Basic Study of Laser Beam Applications to Space

至于光学天线，已经编制了一个计算机程序来成形反射器。结果表明，与高斯光学相比，天线增益可提高1.5dB，重量可减轻40%。其次，针对双反射面天线的情况，分析了由于支撑结构和制造误差引起的特性退化。当厚度误差为5 mm时，孔径分布应从肩部的矩形逐渐变细，F/D值应大于0.5。用数控加工机加工了一个光学天线，并用近场法进行了测量。振幅分布接近于期望值。为了测量在干涉现象中起重要作用的电光常数，采用幅度调制技术，实现了一种简单、高精度的测量装置。成功地测量了质子交换铌酸锂波导的电光常数。并首次定量测量了光折变灵敏度，提出了根据光信号功率与噪声功率之比来调整编码比的编码方案。

As for optical antennas, a computer program has been made to shape reflectors. It is shown that the antenna gain can be improved by 1.5dB and the weight can be reduced by 40 percent in comparison with Gaussian optics. Next, the characteristics degradation due to support structures and manufacturing errors is analyzed for the case of dual reflector antennas. It is clarified that, If the manufacturing error amounts to be 5mmu in thickness, the aperture distribution should be tapered from a rectangular pattern at the shoulders, and the F/D value should be larger than 0.5. The reflector curves are typically aspheherical ones.An optical antennas has been manufactured by an NC machine, and measured using the near-field method. The amplitude distribution is close to the desired one. Phase distribution in the near field and the far field patterns should be measured later.In order to measure electrooptical contants which play an important role in the interference phenomena, a simplified and highly accurate measurement facility is realized with amplitude modulation scheme. The electrooptical constant of a proton-exchanged LiNb03 waveguide has been successfully obtained. And the photo refractive sensitivity has been measured quantitatively for the first time.The coding scheme to adapt the coding ratio according to the ratio of optical signal power and the noise power is proposed.