High-brightness scalable continuous-wave single-mode photonic-crystal laser.

Realizing large-scale single-mode, high-power, high-beam-quality semiconductor lasers, which rival (or even replace) bulky gas and solid-state lasers, is one of the ultimate goals of photonics and laser physics. Conventional high-power semiconductor lasers, however, inevitably suffer from poor beam quality owing to the onset of many-mode oscillation1,2, and, moreover, the oscillation is destabilized by disruptive thermal effects under continuous-wave (CW) operation3,4. Here, we surmount these challenges by developing large-scale photonic-crystal surface-emitting lasers with controlled Hermitian and non-Hermitian couplings inside the photonic crystal and a pre-installed spatial distribution of the lattice constant, which maintains these couplings even under CW conditions. A CW output power exceeding 50 W with purely single-mode oscillation and an exceptionally narrow beam divergence of 0.05° has been achieved for photonic-crystal surface-emitting lasers with a large resonant diameter of 3 mm, corresponding to over 10,000 wavelengths in the material. The brightness, a figure of merit encapsulating both output power and beam quality, reaches 1 GW cm-2 sr-1, which rivals those of existing bulky lasers. Our work is an important milestone toward the advent of single-mode 1-kW-class semiconductor lasers, which are expected to replace conventional, bulkier lasers in the near future.

Development of Needle Guide Unit Considering Buckling Bone-Perforation Control Strategy Based on Computed Tomography-Guided Needle Insertion Robot.

A computed tomography (CT)-guided robotic assistance system is useful for needle insertion into metastatic carcinoma of vertebrae, which has limited pathways. However, the use of conventional needles in this procedure can result in bone fracture in the perforation area caused by the reaction force of the inserted needle. In this study, we developed a multistage retractable needle guide unit that avoids the buckling and crushing of the needle tip that commonly occur in 25-gauge ultrafine needles. First, we clarified a relationship between the shape of the guide and the termination factor when a buckling load is applied to the needle. Next, we revealed the point at which the plastic deformation of the needle occurred when the bone is drilled. Based on these results, we developed a guide unit with the reaction force set to an appropriate value. Finally, an evaluation test of bone needle insertion was conducted on porcine vertebrae with using the developed needle guide unit equipped with a 25-gauge needle. The needle penetrated the vertebra without buckling or crushing of the needle tip, which demonstrates the value of this multistage retractable needle guide unit when ultrafine needles are required. Clinical Relevance- Cancer tumors often metastasize to bones. There is a treatment called percutaneous vertebroplasty which restores the patient's quality of life by injecting poly (methyl methacrylate) (PMMA) into a bone. It helps to reinforce the bone that has become brittle due to cancer metastasis to the vertebral body or osteoporosis. This treatment often involves puncture of the vertebrae but the limited puncture pathway makes it difficult to perform the treatment manually. Therefore it is necessary to construct a system that supports accurate puncture by a robot such as the proposed method.

General recipe to realize photonic-crystal surface-emitting lasers with 100-W-to-1-kW single-mode operation.

Realization of one-chip, ultra-large-area, coherent semiconductor lasers has been one of the ultimate goals of laser physics and photonics for decades. Surface-emitting lasers with two-dimensional photonic crystal resonators, referred to as photonic-crystal surface-emitting lasers (PCSELs), are expected to show promise for this purpose. However, neither the general conditions nor the concrete photonic crystal structures to realize 100-W-to-1-kW-class single-mode operation in PCSELs have yet to be clarified. Here, we analytically derive the general conditions for ultra-large-area (3~10 mm) single-mode operation in PCSELs. By considering not only the Hermitian but also the non-Hermitian optical couplings inside PCSELs, we mathematically derive the complex eigenfrequencies of the four photonic bands around the Γ point as well as the radiation constant difference between the fundamental and higher-order modes in a finite-size device. We then reveal concrete photonic crystal structures which allow the control of both Hermitian and non-Hermitian coupling coefficients to achieve 100-W-to-1-kW-class single-mode lasing.

Direct C-H Carboxylation Forming Polyfunctionalized Aromatic Carboxylic Acids by Combined Brønsted Bases.

CO2 fixation into electron-deficient aromatic C-H bonds proceeds with the combined Brønsted bases LiO-t-Bu and LiO-t-Am/CsF/18-crown-6 (t-Am = CEtMe2) under a CO2 atmosphere to afford a variety of polyfunctionalized aromatic carboxylic acids.

Robotic Cytology using Extra-Fine Needles : -Proposal of Puncture Control Strategy for Increasing Collection Amount.

Fine needle aspiration cytology requires accurate needle insertion into a tumor and sufficient amount collection of samples, which highly depends on the skill of the physician. The advantage of the diagnosis is to minimize the tissue damage with the fine needle, while, when the amount of the sample sucked from the lesion is not enough for the definite diagnosis, the procedure has to be repeated until satisfying them. Although numerous research reported a robot-assisted insertion method to improve the accuracy of needle placement with fine needles, there was less research to address the efficient tissue collection. Ideally, the amount of the samples can be satisfied for the diagnosis even if an extra-fine needle (e.g. 25-gauge) is used. This paper proposes a novel needle insertion method for increasing the amount of the tissue sample with the extra-fine needle. The proposed insertion method comprises the round-trip insertion motion and trajectory rerouting with the nature of the bevel-tipped needle. The phantom study's result showed the equivalency of the aspiration amount between a physician's manual procedure with a 22-gauge needle and the proposed method with a 25-gauge needle (4.5 ± 1.0 mg vs 5.1 ± 0.7 mg). The results suggested that the proposed robotic aspiration method can increase the sampling amount with the extra-fine needle in the fine needle aspiration cytology.

Quantitative Evaluation of Bleeding during Blood Vessel Puncture Caused by Fine Needle in Lower Abdomen.

Inserting a fine needle presents a trade-off problem between safety and accuracy. As one of the serious complications due to tissue damages during needle insertion, severe bleeding often occurs owing to blood vessel puncture. However, there are few researches to evaluate the safety quantitatively regarding bleeding during the fine needle insertion. Therefore, the purpose of this study was the quantitative evaluation of the amount of bleeding due the artery and vein puncture depending on the needle size. We developed a blood circulation system for measuring the amount of bleeding due to blood vessel puncture. Using the system, the amount of bleeding due to different needle sizes was evaluated. The results suggested that the amount of bleeding per unit time increased depending on the needle radius. According to ordinal safety standards, the 22-gauge needle is appropriate for insertion into the lower abdomen.