Self-Seeding Warm-Season Legumes for Low-Input Forage Production in the Southern Great Plains of the USA

In the southern Great Plains (SGP) of the USA warm-season legumes can improve the quality of available forage in pasture systems based on perennial warm-season grasses. Legumes that persist through self-seeding may be especially useful in low-input systems where resources for annual replanting are limited. The productivity and capacity for self-seeding of Korean lespedeza (Kummerowia stipulacea [Maxim.] Makino) and Verano stylo (Stylosanthes hamata [L.] Taub.) were tested in controlled environment and in field plots in the SGP. At similar levels of accumulated temperature, germination of Korean lespedeza was unaffected by day/night temperature regimes between 15/15&degC and 30/15&degC. In contrast, at similar accumulated temperatures, germination of Verano stylo increased with higher daytime maximum temperature up to 30&degC. Seedling growth of both species was reduced by shading, in proportion to the reduction in photosynthetic flux density. Growth of Korean lespedeza up to five weeks after emergence was greatest under a 22.5/7.5&degC temperature regime but that of Verano stylo was greatest at 30/15&degC. In the field Korean lespedeza was a prolific seeder and productive of forage though susceptible to significant loss of leaf material in late summer and fall. Verano stylo did not reseed effectively and was not a reliable forage producer.

An analysis of undulator optimization in self-seeding free electron lasers

A simple analysis is given for the optimum length of undulator in a self-seeding free electron laser （FEL）. The obtained relations show the correlation between the undulator length and the system parameters. The power required for the seeding in the second part of the undulator and the overall efficiency of monochromatizating the seeding determine the length of the first part of the undulator; the magnitude of seeding power dominates the length of the second part of the undulator; the whole length of the undulator in a self-seeding FEL is determined by the overall efficiency for getting coherent seed, and is about half as long again as that of SASE, not including the dispersion section. The requirement of the dispersion section strength is also analyzed.

Physical design of a wavelength tunable fully coherent VUV source using a self-seeding free electron laser

In order to meet the requirements of the synchrotron radiation users, a fully coherent VUV free electron laser （FEL） has been preliminarily designed. One important goal of this design is that the radiation wavelength can be easily tuned in a broad range （70 170 nm）. In the light of the users＇ demand and our actual conditions, the self-seeding scheme is adopted for this proposal. Firstly, we attempted to fix the electron energy and only changed the undulator gap to vary the radiation wavelength; however, our analysis implies that this is difficult because of the great difference of the power gain length and FEL efficiency at different wavelengths. Therefore, we have considered dividing the wavelength range into three subareas. In each subarea, a constant electron energy is used and the wavelength tuning is realized only by adjusting the undulator gap. The simulation results show that this scheme has an acceptable performance.

BRIGHT:the three-dimensional X-ray crystal Bragg diffraction code

In pursuit of a fully coherent X-ray free-electron laser(FEL), highly reflective Bragg crystals are used and will be used as a highly selective spectral filter in hard X-ray self-seeding FELs and X-ray FEL oscillators(XFELO), respectively. However, currently, when simulating self-seeding and XFELO, the three-dimensional effect of Bragg diffraction is not fully considered. In this paper, we derive a comprehensive solution for the response function of the crystal in Bragg diffraction. A three-dimensional X-ray crystal Bragg diffraction code, named BRIGHT, is introduced, which can be combined with other FEL-related codes, e.g., GENESIS and OPC. Performance and feasibility are assessed using two numerical examples,namely a self-seeding experiment for the linac coherent light source and XFELO options for Shanghai high repetition rate XFEL. The results indicate that BRIGHT provides a new and useful tool for three-dimensional modeling of FEL.

Self-seeded FEL wavelength extension with high-gain harmonic generation

We study a self-seeded high-gain harmonic generation（HGHG） free-electron laser（FEL） scheme to extend the wavelength of a soft X-ray FEL. This scheme uses a regular self-seeding monochromator to generate a seed laser at the wavelength of 1.52 nm, followed by a HGHG configuration to produce coherent, narrow-bandwidth harmonic radiations at the GW level. The 2nd and 3rd harmonic radiation is investigated with start-to-end simulations.Detailed studies of the FEL performance and shot-to-shot fluctuations are presented.

A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser

A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser (FBG-ECL) and a Mach-Zehnder interferometer (MZI) were reported in this paper. The MZI provided a Q-switching with response time in the order of micro-seconds. The FBG-ECL provided narrow pulses as seeds to shorten the Q-switched pulses. Experimentally, pulse width of 0.8 μs was measured, which was one fifth of the pulse width without self-seeding.

Self-seeded quantum-dash laser based 5 m–128 Gb/s indoor free-space optical communication

We demonstrate an indoor 5 m free-space optical wireless coherent communication in mid L-band（1606.7 nm）by employing a tunable self-seeded InAs/InGaAlAs/InP quantum-dash（Qdash） laser as a subcarrier generator for 128 Gb/s dual-polarization quadrature phase shift keying（DP-QPSK） modulation signal. The bare Qdash laser diode displays ~6 nm self-locked Fabry-Perot mode tunability with ~30 dB side mode suppression ratio（SMSR） and ~10 dBm mode power across the tuning range, thus encompassing ~10 modes with an achievable capacity of 1.28 Tb/s（10 × 128 Gb∕s） and potentially qualifying the source requirements for future access networks.

Self-seeded quantum-dash laser based 5 m-128 Gb/s indoor free-space optical communication: erratum

On page 100604-3 in our work [1], the caption for Fig. 2 should be ＂at the 98% output of the 2：98 coupler＂ （not ＂at the 2% output of the 2：98 CP＂）.

Tunable self-seeded multi-wavelength Brillouin-erbium fiber laser based on few-mode fiber filter

A tunable self-seeded multi-wavelength Brillouin-erbium fiber laser(BEFL) is proposed and demonstrated based on a few-mode fiber filter(FMFF) with varying temperature. The FMFF configuration is a section of uncoated few-mode fiber(FMF) sandwiched between two up-tapers. As the temperature varies from 25 °C to 125 °C, the transmission spectrum of FMFF moves towards the longer wavelength. The self-excited Brillouin pump is internally achieved by cascaded stimulated Brillouin scattering(SBS) in the single mode fiber(SMF). Then employing the FMFF temperature variation characteristics in the ring cavity fiber laser, the multi-wavelength of the output laser can be tuned, and the tunable range is about 8.0 nm. The generation of up to 15 Brillouin Stokes wavelengths with 16 d B optical signal-to-noise ratio(OSNR) is realized.