| The RF discharge techno Logy is a laser pump method developed in recent years. Compared to DC discharge, RF discharge has many advantages, such as low exciting voltage, high efficiency, capable of high speed modulation, no cathode sputtering, high output power, long life, power supply for multi-waveguides, compactness, etc. The application of waveguide elements decreases the size of lasers, and the laser modes can be well controlled. The electron-optical Q switching RF discharge excited waveguide CO2 laser is a suitable light source for radar for its small volume, high repetition rate, wide tunable frequency range, programmable & steady output, capability of working in harsh environment,and the particular wavelength fall into the atmosphere transmitting window. CO2 laser has been widely used in the military, aviation, meteorology, laser machining etc. for its narrow beam, good directionality, high measuring accuracy high, resolving ability, initiative imaging ability and the good atmospheric transmitting ability. In this paper, the development history of CO2 laser has been reviewed. Analysis has been made on the gas RF discharge exciting theory, the impedance matching, the basic theory of wave-guide lasers, the electron-optical Q switching and the cavity dumping.Compared to electron-optical Q switching, the electron-optical cavity dumping technique capable of acquiring higher repetition rate, peak power and faster pulse front. The FWHM of electron-optical cavity dumping waveguide CO2 is about ten ns or above, which can be used to get higher detection precision for radar with pulse front。 to get effective intermediate frequency signals, there should be 3 to 5 signals in the envelop of laser pluse. Hense when the pulse width of the cavity dumping induced laser from the master laser is too narrow, the signal process of the radar system will be serieously influenced. In this paper, theoretical and experimental research have been made on the electron-optical cavity dumping and Q switching RF waveguide CO2 laser. Several major parameters influencing the output pulse of the RF waveguide electron-optical cavity dump lasers have been analyzed. By changing the upper front rising time of the high voltage applied on the CdTe electron-optical crystal and the reflectivity of the Brewster angle, theoretical analysis has been made on the pulse width and the variation of the peak power of pulse.In this paper, a compact RF discharge excited waveguide CO2 laser is presented, which is used as the master oscillator in the radar. This design has combined a Degnan and Hall Case III coupling configurationand U-folded cavity, that is, the mirror-waveguide space is folded and there is only one ceramic waveguide in the whole cavity. The ceramic waveguide is 320mm long and its section has a 2.5mm^2 bore. The fundamental mode beam has been acquired. Without catalyzer, the U-folded laser' s output reaches 7, while the corresponding unfolded laser, 10W. By changing these parameters, in an home-made CdTe E-0 cavity-dumped double channel RF excited CO2 waveguide lasers, which might be used as a light sources in a heterodyne imaging lidar system, we have obtained the cavity dumped pulses width at FWHM from 20ns to 30ns.
|
PDF Full Text Request