Open AccessComplex phase masks for OH suppression filters in astronomy: part I: design
Author(s) -
Aashia Rahman,
Kalaga Madhav,
Martin Roth
Publication year - 2020
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.402989
Subject(s) - optics , aperiodic graph , astronomical interferometer , phase (matter) , interferometry , grating , fiber bragg grating , physics , fabry–pérot interferometer , beam splitter , optical fiber , filter (signal processing) , fabrication , materials science , computer science , wavelength , laser , medicine , alternative medicine , mathematics , pathology , combinatorics , quantum mechanics , computer vision
The design of a complex phase mask (CPM) for inscribing multi-notch fiber Bragg grating filters in optical fibers for OH suppression in astronomy is presented. We demonstrate the steps involved in the design of a complex mask with discrete phase steps, following a detailed analysis of fabrication constraints. The phase and amplitude of the complex grating is derived through inverse modelling from the desired aperiodic filter spectrum, following which the phase alone is encoded into the surface relief of a CPM. Compared to a complicated "running-light" Talbot interferometer based inscription setup where the phase of the inscribing beam is controlled by electro- or acousto-optic modulators and synchronized to a moving fiber translation stage, CPM offers the well-known convenience and reproducibility of the standard phase mask inscription technique. We have fabricated a CPM that can suppress 37 sky emission lines between 1508 nm to 1593 nm, with a potential of increasing to 99 channels for suppressing near-infrared (NIR) OH-emission lines generated in the upper atmosphere and improving the performance of ground-based astronomical telescopes.