In order to achieve the highest peak power of radiation pulse and highest output energy, the primary circuit parameters
are investigated to optimize the discharge circuit performance of the laser. The structure and the discharge circuit of the
laser are discussed at first. To realize synchronous discharge in two discharge channels, the conjunct electrode device for
two pairs of discharge electrodes is designed. Finally, the results of the experiments on the primary circuit parameters are
given. The discharge is most stable at a pressure of 5.33×104Pa when the pressure of gaseous mixture CO2:N2:He=1:1:3
is changed from 2.67×104 Pa to 6.67×104 Pa. The ratio of storage capacitance to peak capacitance is chosen to be about
1.5-7/3, because residual voltage is lower on this condition and residual voltage is adverse to discharge. When the
inductance 330&mgr;H is used, the homogeneous glow discharge in a widest voltage range is obtained. The duration of when the stimuli voltage is increased in
homogeneous glow discharge condition. The discharge circuit allows
charge and discharge and the magnitude of residual voltage decrease the homogeneous glow discharge in a wide range
of pressure of gaseous mixture when these circuit parameters are used. Thus it offers reference to the improvement of
output characteristic of TEA CO2 laser with two discharge channels.
Five temperature model is used to describe the process of the dynamics preferably in the transversely excited atmospheric-pressure (TEA) CO2 laser. In this paper five temperature vibrational dynamics and vibrational-rotational dynamics are analyzed and calculated. All physical constants and relaxation rates related to this model are examined. The laser pulse waveform can be calculated when varied laser's parameters. The output power and energy can be obtained from calculated intensity, it can provide theoretical basis for laser design. Theoretical arithmetic shows a good agreement with the experimental result.
The wavelength of CO2 laser radiation is in the spectral range of 9-11μm. So the rapidly tuning TEA CO2 laser is an ideal optical source and core parts of laser differential absorption lidar (LDIAL). To expand the spectrum of TEA CO2 laser and the amount of the atmospheric gases controllable by the LDIAL, laser spectrum of carbon-13 oxygen-16 isotopic species of carbon dioxide is investigated. The spectroscopic constants and wavelength of the two laser band 00011-10001 and 00011-10002 are calculated. Using the spectrum analyzer the spectrum of the TEA CO2 laser in which 13C1602 is used as working gas is obtained. The used laser is a rapidly tuning miniature TEA CO2 laser. The cavity of the TEA CO2 laser is 200 mm in diameter and 400 mm in length. The main electrodes are a pair of Chang's aluminum electrodes. Tuning mechanism consists of diffraction grating, trigger controller and high frequency stepping motor. The experimental wavelengths are in good agreement with the calculated data. Compared with common C02, the emission line range of 13C1602 is expanded toward the longer wavelength, the longest wavelength of the TEA 13C1602 laser is 11.347 μm.
In the present work, directed toward using differential absorption lidar (DIAL) for measuring concentrations of pollutant gases, a galvanometer-driven mirror to scan a fixed diffractive grating for rapidly tuning a TEA CO2 laser is reported. It is well known that the ground- or air-basing DIAL is an effective tool for remote measurement of pollutant gaseous concentration of the atmosphere over large areas. It has, practically in real time, the ability to remotely detect various gas concentrations in the atmosphere, because many pollutant gases have strong absorption lines within the spectral range of CO2 laser wavelength tuning. In addition, the radiation of CO2 laser is safe for the human eye and is well distributed in the atmosphere, coinciding with the “transparency window” of the atmosphere. Therefore the wavelength tunable TEA CO2 laser is an ideal optical source for DIAL. The tuning is performed by generating and applying appropriate signals to the galvanometer, which rotated a silver mirror in order to scan the fixed grating. The device is driven by a programmable signal generator with resolution sufficient to rotate the mirror in discrete intervals as small as 70μrad, which is more than sufficient to find the optimum position for any lasing transition.
Due to their interesting physical and chemical parameters, tunable transversely excited atmospheric-pressure(TEA) CO2 lasers are widely utilized in scientific and industrial applications. The CO2 differential absorption lidar (DIAL) is an effective tool for remote measurement of pollutant gaseous concentration of the atmosphere over large areas. Many pollutant gases have strong absorption lines within the spectral range of CO2 laser wavelength tuning. In addition, the radiation of CO2 laser is well distributed in the atmosphere, coinciding with the "transparency window" of the atmosphere. Therefore the wavelength tunable TEA CO2 laser is an ideal optical source for DIAL. Most existing instruments for measuring the laser wavelength are only suitable for the measurement of continuous wave and stable frequency output. With the attempt of measuring the wavelength of pulsed TEA CO2 laser, an experimental setup is established which consists of two main portions, namely auto-scanning grating monochromator as the color dispersion system and Boxcar integrator. In the experiment of tuning TEA CO2 laser, the wavelength of CO2 laser is observed and measured by means of integrating method. The accuracy of measurement in the mid-infrared region attains 1nm.
In the present work, directed toward using differential absorption lidar (DIAL) for measuring concentrations of pollutant gases, a monolithic microprocessor-controlled tuning and triggering system for rapidly tuning a TEA C02 laser is reported. It is shown that it is possible to utilize a high frequency stepping motor and a diffraction grating to rapidly select wavelength over rotational transitions in the 9.2-10.8 jtm region of the laser spectrum. The tuning is performed by applying appropriate signals to the stepping motor, which is coupled to the grating via a precision gear box. The microprocessor controls motion of the motor which rotates the correct angle for a given wavelength together with the grating. Many of pollutants have strong absorption lines in the 9-11 im region, therefore the wavelength tunable transversely excited atmospheric-pressure (TEA) CO2 laser becomes an ideal optical source for DIAL.