Lidar Transmitter Research Articles

Frequency fidelity of a compact CO_2 Doppler lidar transmitter

The cw, interpulse, and intrapulse frequency stabilities of a compact, sealed-off CO(2) Doppler lidar transmitter are characterized. A cw stability of 1 part in 5 x 10(11) for 1-s averaging times, maximum pulse-to-pulse frequency deviations of +/-49 kHz for periods of seconds at a pulse repetition frequency of 1 kHz, and pulses with low-frequency chirp are demonstrated in a instrument suitable for the field.

Frequency monitoring a LIDAR transmitter for pulse-by-pulse analysis and control

An electronic technique is described whereby the heterodyne mixing frequency of a pulsed LIDAR transmitter is displayed on a color-coded linear bar graph. The technique is of great utility for manually fine tuning the laser output frequency when the use of conventional frequency counters and spectrum analyzers is impractical in a rapidly firing system.

Limits to the accuracy of lidar measurements of hydrooptical parameters

The specific manifestation of the amplification of backscattering due to surface waves, caused by angular misorientation of the optic axes of the lidar transmitter and detector, was investigated theoretically and in model experiments. This effect limits the accuracy of the internal reference method with normalization to the spontaneous Raman scattering signal, widely used in lidar experiments. Measurement errors may also arise as a result of nonlinear optical interactions caused by random focusing of the probe beam by surface waves.

Unstable resonator antenna properties in coherent lidar applications: a comparative study

We investigate the antenna parameters of a coherent lidar in the far-field diffraction-limited regime, where the lidar transmitter consists of an unstable resonator with a Gaussian reflectivity profile output coupler. A figure-of-merit combining laser transmitter energy extraction efficiency with the far-field attributes of a given cavity configuration has been used to compare the lidar performance and relative merits of such systems as they relate to those of conventional unstable cavities with diffractive output coupling.

Mesopause temperatures derived from probing the hyperfine structure of the D 2 resonance line of sodium by lidar

In the 80–100 km altitude region free sodium atoms are abundant enough to allow the probing of the Doppler widened hyperfine structure (hfs) of the D 2 resonance transition by ground-based lidar and hence to deduce atmospheric temperatures. We discuss the dependence of the observed shape of the hfs on the temperature, on geographic location and on polarization of the lidar, on differential extinction, and on the bandwidth of the lidar transmitter. The results are applied to new measurements of the mesopause sodium hfs structure obtained by the University of Bonn lidar.

Simultaneous remote measurements of atmospheric temperature and humidity using a continuously tunable IR lidar

The possibility of accurate remote measurements of temperature and humidity using a three-wavelength differential absorption technique is discussed. Selection of water vapor absorption lines for the measurement promises highest accuracy for temperature measurements and also allows the simultaneous determination of absolute humidity. Preliminary measurements of average temperature and humidity over a 775-m long path using a continuously tunable infrared lidar are reported. For the temperature measurements a relative accuracy of 1.4 degrees C was observed. The absolute error, however, is presently ~5 degrees C due to inaccuracies in the wavelength selection of the lidar transmitter. Humidity was measured with a 1.5% relative error limited by return signal fluctuations. The method is feasible for depth resolved measurements of temperature and humidity.