Focusing optical phased array for tissue interrogation with improved side-lobe suppression and simplified beam steering

Biomedical Optics Express, vol. 17, pp. 12

Abstract

retinal characterization via optical stimulation. The interrogation beam formers, based on curved grating emitters and optical phased arrays, are designed to achieve transverse focusing with spot sizes in the 1-2 µm range to target single cells. The experimentally realized focusing optical phased arrays show suppressed side-lobes, with approximately 11.5% of the power in each side-lobe and ∼60% in the main lobe, reducing unintentional cellular excitation. Additional design refinement enables further suppression of the side-lobes to a few percent of the total power. Additionally, we demonstrate a compact design of meandered thermal phase shifters implemented across the array that allow push-pull steering in the transverse direction as well as focusing and defocusing of the beam, with a total of only four control signals. Transverse angular steering by ±5.1° and axial translation of the focal spot by 204 µm are demonstrated with tuning currents below 50 mA, together with longitudinal angular steering by 4.26° obtained by means of wavelength tuning in a ± 15 nm range centered on 525 nm.

Authors 7

1. Pedram Hosseini Aachen Institute of Integrated Photonics (IPH)

   RWTH Aachen University

   Affiliation as printed

   Institute of Integrated Photonics, RWTH Aachen University, Campus Boulevard 73, 52074 Aachen, Germany

2. ALI TABATABAEI-MASHAYEKH Aachen Institute of Integrated Photonics (IPH)

   RWTH Aachen University

   Affiliation as printed

   Institute of Integrated Photonics, RWTH Aachen University, Campus Boulevard 73, 52074 Aachen, Germany

3. Alvaro Moscoso‐Mártir Aachen Institute of Integrated Photonics (IPH)

   RWTH Aachen University

   Affiliation as printed

   Institute of Integrated Photonics, RWTH Aachen University, Campus Boulevard 73, 52074 Aachen, Germany

4. Rebecca Rodrigo Aachen Institute of Integrated Photonics (IPH)

   RWTH Aachen University

   Affiliation as printed

   Institute of Integrated Photonics, RWTH Aachen University, Campus Boulevard 73, 52074 Aachen, Germany

5. Sandra Johnen Aachen

   RWTH Aachen University · Universitätsklinikum Aachen

   Affiliation as printed

   University Hospital of RWTH Aachen

6. Florian Merget Aachen Institute of Integrated Photonics (IPH)

   RWTH Aachen University

   Affiliation as printed

   Institute of Integrated Photonics, RWTH Aachen University, Campus Boulevard 73, 52074 Aachen, Germany

7. Jeremy Witzens Aachen Institute of Integrated Photonics (IPH)

   RWTH Aachen University

   Affiliation as printed

   Institute of Integrated Photonics, RWTH Aachen University, Campus Boulevard 73, 52074 Aachen, Germany