A lidar based on UV laser is developed to observe air quality in Beijing. The initial laser wavelength is 1064 nm, and an emission wavelength of 355 nm is obtained after the second-harmonic generation and third-harmonic generation. The output energy is 30 mJ/pulse, and the pulse width is 7 ns. Echo signals are collected by a 304.8 mm diameter Newtonian telescope. With high-power ultraviolet laser excitation, the intensity of atmospheric pollutants is studied by the laserinduced fluorescence (LIF). The Mie scattering is detected simultaneously and both signals are detected by the photomultiplier tubes (PMT). The system is calibrated by a series of experiments. The aerosol extinction coefficient retrieved by Mie signal from this system agrees well with that from another lidar with a laser wavelength of 532 nm. The fluorescence efficiency of atmospheric pollutants are obtained by calculating the fluorescence-to-Mie ratio (FMR). The time and spatial resolution of the system are 5 s and 7.5 m, respectively. The continuous change of air quality over a period of time is studied by the mean value of FMR. Many observations are carried out under different air quality conditions, and the experimental results are in good agreement with the results of the ground observation station. In summary, this method based on UV laser is feasible in the field of atmospheric remote sensing and have potential applications in the field of air quality monitoring.
In this paper, the laser-induced fluorescence (LIF) technology is utilized for rapid assessment of the purity of quartz glass, especially for the screening of high-purity quartz glass. A 355 nm laser was applied as excitation source to induce the fluorescence signal of the quartz glass samples. The fluorescence signal is then transmitted to the spectrometer through an optical fiber for spectral acquisition. Because only the impurities in quartz glass induce fluorescence, purity quartz glasses does not have a distinct fluorescence signals or fluorescence peaks. The purity evaluation of high-purity quartz glass can be achieved by analyzing the obtained signals. The standard deviation and the ratio of the maximum to minimum values of the signals were calculated to indicate the intensity of the fluorescent peak of the signal. The thresholds were then set to distinguish between high-purity and low-purity quartz glasses. The method has the advantages of high speed, high precision and high reliability, and is of great significance for the rapid screening of quartz glass with high purity requirements.
We have designed and demonstrated an all-fiber laser which can switch the operation mode between the pulsed mode and the continuous mode. Under the pulsed operation mode, the maximum output pulse energy is measured to be 120 μJ with a pulse width of 400 ns. The pulse width is continuously adjustable between 100 ns and 600 ns. Under continuous operation mode, the maximum output power is 2 W. Switching between these two operation modes can be done with simple instructions within several milliseconds. Large-mode-area (LMA) fiber amplifiers are adopted to support the high peak power. The LMA fiber amplifiers are coiled in a circle with a diameter of 25 cm and the high order transverse mode are suppressed by the bending loss. The M squared factors of the designed laser are 1.204 on x-axis and 1.293 on y-axis. This laser is optimized for coherent Doppler lidar system that can detect at both the near (within several tens of meters) and far distance (more than a dozen kilometers).
We present the performance of the portable wind light detection and ranging (LIDAR) system based on the 1.55-μm all-fiber technology in the atmospheric boundary layer. The LIDAR is 23.9 kg in weight, 50 cm in height, 35 cm in width, and 27 cm in depth, and the system’s local oscillator (LO) light power, pulse energy, and pulse width are adjustable. The LO light power is optimized to 3 mW, to minimize the effect of the relative intensity noise. The transmitting pulse energy is reduced to 19 μJ, to minimize the system’s power consumption while covering a detection height of >1 km in clear-sky condition. The pulse width is variable from 100 to 400 ns corresponding to a minimum resolution from 15 to 60 m. The signal-to-noise ratio performance experiment shows that this system can detect as high as 2.1 km. Field experiments compared with radiosonde and anemometer show that this system presents a detection accuracy of better than 1 m / s and 10 deg.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.