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Chiral metasurfaces have been proven to possess great potential in chiroptical applications. However, the multiband chiral metasurface with near-perfect circular dichroism has not been well studied. Also, the widely used bilayer metasurface usually suffers from the interlayer alignment and weak resonance. Here, we propose a twisted Moiré metasurface which can support three chiral bands with near-unity circular dichroism. The Moiré metasurface can remove the restriction of interlayer alignment, while maintaining a strong monolayer resonance. The two chiral bands in the forward direction can be described by two coupled-oscillator models. The third chiral band is achieved by tuning the interlayer chiral mode on resonance with the intralayer mode, to eliminate the parallel and converted components simultaneously. Finally, we study the robustness and tunability of the triple-layer Moiré metasurface in momentum space. This work provides a universal method to achieve three near-unity circular dichroism bands in one metasurface, which can promote applications of chiral metasurfaces in multiband optical communication, chiral drug separation, sensing, optical encryption, chiral laser, nonlinear and quantum optics, etc.

Bound states in continuum (BICs) are believed to have the ability to achieve high quality factor (Q factor) resonances, which is very important for plasmonics. However, the study of plasmonic BICs is not sufficient. Herein, we design and fabricate a metal−insulator−metal (MIM) metasurface and demonstrate a one-dimensional plasmonic BIC experimentally. The even-order localized surface plasmon resonance (LSPR) modes have even parity at normal incidence. The symmetry-protected BIC can be achieved at Γ point. The band structure can be tuned by strong coupling between the localized plasmonic resonance and plasmonic lattice mode. Interestingly, two of the hybrid modes are also BICs. Although BICs cannot interact with the far field, we successfully demonstrate BIC splitting through far-field excitation. By further tuning the pitch of the MIM grating, the Friedrich–Wintgen BIC is also observed. Finally, we propose and preliminarily demonstrate an ultrathin bandpass spatial filter. These findings provide a new platform to study optical multipole BICs and can have applications in fields such as nano lasers, ultrasensitive sensors, filters, nonlinearity enhancement, and quantum optics.

Bound states in the continuum (BICs) have been observed in a variety of systems. A plasmonic BIC offers interesting opportunities, since a surface plasmon is known to confine light to the nanometer scale. However, the observation and manipulation of plasmonic BICs is a challenge due to the intrinsic loss of metals. Here, we study plasmonic BICs in the visible range in a one-dimensional all-metallic grating. First, by tuning the resonances of localized and propagating surface plasmon modes to resonance, we successfully observe symmetry-protected plasmonic BICs in an all-metallic system. Next, by continuously tuning the localized mode, we demonstrate topological band inversion characterized by a Zak phase transition. In addition, we engineer off-\ensuremath{\Gamma}-point BICs and confirm their formation mechanism. Finally, we experimentally determine that the quality ($Q$) factor of a 10-groove structure can exceed 60, about one order of magnitude greater than conventional metallic structures. The simulations reveal that, with more grooves, the $Q$ factor can be over 200. The plasmonic BICs in the visible range demonstrated in this paper pave the way to promising applications in lasers, sensors, light-matter interactions, nonlinear optics, and quantum optics.

The color and/or chromaticity controllability of random lasing is a key factor to promote practical applications of random lasers as high luminance sources for speckle-free imaging. Here, white coherent random lasing with tunable chromaticity is obtained by using broadband enhancement Au-Ag nanowires as scatterers and the resonance energy transfer process between different dyes in the capillary microfluidic channel. Red, green and blue random lasers are separately fabricated with low thresholds, benefiting from the plasmonic resonance of the nanogaps and/or nanotips with random distribution and sizes within Au-Ag nanowires and positive optical feedback provided by the capillary wall. A white random laser system is then designed through reorganizing the three random lasers. And, the chromaticity of the white random laser is flexibly tunable by adjusting pump power density. In addition, the white random laser has anisotropic spectra due to the coupling role between the lasers. This characteristic is then utilized to obtain different random lasing with different chromaticity over a broad visible range. The results may provide a basis for applying random laser in the field of high brightness illumination, biomedical imaging, and sensors.

Plasmonic nanostructures provide a new way to improve nonlinear optical effects. As a mode of surface plasmons (SP), localized SPs can highly localize and enhance electromagnetic fields within a subwavelength volume. In this work, we developed a one-dimensional V-groove Ag nanograting. Through simulation, we realized triple-resonance enhanced four-wave mixing (FWM), in which both the excitation and signal waves are in resonance with LSPRs modified by propagating SPs, and can perfectly overlap with each other in each single nanogroove. Compared with that from a flat Ag plate, the FWM enhancement factor can be over six orders of magnitude. Next, we filled the Ag V-groove with nonlinear polymer 2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene and further improved the enhancement factor to eight orders of magnitude, together with a conversion efficiency of 1.02 × 10 − 2 . Finally, by changing the water filling ratio, the FWM signal is tuned over 180 nm, while keeping the enhancement factor over seven orders of magnitude.

Acquisition granularity and acquisition span are two important indexes to analyze the active power of renewable energy power stations, and it is important for the analysis of the intermittent energy output power to determine the acquisition granularity of the data. An acquisition granularity calibration method of the photovoltaic output power based on data mining technology is proposed in this paper. The sensitivity changing characteristics of the time series and the sum of the output power are respectively extracted by the multi-scale descriptive statistical analysis and interpolation method. A “power trapezoidal continuous changing state” method is proposed to establish a multi-objective optimization model for the acquisition granularity calibration of the photovoltaic output power. Genetic algorithm (GA) and Particle swarm optimization (PSO) algorithm are respectively used to solve the model and determine the optimal acquisition granularity of the photovoltaic output power. The sensitivity of the acquisition granularity of the data to the capacity of the energy storage system is analyzed, and the energy storage system with the optimal acquisition granularity can’t only effectively smooth the fluctuation of the photovoltaic output power but also keep the main information of the data. The simulation tests of the annual actual operation data at a photovoltaic power station with the installed capacity of 14 MW in China verify the validity of the model. The simulation results show when the acquisition granularity of the photovoltaic output power takes 45 s, it can satisfy the accuracy of the required data for the capacity configuration of the energy storage system. The method proposed in this paper provides a theoretical basis for the intermittent energy applications and has a certain engineering application prospects.

Summary The acquisition granularity (time feature quantity) and sampling span (spatial feature quantity) of the data are the feature factors to analyze the active power of renewable energy power stations. According to the time and space characteristics of photovoltaic (PV) power stations, the acquisition granularity and sampling span calibration methods of PV output power based on data mining technology are proposed this paper. The initial range of the acquisition granularity is determined by analyzing the maximum-order difference components of the PV output power. Through deeply mining the continuous change state of the PV output power, an acquisition granularity calibration method of the PV output power based on the multiobjective optimization model is proposed from time characteristics. The particle swarm optimization algorithm is used to solve the model to obtain the optimal the acquisition granularity of the PV power station. Through the analysis of the sample information entropy change trend of the PV output power, a sampling span calibration method of the PV output power based on the information entropy theory is proposed from space characteristics. The sensitivity analysis of the acquisition granularity and sampling span of the data to the capacity of energy storage systems is realized by the smooth control of the PV output power using first-order low filters. The simulation tests of the annual history operating data at a PV power station with the installed capacity of 40 MW in China verify the validity of the provided methods. The simulation results show when the acquisition granularity takes 60 seconds and the sampling span takes 33 days, it can satisfy the accuracy of the required data of energy storage systems to realize the smooth control of the PV output power.

The working threshold is an important parameter to assess the performance of cavity-free random lasers. Here, the temporal profile measurement is proposed as an alternative method to determine the thresholds of the surface plasmon based random lasers pumped by ns pulses based on analyzing the delay time (tDelay) and rising time (tR) of the emission signal. The obvious and slight inflection points of the curves of tDelay and tR varying with the pump power density are observed as indicators for the thresholds of random lasing and for the transition of lasing mode, respectively. The proposed method supplies consistent values to those supplied by traditional methods in frequency-domain for the random systems with different gain length. The demonstrated temporal profile approaches are free from the spectrometers and may be as a candidate for measuring the threshold of random lasers in ultrafast optics, nonlinear optics and bio-compatible optoelectronic probes.

Multicolor random lasing has broad potential applications in the fields of imaging, sensing, and optoelectronics. Here, silver nanoflowers (Ag NF) with abundant nanogaps are fabricated by a rapid one-step solution-phase synthesis method and are first proposed as effective broadband plasmonic scatterers to achieve different color random lasing. With abundant nanogaps and spiky tips near the surface and the interparticle coupling effect, Ag NFs greatly enhance the local electromagnetic field and induce broadband plasmonic scattering spectra over the whole visible range. The extremely low working threshold and the high-quality factor for Ag NF-based random lasers are thus demonstrated as 0.24 MW cm−2 and 11,851, respectively. Further, coherent colorful random lasing covering the visible range is realized using the dye molecules oxazine (red), Coumarin 440 (blue), and Coumarin 153 (green), showing high-quality factor of more than 10,000. All these features show that Ag NF are highly efficient scatterers for high-performance coherent random lasing and colorful random lasers.

This paper presents a low-power 14-bit single-slope based column-level ADC for 384 × 288 size uncooled infrared imager. In this work, a passive sample and hold structure is proposed to minimize the ADC's power consumption. Moreover, the proposed ADC makes use of a low-power TDC with DLL-based 3-bit gray counter, which improves the ADC's power performance. A 17µm pixel pitch 384×288 uncooled infrared ROIC was fabricated with 0.18µm CMOS process to verify the proposed ADC, the measured INL is below ± 2LSB, and the RMS noise is 0.6LSB. The measured power consumption of the ROIC is 100mW.

Joule heating effect of micro-bolometer sensors heats the elements rapidly during readout, and longtime heating might cause permanent damage of the detector. To solve this problem, we proposed a self-protection scheme based on an analog row select length of time detection circuitry. The protection circuit is effective for various sequential errors and improves the robustness of the whole detector. By implementing a cascaded OR-gate logic with trimmed edge delay, the row-level selection circuit layout is more regular with reduced area. To verify the proposed scheme, a 640$\times$512 array format uncooled infrared detector with 17$\mu$m pixel pitch is designed and fabricated in 0.18$\mu$m CMOS process. Power consumption of the circuits is below 50$\mu$W and the measured protection threshold of row period is around 360$\mu$s.

A multiplexed 16-bit 64-channel ADC for multi-sensors measurement system is presented. In order to directly interface with multi-type sensors without input impedance transformation buffers used in conventional designs. A dual signal-processing path architecture and a data fusion algorithm are utilized in this work for signal conditioning and quantization. Through the above solutions, this ADC saves considerable amount of power consumption and area cost, therefore enables much more channels and easier system integration. A prototype circuit has been designed in 0.18μm CMOS process. Simulation results reveal 98. 2dB total harmonic distortion (THD) and 14.8-bit ENOB with full-scale input at IMSPS.

Highly integrated uncooled infrared imagers with micro-bolometer detectors usually feature on-chip low dropout regulators, biasing, non-uniformity correction and analog-to-digital converters. In this work, we presented a full-digital low-noise readout integrated circuit(ROIC) with single analog power supply and enhanced biasing noise rejection. A novel multiple biasing generator is proposed which significantly reduces the startup time when powered up and keeps low noise equivalent temperature difference(NETD) contribution. To test the proposed scheme, a $384 \times 288$ array format uncooled infrared detector with 17 $\mu$ m pixel pitch is designed and fabricated in 0.18 $\mu$ m CMOS process. Simulated RMS noise of the biasing voltage for skimming resistors is below 7$\mu$ V and the startup time is reduced to 40ms.

A new multi-level time-to-digital converter (TDC) method capable of reaching high linearity and long dynamic range is presented in this paper. The method is based on a coarse counter and a two-level interpolator with a two-step synchronizer. This method solves the misalignment problem and guarantees synchronized and compatible total results. The synchronizer avoids the meta stability problem. With simulated 45% reduced minimum unit delay, the compensating delay line is shortened in coarse residue restoration. This work could be easily assembled in a multi-channel TDC chip and is aimed for applications such as APD based 3-D ranging.

On-chip coherent light source has always been fascinating and intriguing due to its various potential applications. In the past decades, there has been some progress in the development of chip coherent light (e.g., nanolaser, Bose-Einstein condensation and nonlinear optical effects). However, these methods strictly depend on materials and extreme experimental conditions, and are usually not tunable. Here, a hybrid structure is designed which combines a chirped surface plasmon metasurface with a monolayer transition metal dichalcogenide (TMDC) to achieve a coherent second harmonic generation (SHG) covering the entire visible light spectrum. Using only finite number of metallic grooves, a continuous resonance tuning is obtained. By translating the metasurface in space, a space-frequency locking SHG is demonstrated. Although the Q factor of the surface plasmon cavity is low, its near-field enhancements of both fundamental and SH waves are still obvious. Significantly, the broad linewidth of plasmonic cavity leads to a large degree of overlap between adjacent localized modes, that enables the tuning of the output wavelength continuously at room temperature. Meanwhile, the exciton resonance also plays an important role. This monolithic tunable device demonstrates the potentials of 2D material-plasmon hybrid metasurface and to construct an efficient broadband tunable on-chip coherent light source.

A low-power time-to-digital converter (TDC) scheme for column-level single-slope analogue-to-digital converters for infrared imager is presented. This scheme greatly improves the TDC's timing precision with a novel 3-bit fine gray counter, which makes use of multi-phase clocks from a delay-lock-loop. Aimed for 384 × 288 array size uncooled infrared imager with 17 μm pixel pitch, the TDC circuits have been developed and simulated employing 0.18 μm CMOS technology. Compared with conventional two-step TDC methods, this method saves more chip area and reduces the sampling power consumption by >50%, and also eliminates the coarse-fine inconsistency problem with a simulated ±0.1 least-significant-bit differential non-linearity performance.

A cylindrical dimmer system is proposed to realize broadband field enhancement for terahertz (THz) electromagnetic wave. A surface-textured crescent-shaped cylinder is proposed to red-shift the absorption spectrum comparing to the traditional crescent-shaped cylinder based on the concept of spoof surface plasmons. Such cylinders made of ferroelectric polyvinylidene fluoride can realize the electromagnetic wave harvesting at terahertz frequencies with a broadband and huge absorption cross section. Two such cylinders in close proximity could achieve considerable electromagnetic field enhancement and field confinement in the gap, which could be applied in THz molecules detection, toxic chemical sensing, and safety screening and could break the detection binding that limits the molecules

Linewidth-tunable lasers have great application requirements in the fields of high-resolution spectroscopy, optical communications and other industry and scientific research. Here, the switchable plasmonic scattering of the metal particles with plenty of nanogaps is proposed as an effective method to achieve linewidth-tunable random lasers. By using the nonlinear optical effect of the environment medium, the metal particles demonstrate the transition from local scattering of nanogaps with high spatial frequency to traditional Mie scattering free from detail information with increasing the pump power density. Based on these two scattering processes, random lasers can be continuously driven from a narrow-linewidth configuration exhibiting nanogap effect dominated resonances to a broad-linewidth regime of collectively coupling oscillating among nanowires (or nanoflowers), demonstrating the dynamic range of linewidth exceeds two orders of magnitude. This phenomenon may provide a platform for further studying of the conclusive mechanism of random lasing and supply a new approach to tune the linewidth of random lasers for further applications in high-illumination imaging and biology detection., Comment: 19 pages,6 figures

A mechanically-tunable random laser based on a waveguide-plasmonic scheme has been investigated. This laser can be constructed by spin coating a solution of polydimethylsiloxane doped with the rhodamine 6G organic dye and silver nanowires onto a silicone rubber slab. The excellent overlap of the plasmon resonance peak of the silver nanowires with both the pump wavelength and the photoluminescence spectrum provides the low threshold and tuning properties of the random laser. The random laser wavelength can be tuned from 558 to 565 nm by stretching the soft substrate, which causes reorientation and breakage of the silver nanowires. The polarization state of the random laser can also be changed from random polarization to partial polarization by stretching. The laser performance remains unchanged after the stretching and restoration experiments. These results not only enable easy realization of an ultrathin flexible plasmonic random laser but also provide insights into the mechanisms of three-dimensional plasmonic feedback random lasers.

On the basis of cascade energy transfer between different dye molecules, single-excitation and low threshold coherent random lasing with a high quality factor ( similar to 13 000) over the whole visible range is experimentally observed using gold-silver bimetallic porous nanowires with abundant nanogaps as the scatterers. These nanogaps with different sizes in the bimetallic nanowires can produce continuous plasmonic resonance spectra and provide strong feedback or gain channels for the stimulated emission from different dye molecules. It guarantees a low threshold of lasing. Moreover, multi gain media can provide broad tunability of the emission wavelength when the system is pumped by single-wavelength pulses. It provides excellent flexibility for the design of multicolor output devices.

Periodic Mo/Si multilayer mirrors with high peak reflectivity and broad reflection band for reflecting single attosecond pulse are designed, by optimizing the thickness ratio between the absorber layer and the bilayer. The reflective characteristics of periodic Mo/Si multilayer mirrors with different thickness ratio are analyzed and compared both in frequency domain and in time domain, for picking out optimized thickness ratio to achieve high-efficiency attosecond pulse reflection. According to our simulation, periodic quarter-wavelength Mo/Si multilayer mirrors with different layers all show better pulse reflection capability for incident Gaussian pulses than multilayers with other thickness ratio. When studying the spectral and the temporal responses of periodic multilayer mirrors, the transfer-matrix method and fast Fourier transform have been used in our simulation.

This paper presents a 160×120 size 17µm pixel pitch TEC-less uncooled infrared image sensor with low noise output and low power consumption. Aimed at power-saving TEC-less applications, offset skimming and gain stabilization techniques according to substrate temperature change are proposed and implemented. Each column is integrated with a low-power, low-noise backend readout stage including a CTIA and a 14-bit single-slope ADC. The chip has been realized in 0.35µm process and operates at 100Hz frame rate under 5V/3.3V power supply. Power consumption of the chip is below 50mW. Measurements demonstrate a 2.5LSB RMS temporal output noise, which means 27mK noise equivalent temperature difference (NETD) performance is supposed to be obtained at room temperature.

This paper presents a low-power 14-bit hybrid incremental Σ-Δ/cyclic analog-to-digital converter (ADC) based on pseudo-differential operational amplifier, which is designed for the readout circuit of infrared focal plane array detector. This two-stage hybrid ADC employs an incremental sigma-delta ADC and a cyclic ADC, achieving a good trade-off between accuracy and conversion speed. The two stages share the same analog circuit to reduce area and power consumption. A common-mood feedback module is used to suppress the influence of charge injection, and the effectiveness is demonstrated by detailed theoretical analysis and simulation result. A test chip is fabricated in 0.18 μm CMOS technology. The hybrid ADC in each column is performed in parallel with power consumption of 218.813 μW The simulation result reveals the effective number of bits (ENOB) is 13.775 bits.

This paper presents a low-power 14-bit column-level ADC for 640×512 size uncooled infrared imager. A novel differential-ramp single-slope (DRSS) structure is proposed in this work, which achieves 2x faster conversion speed and 3dB higher SNR performance compared with classical single-slope scheme. Moreover, a novel low-power area-saving result-consistent coarse-fine TDC scheme is proposed. The sensor with 17μm pixel pitch has been realized in 0.5 μm 2P3M CMOS process and applied in the thermal imaging system. Power consumption of per ADC is 120 μW. Measurement results demonstrate an average output RMS noise of 0.5LSB and a maximum nonlinearity of 3LSB.

This paper presents a new low-power readout structure for 1024×6 infrared focal plane array with 1/2 sub-scan time-delay-integration (TDI) and delay-locked-loop-based (DLL-based) analog-to-digital (A/D) function. The circuit is of low power for its passive sampling, delay, and summation completed by capacitor array. Multiple-capacitor structure is also used to make the circuit suffer less from capacitor mismatch. 1/2 sub-scan function and the distribution of detector array contribute to higher resolution in the direction both along the track and across the track. And the TDI function is combined with A/D process in terms of circuit structure and timing sequence, reducing the noise and enhancing the frame rate. The 14-bit ADC is divided into coarse quantization part and fine quantization part. The former is a conventional 11-bit single-ramp ADC and the latter is realized by 8-phase clocks generated by DLL. This circuit also supports bidirectional scanning and two types of detectors whose photo-current flows into or out of the readout circuit.

This paper presents a column-level 14-bit two-stage analog-to-digital converter (ADC) based on pseudo-differential operational amplifier, which is designed for the readout circuit of X-ray sensor array. This low-power hybrid ADC employs an incremental sigma-delta ADC and a cyclic ADC, achieving a good trade-off between accuracy and conversion speed. The two stages share the same analog circuit to reduce area and power consumption. A test chip is fabricated in 0.18μm CMOS technology. The hybrid ADC in each column is performed in parallel with power consumption of 218.813μW. The simulation result reveals the effective number of bits (ENOB) is 13.775 bits.

The design of “stretcher–compressor” using aperiodic multilayers (aMLs) for attosecond pulses in the extreme ultraviolet (EUV) region is presented. We use a single-objective temporal optimization method based on a genetic algorithm (GA) to maximize pulse reflection efficiency for a single mirror. Employing this method, we studied the relationships of optimal number of layers, achievable energy reflectivity, and pulse duration. We then apply the findings to a design of an attosecond “stretcher–compressor” configuration with much improved overall throughput for a near-transform-limited attosecond pulse in a multimirror system.

The defect mode in silver-doped photonic crystals is investigated. 1D and 3D photonic crystals were made by holography using dichromated gelatin mixed with silver nitrate. By controlling the concentration of the silver nitrate, the defect mode was observed in the bandgaps of the holographic photonic crystals. The numerical simulations were made, and the results showed the consistency with the experimental observations.

We experimentally studied the temporal coherence of stimulated Brillouin scattering (SBS) excited by a single-longitude-mode laser. We found that the temporal coherence of SBS is variable but not fixed. In a certain range above the threshold pump energy in which the pulse of the Stokes component is Fourier limited, the coherence length is considerably long, although the temporal coherence decreases with increasing pulse compression rate. If the Fourier transform condition is not satisfied for the pulse of the Stokes component, the temporal coherence decreases rapidly, and the coherence length is much shorter.

Temperature dependence of threshold and gain coefficient of stimulated Brillouin scattering (SBS) was investigated. It was found that the threshold of SBS decreases with the increase of temperature. Based on the definition of the threshold, a new method was proposed for determining the gain coefficient of SBS of the material experimentally by measuring the threshold. It reveals that the threshold and the gain coefficient of SBS of a material are strongly related to temperature.

Surface plasmon resonances on bilayer aluminum nanowire gratings are studied in both theory and experiment. It is found that there are two kinds of surface plasmon on the bilayer metallic gating: longitudinal aluminum/dielectric/aluminum slit and lateral aluminum/dielectric interface waveguide mode. The surface plasmon waveguide mode resonance in the slits makes the grating act as a transverse magnetic (TM)-passing polarizer. With the lateral waveguide mode resonance, certain wavelengths of the incident TM light are translated to aluminum/air or aluminum/substrate waveguide light, and the grating acts as a color filter. With both resonances, the bilayer nanowire grating can be a compact-integrated polarizer and color filter.

A 2-dimensional gradual period photonic heterostructure was made with holography by use of non-uniform swelling effect of dichromated gelatin during processing. In this structure, the symmetric point group of triangle lattice was debased to C2V from C6V. Theoretical analysis and experimental results show that omnidirectional band gap in visible range can be achieved with this kind of heterostructure made by low refractive index materials.

A scheme for a new two-dimensional polarization splitter is proposed based on the transformation optics. When a beam of arbitrary polarization illuminates upon the proposed polarization splitter, the TE (or TM) component is deflected whereas the TM (or TE) component propagates with no deflection. Moreover, the emerging propagation direction of the deflected component can be adjusted by rotating the polarization splitter. The simulation results demonstrated the feasibility and the flexibility of the polarization splitter. Design details and full-wave simulation results are provided.

Although the investigation on photonic band gap materials has been done more than two decades, it is still a big challenge to fabricate three-dimensional photonic crystal (PC) possessing wide band gaps in visible range. In this article, we have reviewed recent progresses on fabricating the PC with low refractive index material in visible range. In contrast to the material with large refractive index, it is cheap to use low refractive index material in fabricating the PC and will be greatly beneficial for future industrial productions. The holographic method to fabricate such a PC has been introduced, applying it to the design of the microlaser has also been discussed.

The principle of a lidar based on Brillouin scattering is introduced. The basic physics of the Brillouin lidar is discussed. The applications of the Brillouin lidar in remote sensing of the ocean, such as measurement of the sound speed and the bulk viscosity of water and detecting submerged objects are investigated. An actual Brillouin lidar system is developed. Also, several basic problems related to Brillouin lidar are studied in detail. The attenuation coefficient of a pulsed laser beam with high pulsed energy in water is investigated; it is helpful to reveal the propagation property of a laser beam in water. The investigations on the threshold value of SBS are made theoretically and experimentally. Finally, a novel phenomena is investigated experimentally, in which Stimulated Raman scattering can be enhanced by stimulated Brillouin scattering.