RESUMO
The transmission spectrum of a narrow-band interference filter is crucial and highly influenced by factors such as the temperature and angle, thus requiring precise and online measurements. The traditional method of measuring the transmission spectrum of an interference filter involves the use of a spectrometer, but the accuracy of this method is limited. Moreover, placing a narrow-band interference filter inside a spectrometer hinders real-time online measurements. To address this issue, there is demand for high-precision online spectral testing methods. In response to this demand, we propose and experimentally validate a fine spectral characterization method for narrow-band interference filters. This method uses a narrow-linewidth tunable laser, achieving a spectral resolution in the MHz range for online testing. Two types of narrow-band interference filters were tested using the constructed laser spectroscopy experimental system, obtaining a transmission spectrum with a spectral resolution of 318 MHz. In comparison to spectrometer-based methods, our proposed method demonstrates higher spectral accuracy, enables online measurements, and provides more accurate measurements for special spectral interference filters. This approach has significant application value and promising development prospects.
RESUMO
A narrowband sodium lidar for measuring mesospheric temperature and wind has been established at YangBaJing, Tibet (90°E, 30°N, 4300 m a.s.l), China. The system is designed and optimized based on important upgrades using new technology. In the lidar system, single-mode 589 nm seed laser is produced by frequency doubling of 1178 nm diode laser with a periodically poled lithium niobate (PPLN) waveguide. The output power of 589 nm continuous-wave laser is up to 1.5 W with the help of a seed-injected Raman fiber amplifier. Furthermore, fast three-frequency switcher is designed with a couple of fiber magneto optical switches (FMOS) for measuring wind and temperature, simultaneously, which greatly reduces the system maintenance. These improvements greatly simplify the lidar system, thus, achieve robust operation with minimum maintenance requirements.