| Lasers and laser technology is one of the greatest inventions of the 20th century.After decades of development,organic dye lasers have become an irreplaceable important component in scientific research,military,medical and other fields,according to its excellent characteristic of wide tuning range and high laser efficiency,which stand out from many kinds of other laser devices.Compared with other types of organic dye lasers,liquid organic dye lasers are the first to be developed successfully and applied in scientific research,industrial production and other fields.Organic dyes in liquid solutions can give full play to the excellent properties of dye molecules,and can produce tunable laser output with high power,narrow linewidth and high pulse energy in the whole visible light range.Unlike lasers in solid state or thin film state,the thermal effect of liquid organic dye laser is not obvious,and it is not easy to bleach the fluorescence which could affect the output efficiency.In addition,liquid organic dye lasers can be continuously tuned over a wide range of wavelengths and can mix several organic dyes to produce new wavelengths of laser output,which shows that the liquid organic dye laser has a very broad application prospect.The core of organic dye laser is organic laser dye,which is generally used as the gain medium of the laser.After pumping light source,the generated fluorescence resonates in a stable resonant cavity and finally forms laser oscillation for output.The molecular weight of organic dye is generally in the range of 200 u?800 u.At present,about one hundred kinds of organic dyes have been maturely applied in lasers.The tuned spectrum can span most of the electromagnetic spectrum,especially the visible spectrum.Commonly used organic dyes generally include Coumarin,Xanthene,Oxazine,Cyanine,etc.Solvatochromism is unique to some organic laser dyes,such as Nile red,which means that the fluorescence/laser spectrum shifts with the change of the solution polarity.When it increases,the wavelength peak shifts bathochromically,while the decreasing polarity could bring the hypochromatic shifts of the wavelength.This characteristic makes it possible to study the organic dye laser with polarity tuning method and the polarity detection technology based on optical sensing.The tunable laser is one of the important light sources in the fields of optics,medicine,biology,etc.The laser-pumped tunable laser has the advantages of compact structure,high output efficiency and low price.In particular,the gain medium of liquid organic dye laser has larger absorption and emission cross sections with higher fluorescence quantum efficiency,which makes it one of the core research contents of tunable lasers.In recent years,the development of lasers and laser systems for optical sensing and detection technology has advanced rapidly.Among them,laser-based trace gas detection technology is an emerging atmospheric environment monitoring technology,which relies on light absorption,fluorescence resonance energy transfer(FRET),Rayleigh scattering and other phenomena,and has more advantages than other techniques based on fluorescence spectrum.This technique,combined with organic dyes with solvatochromism characteristic,could provides new ideas for the detection of trace acid substances in the atmosphere and hydrologyThe main work and research results of this paper are as follows:1.Based on the principle of organic dye lasers,a new type of organic laser/fluorescent dye,Nile red,is introduced.The laser output of Nile red in different organic solvents was obtained in light of its excellent laser properties and solvatochromism characteristic,and the influence of concentration on laser peak and output efficiency was also analyzed.At the same time,a new method of laser wavelength tuning based on solvent polarity is proposed.Organic solvents with different polarities are mixed to change the polarity of the solution environment,and the broadband tunable laser output,ranging from 582 nm to 660 nm,is obtained by combining with the grating tuning technology.In addition,a tandem cuvette structure is designed to obtain the output phenomenon of dual-wavelength "Ratiometric laser",which expands the wavelength shift range caused by the concentration change.2.Littrow and Littman-Metcalf structures were used in side-pumped Nile red lasers,where we achieved continuous tunable laser output in the range of 72 nm and 46 nm by rotating the blazed grating or the tuning mirror,respectively.At the same time,the phenomenon of dual-wavelength laser output can be obtained by tilting the dye cuvette at a small angle.Based on this,the method of theoretical analysis followed by experimental verification is adopted to obtain the laser output of dual-wavelength with whole and separate tuning ability in the resonant cavity of two kinds of structures,which provides ideas for the generation of terahertz light source.3.A novel polarity detection technology using Nile red dye laser is presented.According to the solvatochromism characteristic of Nile red,different concentrations of sulfuric acid were added to Nile red/ethanol solvents in axial pumping structure to change the polarity of the environment,and the corresponding laser spectrum was measured.In addition,using the same tandem cuvette system,the phenomenon of dual-wavelength "Ratiometric laser" output was obtained at low concentrations.According to the relative intensity and peak wavelength corresponding to the concentration of sulfuric acid in the solutions,the concentration of sulfuric acid in the whole range from 0 ppm to 500 ppm was detected.The innovation points of this paper are as follows:1.For the first time,Nile red was used as the gain medium of the organic dye laser and good laser output was obtained when dissolved in organic solvents of different polarity.We mixed solvents with different polarities in proportion,and achieved broadband tunable laser output combined with polarity tuning and grating tuning method.2.A new type of tandem cuvette structure was proposed.Two quartz cuvette were glued together along the axis,and the Rhodamine 6G/ethanol and Nile red/ethanol solvents was held respectively in the front and back cavity of tandem cuvette.In this way,the wavelength tuning caused by concentration change can be expanded.3.In Nile red organic dye laser using side-pumped Littrow and Littman-Metcalf construction,dual wavelength laser output is achieved for the first time by tilting the dye cuvette slightly.After theoretical analysis,the dual-wavelength laser output with whole and separate tuning method is verified in experiments.In addition,this wavelength difference is within the terahertz range,which enables the preparation of terahertz light sources.4.The Nile red organic dye laser was applied to the acidity detection technology,and the whole detection result from the low concentration of 0 ppm to the high concentration of 500 ppm could be achieved by using the tandem cuvette system,which provided a new method for the convenient,efficient and visual detection of trace substance concentration. |
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