tailieunhanh - Advances in optical and photonic devices Part 7

Tham khảo tài liệu 'advances in optical and photonic devices part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Tunable Narrow Linewidth High Repetition Frequency Ce LiCAF Lasers Pumped by the Fourth Harmonic of a Diode-Pumped Nd YLF Laser for Ozone DIAL Measurements 111 Fig. 10. Shape of the pump UV pulse upper trace and the Ce LiCAF laser output pulse lower trace . Fig. 11. Tuning curve of the Ce LiCAF laser. 112 Advances in Optical and Photonic Devices tuning over a broad spectral region from 281 nm to 316 nm while the 263 nm pump energy was 2 mJ pulse. Laser linewidth as measured with the Ocean Optics grating spectrometer with a resolution of nm was approximately - nm when a fused silica dispersing prism was used. The maximum laser output occurred at a wavelength of 290 nm the second much more weak maximum of laser output corresponded to 308 nm. By using a different prism material with a larger dispersion such as sapphire the linewidth can be reduced. With a sapphire dispersion prism the linewidth was reduced to nm. The angular motion required for tuning over 10 nm is approximately for fused quartz and about for sapphire. It can be concluded from Figure 11 that output pulse energy of the Ce LiCAF laser reduces approximately four times regarding the maximum of 1 mJ pulse output at 290 nm when laser wavelength is tuned to 284 nm or to 297 nm on the short- and long-wavelength edge of the tuning curve respectively. 7. High speed wavelength tuning of Ce LiCAF laser Ce LiCAF laser using as a transmitter for lidar has to supply lidar with both the on- and offline wavelengths. As it was shown above wavelength tuning of Ce LiCAF laser was achieved by changing the angle of the rear mirror. A rapid tuning of the laser output wavelength from shot to shot at pulse repetition frequency of 1 kHz was achieved by mounting the HR mirror on a servo-controlled high speed galvanometric deflector. The tuner control system has been designed to provide pairs of pre-selected on and off-line wavelengths À1 and À2 at 1 kHz operation chosen for ozone differential .