We have developed a 1.6 microm carbon dioxide (CO(2)) differential absorption lidar utilizing a quasi-phase-matching optical parametric oscillator (OPO) and a photon-counting detector. The operating wavelengths were chosen based on their low interference from water vapor and low temperature sensitivity. The online wavelength was in the (30012<--0001) band of CO(2), which was insensitive to atmospheric temperature. The established OPO laser achieved a 10 mJ, 200 Hz repetition rate at the online and offline wavelengths. Our observations confirmed the statistical error of 2% with 5 h of accumulation for the CO(2) density profile less than 5.2 km. Also, the statistical error of 1% at an altitude of 2 km was demonstrated. The results of the vertical CO(2) concentrations acquired using a 1.6 microm wavelength are presented.

An experiment for the measurement of atmospheric CO₂ vertical profiles up to a 7 km altitude was successfully conducted using a 1.6 μm ground-based differential absorption Lidar developed by Tokyo Metropolitan University. To achieve a high pulse repetition rate, large power output, and high frequency stabilization, we developed a new 1.6 μm Lidar system using an optical parametric generator (OPG) transmitter. Unlike the previous system's transmitter, OPG does not need a resonator. We amplified its output with two optical parametric amplifiers. We validated our system against an in situ sensor and found the difference between their CO₂ concentration measurements to be 0.06 ppm.

Characteristics of sodium and iron layers in the mesopause region over the equator observed with the resonance scattering lidars installed at Kototabang, Indonesia (0.2 S, 100.3 E) are reported. These lidars were operated during the night. The sporadic sodium layer (Nas) and the sporadic iron layer (Fes) were detected in almost every observing opportunity other latitude regions. Nas and Fes layers appeared almost at the same time and the heights above 90 km. However, Fes layers appeared below 90 km as well. The occurrence of the Nas layer correlated well with that of sporadic E layer which was observed simultaneously by the ionosonde at Kototabang. On the other hand, the occurrences of the Nas and Fes layers does not correlate with that of the wind shear which has been observed simultaneously by the meteor radar at Kototabang. This result is not in agreement with the result of simultaneous observations by the Na lidar and the MU radar at Hachioji (35.6 N) and Shigaraki (34.9 N) in mid-latitude.

A precise measurement of the vertical profiles of carbon dioxide is required for reducing the uncertainty in the carbon budget. In order to achieve measurements of the vertical CO2 distribution with an uncertainty better than approximately 4 ppm, a precise knowledge of the pressure-dependent broadening and shift coefficients of CO2 absorption lines is indispensable. In this paper, we report the measurement of air pressure-induced shift coefficients for eight absorption lines at around 1.57 µm. On average, the pressure shift coefficients are -0.30 MHz/Torr for pure CO2 and -0.24 MHz/Torr under an air-mixed condition.

A solid-state stimulated Raman scattering (SRS) laser oscillation around the 1.6 mm carbon dioxide absorption lines is demonstrated. The stokes output of the SRS radiation at 1.57 mm is generated from the frequency conversion of the 1.35 mm laser radiation of Nd 3þ :KGd(WO 4 ) 2 (Nd:KGW) in the cavity. The maximum output energy was 13.8 mJ with a repetition rate of 10 Hz, in response to the incident laser pumped from the laser diode to the Nd:KGW. To our knowledge, this result of a 1.57 mm intracavity SRS oscillation at CO 2 absorption lines around 1.6 mm is gained for the first time.