Hideya Gamo

Atmospheric turbulence chamber for optical transmission experiment:characterization by thermal method

A turbulence chamber (0.78 x 0.23 x 2.59 m(3)) consisting of ten small electric heater/blowers with an aluminum foil screen and three screens of 2-mm aluminum wire meshes can generate the nearly homogeneous isotropic turbulence within the 0.5 x 0.05 x 2-m(3) region at the 0.11-m height of optical measurements. The temperature structure constant squared C(2)(T) = 52.9 K(2) m(-?) was obtained from the temperature structure function measurements measured by using a differential microthermocouple system. The refractive-index structure constant squared C(2)nat the 632.8-nm wavelength was calculated from C(2)(T):C(2)(n) = 3.00 x 10(-11)m(-?). The average wind velocity and temperature were 0.41 m/sec and 53 degrees C, respectively. From the power spectrum of temperature fluctuations, the inner and outer scales of turbulence are determined: l(o) = 5.0 mm and L(0) = 6.5 cm. The measured temperature structure function and power spectrum of temperature fluctuations satisfy the ? and -5/3 power similarity laws in the inertial subrange, respectively.

Anomalous Intensity Fluctuations in a High-Gain Gas Laser

Recently, spectral characteristics of high gain lasers such as semiconductor diode lasers and Xenon 3.5 pm high gain gas laser have attracted attention because the spectral line width of a semiconductor laser deviates from the Schawlow-Townes formula1) and multimode high-gain Xenon 3.51 μm and He-Ne 3.39 pm gas lasers showed peculiar low frequency fluctuations2).