Click here to sign in with or
Micromirrors are micrometer-scale mirrors that are widely used in many applications, mainly in optical-fiber telecommunications, optical scanners, and optical instrumentation. Micromirrors can be integrated within photonic chips, which can be seen as the miniaturized counterparts of the macroscopic optical benches. In optical communication, micromirrors are important building blocks for cross couplers, variable optical attenuators, and external cavity tunable lasers. In all those applications, the efficiency of coupling light in and out from these micromirrors is a key performance indicator governing the signal quality. In instrumentation, micromirrors are also important building blocks of optical interferometers and optical resonators. In these cases, the coupling efficiency is also a key performance indicator affecting the metrological properties.
In a research paper recently published in the Journal of Optical Microsystems, researchers led by Yasser Sabry of Ain Shams University in Egypt analyzed micromirror behavior depending on different characteristics, such as shape, height, and surface quality. They also analyzed the impact of misalignment of incident light, considering both off-axis misalignment and angular misalignment.
The vast majority of micromirrors are flat, and the corresponding height is usually limited to 80 μm due to microfabrication constraints. Beyond this limit, the verticality and roughness of the etched surface deteriorates. One has to maintain the light spot size smaller than the mirror height to achieve reasonable throughput. Deeper micromirrors are highly desirable, but they are difficult to fabricate. Curved micromirrors are in principle more interesting than flat mirrors, although they are more difficult to fabricate. Many recently reported techniques have demonstrated manufacturing of such micromirrors with both 2D and 3D shapes. The researchers therefore proposed a detailed analysis of the potential of such curved mirrors.
They studied in detail the free-space coupling of Gaussian light beams using flat and curved micromirrors. The theoretical background and the non-ideal effects, such as limited micromirror extent, asymmetry in the curvature of spherical micromirrors, misaligned axes and micromirror surface irregularities were analyzed. The derived formulas were used to study and compare theoretically and experimentally the behavior of flat (1D), cylindrical (2D), and spherical (3D) micromirrors. The analysis focused on the regime of dimensions in which the curved micromirror radius of curvature is comparable to the incident beam Rayleigh range, also corresponding to a reference spot size.
The researchers derived a transfer matrix-based field and power coupling coefficients for general micro-optical systems, accounting for different matrix parameters in the tangential and sagittal planes of the microsystem, taking into account the possible non-idealities. They presented the results in terms of normalized quantities such that the findings remain general and applicable to different situations. Additionally, silicon micromirrors were fabricated with controlled shapes and were used to experimentally validate the coupling efficiency in visible and near infrared wavelengths. Explore further Researchers experimentally prove flat mirror ability to focus light More information: Yasser M. Sabry et al, Critical analysis of in-plane free-space light beam coupling using photonic curved micromirrors, Journal of Optical Microsystems (2022). DOI: 10.1117/1.JOM.2.3.034001 Provided by SPIE Citation: Free-space light coupling using curved micromirrors (2022, July 11) retrieved 14 October 2022 from https://phys.org/news/2022-07-free-space-coupling-micromirrors.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
More from Other Physics Topics
Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form. For general feedback, use the public comments section below (please adhere to guidelines).
Please select the most appropriate category to facilitate processing of your request
Thank you for taking time to provide your feedback to the editors.
Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.
Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Phys.org in any form.
Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.
Medical research advances and health news
The latest engineering, electronics and technology advances
The most comprehensive sci-tech news coverage on the web
This site uses cookies to assist with navigation, analyse your use of our services, collect data for ads personalisation and provide content from third parties. By using our site, you acknowledge that you have read and understand our Privacy Policy and Terms of Use.