Adjustable rotation of multiple vortices produced by diode-pumped Nd:YVO4 lasers using intracavity second harmonic generation.

The criteria for achieving adjustable rotation of optical vortices are analyzed and used to design a diode-pumped solid-state laser that incorporates intracavity second harmonic generation within a concave-flat cavity to produce frequency-doubled Hermite-Gaussian (FDHG) modes. These FDHG modes are subsequently employed to generate various structured lights containing 2, 4, and 6 nested vortices using an external cylindrical mode converter. Through theoretical exploration, we propose that increasing the radius of curvature of the concave mirror and extending the cavity length can enhance the rotational angles of multiple vortices by expanding the adjustable range of phase shift for FDHG modes. Moreover, theoretical analyses assess vortex rotation concerning the positions of a nonlinear medium, successfully validating the experimental observations and elucidating the phase structures of the transformed beams.

Orbital angular momentum densities in the astigmatic transformation of Lissajous geometric laser modes.

Orbital angular momentum densities in the astigmatic transformation of Lissajous geometric laser modes are originally and systematically investigated. The quantum theory of the coherent state is exploited to derive an analytical wave representation for the transformed output beams. The derived wave function is further employed to numerically analyze the propagation dependent orbital angular momentum densities. The parts of the negative and positive regions in the orbital angular momentum density are found to rapidly change in the Rayleigh range behind the transformation.

Investigating the generation and propagation evolution of orange optical vortices using continuous-wave KGW Raman lasers with astigmatic mode transformations.

Various high-order orange beams (HOBs) at 588 nm are produced via off-center pumped Nd:YVO4/KGW Raman lasers. We experimentally confirm that the HOBs can be fairly sustained at the incident pump power of 2.88 W, where the average output powers are overall from 300 mW to 160 mW with increasing the off-center displacements from 0.14 mm to 0.21 mm. The HOBs are further transformed by using an astigmatic mode converter to generate a variety of structured lights with optical vortices. Moreover, theoretical wave functions are analytically derived to characterize the propagation evolution of the converted HOBs. The experimental patterns for all propagating positions are excellently reconstructed by the derived wave functions, and the evolution of phase structures is numerically calculated to manifest the robust optical vortices.

Structured transverse modes governed by maximum entropy principle.

Based on the birefringent effect of the gain medium, a diode-pumped Nd-doped vanadate laser with nearly hemispherical cavity is exploited to emulate the quantum Green functions of two-dimensional commensurate harmonic oscillators. By matching the theoretical calculations to the far-field patterns of lasing modes, the resonant transverse frequencies can be accurately determined up to extremely high orders. The Shannon entropy is further employed to calculate the spatial entanglement of the quantum Green function as a function the transverse frequency. From the resonant transverse frequencies, all lasing modes are confirmed to be in excellent agreement with the maximum entropy states. This discovery implies that the formation of lasing modes is relevant to the coupling interaction between the pump source and the laser cavity.

High-power structured laser modes: manifestation of quantum Green's function.

The distributions of resonant frequencies in an astigmatic cavity are theoretically confirmed to be analogously equivalent to the quantum energy structures of two-dimensional commensurate harmonic oscillators. In the first part [Opt. Lett.45, 4096 (2020)OPLEDP0146-959210.1364/OL.399251] of this two-part series study, the lasing modes were verified to reveal a variety of vortex array structures. Here, in the second part of this two-part series study, the lasing modes are confirmed to agree very well with the quantum Green's functions that correspond to a bundle of Lissajous figures in the high-order regime.

High-power structured laser modes: direct generation of a vortex array.

The frequency degeneracy induced by the astigmatism in a nearly hemispherical cavity is originally exploited to generate vortex array laser modes with the output power up to 300 mW. The inhomogeneous Helmholtz equation is employed to derive the wave function for manifesting the characteristics of the lasing modes. The theoretical wave function explicitly reveals the role of the Gouy phase in the formation of vortex arrays. Numerical analyses are further performed to confirm that the thermal lensing effect in the laser crystal assists the lasing transverse order to increase with increasing pump power. It is believed that the high efficiency enables the present laser modes to be useful in the applications of structured vortex beams.

Origin of continuous curves and dotted spots in laser transverse modes with geometric structures.

The transverse structures of geometric modes in degenerate laser resonators with large astigmatism are systematically investigated by starting from the Gaussian wave packet formulation with ray-wave connections. The overlapping degree D between Gaussian wave packets is derived as an analytic expression that manifests the critical overlapping with D=1. The transverse patterns are confirmed to display a structure of continuous curves or dotted spots, depending on D>1 or D<1, respectively. A thorough comparison between experimental results and numerical calculations is performed to validate the theoretical analysis.

Generalized wave-packet formulation with ray-wave connections for geometric modes in degenerate astigmatic laser resonators.

The parametric equations for periodic rays in degenerate astigmatic laser resonators are derived in a generalized way. The derived parametric equations clearly reveal the formation of Lissajous geometric modes with phase variation along the propagation. Using the representation of a quantum coherent state, a generalized wave-packet formula is derived to connect with the periodic rays of geometric modes. The derived wave-packet formula is not only validated through comparing with various experimental patterns, but also is directly exploited to manifest the spatial asymmetries of Lissajous lasing modes due to a highly transmissive output coupler.

Exploring the self-mode locking and vortex structures of nonplanar elliptical modes in selectively end-pumped Nd:YVO4 lasers: manifestation of large fractional orbital angular momentum.

An end-pumped Nd:YVO4 laser under selective pumping is used to excite lasing modes with transverse patterns performed to exhibit the characteristics of multiple spots arranged on elliptical features near degenerate cavities. The spatial distribution of elliptical lasing modes is clearly revealed to be localized on the nonplanar ray orbits, so-called nonplanar elliptical modes, which possess large fractional orbital angular momentum. Moreover, temporal dynamics for the output emission of nonplanar elliptical modes are verified to obtain self-mode-locked operation. We further numerically manifest not only the influence of radial-asymmetry distributions on the vortex structures of nonplanar elliptical modes, but also the vector field of transverse lasing modes altered with twisting phase structures in the propagation direction.

Exploring vortex structures in orbital-angular-momentum beams generated from planar geometric modes with a mode converter.

It is theoretically demonstrated that the planar geometric mode with a π/2 mode converter, so called the circularly geometric mode, can be solved from the inhomogeneous Helmholtz equation by considering the pump distribution on the lasing mode. Theoretical analysis clearly reveal that the vortex structures of circularly geometric modes are determined by the minimum order of transverse lasing modes, the total number of transverse lasing modes and the degenerate condition in the cavity. Moreover, we experimentally manifest that the circularly geometric mode can be generated from the selective pumped solid-state laser with an external π/2 mode converter. To explore the vortex structures of the generated geometric modes, the interference patterns are performed by an experimental apparatus consisting of a Mach-Zehnder interferometer. The good agreement between experimental observations and numerical calculations confirms the analysis of vortex structures is reliable.

Generation of pseudonondiffracting optical beams with superlattice structures.

We demonstrate an approach to generate a class of pseudonondiffracting optical beams with the transverse shapes related to the superlattice structures. For constructing the superlattice waves, we consider a coherent superposition of two identical lattice waves with a specific relative angle in the azimuthal direction. We theoretically derive the general conditions of the relative angles for superlattice waves. In the experiment, a mask with multiple apertures which fulfill the conditions for superlattice structures is utilized to generate the pseudonondiffracting superlattice beams. With the analytical wave functions and experimental patterns, the pseudonondiffracting optical beams with a variety of structures can be generated systematically.

Ferromagnetic interfacial interaction and the proximity effect in a Co2FeAl/(Ga,Mn)As bilayer.

The magnetic properties of a Co2FeAl/(Ga,Mn)As bilayer epitaxied on GaAs (001) are studied both experimentally and theoretically. Unlike the common antiferromagnetic interfacial interaction existing in most ferromagnet-magnetic semiconductor bilayers, a ferromagnetic interfacial interaction in the Co2FeAl/(Ga,Mn)As bilayer is observed from measurements of magnetic hysteresis and x-ray magnetic circular dichroism. The Mn ions in a 1.36 nm thick (Ga,Mn)As layer remain spin polarized up to 400 K due to the magnetic proximity effect. The minor loops of the Co2FeAl/(Ga,Mn)As bilayer shift with a small ferromagnetic interaction field of +24 Oe and -23 Oe at 15 K. The observed ferromagnetic interfacial coupling is supported by ab initio density functional calculations. These findings may provide a viable pathway for designing room-temperature semiconductor spintronic devices through magnetic proximity effect.

Spontaneous subpicosecond pulse formation with pulse repetition rate of 80 GHz in a diode-pumped Nd:SrGdGa3O7 disordered crystal laser.

We explore the operation of spontaneous mode locking in a diode-pumped Nd:SrGdGa3O7 disordered crystal laser. The first- and second-order autocorrelations are simultaneously performed to evaluate the temporal characteristics. An 80 GHz pulse train with a pulse duration as short as 616 fs is observed. The maximum output power is 415 mW at a pump power of 6.1 W.

Bottle beam generation from a frequency-doubled Nd:YVO4 laser.

We demonstrate, for the first time, the direct generation of a bottle beam with a well-isolated three-dimensional zero-intensity dark core (high potential barrier) from a compact intracavity frequency-doubled Nd:YVO4 laser with a nearly hemispherical cavity. We also numerically calculate the physical properties of the generated bottle beam using a coherent superposition of a series of frequency-locked Laguerre-Gaussian modes.

Characterizing classical periodic orbits from quantum Green's functions in two-dimensional integrable systems: Harmonic oscillators and quantum billiards.

A general method is developed to characterize the family of classical periodic orbits from the quantum Green's function for the two-dimensional (2D) integrable systems. A decomposing formula related to the beta function is derived to link the quantum Green's function with the individual classical periodic orbits. The practicality of the developed formula is demonstrated by numerically analyzing the 2D commensurate harmonic oscillators and integrable quantum billiards. Numerical analyses reveal that the emergence of the classical features in quantum Green's functions principally comes from the superposition of the degenerate states for 2D harmonic oscillators. On the other hand, the damping factor in quantum Green's functions plays a critical role to display the classical features in mesoscopic regime for integrable quantum billiards, where the physical function of the damping factor is to lead to the coherent superposition of the nearly degenerate eigenstates.

Extracting trajectory equations of classical periodic orbits from the quantum eigenmodes in two-dimensional integrable billiards.

The trajectory equations for classical periodic orbits in the equilateral-triangular and circular billiards are systematically extracted from quantum stationary coherent states. The relationship between the phase factors of quantum stationary coherent states and the initial positions of classical periodic orbits is analytically derived. In addition, the stationary coherent states with noncoprime parametric numbers are shown to correspond to the multiple periodic orbits, which cannot be explicable in the one-particle picture. The stationary coherent states are further verified to be linked to the resonant modes that are generally observed in the experimental wave system excited by a localized and unidirectional source. The excellent agreement between the resonant modes and the stationary coherent states not only manifests the importance of classical features in experimental systems but also paves the way to manipulate the mesoscopic wave functions localized on the periodic orbits for applications.

Manifesting the evolution of eigenstates from quantum billiards to singular billiards in the strongly coupled limit with a truncated basis by using RLC networks.

The coupling interaction between the driving source and the RLC network is explored and characterized as the effective impedance. The mathematical form of the derived effective impedance is verified to be identical to the meromorphic function of the singular billiards with a truncated basis. By using the derived impedance function, the resonant modes of the RLC network can be divided into the open-circuit and short-circuit states to manifest the evolution of eigenvalues and eigenstates from closed quantum billiards to the singular billiards with a truncated basis in the strongly coupled limit. The substantial differences of the wave patterns between the uncoupled and strongly coupled eigenmodes in the two-dimensional wave systems can be clearly revealed with the RLC network. Finally, the short-circuit resonant states are exploited to confirm that the experimental Chladni nodal-line patterns in the vibrating plate are the resonant modes subject to the strong coupling between the oscillation system and the driving source.

Thanatophoric dysplasia type I.

Thanatophoric dysplasia is a sporadic, nearly always lethal congenital skeletal dysplasia. It is characterized by shortening of the limbs, a severely small thorax, macrocephaly, and platyspondyly. There are two major subtypes: a short, curved femur characterizes type I, and a straighter femur with cloverleaf skull characterizes type II. Recently, mutations in the fibroblast growth factor receptor 3 (FGFR-3) gene have been identified in both subtypes, which suggest that thanatophoric dysplasia is a genetically homogenous skeletal disorder. Most affected neonates die of respiratory failure, due to narrow thorax with pulmonary hypoplasia. Antenatal sonographic diagnosis is feasible in the second trimester of pregnancy, but differentiating thanatophoric dysplasia from non-lethal skeletal disorders is very important. At the present time, however, prenatal genetic screening seems unpractical.

[Another reason for cyanosis--methemoglobinemia].

Intraoperative cyanosis is an utmost emergency for anesthesiologist. If the patient has adequate control ventilation, and normal cardiac pulmonary physiology, then methemoglobinemia must be considered. Reported here is a normal female with dark color lip on the second day after her second parturition and was undergoing tubal ligation. Twenty minutes after induction of general anesthesia and endotracheal intubation, dark blood at the incision site was noted by the operator. After emergent check up of the anesthesia machine, tubings, breathing sound and arterial blood gas, there was only one suspicion left. Methemoglobinemia was confirmed by the hematological examination. Methemoglobinemia is a product from the oxidation of the iron atom in the heme ring when oxygen dissociates from it. This process exists in nature, but can also be induced by nitrate or nitrite-containing drugs or foods or benzene-like organic compounds. Methemoglobinemia can be differentiated from normal hemoglobin by mass spectrometry. If acute illness develops, patients should be treated with methylene blue. Otherwise ascorbic acid will do. This case is reported to remind all anesthesia personnel about one of the rare but serious hemoglobinopathy.

Hemoclip-assisted endoscopic polypectomy of large superior duodenal angle polyp using a needle knife.

Endoscopic polypectomy of a large polyp can be difficult due to inability to snare the polyp. The difficulty may increase when the polyp is located at turning corner of the bowel. We presented a case of a 3 cm-sized large pedunculated polyp located at the superior duodenal angle that was not amenable to conventional snare polypectomy, but was instead successfully resected by hemoclip-assisted and needle knife method. Such experience has not been reported in the English literature.