Recently, we have developed the high output power laser amplifier using Er,Yb:glass planar waveguide in order to
increase the measurable range of our 1.5 μm coherent Doppler LIDAR (CDL). In this paper, we introduce this
development and demonstration of a long range wind sensing using the developed system. The transmitted pulse has a
peak power of 2.4 kW and a width of 580 ns (i.e. pulse energy of 1.4 mJ) with a pulse repetition frequency of 4 kHz, in
addition to a nearly diffraction limited beam quality. With this laser amplifier, we demonstrate the measurable range of
more than 30 km. According to our own research, this is the longest measurable range demonstration for wind sensing
CDLs.
We have developed a 1.5-μm eye-safe wavelength high average power laser amplifier using an Er,Yb:glass planar
waveguide for coherent Doppler LIDAR. Large cooling surface of the planar waveguide enabled high average power
pumping for Er,Yb:glass which has low thermal fracture limit. Nonlinear effects are suppressed by the large beam size
which is designed by the waveguide thickness and the beam width of the planar direction. Multi-bounce optical path
configuration and high-intensity pumping provide high-gain and high-efficient operation using three-level laser material.
With pulsed operation, the maximum pulse energy of 1.9 mJ was achieved at the repetition rate of 4 kHz. Output average
power of the amplified signal was 7.6W with the amplified gain of more than 20dB. This amplifier is suitable for
coherent Doppler LIDAR to enhance the measurable range.
Accidents to airliners caused by air turbulence have been increasing in recent years. At present there is no sure way of
avoiding encounters with clear air turbulence (CAT) because conventional airborne weather radars cannot detect
turbulence in clear conditions. The Japan Aerospace Exploration Agency (JAXA) is therefore developing a Doppler
LIDAR (Light Detection and Ranging) which can measure wind speeds ahead of an aircraft even in clear air. Turbulence
prediction in flight has already been demonstrated using experimental Doppler LIDARs, and the latest prototype aims at
turbulence detection up to 5 nautical miles (9 km) ahead at jet airliner cruising altitudes. Wind velocity measurement by
LIDAR is difficult at high altitude because of low aerosol particle density. Regular atmospheric observation flights are
therefore being made to establish the basic specifications of a practical device. Furthermore, since air turbulence
information should be displayed on the flight deck, a graphical turbulence display is also being studied. This paper
describes the development of the airborne wind measurement system and presents examples of flight experiment results.
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