8 W 240 fs diode-pumped Yb:Y2O3 ceramic thin-rod femtosecond amplifier.

A diode-pumped Yb:Y2O3 ceramic thin-rod amplifier which operates in the femtosecond regime is studied here. In a single-stage and direct four-pass amplification scheme, the amplifier delivers maximum output power of 8.1 W at a center wavelength of 1030.5 nm and spectral bandwidth of 4.8 nm. Assume a sech2-shaped pulse, a pulse duration of 239 fs is measured, exhibiting a time-bandwidth product value of 0.324. To the best of our knowledge, our Yb:Y2O3 ceramic thin-rod femtosecond amplifier exhibits the shortest pulse duration with Watt-level output power among all Yb:Y2O3-based femtosecond amplifiers.

Comparative study of Yb:KYW planar waveguide lasers Q-switched by direct- and evanescent-field interaction with carbon nanotubes.

Both direct- and evanescent-field interactions with carbon nanotubes (CNTs) are applied to achieve stable Q-switched operation of Yb:KYW planar waveguide lasers. The performance characteristics were investigated in a same cavity configuration and analyzed in detail in the following three cases, CNTs deposited onto end mirror (M-coating), output coupler (OC-coating) and top surface of the planar waveguide (WG-coating). Maximum output powers, repetition rates, and minimum pulse durations are 61 mW, 1103 kHz and 215 ns for OC-coating, 39 mW, 1052 kHz and 275 ns for WG-coating, and 26 mW, 1119 kHz and 217 ns for M-coating, respectively. From the calculation of the configuration-dependent stability range, the beam size and the electric field distribution in the Yb:KYW planar waveguide, it is confirmed that the evanescent-field interaction scheme makes stable Q-switching possible with much lower intensities at saturable absorber compared to the direct-field interaction scheme in the presented waveguide laser operation.

Graphene mode-locked femtosecond Cr2+:ZnS laser with ~300 nm tuning range.

Graphene has proved to be an excellent broadband saturable absorber for mode-locked operation of ultrafast lasers. However, for the mid-infrared (mid-IR) range where broadly tunable sources are in great needs, graphene-based broadly tunable ultrafast mid-IR lasers have not been demonstrated so far. Here, we report on passive mode-locking of a mid-IR Cr:ZnS laser by utilizing a transmission-type monolayer graphene saturable absorber and broad spectral tunability between 2120 nm and 2408 nm, which is the broadest tuning bandwidth ever reported for graphene mode-locked mid-IR solid-state lasers. The recovery time of the saturable absorber is measured to be ~2.4 ps by pump-probe technique at a wavelength of 2350 nm. Stably mode-locked Cr:ZnS laser delivers Fourier transform-limited 220-fs pulses with a pulse energy of up to 7.8 nJ.

Carbon nanostructure-based saturable absorber mirror for a diode-pumped 500-MHz femtosecond Yb:KLu(WO4)2 laser.

We report a diode-pumped Yb:KLu(WO(4))(2) (Yb:KLuW) laser passively mode-locked by employing a carbon nanostructure-based multi-functional saturable absorber mirror. Two types of carbon nanostructures, single-walled carbon nanotubes (SWCNTs) and graphene, were deposited on a single dielectric mirror and applied both for stable mode-locking of the Yb:KLuW laser near 1050 nm in a compact cavity configuration. The carbon nanostructure mode-locked laser delivers 157-fs pulses with output powers of up to 85 mW at a repetition rate of 500 MHz.

Yb:KYW planar waveguide laser Q-switched by evanescent-field interaction with carbon nanotubes.

We report Q-switched operation of a planar waveguide laser by evanescent-field interaction with single-walled carbon nanotubes deposited on top of the waveguide. The saturable-absorber-integrated gain medium, which operates based on evanescent-field interaction, enables the realization of a diode-pumped 2.5-cm-long Q-switched Yb:KYW waveguide laser emitting at 1030 nm. With such a compact cavity design, we achieve maximum output powers of up to 30 mW, corresponding to a single-pulse energy of 124 nJ, at 241 kHz repetition rate. The shortest pulse duration of 433 ns is generated at a repetition rate of 231 kHz.

Optimal Hyperspectral Band Selection for Tissue Oxygenation Mapping with Generative Adversarial Network.

Tissue oxygenation assessment using hyperspectral imaging is an emerging technique for the diagnosis and pre- and post-treatment monitoring of ischemic patients. However, the high spectral resolution of hyperspectral imaging leads to large data sizes and a long imaging time. In this study, we propose a method that utilizes multi-objective evolutionary algorithms to determine the optimal hyperspectral band combination when developing a deep learning model for predicting tissue oxygenation from hyperspectral images. Our results confirm that the deep learning model effectively predicts tissue oxygenation images for various oxygenation states. Moreover, we demonstrate that a high-performance prediction model can be developed using only a small number of spectral bands, indicating the potential for more efficient non-contact tissue oxygenation mapping with the proposed method.Clinical Relevance- The proposed method allows for the non-contact and efficient acquisition of two-dimensional tissue oxygenation information in various oxygenation states.

[Paneth Cell Carcinoma of the Stomach].

Paneth cell carcinoma is a rare carcinoma composed predominantly or purely of malignant Paneth cells. An 83-year-old woman presented for evaluation of an elevated lesion in the stomach. On endoscopy, a 15 mm, discolored, elevated lesion with a central depression was found on the greater curvature of the gastric lower body. Endoscopic forceps biopsy revealed chronic gastritis with intestinal metaplasia. Magnifying endoscopy revealed an irregularly oval/tubular microsurface pattern and an irregular loop microvascular pattern with a demarcation line, suggestive of early gastric cancer. Therefore, endoscopic submucosal dissection was performed. Histopathological examination revealed a well-differentiated tubular adenocarcinoma limited to the muscularis mucosae and the tumor cells contained coarse eosinophilic granules in the cytoplasm. These tumor cells were diffusely and strongly stained for lysozyme, confirming the tumor diagnosis as Paneth cell carcinoma. Herein, we report a rare case of Paneth cell carcinoma and its endoscopic and histopathologic findings.

High-quality, large-area monolayer graphene for efficient bulk laser mode-locking near 1.25 µm.

High-quality monolayer graphene as large as 1.2×1.2 cm2 was synthesized by chemical vapor deposition and used as a transmitting saturable absorber for efficient passive mode-locking of a femtosecond bulk solid-state laser. The monolayer graphene mode-locked Cr:forsterite laser was tunable around 1.25 µm and delivered sub-100 fs pulses with output powers up to 230 mW. The nonlinear optical characteristics of the monolayer graphene saturable absorber and the mode-locked operation were then compared with the case of the bilayer graphene saturable absorber.