All-fiber Yb-doped laser mode-locked by nanotubes

Single-wall carbon nanotubes (SWNTs) and graphene have emerged as promising saturable absorbers (SAs), due to their broad operation bandwidth and fast recovery times [1-3]. However, Yb-doped fiber lasers mode-locked using CNT and graphene SAs have generated relatively long pulses. All-fiber cavity designs are highly favored for their environmental robustness. Here, we demonstrate an all-fiber Yb-doped laser based on a SWNT saturable absorber, which allows generation of 8.7 ps-long pulses, externally compressed to 118 fs. To the best of our knowledge, these are the shortest pulses obtained with SWNT SAs from a Yb-doped fiber laser. © 2013 IEEE.

Reproduction mode of an artificial allotetraploid carp (Pisces; Cyprinidae)

Mature eggs of allotetraploid carp were activated by inactive sperm or crossed with normal sperms of common carp (Cyprinus carpio), crucian carp (Carassius auratus), Chinese blunt snout bream (Megalobrama amblycephala), Hemiculter leucisculus and Pseudorasbora parva. Chromosome counts showed that all offspring of these crosses presented a mode number of 200 chromosomes (4n = 200), and their morphological traits are much like maternal. Microsatelite marker and RAPD patterns between allotetraploid maternal and its offspring, reproduced from different paternal species, were identical. Cytological, morphological and molecular evidences suggested that allotetraploid carp female nucleus would not fuse with any male nucleus and its reproduction mode might be gynogenesis and therefore their offspring are retaining their tetraploidy and give origin to clonal individuals.

STUDY ON THE MODE OF PRIMARY CONTROL IN THE EGG OF GYNOGENETIC CRUCIAN CARP FOR INHIBITING THE DEVELOPMENT OF 2 TYPES OF SPERM NUCLEI

By comparing the different developmental characteristics of two types of sperm nuclei which were from gynogenetic fish (crucian carp) and amphimictic fishes (red carp, red goldfish and sex-reversal red carp) respectively in the eggs of gynogenetic crucian carp, it was preliminarily revealed that there existed selective inhibiting actions of the primary control in the eggs of crucian carp for inhibiting the development of the two types of sperm nuclei. To homologous sperms, the primary control showed weak effect, thus leading to the decondensation of homologous sperm nuclei at different degrees in the eggs of crucian carp. But to heterologous sperms, the primary control showed strong effects, resulting in the total inhibition of the development of heterologous sperm nuclei. Moreover, our experimental results also showed that the different developmental behavior of the two types of sperm nuclei might have a great relationship to the changes of the sex ratio in the population of gynogenetic crucian carp. The infiltration of "the genetic materials in sperm nuclei" into the female nucleus at random might play an important role in male emergence in the naturally gynogenetic population of crucian carp.

Mode Simulation for Midinfrared Microsquare Resonators With Sloped Sidewalls and Confined Metals

EQUILATERAL-TRIANGLE; MU-M; LASERS; MICROLASERS; MICRODISK Abstract: Mode characteristics for midinfrared microsquare resonators with sloped sidewalls and confined metal layers are investigated by finite-difference time-domain (FDTD) techniques. For a microsquare with a side length of 10 mu m, the mode quality (Q)-factors of 8329, 4772, and 2053 are obtained for TM5,7 mode at wavelength 7.1 mu m by three-dimensional FDTD simulations, as the tilting angles of the side walls are 90 degrees, 88 degrees, and 86 degrees, respectively. Furthermore, microsquare resonators laterally surrounded by SiO2 and metal layers are investigated by the two-dimensional FDTD technique for the metal layers of Au, Ti-Au, Ag-Au, and Ti-Ag-Au, respectively.

A Single-Fundamental-Mode Photonic Crystal Vertical Cavity Surface Emitting Laser

Single-fundamental-mode photonic crystal (PhC) vertical cavity surface emitting lasers (VCSEL) are produced and their single-fundamental-mode performances are investigated and demonstrated. A two-dimensional PhC with single-point-defect structure is fabricated using UV photolithography and inductive coupled plasma reactive ion etching on the surface of the VCSEL's top distributed Bragg-reflector. The PhC VCSEL maintains single-fundamental-mode operating with output power 1.7 mW and threshold current 2.5 mA. The full width half maximum of the lasing spectrum is less than 0.1 nm, the far field divergence angle is less than 10 degrees and the side mode suppression ratio is over 35 dB. The device characteristics are analyzed based on the effective index model of the photonic crystal fiber. The experimental results agree well with the theoretical expectation.

Mode Characteristics for Square Resonators With a Metal Confinement Layer

Microsquare resonators laterally confined by SiO2/Au/air multilayer structure are investigated by light ray method with reflection phase-shift of the multiple layers and two-dimensional (2-D) finite-difference time-domain (FDTD) technique. The reflectivity and phase shift of the mode light ray on the sides of the square resonator with the semiconductor/SiO2/Au/air multilayer structure are calculated for TE and TM modes by transfer matrix method. Based on the reflection phase shift and the reflectivity, the mode wavelength and factor are calculated by the resonant condition and the mirror loss, which are in agreement well with that obtained by the FDTD simulation. We find that the mode factor increases greatly with the increase of the SiO2 layer thickness, especially as d < 0.3 mu m. For the square resonator with side length 2 mu m and refractive index 3.2, anticrossing mode couplings are found for confined TE modes at wavelength about 1.6 mu m at d = 0.11 mu m, and confined TM modes at d = 0.71 mu m, respectively.

Investigation of mode radiation loss for microdisk resonators with pedestals by FDTD technique

Mode radiation loss for microdisk resonators with pedestals is investigated by three-dimensional (3D) finite-difference time-domain (FDTD) technique. For the microdisk with a radius of 1 mu m, a thickness of 0.2 mu m, and a refractive index of 3.4, on a pedestal with a refractive index of 3.17, the mode quality (Q) factor of the whispering-gallery mode (WGM) quasi-TE7,1 first increases with the increase of the radius of the pedestal, and then quickly decreases as the radius is larger than 0.75 mu m. The mode radiation loss is mainly the vertical radiation loss induced by the mode coupling between the WGM and vertical radiation mode in the pedestal, instead of the scattering loss around the perimeter of the round pedestal. The WG M can keep the high Q factor when the mode coupling is forbidden.

Mode characteristics of metallically coated square microcavity connected with an output waveguide

Mode characteristics of a square microcavity with an output waveguide on the middle of one side, laterally confined by an insulating layer SiO2 and a p-electrode metal Au, are investigated by two-dimensional finite-difference time-domain technique. The mode quality (Q) factors versus the width of the output waveguide are calculated for Fabry-Peacuterot type and whispering-gallery type modes in the square cavity. Mode coupling between the confined modes in the square cavity and the guided modes in the output waveguide determines the mode Q factors, which is greatly influenced by the symmetry behaviors of the modes. Fabry-Peacuterot type modes can also have high Q factors due to the high reflectivity of the Au layer for the vertical incident mode light rays. For the square cavity with side length 4 mu m and refractive index 3.2, the mode Q factors of the Fabry-Peacuterot type modes can reach 10(4) at the mode wavelength of 1.5 mu m as the output waveguide width is 0.4 mu m.

Mode Analysis and Design of a Low-Loss Photonic Crystal 60 degrees Waveguide Bend

The guided modes of a two-dimensional photonic crystal straight waveguide and a waveguide bend are studied in order to find the high transmission mechanism for the waveguide bend. We find that high transmission occurs when the mode patterns and wave numbers match, while the single-mode condition in the waveguide bend is not necessarily required. According to the mechanism, a simply modified bend structure with broad high transmission band is proposed. The bandwidth is significantly increased from 19 to 116 nm with transmission above 90%, and covers the entire C band of optical communication.

Compact voltage-mode multi-valued literal gate using nanoscale ballistic MOSFETs

A CMOS voltage-mode multi-valued literal gate is presented. The ballistic electron transport characteristic of nanoscale MOSFETs is smartly used to compactly achieve universal radix-4 literal operations. The proposed literal gates have small numbers of transistors and low power dissipations, which makes them promising for future nanoscale multi-valued circuits. The gates are simulated by HSPICE.

Mode coupling and vertical radiation loss for whispering-gallery modes in 3-D microcavities

The characteristics of whispering-gallery modes (WGMs) in 3-D cylindrical, square, and triangular microcavities with vertical optical confinement of semiconductors are numerically investigated by the finite-difference time-domain (FDTD) technique. For a microcylinder with a vertical refractive index 3.17/3.4/3.17 and a center layer thickness 0.2 mu m, Q-factors of transverse electric (TE) WGMs around wavelength 1550 nm are smaller than 10(3), as the radius R < 4 mu m and reach the orders of 10(4) and 10(6) as R = 5 and 6 mu m, respectively. However, the Q-factor of transverse magnetic (TM) WGMs at wavelength 1.659 mu m reaches 7.5 x 10(5) as R = 1 mu m. The mode coupling between the WGMs and vertical radiation modes in the cladding layer results in vertical radiation loss for the WGMs. In the microcylinder, the mode wavelength of TM WGM is larger than the cutoff wavelength of the vertical radiation mode with the same mode numbers, so TM WGMs cannot couple with the vertical radiation mode and have high Q-factor. In contrast, TE WGMs can couple with the corresponding vertical radiation mode in the 3-D microcylinder as R < 5 mu m. However, the mode wavelength of the TE WGM approaches (is larger than) the cutoff wavelength of the corresponding radiation modes at R = 5 mu m (6 mu m), so TE WGMs have high Q-factors in such microcylinders too. The results show that a critical lateral size is required for obtaining high, Q-factor TE WGMs in the 3-D microcylinder. For 3-D square and triangular microcavities, we also find that the Q-factor of TM WGM is larger than that of TE WGM.

Passively mode-locked YVO4/Nd : YVO4 composite crystal laser with a semiconductor saturable absorber as a high reflector

A passively mode-locked diode end-pumped YVO4/Nd:YVO4 composite crystal laser with a five-mirror folded cavity was first demonstrated in this paper by using a low temperature semiconductor saturable absorber mirror grown by metal organic chemical vapor deposition. Both the Q-switching and continuous-wave mode locking operation were realized experimentally. A stable averaged output power of 10.15 W with pulse width of about 11.2-ps at a repetition rate of 113 MHz was obtained, and the optical-to-optical efficiency of 43% was achieved.

Experimental study on a diode-pumped passively mode-locking Nd : GdVO4/SESAM laser

We demonstrate a low-threshold and efficient diode-pumped passively continuous wave (CW) mode-locked Nd:GdVO4 laser with a reflective semiconductor saturable absorber mirror (SESAM). The threshold for the continuous wave was 0.36 W, and it is the lowest threshold for a continuous wave in a passively mode-locked Nd:GdVO4 laser to our knowledge. The maximum average output power of 1.82 W was obtained at a pump power of 6.65 W with a slope efficiency of about 29%. The CW mode-locked pulse duration was measured to be about 10.5 ps with a 116-MHz repetition rate.

Diode-pumped passively mode-locked YVO4/Nd : YVO4 composite crystal laser with LT-In0.25Ga0.75As saturable absorber

A passively mode-locked all-solid-state YVO4/Nd:YVO4 composite crystal laser was realized with a low temperature (LT) In0.25Ga0.75As semiconductor saturable absorber mirror. The saturable absorber was used as nonlinear absorber and output coupler simultaneously. Both the Q-switch and continous-wave mode locking operation were experimentally realized. At a pump power of 4 W, the Q-switched mode locking changed to continuous wave mode locking. An average output power of 4.1 W with 5 ps pulse width was achieved at the pump power of 12 W, corresponding to an optical-optical conversion efficiency of 34.2%.