mm. To overcome the limitations deflection free, unclamped large-sized wafer, two OPDs representing...
The importance of dimensional metrology has gradually emerged from fundamental research to high-technology industries. In the era fourth industrial revolution, absolute distance measurements are required cope with various applications, such as unmanned vehicles, intelligent robots, and positioning sensors for smart factories. cases, size, weight, power, cost (SWaP-C) should essentially be restricted. this paper, sub-100 nm precision based on an amplitude-modulated continuous-wave laser...
We present a polarization-maintaining (PM) type of Er-doped fiber linear oscillator designed to produce femtosecond laser pulses with high operational stability. Mode locking is activated using semiconductor saturable absorber mirror (SESAM) attached one end the PM oscillator. To avoid heat damage, SESAM mounted on copper-silicon-layered sink and connected through buffer dissipating residual pump power. A long-term stability test performed prove that proposed design maintains soliton-mode...
When manufacturing glass substrates for display devices, especially large-sized ones, the time-varying spatial temperature gradient or distribution on samples is remarkably observed. It causes serious degradation of thickness measurement accuracy due to combination thermally expanded and temperature-dependent refractive index. To prevent minimize in accuracy, over an entire substrate has be known real time synchronization with specify index sample based exact mathematical model In this...
Abstract The electro-optic comb (EO comb) with a relatively wide mode spacing of 25 GHz can be resolved into individual frequency modes commercially available high-resolution spectrometer. EO has numerous discrete modes, which serve as light source for monochromatic laser interferometer to realize the meter. In this study, method measuring absolute distances based on multi-wavelength principle is proposed and demonstrated by simultaneously implementing 102 interferometers using an comb. A...