Spectrally flat mid-infrared supercontinuum pumped by a high power 2 µm noise-like pulse.

We demonstrate spectrally flat high-power mid-infrared supercontinuum (MIR SC) generation with record-breaking power of 33.1 W and power conversion efficiency of 75.06%. It is pumped by a 2 µm master oscillator power amplifier system consisting of a figure-8 mode-locked noise-like pulse seed laser and dual-stage Tm-doped fiber amplifiers with repetition rate of 4.08 MHz. Through cascading a piece of ZBLAN fiber with 13.5 µm large core diameter by direct-low-loss fusion splicing, SCs with spectral ranges of 1.9-3.68 µm, 1.9-3.84 µm, 1.9-4.02 µm and average powers of 33.1 W, 29.8 W, 25.9 W are generated. To the best of our knowledge, all of them have achieved the highest output power under the same condition of MIR spectrum range. This high-power all-fiber MIR SC laser system has relatively simple architecture, high efficiency and flat spectrum, demonstrating the advantages of 2 µm noise-like pulse pump in high-power MIR SC generation.

2.3-µm single-frequency Tm: ZBLAN fiber amplifier with output power of 1.41 W.

We present here the first watt-level single-frequency thulium-doped ZBLAN fiber amplifier system operating at a wavelength of 2.3 µm. Continuous-wave output of up to 1.41 W was generated from a two-stage Tm: ZBLAN fiber amplifier with direct ground-state pumping at 793 nm. Seeded by a single-frequency distributed feedback diode laser at 2332 nm, the thulium-doped ZBLAN fiber amplifier emitted a laser with linewidth no more than 10 MHz at maximal output power. This study examines the impact of a 2.3-µm seed on the competitive laser transition of 2 µm. The findings indicate that direct pumping of a Tm fiber amplifier holds the potential for achieving higher power output within the 2.3-µm band.

High-gain single-frequency Tm3+-doped ZBLAN fiber amplifier at 2.33 µm.

We report here, to the best of our knowledge, the first high-gain, single-frequency Tm3+-doped fiber amplifier operating at the 2.3-µm band with conventional ground-state pumping transition (3H6→3H4) at 793 nm. The gain fiber is an 8.5-m-long ZBLAN fiber with a Tm3+ doping concentration of 3 mol.%, and the seed is a single-frequency distributed feedback diode laser operated at 2331.9 nm. A gain up to 24.1 dB is generated for ∼14 W of launched pump power with the maximum output power of 246 mW. The competitive 3F4 →3H6 laser transition at ∼2 µm is also investigated, and the prospects for further power scaling are discussed.

2.1 µm, 1.52 µJ square-wave noise-like pulse from an all-fiber figure-of-9 Ho-doped oscillator and single-stage amplifier.

A 2.1 µm, high energy square-wave noise-like pulse (NLP) in an all-fiber Ho-doped fiber laser is proposed, which consists of an oscillator and a single-stage amplifier. In the figure-of-9 oscillator, mode-locking is achieved based on the nonlinear amplifying loop mirror, employing a long gain fiber to provide sufficient gain in 2.1 µm band and optimizing the cavity length to obtain maximum pulse energy output. With appropriate pump power and polarization state, the oscillator emits a 175.1 nJ square-wave NLP with center wavelength of 2102.2 nm and spike width of 540 fs. The 3-dB spectral width and pulse envelope width are 11.2 nm and 6.95 ns, respectively. The single-stage amplifier employs a bi-directional pump scheme. After amplification, 5.8 W NLP with a slope efficiency of 56.8% is obtained. The pulse energy of NLP is scaled to 1.52 µJ, which is the highest pulse energy of NLP at 2.1 µm to the best of our knowledge. The obtained high-energy square-wave NLP-fiber laser has great potential in mid-infrared laser generation.

Hectowatt-level GHz burst-mode all-fiber laser based on dissipative soliton resonance.

We demonstrate a high power Yb-doped burst-mode all-fiber laser system operating at GHz intra-burst repetition rate. To our knowledge, it is the first report utilizing dissipative soliton resonance (DSR) to generate tunable burst-mode rectangular pulses. Due to the tunable duration and the rapid rise/fall time for DSR pulses, a 1-10 ns adjustable burst pulse duration is achieved. The intra-burst with sinusoidal waveform can be tuned from 0.8 GHz to 1.5 GHz and actively modulated by an electro-optic modulator (EOM). Amplified by a three-stage Yb-doped fiber amplifier (YDFA), the output power achieves 304 W at 10 ns of burst duration, and the maximum peak power reaches over 50 kW at 2 ns of burst duration. This laser system is anticipated to be applied to generate high power arbitrary microwave signal.

Pulse evolution and multi-pulse state of coherently coupled polarization domain walls in a fiber ring laser.

Pulse evolution and multi-pulse state of coherently coupled polarization domain walls (PDW) is experimentally demonstrated in a novel fiber ring laser. Versatile pulse shapes benefit by wide range moving of PDW in the weakly birefringent fiber. The 8.6 m short-cavity structure is more compact and accessible based on a 976 nm pump with nearly zero negative dispersion (-0.0002 ps2). Besides, multi-pulse patterns such as PDW splitting, harmonic mode-locking, and periodic soliton collision are also observed under larger net negative dispersion (-3.09 ps2) and 151m-longer cavity. This is the first demonstration of coherently coupled PDW in a fiber laser using a bandpass filter and the formation of coherently coupled PDW is ascribed to the BPF's force filtering.

High-power mid-infrared supercontinuum generation in a fluoroindate fiber with over 2 W power beyond 3.8 µm.

An all-fiber mid-infrared supercontinuum (MIR-SC) laser source with a power of over 2 W beyond 3.8 µm is demonstrated. The SC laser involves a silica-fiber-based SC laser as a pump source and a piece of fluoroindate (InF3) fiber as a nonlinear medium. The influence of pump pulse repetition rate on the SC characteristics is carefully studied. In the InF3 fiber, the pump pulse with spectral coverage of 1.9-2.6 µm is converted into MIR-SC with a broadest spectral coverage of 1.9-4.9 µm and a maximal average power of 11.8 W. Up to 2.18 W is measured in the spectral region beyond 3.8 µm, which, to the best of the authors' knowledge, demonstrates the record SC power in this waveband to date.

Mid-infrared supercontinuum generation in an all-fiberized Er-doped ZBLAN fiber amplifier.

A high power mid-infrared (MIR) supercontinuum (SC) is demonstrated in a strictly all-fiberized Er-doped ZBLAN fiber amplifier (EDZFA). The EDZFA is seeded by a 2.0-3.5 µm fiber-based SC laser and pumped at 976 nm. At pulse repetition rate of 500 kHz, the output SC spanning from 2.7 to 4.2 µm reaches a record output power of 4.96 W with an overall slope efficiency of 17.3%. This Letter, to the best of our knowledge, demonstrates the first all-fiberized in-amplifier SC generation in the MIR region, which has significant potential for further power scaling.

[Study on quality evaluation method of classical prescription Mahuang Decoction primary standard substances].

This study aimed to establish the HPLC characteristic chromatogram and content determination method for index components with the primary standard substances of the classical prescription Mahuang Decoction, and to provide data basis for the establishment of its quality standard and the development and utilization of compound preparations. First, HPLC was used to establish the material reference chromatograms of Mahuang Decoction, and 15 batches of standard samples of Mahuang Decoction were determined. Their similarity was calculated by the median method. Secondly, the content of the standard substances was determined and a simplecontent determination method was established by HPLC. Relevant methodology was investigated, and the extraction ratio, index component transfer rate and moisture content of 15 batches of primary standard samples were calculated. The results showed that the two sets of HPLC methods had their own characteristics. The six chromatographic peaks identified from the 10 common peaks in the former characteristic chromatogram covered all the herbal medicines in the standard substances, which can better indicate the quality characteristics of the standard substances of Mahuang Decoction. The latter method(content determination method) was simple and practical, so it was suitable for establishing the quality standard of its compound preparation. Two sets of methods were jointly used to evaluate the quality of 15 batches of Mahuang Decoction. The results were as follows: the similarity of 15 batches of samples was greater than 0.90; the average extraction ratio was 18.1%; the average moisture content was 9.7%; the average content and transfer rate of the standard ingredients ephedrine hydrochloride and total pseudoephedrine hydrochloride were 2.3% and 26.7% respectively, and the average content and transfer rate of amygdalin were 2.2% and 48.3% respectively. None of the data showed dispersion(beyond 70%-130% of the mean value), which met the application data requirements for the substance standards of ancient classical Chinese herbal compound preparations(draft for comments). Based on the above research, the primary substance quality standard of Mahuang Decoction was established in order to provide reference for the development and research of the compound preparation of Mahuang Decoction.

Ultra-efficient, 10-watt-level mid-infrared supercontinuum generation in fluoroindate fiber.

A 10-watt-level mid-infrared supercontinuum (SC) spanning 0.8-4.7 µm with ultra-high-power conversion efficiency is generated in a piece of fluoroindate (InF3) fiber. The pump laser is a master oscillator power amplifier system seeded by a mode-locked fiber laser operating at 1956 nm with pulse repetition rate and pulse duration of 33 MHz and 60 ps, respectively. A piece of InF3 fiber is fusion spliced to the output end of the pump light source with a low fusion splicing loss of 0.12 dB. An endcap made of multimode aluminum fluoride fiber is used to protect the fiber tip from possible optical or thermal damage. Benefiting from the fiber endcap as well as the low-loss splicing joint between silica and InF3 fiber, high-power SC generation is achieved with maximal output power of 11.3 W. Furthermore, the long wavelength edge of the obtained SC spectrum is extended to 4.7 µm. This Letter, to the best of our knowledge, not only demonstrates the first 10-watt-level SC generation in InF3 fibers, but also achieves record power conversion efficiency of 66.5% among reported 10-watt-level fluoride-fiber-based SC laser sources.

Watt-level mid-infrared supercontinuum generation from 2.7 to 4.25 µm in an erbium-doped ZBLAN fiber with high slope efficiency.

A watt-level mid-infrared supercontinuum (MIR-SC) spanning 2.7 to 4.25 µm is generated in an erbium-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber amplifier (EDZFA). A broadband fiber-based SC covering 2.2-3.1 µm region is used to seed the amplifier. The generated SC has a maximum output power of 1.75 W with an overall slope efficiency of 20.5%. A normalized root mean square (RMS) in power of 0.5% shows that our system is highly stable. This research, to the best of the authors' knowledge, demonstrates both the record power and the record slope efficiency of in-amplifier MIR-SC generation to date.

All-fiberized, multi-watt 2-5-µm supercontinuum laser source based on fluoroindate fiber with record conversion efficiency.

A strictly all-fiberized, multi-watt 2-5-µm supercontinuum (SC) laser source with high conversion efficiency is presented. A broadband thulium-doped fiber amplifier with spectral coverage of 2-2.7 µm is used to pump a piece of single-mode fluoroindate (InF3) fiber. A fusion-spliced joint with loss down to 0.07 dB is achieved between a piece of silica fiber and the InF3 fiber, which retains all-fiber structure and efficient pump power coupling. A 1.35-W SC with spectral coverage of 1.5-5.2 µm and a 4.06-W SC with spectral coverage of 1.9-5.1 µm are obtained with record conversion efficiencies of 59.5% and 63.3%, respectively. Furthermore, measured output power has a normalized root mean square superior to 0.4%, which indicates the excellent power stability of the system. This research, to the best of the authors' knowledge, demonstrates both record output power and record conversion efficiency of InF3-fiber-based mid-infrared-SC laser sources to date. It is also the first report on strictly all-fiberized SC generation in InF3 fibers.

15.2 W spectrally flat all-fiber supercontinuum laser source with >1 W power beyond 3.8 µm.

In this Letter, a high-power 1.9-4.2 µm supercontinuum (SC) laser source with a real all-fiber structure is reported. A 12 m length of ZBLAN fluoride fiber was used as the nonlinear medium, which was pumped by a thulium-doped fiber amplifier through a firm fusion-spliced joint between silica fiber and itself. The obtained SC laser had a high spectral flatness with a maximal 10 dB bandwidth of 2090 nm spanning from 1960 to 4050 nm. A record power of 15.2 W for an all-fiber mid-infrared SC laser was measured. The average spectral power density of this SC laser was as high as 7.2 mW/nm. In particular, the SC power beyond 3.0 and 3.8 µm was 8.1 and 1.08 W which corresponded to a power ratio of 53.2% and 7.1%, respectively. This Letter, to the best of our knowledge, represents the brightest all-fiber mid-infrared SC laser, and provides a promising high-power pump light for SC generation in cascaded chalcogenide fibers.

0.6-3.2 µm supercontinuum generation in a step-index germania-core fiber using a 4.4 kW peak-power pump laser.

An ultra-broadband supercontinuum was generated in a short piece of step-index germania-core fiber using a fiber laser with a peak power of 4.4 kW. The pure germania core made this fiber capable of propagating light towards the desirable mid-infrared region. The spectral broadening characteristics towards the mid-infrared region under different lengths of germania-core fiber were investigated using pump pulses of 4.4 kW and 1.1 ns at 1550 nm. The large nonlinear refractive index of germania and the small core size of germania-core fiber produced a nonlinear coefficient as high as 11.8 (W km)-1 at 1550 nm, which was beneficial for supercontinuum generation. The pump wavelength was located in the anomalous dispersion regime and close to the zero dispersion wavelength of this germania-core fiber, 1.426 µm. Eventually, an ultra-broadband supercontinuum source with a spectrum spanning from 0.6 to 3.2 µm was obtained and had a total output power of 350 mW at an optimized germania-core fiber length of 0.8 m. This work is the first demonstration, to the best of our knowledge, of a germania-core fiber-based ultra-broadband supercontinuum source that spans from the visible region to the mid-infrared region.

Mid-infrared supercontinuum generation based on cascaded Raman scattering in a few-mode As2S3 fiber pumped by a thulium-doped fiber laser.

By pumping a 1.7-m-long As2S3 fiber at 2050 nm directly, a fiber-based mid-infrared supercontinuum (SC) source with an output power of 366 mW is demonstrated. This is the first experimental demonstration to obtain such a mid-infrared SC in a piece of chalcogenide fiber pumped at 2 µm directly. The cut-off wavelength of the As2S3 fiber is 3.5 µm, indicating that it could support several modes at around 2 µm. It is found that nonlinear spectral broadening mechanisms in the few-mode chalcogenide fiber could be affected through adjusting the butt-coupling position. That is because different positions will excite different modes that correspondingly possess different nonlinearity and dispersion characteristics. When stimulated Raman scattering (SRS) corresponding to the excitation of the fundamental mode becomes dominant in this few-mode fiber, an efficient cascaded SRS-based SC is obtained with five Stokes peaks ranging from 2 µm to 3.4 µm. Results from numerical simulation are in accord with the experimental results, showing that it is feasible to obtain an SRS based mid-infrared SC in a step-index As2S3 fiber by using a 2 µm high peak power picosecond laser to pump directly.

Mid-infrared supercontinuum generation in step-index As2S3 fibers pumped by a nanosecond shortwave-infrared supercontinuum pump source.

A supercontinuum (SC) source spanning from 2 to 4 µm is demonstrated in As2S3-chalcogenide fibers pumped by a nanosecond supercontinuum pump source in the normal dispersion region. In this experiment, two pieces of 3-m-long step-index As2S3 fiber with different core diameters of 7 µm and 9 µm are pumped by a 1.9-2.5 µm nanosecond supercontinuum source. The zero dispersion wavelengths are both beyond 6.6 µm, thus cascaded stimulated Raman scattering is believed to be the dominant mechanism responsible for spectral broadening. With a low peak pump power of ~2.9 kW, both of the output spectra have extended to 4 µm with enhanced power distribution in the MIR region. The maximum output power of the mid-infrared supercontinua is ~140 mW. To the best of our knowledge, it is the first supercontinuum extenting to 4 µm in an As2S3 fiber pumped by shortwave-infrared SC pluses in the normal dispersion region.

Highly stable, monolithic, single-mode mid-infrared supercontinuum source based on low-loss fusion spliced silica and fluoride fibers.

A 0.8 to 4.5 µm highly stable all-fiber spliced mid-infrared supercontinuum (SC) source was presented. The joint between the single-mode (SM) pump silica fiber and the ZBLAN fiber (ZrF4 - BaF2 - LaF3 - AlF3 - NaF, a type of fluoride fiber) was fusion spliced, which greatly improved the SC's stability. The low-loss splicing was guaranteed by the similar mode field areas of the fundamental mode LP(01) of the silica and ZBLAN fibers. At the splicing joint the ZBLAN fiber enveloped the silica fiber, thus increasing the robustness of the splice. A low splicing loss of less than 0.1 dB was calculated, which ensured that the whole SC source was very reliable. The SC had a maximal average power of 550.8 mW with a 1.5 dB spectral bandwidth ranging from 2642 to 4065 nm. In particular, the SC power for λ>3.8 µm was measured to be 116.1 mW with a power ratio of ∼21.1% of the total SC power. Perfect Gaussian beam profiles of the SC source demonstrated its SM operation. Over 12 h of continuous operation of this SC source showed its outstanding power stability with a root mean square variation of 0.59%, which also demonstrated the high quality of the fusion spliced joint.

1.9-3.6 µm supercontinuum generation in a very short highly nonlinear germania fiber with a high mid-infrared power ratio.

In this Letter, a high-power supercontinuum (SC) laser source which spanned from 1.9 to 3.6 µm with an all-fiber configuration was reported. This SC laser was obtained by concatenating a thulium-doped fiber amplifier (TDFA) and a 12 cm long highly nonlinear germania fiber. A 1.9-2.7 µm SC laser from the TDFA was spectrally broadened continuously into the mid-infrared region (>3 µm) in the following germania fiber. When the repetition rate was 2 MHz, the obtained SC laser had a maximum output power of 6.12 W with an optical conversion efficiency of 15.3% with respect to the TDFA pump power. The SC laser had a spectral bandwidth of 1506 nm ranging from 1944 to 3450 nm at the -20 dB level. The SC power with wavelengths >3 µm was 2.9 W, corresponding to a high power ratio of 47.4% in the mid-infrared region. The achieved power ratio in the mid-infrared region, as well as the long wavelength cutoff, to the best of our knowledge, were the best results ever reported in germania fibers.

[Adverse reactions and countermeasures of drugs for children in China].

In recent years, the clinical medication safety for children has gained wide public concern. Because of the growth and development characteristics of the children and drug usage conditions for children, the adverse reactions of drugs in clinic are more common in children than those in adults. In this paper, the common adverse drug reactions and their causes would be briefly introduced, and some suggestions would be put forward on how to reduce the incidence of adverse drug reactions.

[A multi-center, double-blind, placebo-controlled, randomized trial for effect of Longxue Tongluo capsule in treatment of patients of atherosclerotic thrombotic cerebral infarction with blood-stasis syndrome in convalescence].

To evaluate the effectiveness and safety of Longxue Tongluo capsule on patients of atherosclerotic thrombotic cerebral infarction convalescence with blood-stasis syndrome, a double-blind, randomized controlled, multi-center clinical trial was conducted. A total of 160 eligible patients were randomly divided into treatment group and control group, with 80 patients in each group, and all of them were orally given Troxerutin pill(three pills each time, three times daily). Longxue Tongluo capsule was applied in the treatment group, while placebo was applied in the control group(two capsules each time, three times daily) for 4 weeks. Main outcomes were measured by ITT analysis. The neurological function deficits scale showed a decrease of 5.17±2.60 in the treatment group, while 4.31±2.31 in the control group, with significant differences between the two groups(P<0.05); the reduction rate in the treatment group (37.2±15.8)% was significantly higher than that in the control group (29.9±15.3)%(P<0.05). In terms of the comprehensive curative effect by ITT, the effective rates in the treatment and control group were 31.6% and 13.5%, respectively(P<0.05). With respect to the efficacy of traditional Chinese medicine syndrome by ITT, the total effective rate of the treatment group was significantly higher than the control group 88.2% vs 68.9%, P<0.05. Three cases of adverse events occurred in this study, including 1 case of diarrhea in treatment group and 2 cases of skin itch and upper respiratory infection in control group. In conclusion, Longxue Tongluo capsule is effective and safe in the treatment of patients of atherosclerotic thrombotic cerebral infarction convalescence with blood-stasis syndrome, and can effectively alleviate the patients' nerve function defect degree and invalidism, with a good effect on blood stasis syndrome.