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The accumulation of pigments affects the color of rice hulls while only limited information is known about its underlying mechanisms. In the present study, a rice brown hull 6 (bh6) mutant was isolated from an ethane methyl sulfonate (EMS)-induced IR64 mutant bank. Brown pigments started to accumulate in bh6 rice hulls after heading and reached a higher level in mature seeds. Some major agronomic traits including panicle length and 1000-grain weight in bh6 were significantly lower than those in its corresponding wild type IR64, while other agronomic traits such as plant height, growth duration and seed-setting rate were largely similar between the two genotypes. The analysis of pigment content showed that the contents of total flavonoids and anthocyanin in bh6 hulls were significantly higher than those in IR64 hulls. Our results showed that the brown hull phenotype in bh6 was controlled by a single recessive gene which locates on the long arm of chromosome 9. Sequencing analysis detected a single base substitution (G/A) at position 1013 of the candidate gene (LOC_Os09g12150) encoding an F-box domain-containing protein (FBX310). Functional complementation experiment using the wild type allele can rescue the phenotype in bh6. Thus, we named this mutated gene as OsFBX310bh6, an allele of OsFBX310 functioning as an inhibitor of brown hull. The isolation of OsFBX310bh6 and its wild type allele can provide useful experimental materials and will facilitate the studies on revealing the mechanisms of flavonoid metabolism in monocot plants.

Heat stress at the pollen mother cell (PMC) meiotic stage leads to pollen sterility in rice, in which the reactive oxygen species (ROS) and sugar homeostasis are always adversely affected. This damage is reversed by abscisic acid (ABA), but the mechanisms underlying the interactions among the ABA, sugar metabolism, ROS and heat shock proteins in rice spikelets under heat stress are unclear. Two rice genotypes, Zhefu802 (a recurrent parent) and fgl (its near-isogenic line) were subjected to heat stress of 40°C after pre-foliage sprayed with ABA and its biosynthetic inhibitor fluridone at the meiotic stage of PMC. The results revealed that exogenous application of ABA reduced pollen sterility caused by heat stress. This was achieved through various means, including: increased levels of soluble sugars, starch and non-structural carbohydrates, markedly higher relative expression levels of heat shock proteins (HSP24.1 and HSP71.1) and genes related to sugar metabolism and transport, such as sucrose transporters (SUT) genes, sucrose synthase (SUS) genes and invertase (INV) genes as well as increased antioxidant activities and increased content of adenosine triphosphate and endogenous ABA in spikelets. In short, exogenous application of ABA prior to heat stress enhanced sucrose transport and accelerated sucrose metabolism to maintain the carbon balance and energy homeostasis, thus ABA contributed to heat tolerance in rice.

The spontaneous emmission (SE) progress of polarized atoms in a stratified structure of air-dielectric (D0-metal(M)-dielectric(D1)-air can be controlled effectively by changing the thickness of the D1 layer and rotating the polarized direction of atoms. It is found that the normalized SE rate of atoms located inside the D0 layer crucially depends on the atomic position and the thickness of the D1 layer. When the atom is located near the D0-M interface, the normalized atomic SE rate as a function of the atomic position is abruptly onset for the thin D1 layer. However, with the increasing thickness of the D1 layer, the corresponding curve profile exhibits plateau and stays nearly unchanged. The substantial change of the SE rate stems from the excitation of the surface plasmon polaritons in metal-dielectric, and the feature crucially depends on the thickness of D1 layer. If atoms are positioned near the D0-air interface, the substatial variation of the normalized SE rate appears when rotating the polarized direction of atoms. These findings manifest that the atomic SE processes can be flexibly controlled by altering the thickness of the dielectric layer D1 or rotating the orientation of the polarization of atoms.

The optical quality of Er3+, Yb3+: BaWO4 crystal was grown by Czochralski method. Absorption spectra were measured and energy levels were assigned. According to Judd-Ofelt theory, the spectral strength parameters of Er3+ ion were fitted to be ω2 =0.3926 x 10−20 cm2, ω4 =0.0721 x 10−20 cm2, ω6 =0.0028 x 10−20 cm2. Emission peaks centered at around 523, 544 and 670 nm were observed under 334 nm He-Cd laser excitation and emission peaks centered at 1001 and 1534 nm were detected under 976 nm laser excitation. Strong green emission was also observed when the crystal was pumped with 808 nm and 976 nm laser. The mechanisms of frequency upconversion and sensitization were analyzed.

We experimentally investigate the antiphase dynamics phenomenon that occurs in a diode-pumped passively Q-switched Yb:YAG multimode laser with a Nd,Cr:YAG saturable absorber. Due to the effect of spatial hole burning, the multimode lasers with one, two, or three modes at different pump power are observed, and the pulses sequences display classic antiphase dynamics.

We demonstrate the characteristics of relatively low saturation intensity using co-doped Nd, Cr:YAG as saturable absorber for passively mode locking the Nd:YAG laser. The difference of the saturation intensity between Q-switched and mode-locked operation in co-doped Nd, Cr:YAG was only one to two orders of magnitude, while Cr:YAG was generally reported at a difference of five orders of magnitude. More than 80% mode locking modulation depth was achieved at an incident pump power of 4.4W, corresponding to an intracavity intensity of 6×104W/cm2, using a 68cm long plano-concave cavity.

We report an efficient pumping scheme which involves a direct excitation of the upper lasing level of a four-level laser in a Nd-doped Ca3(NbGa)2-xGa3O12 (Nd:CNGG) by using a tunable Tr.sapphire, 700–920 nm, cw pump source. The slope efficiency is improved from 10.5% of the traditional band pumping at 808nm to 21.8% of the direct pumping at 882 nm. The influence of pumping wavelength on lasing is discussed. We present a scheme of double pumping for lasing.

We report, for the first time to our knowledge, a diode-pumped passive Q-switched 946 nm Nd:YAG laser by using a GaAs as saturable absorber. The maximum average output power is 1.24 W at an incident pump power of 15 W, corresponding to a slope efficiency of 10%. Laser pulses with pulse duration of 70 ns and repetition rate of 330 kHz are generated.

We demonstrate a diode-pumped passive Q-switched 946 nm Nd:YAG laser with a diffusion-bonded composite laser rod and a co-doped Nd,Cr:YAG as saturable absorber. The average output power of 2.1 W is generated at an incident pump power of 14.3 W. The peak power of the Q-switched pulse is 643 W with 80 kHz repetition rate and 40.8 ns pulse width. The slope efficiency and optical conversion efficiency are 17.6% and 14.7%, respectively.

We report a diode-pumped self-Q-switched 1064-nm Cr,Nd:YAG laser with pulse duration in the range of 16-18 ns. The maximum average output power up to 7 W, corresponding to a slope efficiency of 33%, is obtained in a simple and compact linear cavity by using a plane-concave output coupler with a transmittance of 15%. The laser operates at TEM(00) mode with a pump power of 14.2 W.

Using Nd3+,Cr4+:YAG as a laser crystal and saturable absorber simultaneously, we obtain a self-Q-switched and mode-locking laser at 1.06 μm with straight cavity structure. Self mode-locking phenomenon was observed at an intracavity intensity of only about 2000 W/cm2. More than 90% modulation depth is achieved at an intracavity intensity of less than 3.0×104 W/cm2 for the first time. The Q-switched pulse width and repetition rate are found to be connected with the cavity length and the output power.

We report for the first time on the observation of self-mode-locking in a diode pumped self-Q-switched (SQS) Nd3+,Cr4+:YAG laser. This phenomenon results from significant excited state absorption of the Cr4+ ions in the co-doped host during the SQS laser pulses. The self-mode-locking occurs already slightly above the SQS laser threshold. Experiments using relatively low saturable intensity achieved a modulation depth of more than 40%.

We carried out the operation of an intracavity frequency-doubled self-Q-switched Nd, Cr: YAG/KNbO3 946/473 nm microchip laser pumped by a Ti:sapphire laser. The overall cavity length was about 4 mm. The maximum average blue power of 12 mW was achieved with a repetition rate of 13 kHz at an absorbed pump power of 545 m W. The pulses of the 4 73 nm laser had a duration of 7 ns and a peak power of 132 W at this pump level. The conversion efficiency was 2.2% with respect to the absorbed pump power of a 808 nm laser.

By observing the fundamental and second harmonic emission from a plasma produced by a 150 fs, 5 mJ laser at 800 nm, the electron temperature, the expansion speed and the scalelength of the plasma have been diagnosed. Moreover the polarization of the fundamental and second harmonic emission has been studied. This could be a useful diagnostic for modulation at the critical surface of the plasma.

We report a design of diode-pumped high power Nd:GdVO4/LBO red laser with a compact linear cavity, which can output 820-mW red light at 670 nm with an optical conversion efficiency of 9.6%. The maximum output power of the fundamental light at 1.34 mum was 4 W with a slope efficiency of 45%.

The improvement on the calculation of anti-Stokes energy transfer rate is studied in the present work. The additional proportion coefficient between Stokes and anti-Stokes light intensities of quantum Raman scattering theory as compared with the classical Raman theory is introduced to successfully describe the anti-Stokes energy transfer. The theoretical formula for the improvement on the calculation of anti-Stokes energy transfer rate is derived for the first time in this study. The correctness of introducing coefficient exp{ΔE/kT} from well-known Raman scatter theory is demonstrated also. Moreover, the experimental lifetime measurement in Er0.01YbxY1–0.01-x VO4 crystal is performed to justify the validity of our important improvement in the original phonon-assisted energy transfer theory for the first time.

The BaWO4: Tm3+ single crystals of optical quality have been grown by the Czochralski technique. The lattice parameters of crystals with different doping concentrations were determined by XRD. The absorption spectra were measured at room temperature. And the optical parameters, such as transition line intensity, oscillator strength and absorption section were calculated by using Juud-Ofelt theory. The three intensity parameters were fitted to be Omega(2) = 4.04 x 10(-20) cm(2), Omega(4) = 0.509 x 10(-20) cm(2), Omega(6) = 0.134 x 10(-20) cm(2), respectively. The lifetime, branching ratio and integrated stimulated-emission cross section were obtained. Ultra-visible fluorescence was measured and analyzed. The red up-conversion luminescence with wavelengths 689 nm and 704 nm corresponding to the transition from F-3(3) to H-3(6) was observed under Ti-sapphire laser and LD laser, respectively.