Wide band frequency converters for Lidar systems

Estimations are carried out on creation possibilities of all solid state laser sources capable significantly or fully to solve the problem of the universal Aerosol-Gas Lidar System design. Best existing Ho 2+ :ILF and Nd:YAG lasers supplied with LBO, KTA, KTP, BBO, CLBO, DLAP; GaSe, GaSe:In, AgGaxIn1-xSe2, LiInS2, LiInSe2, AgGaS2, AgGaxIn1-xS2, and HgGa2S4 frequency converters are considered. The investigation results show development of UV to FIR laser source is really to carry out with efficiencies from one-two up to several tens per cents in several ways. Two basic tasks of the remote sensing of the atmosphere, that are solved with the help of Lidar systems, include determination of the relative contents of aerosols and gas components of both type natural and anthropogenical origin. In the last case realization of the most sensitive method of optical measurements, i.e. method of differential absorption, has widest distribution. About all known laser systems were used in Lidar systems of both mentioned purposes but nevertheless their one common disadvantage was excluded. Universal Lidars, capable to solve both tasks are not created yet at least in any significant for practice degree. In the case significant degree means the control of both fine and large scale aerosol fraction s, and also most distributed gas polluters in the atmosphere of industrial cities: nitrogen, sulfur and carbon oxides; ozone, methane and others light hydrocarbons. The aerosol control has to be carried out at the wide part of the spectral transparency range of the atmosphere. Namely it is at the spectral region from the shortest wavelength (200 nm and less) and up to as long wavelength as 14 µm. Determination of the particle number and size distribution of the natural aerosol, it dynamics is important for atmospheric physics investigation. So as same determination for the fine aerosol is important, for example, for reveal of anthropogenical aerosol of special purposes. Large scale aerosol fraction of antropogenical origin is reasonable for determination at the longer, middle IR wavelengths. The interfering influence from the natural aerosol in this case will be minimized. Multi frequency or frequency tunable emission has to be used for best results in both cases. The NO, O3 and SO2 gases are determined often at the wavelength range close to 300 nm for two reasons: just here are maximal both differential absorption cross section of spectral structures and aerosol backscatter coefficient. The appropriate measurements traditionally are carried out with use of frequency converted dye and eximer laser emissions. Visible range is suitable for the NO2 control only, for example, with use of argon laser but near IR one for methane control at wavelength of 1.33, 1.57, 1.65 and 2.32 µm overtone bands. High, 1.7 ppm, background methane concentration, available sensitive detectors and semiconductor lasers with somewhat acceptable parameters, so as optical parametric oscillators (OPOs), promote this. At a short wavelength part of the middle IR the remote sensing of the total methane and light hydrocarbons contents, and component analysis, is carried out with help of multi stage LiNbO3, KTP and KTA OPOs. Its are lasing at the wavelength shorter than about 4 µm. The control of average methane content is possible with use of low power two frequency He-Ne lasers also. Component analysis of light hydrocarbons and O 3 can be carried out with use of powerful 9-11 µ 2 lasers too. Earlier it have been shown 1 that by using in Lidars of CO 2 lasers supplied with high efficiency harmonic and combination