Continuous-relief diffractive microlenses for laser beam focusing.

Matthew Day,David Cox,Graham Marshall,Alastair G Sinclair,Kaushal Choonee,Mark Thompson

doi:10.1364/oe.25.026987

Matthew Day, David Cox + Show 4 more

Open Access

https://doi.org/10.1364/oe.25.026987

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Abstract

Microscale, continuous-profile, diffractive lenses have been fabricated and characterized. Lenses designed to operate at λ0 = 405 nm were created by focused ion beam milling of a glass substrate. The micro-structured profile was analysed by confocal microscopy and optical performance was quantified by measurements of the transmitted laser beam profile. Lenses of size 125 μm × 125 μm, containing up to 18 annuli and focusing at 400 μm, 450 μm and 500 μm have been made. Measured focused beams were in excellent agreement with the predicted performance. A maximum diffraction efficiency of 84 % and side-lobe suppression down to the 10-4 level can be achieved. The suitability of the lenses for interfacing with trappedion systems is outlined.

Highlights

A wealth of research has been conducted into quantum information processing using trapped ions [1,2,3]
The glass substrates were coated with a thin (∼ 50 nm) layer of Al prior to milling so as to avoid artifacts due to charge buildup; the metal in the lens area was removed by the impinging beam but empirically, we find that the fabrication process was not affected despite the area of the lens
Using lens design A as a template, a suitable focused ion-beam (FIB) milling recipe was developed over several iterations

Summary

Introduction

A wealth of research has been conducted into quantum information processing using trapped ions [1,2,3]. One of several challenges is to create systems that can be scaled to control a large number of ions. Much effort has been expended investigating different approaches to microfabricated, segmented, ion trap devices [4,5,6,7,8]; the availability of suitable trap chips is only one part of the challenge. Bulk optical elements cannot be scaled to address and image many individual particles stored at distinct locations in these devices [9]. This is true for experiments with neutral atoms in chip-scale devices for quantum technology applications [10,11,12].

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