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Publisher：Optics Letters  

Spectral peaking in an optical fiber is a useful phenomenon for comb mode filtering and wavelength standards. However, for highly sensitive spectroscopic applications, it is important to suppress the pedestal components. Here we propose and demonstrate pedestal-suppressed spectral peak generation using a nonlinear fiber loop mirror with a molecular gas cell. The physical mechanism and fundamental properties were investigated numerically, and the output characteristics were examined experimentally. Almost background-free spectral peaks were generated successfully in the 1.65-µm wavelength range using a CH4 gas cell. The maximum signal-to-background ratio was more than 30 dB. Stable operation without any feedback control was achieved. It is expected that the proposed method is useful for highly sensitive spectroscopic applications.

DOI： 10.1364/OL.499798

Web of Science

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PubMed

Publisher：Optics Express  

Spectral peak generation is a recently reported phenomenon that narrow spectral dips of the optical spectrum turn into sharp peaks as they propagate through nonlinear optical fibers. We demonstrated the nonlinear polarization rotation-based spectral peak mode filtering to increase the signal-to-background ratio (SBR). The spectral peaks with almost constant frequency separation were generated from the femtosecond pulses absorbed by the CH4 gas through the highly nonlinear fiber. The generated spectral peaks were filtered through the polarizing beam splitter by the nonlinear polarization rotation, and the SBR was improved from 9 dB to ∼20 dB. The spectral peak generation phenomenon and the mode filtering were numerically confirmed by solving the coupled nonlinear Schrödinger equations. The demonstrated method can generate strong comb modes with wide frequency spacing which are useful for highly sensitive environmental gas sensing spectroscopy. The wavelengths of the spectral peaks are fixed by the absorption spectra of the used gas cells. Therefore, this method can generate high quality spectral peaks of any wavelengths with wide spectral ranges through proper combinations of gas cells.

DOI： 10.1364/OE.496731

Web of Science

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PubMed

Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

DOI： 10.1117/12.2659569

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Publisher：2023 Conference on Lasers and Electro-Optics, CLEO 2023  

We demonstrated freely controllable spectral peak generation using 206 MHz figure-9 fiber laser comb, LCOS-SLM, and nonlinear fibers. Selected comb modes were extracted as the spectral peaks with high signal to background ratio >30 dB.

Scopus

Publisher：2023 Conference on Lasers and Electro-Optics, CLEO 2023  

We proposed mode-filtering technique of spectral peaks using nonlinear polarization rotation in optical fiber. Intense, narrow multiple spectral peaks with ~20 dB background ratio were successfully generated with CH4 gas cell and nonlinear fiber.

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Applied Sciences (Switzerland)  

Featured Application: Biomedical imaging, Environmental spectroscopy, LIDAR, Medicine, and Laser processing. In this paper, we have demonstrated a dispersion-managed, high-power, Tm-Ho co-doped ultrashort pulse fiber laser using a single walled carbon nanotube (SWNT) dispersed in polyimide film. An in-line type spectral filter was developed to control the output pulse spectra. Two SWNT films with different modulation depths were examined as a mode-locker. Normal dispersion fiber was used in the fiber laser oscillator, and dependence on net cavity dispersion was investigated. Passive mode-locking was achieved in a wide dispersion range, from −0.319 to +0.101 ps2. Stable soliton mode-locking operation and dissipative soliton mode-locking operations were observed. The pumping efficiency was ~3 times higher than that in a Tm-doped fiber laser with a similar configuration. The developed fiber laser showed self-start and stable operations, and this laser is useful for practical applications.

DOI： 10.3390/app122312369

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Publisher：2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings  

We demonstrated spectral peaking phenomenon in fiber laser cavity for the first time. Ultrashort soliton pulse with multiple sharp spectral peaks were successfully generated in Er-doped SWNT fiber laser with HCN gas cell.

Scopus

Publisher：2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings  

Speckles in OCT hinder visibility of finescale structures. We demonstrated speckle reduced OCT imaging using 1.7 μm tunable Quasisupercontinuum fiber laser source, and the improvement of image contrast in deep tissue imaging was successfully confirmed.

Scopus

Publisher：2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2022 - Proceedings  

Thermally induced optical pass difference of the thin-disk laser with anisotropic Yb:KRE(WO4)2 crystal, which is promising broadband gain media, was calculated. The results show that the OPD is sufficiently small even at 9.6 kW/cm2 pumping.

DOI： 10.1109/CLEO-PR62338.2022.10432035

Scopus

Publisher：2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2022 - Proceedings  

Arbitrary controlled spectral peak generation was demonstrated using ultrashort pulse fiber laser and spectral filter with LCOS-SLM. The intense, sharp spectral peak with record high contrast up to 143 was successfully obtained.

DOI： 10.1109/CLEO-PR62338.2022.10432708

Scopus

Publisher：2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2022 - Proceedings  

Characteristics of spectral peaking in fiber laser were investigated both experimentally and numerically. Ultrashort soliton pulse with multiple sharp spectral peaks were generated stably. The peak intensity was increased exponentially for the magnitude of absorption.

DOI： 10.1109/CLEO-PR62338.2022.10432524

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

We report, to the best of our knowledge, the highest power conductive-cooled active-mirror amplifier (CcAMA) using Yb:YAG with a pulse energy of 10 J. By using four liquid-nitrogen circulating cooled laser heads, we achieved a repetition rate, pulse energy, and average power of 33.3 Hz, 9.3 J, and 310 W, respectively. The problem of wavefront distortion, which is difficult to solve with a large-aperture active-mirror laser, is suppressed by using reinforcing materials with the same thermal expansion coefficient. We have confirmed that the wavefront distortion is small (0.15 lambda P-V per head) at 100 Hz operation, which paves the way for 100 Hz operation with the CcAMA concept. (C) 2021 Optical Society of America

DOI： 10.1364/OL.414926

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Publisher：Optics InfoBase Conference Papers  

A stable operation of 1.1 J/100 Hz 10 ns laser pulses were achieved from a single cryogenically cooled Yb:YAG rod amplifier with ink-cladding. The efficiency and gain coefficient were 44% and 383, respectively.

Scopus

Language：English   Publisher：Optics InfoBase Conference Papers  

We have developed a conductive-cooled Yb:YAG active-mirror amplifier with an diameter of 50 mm and a liquid-nitrogen circulation system. The high thermal capability that enables 10 J, 50 Hz laser amplification was demonstrated successfully.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1364/OL.43.005451

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：OSA - The Optical Society  

The first Kerr-lens mode-locked Yb:Lu2O3 ceramic thin-disk laser was demonstrated. The shortest pulse duration was 177 fs with 3.2 W output power. The output power of 17 W with 588 fs pulses was also demonstrated.

DOI： 10.1364/CLEO_SI.2018.SF2N.5

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

Highly transparent ceramic is an attractive gain medium for high-power lasers due to its high fracture toughness, homogeneity, and size scalability. Here we report the first Yb3+-doped CaF2-LaF3 ceramics laser. Codoping of La3+ ion can reduce the formation of Yb2+ ions and enhance the laser efficiency. In the laser experiment, the maximum output power of 4.36 W and the maximum slope efficiency of 69.5% were obtained with a 3% La, 2% Yb sample and a 2% La, 1% Yb sample, respectively. Due to the combined properties of Yb: CaF2 and a ceramic laser gain medium, Yb: CaF2-LaF3 ceramic is a promising gain medium for a high-power ultrashort pulse laser and amplifier. (C) 2017 Optical Society of America

DOI： 10.1364/OL.42.001724

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Other Link： http://orcid.org/0000-0002-7082-6145

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：OSA - The Optical Society  

CW Yb: Lu2O3 ceramic thin-disk laser with the maximum output power of 174 W was demonstrated. Slope efficiency was 54%. Disk temperature during lasing was observed and maximum temperature was 84.1 °C under 5.5 kW/cm2 pumping.

DOI： 10.1364/ASSL.2017.JM5A.32

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：OSA - The Optical Society  

We demonstrated SWCNT-assisted Kerr-lens mode-locked Yb:CaF2 laser. The pulse duration of 87 fs with 260-mW output power and the shortest pulse duration of 77 fs with 94-mW output power were obtained.

DOI： 10.1364/CLEO_AT.2017.JTh2A.130

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

Yb:LuAG is a promising gain medium for high-power lasers due to its high thermal conductivity and large emission cross section. Although narrowband gain media such as Yb: LuAG are not considered to be suitable for the generation of sub-100 fs pulses, we have achieved generation of 91 fs pulses with Yb: LuAG ceramic by the Kerr-lens mode-locking (KLM) technique. The obtained average power, pulse energy, and peak power were 1.64 W, 20.0 nJ, and 220 kW, respectively. These are, to the best of our knowledge, the first demonstration of KLM and the new records based on both Yb: LuAG ceramic and single crystal. (C) 2016 Optical Society of America

DOI： 10.1364/OL.41.004570

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Other Link： http://orcid.org/0000-0002-7082-6145

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We prepared transparent Yb:CaF2-LaF3 ceramics with different combinations of doping concentrations of Yb3+ and La3+ and obtained CW laser operation with maximum output of 3.97 W. The maximum slope efficiency was as high as 73.1%.

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