ABSTRACT
High-frequency, high-power picosecond lasers have important and wide-ranging applications in laser ranging, optoelectronic countermeasures, and ultrafine industrial processing. Pulse compression based on stimulated Brillouin scattering (SBS) can achieve a highly efficient picosecond laser output, while improving the peak power and beam quality of the laser. In this paper, a generator-amplifier two-cell structure with frequency-detuning was proposed to achieve a pulse output that combines high compression ratio and high energy reflectivity. The experiment proved that under a pump pulse width of 15â ns and repetition frequency of 10â Hz, when the generator cell and amplifier cell media were selected as HT-230, the highest energy reflectivity of 46% and narrowest compression pulse width of 1.1â ns were achieved, and the pulse compression ratio was 13.6. When the amplifier cell was selected as FC-770 and the generator cell was selected as HT-230, an energy reflectivity of 52% and a compression pulse width of 840 ps could be achieved simultaneously, and the pulse compression ratio was 18.
ABSTRACT
In September 2022, rice spikelets rot disease (RSRD) was investigated in Songjiang District (30.94132N, 121.18393E), China, leading to a 26.77% yield loss. At the heading stage, infected spikelets exhibited small, yellowish-brown dots with water-stained husks, subsequently coalescing to form irregular brown to black lesions. Later, the lesions were enlarged and rotted, which eventually caused blighted grains. About 10% of husked grains showed black spots. 30 infected grains and 30 husked grains with black spots were surface sterilized in 75% ethanol for 2 min, then rinsed with ddH2O and plated on PDA medium at 28°C in darkness for 4 d. 22 and 13 fungal isolates with similar morphology were obtained in shriveled and husked grains, respectively. Three isolates (SJTU1, SJTU2 and SJTU3) were selected by the single-spore isolation method. The colonies were brown to blackish green, smooth, and contained a large number of stolons with a few aerial mycelia in the center. Hyphae and conidiophores were blackish green, thick-walled, branched with septa. Conidia were 14.77 to 26.82×4.74 to 11.36 µm (average 20.42×8.58 µm, n= 100) in size, lightly curved with blackish green. Conidia with three septa and four cells, apical and basal cells transparent, middle cell unequal in size. Based on morphological characteristics, the isolates were preliminarily identified as Curvularia plantarum (Raza et al. 2019). The genomic DNA of the three isolates (SJTU1 to 3) was extracted for molecular identification. 3 pairs of primers ITS1/TTS4 (Peever et al. 2004), gpd1/gpd2 (Berbee et al. 1999), and EF-983F/EF-2218R (Rehner and Buckley 2005) were used to amplify ITS, GAPDH, and EF1-α genes, respectively. These sequences were all uploaded in GenBank (ITS: OR726053 to 55; EF1-α: OR732471 to 73; GAPDH: OR732474 to 76). According to data in GenBank, the ITS, EF1-α, and GAPDH genes of 3 isolates (SJTU1 to 3) showed 99-100% identity (573/575 bp, 542/543 bp, and 531/531 bp) to the ITS (MW581905, MN044755, and MN215690), 99-100% identity (869/869 bp, 868/869 bp, and 855/856 bp) to the EF1-α (MN263982 to 83, and MT628901), and 99-100% identity (543/544 bp, 528/528 bp, and 540/540 bp) to the GAPDH (MT628902, MN264120, and MT432926) gene of C. plantarum, respectively. The phylogenetic analysis by Maximum Likelihood (ML) method based on the concatenated sequences of ITS, EF1-α, and GAPDH genes showed that the three isolates (SJTU1 to 3) clustered with C. plantarum. According to morphology and molecular identification, these fungal isolates were identified as C. plantarum. Pathogenicity tests were conducted in the field used only for inoculation with pathogens by spraying 30 spikelets of rice cultivar 'Song1013' at the heading stage with conidial suspension (5 × 105 conidia/mL). 30 spikelets sprayed with ddH2O were designated as control. The test was conducted 3 times at 22 to 31°C with 78 to 89% RH. All the inoculated spikelets exhibited similar symptoms to those of the infected spikelets in paddy at 10 d after spraying, while the control spikelets remained healthy. All reisolated strains from infected spikelets were identified the same as the original inoculated strains by morphology and ITS sequences, fulfilling Koch's postulates. To our knowledge, this is the first report of C. plantarum causing RSRD in China. The discovery of this new disease and its pathogens will facilitate the provision of pathogenically relevant information vital for management strategies to RSRD caused by C. plantarum in the future.
ABSTRACT
Analyzing the longitudinal-mode of a pump can significantly prevent optical damage to solid media and expand the applications of solid media in high repetition rate stimulated Brillouin scattering (SBS). In this study, a Fabry-Pérot etalon was used to control the number of longitudinal-mode in a pump laser output. We studied the output characteristics of SBS in fused silica by considering both single- and multi-longitudinal-mode pumping. We analyzed and compared variations in the SBS threshold, energy reflectivity, linewidth, and waveform characteristics. The experimental results indicated that a pump operating in a single-longitudinal-mode had a 14% lower SBS threshold than one operating in a multi-longitudinal-mode. The proportion of the weak longitudinal-mode in the multi-longitudinal-mode was close to the threshold difference. The damage threshold of the multi-longitudinal-mode pumps was approximately 35 mJ (@12â ns, f = 300 mm). The Stokes linewidth and waveform exhibited opposite trends as the energy changed. Due to the time-bandwidth product, the linewidth and waveform tended to converge towards the pump. This study emphasizes the importance of using a single-longitudinal-mode pump in the development and use of solid-state SBS gain media.
ABSTRACT
Stimulated Brillouin scattering (SBS) is a non-linear process which has the capacity to improve the beam quality and pulse characteristics of laser beams. In this paper, we theoretically and experimentally study the process of SBS in fused silica. In particular, we examine the energy reflection and pulse compression of input laser pulses as functions of focus position, pump energy and beam diameter. We utilized coupled wave equations and a distributed noise model to simulate the reflected energy and time waveform under different gain parameters. An experimental system is constructed and used to qualify the numerical simulations. The results reveal that the threshold for the SBS process and the energy reflectivity significantly change with laser focus position under the same pump and focusing parameters. Ultimately, the gain characteristics of the SBS material is the primary factor that influences the SBS output. This work presented here offers insight into the operation of short-length solid-state SBS lasers and serves as a basis for the design and optimization of such systems.
ABSTRACT
Free-space Brillouin lasers (BLs) are capable of generating high-power, narrow-linewidth laser outputs at specific wavelengths. Although there have been impressive experimental demonstrations of these lasers, there is an absence of a corresponding theory that describes the dynamic processes that occur within them. This paper presents a time-independent analytical model that describes the generation of the first-order Stokes field within free-space BLs. This model is based on the cavity resonance enhancement theory and coupled wave equations that govern the processes of stimulated Brillouin scattering (SBS). This model is validated using an experimental diamond BL to numerically simulate the influence of the cavity design parameters on the SBS threshold, pump enhancement characteristics, and power of the generated Stokes field. Specifically, the model is used to determine the SBS cavity coupler reflectance to yield the maximum Stokes field output power and efficiency, which is also a function of the pump power and other cavity design parameters. This analysis shows that the appropriate choice of Brillouin cavity coupler reflectance maximizes the Stokes field output power for a given pump power. Furthermore, the onset of higher-order Stokes fields that are undesirable in the context of single-frequency laser operation were inhibited. This study aids in understanding the relationship between the cavity parameters and resultant laser characteristics for the design and optimization of laser systems.
ABSTRACT
Rice false smut, caused by Ustilaginoidea virens, has become one of the most devastating grain diseases of rice worldwide. Understanding the genetic diversity of U. virens is essential for efficient disease control and breeding for disease resistance. However, little is known about the genetic variation of U. virens from different rice cultivars. We investigated the genetic diversity and pathogenic variation of U. virens isolates from 10 rice cultivars in Zhejiang, China. A total of 260 polymorphic loci and 27 haplotypes were identified based on the 2,137-bp combined DNA fragments of all individuals; hap_4 was the most common haplotype, represented by 41 isolates. Phylogeny indicated that all isolates were divided into four genetic groups. Group I was the largest, with 98 isolates, distributed mainly in eight cultivar populations, whereas 90% of the isolates collected from a Changxiang cultivar were clustered in Group IV. Furthermore, the pairwise FST values exhibited significant genetic differentiation in 27 of the pairwise comparisons between populations, accounting for 23.21% of the total genetic variation. The genetic composition of the isolates of the CX population was distinguishable from that of the other nine populations, and genetic recombination was found in a few isolates. Finally, 27 haplotype representative isolates showed high variation in pathogenicity, and the isolates from the genetic subpopulation I were likely to be more virulent than those from genetic subpopulations II and III. Collectively, these findings suggest that differences in rice cultivars play an important role in the genetic variation of U. virens.
Subject(s)
Hypocreales , Oryza , Ustilaginales , Oryza/genetics , Plant Diseases , Plant Breeding , Hypocreales/genetics , Genetic VariationABSTRACT
Past decades have witnessed the generation of new stretchable photodetectors in electronic eyes, health sensing, wearable devices, intelligent monitoring and other fields. Stretchable devices require not only outstanding performance but also excellent flexibility, adaptability and stability. Innovative strategies have been proposed to realize the stretchability of devices. In addition, novel functional materials including zero-dimensional nanomaterials, one-dimensional inorganic nanomaterials, two-dimensional layered materials, organic materials, and organic-inorganic composite materials with excellent properties are emerging to continuously improve the performance of devices. Here, the recent research progress of stretchable photodetectors in terms of both various design methods and functional materials is outlined. The optical performance and stretchable properties are also comprehensively reviewed. Finally, a summary and the challenges associated with the application of stretchable photodetectors are presented.
ABSTRACT
The beam spatial intensity distribution is critical to laser applications both in the scientific and the industrial fields. Here, a method for beam spatial intensity modification based on stimulated Brillouin amplification (SBA) is proposed, which provides an alternative approach of laser beam shaping accompanied by efficient energy amplification. Three beam shaping schemes based on SBA has been demonstrated and evaluated in theoretical simulation and experiments with pulsed laser. The results indicate that the spatial distribution can be modified by manipulation of the beam polarization and the intensity. Finally, the shaped Stokes beam has been modified into the flat-top distribution with the output pulse energy increasing to 4.43 times of the input energy, proving the feasibility of SBA spatial shaping method.
ABSTRACT
Delayed self-heterodyne interferometry is a commonly used technique for the measurement of laser linewidth. It typically requires the use of a very long delay fiber when measuring narrow linewidth (especially linewidths in the kHz-range) lasers. The use of long fibers can result in system losses and the introduction of 1/f noise that causes spectral line broadening. In this paper, we present a calculation method for processing the output of a delayed self-heterodyne setup using a short length of delay fiber, to determine laser linewidth. The method makes use of pairs of data points (corresponding to adjacent maxima and/or minima) in the signal generated from the self-heterodyne setup to determine the laser linewidth. Here, the power ratio or amplitude difference of the signal at these data points is of importance. One of the key benefits of this method is that it avoids 1/f noise which would otherwise be introduced into the measurement through the application of long fibers. The experimental results highlight that the method has a high calculation accuracy. Furthermore, the capacity for the method to utilize different pairs of data points in the self-heterodyne output to determine the laser linewidth, imparts a high degree of flexibility and usability to the technique when applied to real-world measurements.
ABSTRACT
In this work we demonstrate the compression of laser pulses at a high repetition rate, using transient stimulated Brillouin scattering (SBS). Output pulses with pulse durations close to the quarter-acoustic wave oscillation period (τf) was obtained. We find that the primary factors which limit the compression of pulses under high repetition-rate, transient conditions are the inherently low gain in the transient regime, thermal accumulation within the SBS medium and optical breakdown. We show that short phonon lifetimes can suppress the trailing edge amplification of the output pulse, while also reducing the threshold and improve energy efficiency. In this work, we demonstrate the generation of output laser pulses with a repetition-rate of 200â Hz and an average pulse duration of 1.08τf using the electronic-fluorinated liquid FC-43. Due to the fast decay of the acoustic field, compressed pulses with duration <τf were also observed. We also demonstrate efficient output of pulses with repetition-rate of 200â Hz and energy efficiency of up to 40% using the heat transfer fluid HT-230.
ABSTRACT
Stimulated Brillouin scattering (SBS), with its advantages of low quantum defect and narrow gain bandwidth, has recently enabled an exciting path toward narrow-linewidth and low-noise lasers. Whereas almost all work to date has been in guided-wave configurations, adaptation to unguided Brillouin lasers (BLs) offers a greater capacity for power scaling, cascaded Stokes control, and greater flexibility for expanding wavelength range. Here, we report a diamond Brillouin laser (DBL) employing doubly resonant technology at 1064â nm. Brillouin output power of 22.5 W with a linewidth of 46.9 kHz is achieved. The background noise from the pump amplified spontaneous emission (ASE) is suppressed by 35â dB. The work represents a significant step toward realizing Brillouin oscillators that simultaneously have high power (tens-of-watts+) and kHz-linewidths.
ABSTRACT
Delayed self-heterodyne/homodyne measurements based on an unbalanced interferometer are the most used methods for measuring the linewidth of narrow-linewidth lasers. They typically require the service of a delay of six times (or greater) than the laser coherence time to guarantee the Lorentzian characteristics of the beat notes. Otherwise, the beat notes are displayed as a coherent envelope. The linewidth cannot be directly determined from the coherence envelope. However, measuring narrow linewidths using traditional methods introduces significant errors due to the 1/f frequency noise. Here, a short fiber-based linewidth measurement scheme was proposed, and the influence of the noise floor on the measurement of the laser linewidth using this scheme was studied theoretically and experimentally. The results showed that this solution and calibration process is capable of significantly improving the measurement accuracy of narrow linewidth.
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The anti-reflection properties of hard material surfaces are of great significance in the fields of infrared imaging, optoelectronic devices, and aerospace. Femtosecond laser processing has drawn a lot of attentions in the field of optics as an innovative, efficient, and green micro-nano processing method. The anti-reflection surface prepared on hard materials by femtosecond laser processing technology has good anti-reflection properties under a broad spectrum with all angles, effectively suppresses reflection, and improves light transmittance/absorption. In this review, the recent advances on femtosecond laser processing of anti-reflection surfaces on hard materials are summarized. The principle of anti-reflection structure and the selection of anti-reflection materials in different applications are elaborated upon. Finally, the limitations and challenges of the current anti-reflection surface are discussed, and the future development trend of the anti-reflection surface are prospected.
ABSTRACT
Rice false smut, caused by Ustilaginoidea virens, is one of the most destructive fungal diseases in rice-growing countries. Studies of the genetic diversity, evolution, and pathogenicity of U. virens can provide more information for disease control and cultivar breeding. Contrary to previous studies on the genetic diversity of different geographical populations of U. virens, this study analyzed the genetic variation of U. virens from different panicles of the same rice cultivar in a field in Yunnan Province using single nucleotide polymorphism molecular markers. A total of 183 polymorphic loci and five haplotypes, hap_1 to hap_5, were identified based on the 1,350-bp combined DNA fragment of 127 isolates, showing some genetic diversity. Hap_1 and hap_3 had the highest occurrence, indicating they were the dominant haplotypes in the field. Further analysis showed that most rice panicles could be coinfected by different haplotypes, and even a few spikelets could be coinfected by multiple haplotypes. The phylogeny indicated that all isolates were divided into five genetic groups. Groups I, II, and III clustered together and were distinguished from Groups IV and V. Significant genetic variations in five pairwise comparisons of panicle populations, accounting for 72.45% of the total variation, were found according to FST values. This variation might be caused by different field microenvironments and the uneven distribution of inoculum sources. An unweighted pair-group method with arithmetic means dendrogram and the population structure revealed that the genetic composition of the isolates collected from YN1, YN2, and YN4, which were dominated by the same genetic subgroup, was different from that collected from YN3. Finally, genetic recombination was found in 11 isolates; hap_2 and hap_5, probably as genetic recombination progenies produced by sexual hybridization between hap_1 and hap_3, acquired a greater virulence than their ancestors according to population structure and pathogenicity analyses. These results will help us understand the genetic diversity, evolution, and infection process of U. virens and aid in the development of more effective management strategies for rice false smut, including new cultivars with improved resistance.
Subject(s)
Oryza , Ustilaginales , China , Hypocreales , Oryza/microbiology , Plant Breeding , Plant Diseases/microbiology , Polymorphism, Single Nucleotide , Virulence/geneticsABSTRACT
Rice false smut caused by Ustilaginoidea virens is one of the most devastating fungal diseases of rice panicles worldwide. In this study, two novel molecular markers derived from single nucleotide polymorphism-rich genomic DNA fragments and a previously reported molecular marker were used for analyzing the genetic diversity and population structure of 167 U. virens isolates collected from nine areas in the Sichuan-Chongqing region, China. A total of 62 haplotypes were identified, and a few haplotypes with high frequency were found and distributed in two to three areas, suggesting gene flow among different geographical populations. All isolates were divided into six genetic groups. Groups I and VI were the largest, with 61 and 48 isolates, respectively. The pairwise FST values showed significant genetic differentiation among all compared geographical populations. Analysis of molecular variance showed that intergroup genetic variation accounted for 40.17% of the total genetic variation, while 59.83% of genetic variation came from intragroup genetic variation. The unweighted pair-group method with arithmetic means dendrogram and population structure revealed that the genetic composition of isolates collected from Santai, Nanchong, Yongchuan, and Wansheng dominated by the same genetic subgroup was different from those collected from other areas. In addition, genetic recombination was found in a few isolates. These findings will help to improve the strategies for rice false smut management and resistance breeding, such as evaluating breeding lines with different isolates or haplotypes at different elevations and landforms.
Subject(s)
Hypocreales , Oryza , Genetic Variation , Hypocreales/genetics , Plant DiseasesABSTRACT
Non-collinear stimulated Brillouin scattering (SBS) amplification can obtain high peak power Stokes output while ensuring the stability, but the frequency mismatch reduces the energy conversion efficiency of the system. In this paper, a dual-frequency pulse laser based on acousto-optic crystal modulation is designed. The output pulse pair can be used as pump and Stokes light, respectively, which realizes the active frequency matching of the gain medium Brillouin frequency shift during the SBS amplification process and helps to maintain ideal energy conversion efficiency. The dual-frequency laser finally produced a laser pulse pair with a pulse width adjustment range of 100 ps-50 ns, a frequency shift range of 0 GHz-2 GHz, and the polarization extinction ratio (PER) reaches 20.82dB.
ABSTRACT
We report a diamond Raman laser that is continuously-tunable across the range from 590 nm to 625 nm producing continuous wave output with up to 8 W. The system is based on an all-fiber and tunable (1020-1072 nm) Yb-doped pump laser with a spectral linewidth of 25 GHz that is Raman-shifted and frequency doubled in a cavity containing diamond and a lithium triborate second harmonic crystal. Despite the broad pump spectrum, single frequency output is obtained across the tuning range 590-615 nm. The results reveal a practical approach to obtain tunable high-power single-frequency laser in a wavelength region not well served by other laser technologies.
ABSTRACT
Despite their extremely high thermal conductivity and low thermal expansion coefficients, thermal effects in diamond are still observed in high-power diamond Raman lasers, which proposes a challenge to their power scaling. Here, the dynamics of temperature gradient and stress distribution in the diamond are numerically simulated under different pump conditions. With a pump radius of 100 µm and an absorption power of up to 200 W (corresponding to the output power in kilowatt level), the establishment period of thermal steady-state in a millimeter diamond is only 50 µs, with the overall thermal-induced deformation of the diamond being less than 2.5 µm. The relationship between the deformation of diamond and the stability of the Raman cavity is also studied. These results provide a method to better optimize the diamond Raman laser performance at output powers up to kilowatt-level.
ABSTRACT
A photonic crystal fiber-based chirped pulse amplification delivering 272 fs pulses of 66.4 µJ energy at a repetition rate of 500 kHz is presented, resulting in an average/peak power of 33.2 W/244 MW. A single grating is adopted for the pulse width stretching and compression, which leads to high-compactness and low cost of the system. The output beam is near-diffraction-limited (M2 = 1.1 ± 0.05) with a power stability better than 0.5%. The cutting of alumina ceramic substrate and flexible printed circuit are demonstrated by using the laser system. The results indicate that the laser is competent for industrial applications.
ABSTRACT
A surface plasmon resonance (SPR) sensor based on a dual-side polished microstructured optical fiber (MOF) with a dual core is proposed for a large analyte refractive index (RI; na) detection range. Gold is used as a plasmonic material coated on the polished surface, and analytes can be directly contacted with the gold film. The special structure not only facilitates the fabrication of the sensor, but also can work in the na range of 1.42-1.46 when the background material RI is 1.45, which is beyond the reach of other traditional MOF-SPR sensors. The sensing performance of the sensor was investigated by the wavelength and amplitude interrogation methods. The detailed numerical results showed that the proposed sensor can work effectively in the na range of 1.35-1.47 and exhibits higher sensitivity in the na range of 1.42-1.43.