Performance of a 200 mm Diameter Achromatic HWP with Laser-Ablated Sub-Wavelength Structures

for the LiteBIRD collaboration

Research output: Contribution to journalArticlepeer-review


We laser-ablated sub-wavelength structures (SWS) on 200 mm diameter birefringent sapphire disks to produce broadband anti-reflection coating (ARC). The disks were assembled into a stack of five plates making an achromatic half-wave plate (AHWP) suitable for operation between 40 and 140 GHz. We report on the SWS fabrication and transmission measurements of the stack at room temperature. From the measurements, we compute a band average transmission and modulation efficiency for nine spectral bands that correspond to the frequency coverage of the LiteBIRD Low-Frequency Telescope (LFT). We also assess the level of instrumental polarization the AHWP exhibits. We discuss paths for further development to minimize the instrumental polarization from the AHWP. This work is a development milestone toward the implementation of an AHWP for the LiteBIRD satellite.

Original languageEnglish
Pages (from-to)346-356
Number of pages11
JournalJournal of Low Temperature Physics
Issue number5-6
Publication statusPublished - Jun 2023


  • Broadband achromatic half-wave plate
  • Broadband anti-reflection
  • Cosmic microwave background
  • Laser machining
  • Millimeter-wave instruments

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • General Materials Science
  • Condensed Matter Physics


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