Prototype design and evaluation of the nine-layer achromatic half-wave plate for the LiteBIRD low frequency telescope
Prototype design and evaluation of the nine-layer achromatic half-wave plate for the LiteBIRD low frequency telescope
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DOI：
10.1117/12.2312431
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发表时间：
2018-07
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影响因子：
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通讯作者：
K. Komatsu;T. Matsumura;M. Hazumi;H. Imada;H. Ishino;N. Katayama;Y. Sakurai;H. Sugai;R. Takaku
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文献类型：
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作者：
K. Komatsu;T. Matsumura;M. Hazumi;H. Imada;H. Ishino;N. Katayama;Y. Sakurai;H. Sugai;R. Takaku
LiteBIRD是一个卫星项目，以前所未有的精度测量CMB的偏振。LiteBird在日地第二拉格朗日点对全天进行了三年的观测。LiteBIRD的目标是在大角度尺度下观察B模式偏振，并测量张量与标度比r，精度小于0.001，探索暴胀的能量尺度。为了降低系统的1/f噪声和系统性，我们计划在两个望远镜的每个孔径处使用连续旋转半波片（HWP）作为偏振调制器。其中一个望远镜称为低频望远镜（LFT），覆盖34至270 GHz的频率范围，要求HWP在宽带宽中具有高调制效率。我们采用Pancharatnam型消色差HWP（AHWP）来实现宽带覆盖。AHWP由九层堆叠的HWP组成，其光轴相互旋转，角度针对LFT带宽进行了优化。本文报道了我们研制的九层AHWP的进展情况以及调制效率和相位随频率变化的测量结果。
LiteBIRD is a satellite project to measure the polarization of the CMB with an unprecedented accuracy. LiteBIRD observes all sky for three years at the sun-earth second Lagrange point. The goal of LiteBIRD is to observe the B-mode polarization at large angular scales and to measure the tensor-to-scaler ratio r with an accuracy less than 0.001, exploring the energy scale of the inflation. In order to mitigate the system 1/f noise and systematics, we plan to use continuous rotating half-wave plates (HWPs) as a polarization modulator at each aperture of two telescopes. One of the telescopes, called a low frequency telescope (LFT), covers the frequency range from 34 to 270 GHz, requiring the HWP to have a high modulation efficiency in the wide bandwidth. We employ a Pancharatnam-type achromatic HWP (AHWP) to achieve the broadband coverage. The AHWP consists of nine layer stacked HWPs with the optic axes mutually rotated by the angles optimized for the LFT bandwidth. In this paper, we report our development status of the nine layer AHWP and measurement results on the modulation efficiency and the phase as a function of frequency.