Hirotake Fukuoka

Cesium vapor laser pumped by a volume-Bragg-grating coupled quasi-continuous-wave laser-diode array

The experimental demonstration of a broad-area Quasi-continuous-wave (QCW) laser-diode array pumped cesium vapor laser is reported in this letter according to our experimental results. We used a volume-Bragg grating to narrow the spectral linewidth for acquirement of enough resonance transitions. A glass cylindrical cell filled with cesium/buffer gas was set in an end-pumped flat-concave cavity and the gas pressure was set lower than 1atm. Using the QCW drive mode with the repetitive rate and pulse width of 1kHz and 50μs, respectively, 13.45μJ pulse energy has been achieved with the slope efficiency of about ∼1.8%.

Coherent 2 μm differential absorption and wind lidar with conductively cooled laser and two-axis scanning device

A coherent 2 microm differential absorption and wind lidar (Co2DiaWiL) was developed to measure CO(2) concentration and line-of-sight wind speed. We conductively cooled a pumping laser head to -80 degrees C and diode arrays to approximately 20 degrees C. A Q-switched laser outputs an energy of 80 mJ (pulse width 150 ns (FWHM), pulse repetition frequency up to 30 Hz). CO(2) measurements made over a column range (487-1986 m) for 5 min accumulation time pairs achieved 0.7% precision. Line-of-sight wind speeds for ranges up to approximately 20 km and returns from a mountainside located 24 km away from the Co2DiaWiL were obtained.

Partial CO2 Column-Averaged Dry-Air Mixing Ratio from Measurements by Coherent 2-μm Differential Absorption and Wind Lidar with Laser Frequency Offset Locking

AbstractA coherent 2-μm differential absorption and wind lidar (Co2DiaWiL) with a 2-μm single-frequency Q-switched laser with laser frequency offset locking was used for long-range CO2 measurement. The frequency stabilization of the single-frequency λ on pulsed laser was 1.0 MHz. Experimental horizontal CO2 measurement over a column range of 2.6–5.6 km and 900 shot pairs (1-min integration time) was conducted on 22 October 2009 to examine the detection sensitivity of the Co2DiaWiL. The achieved precision was less than 2.1%. The root-mean-square of the differences between the 30-min CO2 averages measured by the Co2DiaWiL and a ground-based in situ instrument was 0.9% (3.5 ppm). Experimental vertical CO2 measurements were conducted in February 2010 and January and February 2011. The partial CO2 column-averaged dry-air mixing ratios (XCO2) for an altitude between 0.4 and 1.0 km in 2010 and 2011 were 403.2 ± 4.2 and 405.6 ± 3.4 ppm, respectively. In the paper, the Co2DiaWiL results were well validated careful...

Conductive-cooled 2micron laser for CO2 and wind observations

We have developed 2micron Q-switched lasers with conductive-cooled side pumped laser head. Q-switched output of 100mJ at 20Hz has been achieved in a Tm,Ho:YLF laser oscillator with a composite rod. The experiments showed that very good thermal conduction is held between rod and heat sink. This laser head may be used for laser amplifier of 500mJ output. Another type of Tm,Ho:YLF laser head has been developed for the oscillator of 50-100mJ output at 20-40Hz. These 2micron lasers are applied to coherent lidar systems, which will be used to measure atmospheric CO2 and wind profiling.

2-um Coherent Lidar Technology Developed at NICT: Past, Current, and Future

We present a development and research of the 2-µm coherent lidar with a conductively-cooled laser-diode-pumped single-frequency Q-switched Tm,Ho:YLF pulse laser developed at the NICT.

Development of coherent 2-μm differential absorption and wind lidar with laser frequency offset locking technique

We developed a coherent 2-μm differential absorption and wind lidar to measure CO2 concentration and line-of-sight wind speed. The wavelength of on-line laser was set at the R30 absorption line center of CO2 and the atmospheric transmission for the on-line backscattered signal caused by CO2 is large. Measurable range of CO2 measurement was limited. A laser frequency offset locking system was installed into the laser system to improved measurable range of CO2 measurement. Two single-frequency continuous wave lasers are used for the laser frequency offset locking. One laser (center, λCenter) of the two continuous lasers is directly locked to the R30 absorption line center of CO2 and the other (on-line, λOn) is frequency-shifted to λCenter laser. Although long-range CO2 measurement depends on the laser frequency offset, the installation of the laser frequency offset realized vertical CO2 measurement in a range of up to the upper troposphere.

Conductive-cooled 2-micron laser development for wind and CO2 measurements

We have developing two types of 2micron conductive-cooled lasers for wind and CO2 measurements. One type of lasers is side pumped Tm,Ho:YLF laser operated at 20-40Hz. The laser rod is cooled down to -80C and laser diodes are operated at normal temperature in a vacuum container. With this type of laser, we have built up a coherent lidar system which is used to measure wind and CO2 concentration. Ho:YLF laser end-pumped by Tm:fiber laser is another type oscillator which will be operated at high repetition rate of 200-300 Hz in normal temperature. The laser will have an amplifier. These lasers are conductive-cooled, solid-state, eye-safe and suitable for space applications.

2-μm coherent lidar for CO2 and wind measurements

National Institute of Information and Communications Technology (NICT) has made efforts in order to develop a 2-μm coherent lidar for measuring CO2 concentration and line-of-sight (LOS) wind speed. Experimental horizontal CO2 measurements were made to examine the detection sensitivity of the 2-μm coherent lidar in April and May, 2008, and October, 2009. Experimental vertical CO2 measurements were made for the Greenhouse gas Observing SATellite (GOSAT) data products validation in February 2010 and in January and February 2011. Bias and random error in the LOS wind speed measurements were also investigated in order to evaluate of the 2-μm coherent lidar for wind measurements in 2010. In the paper, we present an overview of our 2-μm coherent lidar developed at the NICT and also of the experimental results.