Search

A tunable blue random laser based on solid waveguide gain films with silver nanoparticles (NPs) and SiO2 NPs is demonstrated. Localized surface plasmon resonance (LSPR) property and multiple scattering are proven playing an important role simultaneously. The tunability of the blue random laser is realized by simply roughing and changing the thickness of the solid waveguide gain films. To our knowledge, it is the first time using this method to achieve a wide wavelength tuning range of ∼24 nm.

Random lasing in a lotus leaf, with a wide tunable spectrum from planar liquid waveguide gain channels is described. The lotus leaf shows multiple scattering from the micro-papilla and nanoscale coralloid tomentum on its surface. The Fraunhofer diffraction pattern demonstrates excellent coherence and directionality for our random laser. The emission spectrum wavelength can be tuned by changing the pump position due to the random distribution of the micro/nano-scale features on the lotus leaf. Potential applications of the random laser include probing micro/nano-scale structural alterations, optical biosensors on chips, and developing a multi-color random laser.

The kinetic processes of Xe (6p[1/2] $_0$ , 6p[3/2] $_2$ , and 6p[5/2] $_2$ ) atoms under the focused condition were investigated. The atomic density of the laser prepared state significantly increases. Therefore, the probability of the energy-pooling between two high-lying atoms increases. There are three major types of the energy-pooling collisions. The first type is the energy-pooling ionization. Once the excitation laser is focused, the obvious ionization can be observed from the side window whenever the laser prepared state is 6p[1/2] $_0$ , 6p[3/2] $_2$ , or 6p[5/2] $_2$ state. Ionization of Xe is attributed to the energy-pooling ionization or a Xe $^*$ atom reabsorbing another excitation photon. The second type is energy-pooling with big energy difference. When the 6p[1/2] $_0$ state is the laser prepared state, the energy-pooling collision between two 6p[1/2] $_0$ atoms can produce one 5d[3/2] $_1$ atom and one 6s $'$ [1/2] $_0$ atom. The third type is energy-pooling with small energy difference. The intensities of fluorescence lines are much stronger that five secondary 6p states act as the upper states, and the rising edges of these fluorescence lines are much steeper. The primary mechanism of generating the secondary 6p atoms is energy-pooling collision instead of collision relaxation. Based on the collision probability, the rate of energy-pooling between two 6p[1/2] $_0$ atoms is deduced (6.39 $\times$ 10 $^8$ s $^{-1}$ ). In addition, the 6s atoms also increase under the focused condition. Therefore, all the fluorescence lines are serious trailing by radiation trapping.

A tunable random laser with a bendable poly (dimethylsiloxane) (PDMS) substrate was described. The substrate is prepared based on soft lithography from lotus leaf, which have the similar surface structure with lotus leaf such as micropapilla. The micro-papilla on the surface of the substrate will provide efficient multiple scattering for the photon generated from gain medium, and the coherent random lasing is emerging because photon form closed-loop path among micropapilla via the scattering. The wavelength of the random laser emission spectrum can be tuned as wide as 26.0 nm by changing the pump position due to the diverse distribution of the micro-scale features on the soft substrate. The random laser provides a promising solution toward the realization of many laser based applications such as integrating optical biosensors on chips, probing micro-scale structural alterations and developing a multi-color even white random laser.

We describe herein a flexible and tunable random laser made from a flexible poly(dimethylsiloxane) substrate. The substrate is prepared by casting via soft lithography from a lotus leaf to produce a micropapilla surface structure similar to that of a lotus leaf. The micropapilla provides efficient multiple scattering for the photons generated in the gain medium, and random lasing emerges because photons undergo closed-loop paths by scattering from three equilaterally arranged micropapillae. Given the diverse distribution of microscale features on the soft substrate, the random laser spectrum can be tuned by as much as 26.0 nm by changing the pump position. Furthermore, the random laser can be easily tuned by about 14 nm by flexing it, which modifies the micropapilla density and thereby changes the reabsorption strength of the laser dye. The photostability of the random laser is ensured by sealing the gain medium (i.e., dye solution) in a closed system. The results provide a promising method to realize a variety of laser-based applications such as optical biosensors on chips, microscale structural alteration detectors, flexible wearable devices, and multicolor (even white) random lasers.

The kinetic processes for the Xe (6p[1/2]0) atoms in Kr, Ar, Ne, and He buffer gases were studied. We found that Kr, Ar, and Ne atoms can be used to switch the amplified spontaneous emission (ASE) channel from 3408 nm (6p[1/2]0-6s'[1/2]1) to 3680 nm (5d[1/2]1-6p[1/2]1), while Xe and He atoms do not show such a phenomenon. This ASE channel switch is mainly ascribed to the fast transfer of 6p[1/2]0 → 5d[1/2]1. On the basis of the rate equations for two-state coupling (energy-transfer processes between the two states are very rapid), the reason why the ASE channel switch effect normally coincides with a double exponential decay of the spontaneous emission at 828 nm (6p[1/2]0-6s[3/2]1) is explained. The actual situations in Xe, Ar, Ne, and He follow this rule. However, the strictly single exponential decay of the spontaneous emission at 828 nm and strong ASE channel switch effect simultaneously emerge in Kr. This indicates that the transfer of 6p[1/2]0 → 5d[1/2]1 in Kr does not occur via two-state coupling, but via two steps of near-resonance collision through the 5s[3/2]2 (Kr) state as the intermediate state (6p[1/2]0 → 5s[3/2]2 (Kr) → 5d[1/2]1). In addition, we found Xe (6p[1/2]0) atoms strongly tend to reach the 6p[3/2]2, 6p[3/2]1, and 6p[5/2]2 states through the 5s[3/2]2 (Kr) state as the intermediate state in Kr. The 5s[3/2]2 (Kr) state plays a very important role in the energy-transfer kinetics for the Xe (6p[1/2]0) atoms. Kr is probably an excellent buffer gas for laser systems based on Xe.

We present the time-resolved character of stimulated Brillouin scattering (SBS) and backward stimulated Raman scattering (BSRS) in heavy water and its application in Coherent Anti-Stokes Raman Scattering (CARS) technique. A nanosecond laser from a frequency-doubled Nd: YAG laser is introduced into a heavy water cell, to generate SBS and BSRS beams. The SBS and BSRS beams are collinear, and their time resolved characters are studied by a streak camera, experiment show that they are ideal source for an alignment-free CARS system, and the time resolved property of SBS and BSRS beams could affect the CARS efficiency significantly. By inserting a Dye cuvette to the collinear beams, the time-overlapping of SBS and BSRS could be improved, and finally the CARS efficiency is increased, even though the SBS energy is decreased. Possible methods to improve the efficiency of this CARS system are discussed too.

Large eddy simulation is carried out to model the flow process in a supersonic chemical oxygen iodine laser. Unlike the common approaches relying on the tensor representation theory only, the model in the present work is an explicit anisotropy-resolving algebraic Subgrid-scale scalar flux formulation. With an accuracy in capturing the unsteady flow behaviours in the laser. Boundary layer separation initiated by the adverse pressure gradient is identified using Large Eddy Simulation. To quantify the influences of flow boundary layer on the laser performance, the fluid computations coupled with a physical optics loaded cavity model is developed. It has been found that boundary layer separation has a profound effect on the laser outputs due to the introduced shock waves. The F factor of the output beam decreases to 10% of the original one when the boundary transit into turbulence for the setup depicted in the paper. Because the pressure is always greater on the downstream of the boundary layer, there will always be a tendency of boundary separation in the laser. The results inspire designs of the laser to apply positive/passive control methods avoiding the boundary layer perturbation.

Multi-line frequency up-conversions are realized in Cs vapor using 718.8 nm pumping laser resonating with the two-photon transition 62S1/2 → 82D5/2 of Cs atom. The pumping beam is converted into a beam including wavelengths of 361.2, 387.7, 455.7 and 621.5 nm. Experiments with collimated and focused pumping configurations are carried out and compared. Spectrum peak at 361.2 nm is strongest under collimated pumping condition, while 387.7 nm is strongest under focused pumping beam. The output beam under focused pumping is more stable than that under collimated pumping. Results in this work may be useful in laser frequency standard, beacon light, laser measuring and optics communications, etc.

In optically pumped laser systems, rare gas lasers (RGLs) are a field of great interest for researchers. Gas laser regimes with metastable Ne, Ar, and Kr atoms have been investigated, while studies of RGLs based on metastable Xe are sparse. In this work, when a strong excitation laser (2.92 mJ/pulse, 7.44 × 105 W/cm2) was applied to excite Xe atoms from the ground state to the 6p[1/2]0 state, an interesting phenomenon emerged: An intense fluorescence of 980 nm (6p[1/2]1–6s[3/2]2) was produced. However, when the energy of excitation laser was decreased to 0.50 mJ/pulse (1.27 × 105 W/cm2), the fluorescence of 980 nm became very weak. Besides, lifetime and decay rate constant of the 6p[1/2]0 state under the condition of E = 2.92 mJ are significantly different from either those measured by other groups or those of E = 0.50 mJ. These phenomena indicate that the high energy of excitation laser should trigger some new kinetic mechanisms. Further works identified that the new kinetic mechanism is the MIR ASE of 3...

We present the design and investigation of a novel chemosorption vacuum pump (CSVP) for discharging the exhaust gases of a chemical oxygen-iodine laser system diluted with carbon dioxide (CO2-COIL). The CSVP comprises two fixed-bed reactors separately filled with CO2/H2O and O2/I2/Cl2 adsorbents, which can efficiently chemically absorb the CO2-COIL exhaust gases at room or higher temperature. We consider the effects of the adsorbents in different specifications and fixed beds of various constructions on the adsorption performance of the CSVP. We develop and study the sealed CO2-COIL system with the CSVP. We achieve a stable operation with a cumulative duration time of 40 s for four runs and an average output power up to 2.0 kW at a Cl2 flow rate of ∼158 mmol/s and a CO2 flow rate of 132 mmol/s. The experimental results indicate that the COIL system with the CSVP performs similarly to a conventional COIL with a vacuum tank. Taking into account that the CSVP is free of vibration and noise, avoids air pollution, is easily operated, and has a short preparation time, we believe that the chemosorption vacuum pump is an excellent alternative pump system for a transportable COIL system.

An experimental study of combustion-driven HBr chemical laser based on D2/NF3 combustion was carried out. The exotherm of the reaction system was analyzed, and the thermal blockage issue of supersonic flow was solved by adjusting the buffer coefficient ω. By optimizing the laser operating conditions, a maximum HBr laser output of 141W was obtained, with the primary laser lines being HBr P1(5) , P1(6) , and P3(6).

A blue random laser based on solid waveguide gain films with silver nanoparticles (NPs) and SiO2 NPs is demonstrated. Located surface plasmon resonance (LSPR) property and multiple scattering are proven playing an important role simultaneously.

Highly doped erbium crystals have complex fine energy levels, which can be used to emit lasers of different wavelengths under different conditions. The mid-infrared multi-wavelength laser of erbium ions has not yet achieved stable laser emission. In this study, the rate equation is used, with consideration of mode competition, to design a mid-infrared Er:YAG pulsed laser that emits four wavelengths at room temperature. The gain of the multi-wavelength erbium laser is related to the Boltzmann distribution coefficient. Based on this, the conditions for multi-wavelength output have been calculated and verified in experiments. A four-wavelength stable output mid-infrared pulsed laser based on Er:YAG was produced. This laser may be applied to remote sensing or gas detection.

The kinetic processes for the Xe (6p[1/2]

The O-2((1)Delta)/I-2 mixing process is one of the most important steps in chemical oxygen-iodine laser (COIL). Based on the chemical fluorescence method (CFM), a diagnostic system was set up to image electronically excited fluorescent I-2(B-3 Pi(o)) by means of a high speed camera. An optimized data analysis approach was proposed to analyze the mixing process of supersonic oxygen-iodine parallel streams, employing a set of qualitative and quantitative parameters and a proper percentage boundary threshold of the fluorescence zone. A slit nozzle bank with supersonic parallel streams and a trip tab set for enhancing the mixing process were designed and fabricated. With the diagnostic system and the data analysis approach, the performance of the trip tab set was examined and is demonstrated in this work. With the mixing enhancement, the fluorescence zone area was enlarged 3.75 times. We have studied the mixing process under different flow conditions and demonstrated the mixing properties with different iodine buffer gases, including N-2, Ar, He and CO2. It was found that, among the four tested gases, Ar had the best penetration ability, whilst He showed the best free diffusion ability, and both of them could be well used as the buffer gas in our experiments. These experimental results can be useful for designing and optimizing COIL systems. (C) 2014 Elsevier Ltd. All rights reserved.

In optically pumped laser systems, rare gas lasers (RGLs) are a field of great interest for researchers. Gas laser regimes with metastable Ne, Ar, and Kr atoms have been investigated, while studies of RGLs based on metastable Xe are sparse. In this work, when a strong excitation laser (2.92 mJ/pulse, 7.44 × 10

Recently, the optically pumped rare gas lasers have been attracted extensive attention. Rare gas laser systems with Ne (2p 5 3p), Ar (3p 5 4p), and Kr (4p 5 5p) atoms have been investigated. However, there are sparse studies based on Xe. In this work, new phenomena, intensive mid-infrared amplified spontaneous emissions (ASEs), are found after two-photon excitation of Xe from the ground state to the 6p[1/2] 0 state. Simultaneously, substantial 6p[1/2] 1 atoms are populated. The thresholds of ASE peak 1 and the generation of 6p[1/2] 1 atoms are both about 1.5 mJ. It indicates that there should exist the relationship between these two phenomena. The ASE signals show broadband spectra. Therefore, it must be yielded by the superposition of Xe 2 * excimer transitions. The mid-infrared ASEs lead to excimers correlating to the 6s’[1/2] 1 enormously generated. Then these excimers dissociate to produce substantial 6p[1/2] 1 atoms. Under some circumstance, the ratio of the 6p[1/2] 1 to 6p[1/2] 0 atoms reaches about 80%. It indicates that the 6p[1/2] 0 atoms strongly tend to decay through the emissions between the excimer states. Using these emissions, continuous-tunable mid-infrared laser with metastable Xe can be promisingly produced.

We have observed frequency up-conversion in Cs vapor. The pulsed pumping laser beam of 767.2 nm was converted to simultaneous collinear ultraviolet and blue radiation of wavelengths 387.7 and 455.6 nm, respectively (double-line frequency up-conversion). We examined properties of this up-conversion such as energy efficiency and pulse widths. An infrared laser of ~2.4 μm was successful in modulating the laser beam of the frequency up-conversion. The modulation shifts the wavelength of the blue radiation and the intensities of both the blue and ultraviolet radiation. At nanosecond grade, such modulations are expected to have applications in near-infrared up-conversion and optical communications.

A new method to improve the resolution of a slightly non-parallel solid etalon is proposed. The method is aimed to reduce the spectrum broadening caused by non-parallel surfaces; it contains a theoretical formula for adjusting image distances, and an algorithm for processing the corresponding fringe patterns. Theoretical consideration, computer simulation, experimental results, and application demonstration are given. The fringe patterns captured by a CCD showed good agreement with the computer simulation, and the resolution of a λ/10-wavefront-error etalon was improved from 3.1 GHz to 0.51 GHz. In comparison with other methods, this new method is convenient and economical.

Combustion parametric optimization for all gas-phase iodine laser driven by D(2)/NF(3)/DCl combustion was performed, and an energy transfer channel called self-pooling of NCl(a) catalyzed by NF(a)/NF(b) was presented. The results show that a flow rate ratio of NF(3) and D(2) of 0.8 to 1.5 and DCl and D(2) of1.5 is necessary for high efficiency of Cl atoms generation. The results also show that NF(a) and NF(b) from the reaction of HN(3) and residual F atoms or from the D(2)/NF(3) combustion have a serious effect on the generation and transport of NCl(a) via the NF(a) direct quenching of NCl(a) or via the catalysis of NF(a)/NF(b) on NCl(a) self-pooling. The generation of NF can be avoided if sufficient DCl was used and the NF(3)/D(2) flow rate ratio was properly controlled.

Iodine flow rate (IFR) measurement is an essential diagnostic tool in the research and optimization of chemical oxygen–iodine laser (COIL) system. Venturi meter or absorption spectroscopy was used to monitor IFR. But it is difficult for Venturi meter to precisely measure IFR. Simple absorption spectroscopy has trouble monitoring IFR due to the contamination on diagnostic windows and aerosol scattering. An advanced absorption spectroscopy for measuring IFR was described in this paper. The method utilizes two wavelengths (e.g. 470 nm and 365 nm) to distinguish between iodine vapor absorption and other optical losses (e.g. contamination and aerosol scattering). It can easily eliminate the influence of the serious contamination and aerosol scattering on IFR measurement and obtain a reliable IFR. The method is about to apply in COIL studies as a routine diagnostic tool.

High press, gravity-independent, singlet oxygen generator (HGSOG) [1] with small reaction zone and high chemical efficiency was designed and fabricated. The mixing, reaction and separation processes happened simultaneously in the reaction zone of HGSOG. The size and the configuration of reaction zone are very important for HGSOG. In this paper, p-τ value was calculated to determine the upper limit of the volume of reaction zone. The condition of gas-liquid separation was calculated to determine the lower limit of the volume of reaction zone. The utilization rate of Cl 2 achieved 90% and the yield of O 2 ( 1 Δ) reached 70%.

Two electrochemical methods for regeneration of Basic Hydrogen Peroxide (BHP) were investigated in this paper, which could be called one-step method and two-step method, respectively, distinguished by the number of steps during the regeneration process. The one-step method converts potassi um chloride solution and oxygen directly to chlorine and BHP by a modified chlor-alkali cell with an oxygen cathode. For the one-step met hod, two reactors of different structure and corresponding regenerating process were designed. The experimental results showed that, for the continuous-type reactor, the highest peroxide concentration was 0.042 mol/L, while for batch-type reactor the highest peroxide concentration was 0.563 mol/L. The two-step method accomplishes the regeneration of BHP by a conventional chlor-alkali cell combined with a fuel cell reactor which could convert hydrogen and oxygen to peroxide in alkaline potassium hydroxide solution. A peroxide concentration of 2.450 mol/L was obtained for the two-step method. Basic hydrogen peroxide; Electrochemical regeneration; Chemical Oxygen-Iodine Laser

A dual-components absorption method based on absorption spectroscopy was described in the paper. It can easily eliminate the influence of the serious contamination and aerosol scattering on IFR measurement by utilizing the absorptions of iodine vapor and chlorine on two different wavelengths respectively. According to the character that there is no other gaseous product in the reaction besides iodine vapor, IFR in real time can be obtained by the connections of the pressure and the flow rate among chlorine remainder, iodine vapor, and the buffer gas. We used this method to measure IFR for the first time at the exit of a chemical iodine generator. The average of IFR is coincident with that calculated by chemical weighting mass.

Singlet oxygen generator (SOG) is the key part of chemical oxygen iodine laser (COIL) which supplies chemical energy for chemical oxygen iodine laser. A novel pre-swirling jet singlet oxygen generator (PJSOG) with rapid separation technology is put forward. In this paper, experimental performances of PJSOG have been studied by means of theoretical and experimental analysis. With excellent phase dispersion and rapid separation performances, PJSOG has several or several decade times specific area than traditional SOGs and high separation efficiency. It can reach more than 95% chlorine utilization and about 60% O 2 ( 1 u yield. The operating stability has also been studied in this paper. The stablerunning time of PJSOG increased with liquid flow structure improvement. With high separation efficiency, high O 2 ( 1 u output coefficient, high utilization coefficient of Cl 2 and excellent operating stability, the novel PJSOG must be a pr omising technology in further research. singlet oxygen generator; phase dispersion; separation; operating stability

A traditional pressure recovery system is the major obstacle to mobile chemical oxygen-iodine laser (COIL) for its huge volume. A cryosorption vacuum pump was used as the pressure recovery system for different buffer gases. It made COIL become a flexible, quiet and pressure-tight. Experiments were carried out on a verti- COIL, which was designed for N 2 and energized by a square-pipe jet singlet oxygen generator (JSOG). The output power with CO 2 was 27.3% lower than that with N 2 , but the zeolite bed showed an adsorption capacity threefold higher for CO 2 than for N 2 in the continuous operation. The great volume efficiency interested researchers.

An optical cavity temperature test method has been established for the HF chemical laser. This method assumes that in HF optical cavity the rotational distribution of vibrationally excited HF molecules meets the statistical thermodynamic distribution, the first overtones (v = 3-1 and 2-0) spontaneous emission spectral intensity distribution is obtained by using OMA V, the optical cavity temperature is calculated by linear fitting the rotational thermal equilibrium distribution formula for each HF vibrationally excited state. This method is simple, reliable, and repeatable. This method can be used to test the optical cavity temperature not only without lasing, but also with lasing.

The supersonic nozzles lower temperature to 170-180 K better for the small signal gain coefficient. But at this temperature, the CO 2 buffer gas may become liquid state. A chemical oxygen-iodine laser (COIL) employing CO 2 as buffer gas and no-flake-nozzle was studied. Some mathematical simulation in three-dimensional computation fluid dynamics was adopted first to validate its usability. New nozzles gave the temperature higher than 400 K and considerable small signal gain coefficient. In the same conditions as simulation, experiments gave a 23% of chemical efficiency and 2.5 kW of output power. And it have got rid of “black area”, which was familiar in the supersonic COIL both in simulation and experimental results.

A user-friendly data acquisition and control system (DACS) for a pulsed chemical oxygen -iodine laser (PCOIL) has been developed. It is implemented by an industrial control computer，a PLC, and a distributed input/output (I/O) module, as well as the valve and transmitter. The system is capable of handling 200 analogue/digital channels for performing various operations such as on-line acquisition, display, safety measures and control of various valves. These operations are controlled either by control switches configured on a PC while not running or by a pre-determined sequence or timings during the run. The system is capable of real-time acquisition and on-line estimation of important diagnostic parameters for optimization of a PCOIL. The DACS system has been programmed using software programmable logic controller (PLC). Using this DACS, more than 200 runs were given performed successfully.

A novel conception of iterative pump number was introduced in this work for the first time. Based on the conservation of energy, the equivalent model for the lasering of solid state laser was built up, the iterative pump number was calculated, and a formula for the output power of laser was given. This formula presented the relationships among the output power of laser, pumping power of diode and the thickness of laser medium. The output power predicted by this formula is consistent with experimental results, so this formula could be an important tool for the designing of parameter for diode pumped solid state laser.

Achieving population inversion through multi-photon cascade pumping is almost always difficult, and most laser medium work under 1-photon excitation mechanism. But for alkali atoms such as cesium, relatively large absorption cross sections of several low, cascading energy levels enable them properties such as up conversion. Here we carried out research on two-photon excitation alkali fluorescence. Two photons of near infrared region are used to excite alkali atoms to n 2 D 5/2 , n 2 D 3/2 or higher energy levels, then the blue fluorescence of (n+1) 2 P 3/2 ,(n+1) 2 P 1/2 →n 2 S 1/2 are observed. Different pumping paths are tried and by the recorded spectra, transition routes of cesium are deducted and concluded. Finally the possibility of two-photon style DPALs (diode pumped alkali laser) are discussed, such alkali lasers can give output wavelengths in the shorter end of visual spectroscopy (400-460 nm) and are expected to get application in underwater communication and material laser processing.

A chemical oxygen-iodine laser (COIL) is an electronic transition, low pressure, high throughput system. The use of this laser demands a suitable pressure recovery system. This paper proposed a novel pressure recovery system based on chemical absorption and the feasibility for COIL with CO 2 as buffer gas (CO 2 -COIL) was investigated. The novel pressure recovery system works by chemisorbing the CO 2 -COIL effluents into two fixed-beds maintained at initial temperature of around 293-323K. Compared with the cryosorption system for N 2 -COIL based on physical absorption, the novel chemisorptions based pressure recovery system has a simpler logistics and a shorter run-to-run preparation time. Two kinds of solid chemo-sorbents were designed and synthesized. One was used for chemisorbing the oxidizing gases such as O 2 ,Cl 2 and I 2 , another was used for chemisorbing the acidic gas such as CO 2 . The capacities of the two sorbents were measured to be 3.12 mmol（O 2 ）/g and 3.84 mmol (CO 2 ) /g, respectively. It indicated that the synthesized sorbents could effectively chemosorb the CO 2 -COIL effluents. Secondly, analog test equipment was set up and used to study the feasibility of the novel pressure recovery system used for CO 2 -COIL. The test results showed that the novel pressure recovery system could maintain the pressure under 6 Torr for tens seconds under the continuous gas flow. It showed that the novel pressure recovery system for CO 2 -COIL based on chemical absorption is feasible.

Sodium based excimer-pump alkali laser (Na-XPAL) is expected to be an efficient method to generate sodium beacon light, but the information about the spectroscopic characters of Na-XPAL remains sparse so far. In this work, we utilized the relative fluorescence intensity to study the absorption spectrum of blue satellites of complexes of sodium with different collision partners. The yellow fluorescence of Na D 1 and D 2 line was clearly visible. After processing the fluorescence intensity and the input pumping laser relative intensity, we obtained the Na-CH 4 system’s blue satellites was from 553nm to 556nm. Meanwhile, we experimentally demonstrated the Na-Ar and Na-Xe system’s wavelength range of blue satellites. Also, it was observed that the Na-Xe system’s absorption was stronger than the other two systems.

Separation performance of a new spray-type singlet oxygen generator (SOG), named strongly swirling flow singlet oxygen generator (SSF-SOG), is studied by computational fluid dynamics (CFD) analysis and experiments. The flow field and the separation performance of the SSF-SOG are analyzed using Fluent® soft firstly, and the results show that the separation performance of SSF-SOG is effective for liquid droplets whose diameters are greater than 5μm. Then, using Phase Doppler Particle Analyzer (PDPA), the diameters of liquid droplets in reaction zone and gas outlet of SSF-SOG are measured. The results show that in the reaction zone the diameters of the liquid droplets mainly concentrated on 10μm, and only a little of droplets of which the diameter are under 5μm are detected in the gas outlet of SSF-SOG, which are well consistent with the results of the CFD analysis on SSF-SOG.

A 2-kW-class chemical oxygen-iodine laser (COIL) using nitrogen buffer gas has been developed and tested since industrial applications of COIL devices will require the use of nitrogen as the buffer gas. The laser, with a gain length of 11.7 cm, is energized by a square pipe-array jet-type singlet oxygen generator (SPJSOG) and employs a nozzle bank with a designed Mach number of 2.5. The SPJSOG has advantages over the traditional plate-type JSOG in that it has less requirements on basic hydrogen peroxide (BHP) pump, and more important, it has much better operational stability. The SPJSOG without a cold trap and a gas-liquid separator could provide reliable operations for a total gas flow rate up to 450 mmol/s and with a low liquid driving pressure of around 0.7 atm or even lower. The nozzle bank was specially designed for a COIL using nitrogen as the buffer gas. The cavity was designed for a Mach number of 2.5, in order to provide a gas speed and static temperature in the cavity similar to that for a traditional COIL with helium buffer gas and a Mach 2 nozzle. An output power of 2.6 kW was obtained for a chlorine flow rate of 140 mmol/s, corresponding to a chemical efficiency of 20.4%. When the chlorine flow rate was reduced to 115 mmol/s, a higher chemical efficiency of 22.7% was attained. Measurements showed that the SPJSOG during normal operation could provide a singlet oxygen yield Y/spl ges/55%, a chlorine utilization U/spl ges/85%, and a relative water vapor concentration w=[H/sub 2/O]/([O/sub 2/]+[Cl/sub 2/])/spl les/0.1.

During the operation of a chemical oxygen iodine laser (COIL) with an unstable resonator of a large Fresnel number, as the output power increases, an instability of the output laser beam will appear, behaving mainly as far-field beam spot drift and deformation. In order to interpret this phenomenon, thermal expansion analysis on the scraper with finite element analysis method and a simulation of the output beam mode of this kind of laser by the method of Fast Fourier Transform were developed. From the experimental measurement and the calculation, we proposed that the presence of the nonuniform temperature distribution of scraper causes the front surface of the scraper to tilt and bulge due to thermal expansion. As the output power is increasing, all the mirror surfaces, especially the scraper's, will absorb more and more heat, causing thermal expansion of the mirror front surface to occur more seriously, thus resulting in the tilting and deformation of the far-field beam spot. The initial misalignment of the direction is also an important factor leading to the far-field beam spot drift and deformation.

By means of a microwave generator, chlorine diluted by helium was dissociated to chlorine atoms that subsequently reacted with hydrogen azide to produce the excited states of NCl(a 1 Δ) and NCl(b 1 Σ). In this paper, the intensity of NCl(a 1 Δ) and NCl(b 1 Σ) emission dependent on the flow rates of different gases was studied. Moreover, the production of NCl(a 1 Δ) and NCl(b 1 Σ) along the reaction tube was also investigated. The results are presented and discussed. The optimum parameters for NCl(a 1 Δ) and NCl(b 1 Σ) production are given, and the quenching rate of NCl(a 1 Δ) by Cl 2 is obtained.

Sodium-ethane excimer pairs are studied and proved to be a great choice of excimer pumped sodium laser (XPNaL) gain media. The lifetime of the sodium D2 line is studied in a sodium-ethane excimer system excited by a 553 nm laser, and the observed phenomenon of lifetime lengthening is discussed. Amplified spontaneous emission (ASE) of the sodium D2 line is successfully obtained, and its time-resolved and spectroscopic characteristics are studied experimentally. According to the intensity of the ASE signal under different sodium vapor atom densities, the sodium D2 line gain feature of sodium-ethane excimer pairs excited by the 553 nm laser is concluded.

A calibrated piston source of light, which simulates a cylindrical-volume luminosity source, has been used to measure the absolute concentration of O-2(a(1)Delta). It is proved that this piston source method is one of the simplest and most convenient ways to measure the O-2(a(1)Delta) concentration in a singlet oxygen generator, especially in real time measurements. Discussions about the method and the results are also given.

The hyperfine gain spectrum of a chemical oxygen-iodine laser (COIL) is investigated experimentally. Six hyperfine lines are obtained in a COIL gain medium as well as an iodine absorption cell. Meanwhile, gain profiles and cavity temperatures are calculated.

A supersonic all gas-phase iodine laser driven by NF 3 /D 2 /DCl/CF 3 I combustion has been experimentally studied. the gain signals of I( 2 P 3/2, F=4)← I( 2 P 1/2 ,F=3) at 1315.246nm and I( 2 P 3/2 ,F=3)← I( 2 P 1/2, F=3) at 1315.222nm were observed with an intensity of 3x10 -5 cm -1 and 1x10 -5 cm -1 respectively. The small signal gain of I( 2 P 3/2 ,F=4)← I( 2 P 1/2 ,F=3) at different location relative to HN 3 injector along the flow direction also was obtained. The experimental results indicate that the AGIL driven by NF 3 /D 2 /DCl/CF 3 I combustion is feasible.

A fluorescence image detection system that can visualize the COIL hot mixing flow field by taking images of the fluorescence of active I2 with a high speed camera was set up. Based on the captured flow field image, O2(a1Δ)/I2 mixing quality was evaluated quantitively by an exclusive image processing program. With this method, the hot supersonic mixing flow field in COIL which uses parallel stream supersonic mixing nozzles with a set of trip tabs was investigated. Meanwhile the effectiveness of the trip tabs was demonstrated.

We have observed unusual blue-shifted radiations in water pumped by a strong 532-nm nanosecond laser. Properties including divergence, polarizations, and pulse shapes of the unusual radiations are measured and compared with those of the regular stimulated Raman scattering (SRS) in water. The unusual radiations are attributed to the parametric anti-Stokes SRS that occurs on the interface of water and ionization plasma (or gas) formed in the laser-induced breakdown of water.

Singlet oxygen generator is the key of chemical oxygen-iodine laser (COIL) which supplies energy for the system. However, the traditional generators have some drawbacks just as the bigger volume and the lower chemical efficiency. Specific surface area is the important factor restricting the development of singlet oxygen generator. Many researches on increasing specific surface area have been done to improve the performance of singlet oxygen generator. A new type eject singlet oxygen generator was introduced in this paper. Ejector was used in gas-liquid reaction. Liquid ejected through the nozzle with high velocity droved by high pressure, and gas ejected into mixing chamber along the tangent of nozzle. Gas and liquid were broken into many small droplets. Gas and liquid reacted in reaction chamber, then the mixture ejected into separator with very high speed. These droplets can produce mount of gas-liquid interface and increase the chemical efficiency of generator. Many numerical simulations have been done on the new type generator According to the simulations, eject singlet oxygen generator is feasible and has prospect. Therefore ejector may be a better type of singlet oxygen generator.

A novel concept of the chemical production of atomic iodine aimed for application in chemical oxygen-iodine laser was proposed. The method is based on nitrogen trichloride spraying auto-decomposition to generate chlorine atoms which subsequently react with iodine donors. Preliminary experimental and computational studies for the reaction system were explored. The experimental results show efficient generations of excited atomic iodine and computational results reveal that a large degree of atomic iodine can be generated via the reaction system including nitrogen trichloride combustion effluents and iodine donors.

The paper describes the theoretical and experimental analysis of centrifugal flow singlet oxygen generator in order to identify the optimal conditions needed to satisfy the COIL requirement. The optimal conditions had been analyzed under Cl2 flow rate, reaction length and generator pressure. The performance was achieved Cl2 utilization of 94% and O2(1Δ) yield of 72%.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report the experimental results of an unstable ring resonator with 90-deg beam rotation for a kilowatt class chemical oxygen iodine laser (COIL). The distributions of near-field phase and far-field intensity were measured. A beam quality of 1.6 was achieved when the COIL average output power was approximately 5 kW.

A dedicated CW chemical oxygen iodine mini-laser is constructed and used to probe the two-dimensional (2-D) distribution of small-signal gains in a supersonic CW chemical oxygen iodine laser (CW COIL). The uneven lateral gain distribution may possibly be explained by boundary layer effects.