The photon-recoil components of the Ca 6573-A line have been resolved using the three-zone optical Ramsey interference technique with an atomic beam. Linewidths as narrow as 3 kHz HWHM (line Q of 8 X 10'0) are reported for zone separations up to 7 cm. An indication of the lightshift-induced contraction of the recoil splitting predicted by C. J. Bordii is obtained. Techniques are discussed which should lead to an optical wavelength/frequency standard with an accuracy of better than 10-l4.
Neutron radiation testing was performed on a total of 125 silicon photodiodes to investigate the changes in the device parameters after neutron exposure. Californium-252 source was used to irradiate these photodiodes with 1 MEV equivalent neutrons having fluences in the range of 5x1Ol1 to lOI4 N/cm2. The photodiode forward voltage drop, ideality factor and series resistance were found to increase after neutron exposure. The increased series resistance was found to cause a degradation in diode photocurrent linearity. An empirical expression for post neutron changes in photodiode linearity is presented. Neutron induced changes in the photodiode shunt resistance and dark current have been modeled using simple expressions. These expressions allow device designers to estimate changes in photocurrent linearity, shunt resistance and dark current after neutron exposure. No post neutron change in the UV quantum efficiency of diodes without rkcombination in the front region was observed. This suggests that neutron irradiation does not affect the Si-Si02 interface recombination velocity of p-n junction diodes.
INTRODUCTIO N
A system is described for stabilizing a cw dye laser frequency to a high-finesse optical cavity. The length of this optical cavity is locked to a CH4-stabilized He-Ne laser with a tunable frequency-offset technique. A very fast servo system using an intracavity KD*P crystal), a long dye laser cavity, and the stabilized optical cavity result in an absolute frequency stability of 1 kHz for an integration time of 10−4 sec and 300 Hz for 300 sec. Intensity is stabilized to one part in 104.
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