An external modulation method is proposed and experimentally demonstrated for the generation of linearly chirped light over broadband with narrow linewidth. Our chirped light source is a combination of an optical recirculating frequency shifter loop and an optical frequency linear sweeper. A linearly chirped light over a range of 200 GHz at a chirp rate of $3.6\times {10}^{16}\mathrm{Hz}/\mathrm{s}$ is generated. The instantaneous linewidth of the chirped light is estimated to be less than 50 kHz.

Frequency-modulated continuous-wave (FMCW) lasers are the key components in FMCW LiDAR systems. In this paper, we develop and implement a rapid linearization algorithm to adaptively pre-distort the injection current, we manage to reduce the residual nonlinearity of the triangular-waveform modulated frequency down to $5.4 \times 10^{-9}$ and $4.1 \times 10^{-9}$ for down- and up-ramp frequency sweeping, respectively. The relative residual nonlinearity for down- and up-ramp frequency sweeping are 0.0020% and 0.0017%, respectively. We use this FMCW laser source with high linearity to implement a LiDAR system. We showcase three-dimensional imaging with the depth contrast and the measurement of the distance and velocity, simultaneously, of a moving object.

We propose and experimentally demonstrate a stable multi-wavelength fiber ring laser operating in the L-band with wavelength spacing of 25 GHz. The mechanism is induced by a polarization rotation intensity equalizer consisting of a semiconductor optical amplifier and polarization devices. A Fabry–Perot filter is inserted into the cavity to serve as a multi-wavelength selection device. Stable L-band multi-wavelength lasing with 3 dB uniformity of 21.2 nm, and simultaneous oscillation of 101 lines with wavelength spacing of 25 GHz, is obtained.

We have experimentally demonstrated a square pulse in a passively mode-locked Yb-doped fiber ring laser operating in the dissipative soliton resonance (DSR) region based on the nonlinear polarization rotation technique. In our experiment, a 1.5-km long single-mode fiber (SMF) is inserted into the cavity to increase the cavity length. The total cavity is 1501.8 m. With increasing pump power, the pulse duration can be tuned from 209.8 ns to 812.4 ns without wave-breaking, and the maximum output single pulse energy is 42.34 nJ. To the best of our knowledge, this is the widest pulse in any Yb-doped mode-locked fiber laser. Moreover, the relationship between pulse width and cavity length is investigated. When the total cavity length is decreased to 1001.8 m and 501.8 m, the tuning range of square pulse is 372.4 ns (from 58.6 ns to 431 ns) and 138 ns (from 26 ns to 164 ns), respectively, and the maximum output single pulse energy is 13.85 nJ and 8.75 nJ, respectively.

Accurate evaluation of morphological and physiological traits is critical for selection of wheat (Triticum aestivum L.) cultivars exhibiting high yield, which is stable over different growing conditions. In order to use selection index based on high yield, high grain quality and drought tolerance in wheat, a set of 145 CIMMYT Wheat Physiological Germplasm Screening Nursery lines and seven local spring wheat varieties were phenotyped and evaluated for physiological and yield traits under two irrigation regimes during the 2011 and 2012 growing seasons in Xinjiang, China. The results showed that drought-stress significantly increased canopy temperature but reduced grain yield, grain weight per spike, normalized difference vegetation index at the flowering and grain filling stages, chlorophyll content at the grain filling stage, grain plumpness, grain number per spike, thousand-grain weight, and plant height. Grain weight per spike, plant height and grain plumpness explained 61.8% of the total phenotypic variation in grain yield under no-stress conditions, where they were the three principal factors most closely related to grain yield. Under drought-stress conditions, canopy temperature at the grain filling stage, plant height and grain plumpness were the three principal factors affecting grain yield, and contributed 44.8% of the total phenotypic variation in grain yield. Finally, ten genotypes, including three local varieties, ‘Xinchun 11’, ‘Xinchun 23’ and ‘Xinchun 29’, with appropriate plant height and high and stable yield under both no-stress and drought-stress conditions over the two years of trials, were identified and can be recommended as core parents for spring wheat drought tolerance breeding in Xinjiang, China.

A method of simultaneous precise multiwavelength tuning using electrical instead of mechanical control is proposed and experimentally demonstrated. This method is achieved by using a single-side-band modulator driven by electrical radio frequency (RF) signals. It is demonstrated that the multiwavelength signals can be simultaneously tuned in frequency by an amount equal to the frequency of the RF signal. A total of 32 wavelengths with a spacing of 100 GHz (i.e., 0.8 nm at the wavelength of 1550 nm) are simultaneously tuned from 4 to 12 GHz experimentally. In principle, the tuning resolution is determined by the resolution of the RF wave generator and the line width of the light source in the system. An acceptable homogenous 20.59-dB side-band-mode suppression ratio is achieved for each wavelength output.