Planar focusing reflectors based on high-contrast-gratings for application in vertical cavity surface emitting lasers

Conventional vertical cavity surface emitting lasers (VCSELs) are constructed from two distributed Bragg reflectors (DBRs) and an active region placed between them. Every DBR consists of two types of materials that alternate eachother several or even several tens of times. One of the main technological problems in the production of VCSELs is relatively small number of materials that are suitable to create DBRs. Moreover, DBRs are sometimes as thick as few micrometers.

The goal of the project is to design more versatile mirrors that can be implemented in VCSELs in place of at least one of the DBRs. A proposed alternative that will be developed in the project is a subwavelength monolithic high contrast grating (MHCG) that will be used to design a flat focusing mirror with a thickness several times smaller than that of the DBRs.

As part of the project, it is planned to design and simulate the performance of focusing MHCG mirrors providing different reflectivities and focal lengths. The structures demonstrating the best performance (e.g., highest reflectivity) will be fabricated in collaboration with an international partner. The focusing properties of the fabricated mirrors will be investigated in Lodz. In addition, the designs of focusing MHCG mirrors will be used to simulate the operation of resonant cavities and determine the validity of their use in VCSELs. In the final stage of the project we will investigate the thermal, electrical and optical parameters of an entire VCSEL designed for 980 nm, in which a focusing MHCG mirror wil be implemented.

Funding:

The project "Planar focusing reflectors based on high-contrast-gratings for application in vertical cavity surface emitting lasers" is supported by the HOMING programme of the Foundation for Polish Science and co-financed by the European Union under the European Regional Development Fund.

Value of the project: 797 678 PLN

Contribution of European Funds: 797 678 PLN

The results of the research were published in the following articles:

• Paulina Komar, Marcin Gębski, James A. Lott, and Michał Wasiak, Chromatic aberration in planar focusing mirrors based on a monolithic high contrast grating, Opt. Express 29 (2021) 30296-30306, doi: 10.1364/OE.433813
• Paulina Komar, Marcin Gębski, James A. Lott, Tomasz Czyszanowski, and Michał Wasiak, Experimental demonstration of light focusing enabled by monolithic high contrast grating mirrors, ACS Appl. Mater. Interfaces 13 (2021) 25533–25539, doi: 10.1021/acsami.1c04871
• Paulina Komar, Marcin Gębski, Tomasz Czyszanowski, Maciej Dems, and Michał Wasiak, Planar focusing reflectors based on monolithic high contrast gratings: design procedure and comparison with parabolic mirrors, Opt. Express 28 (2020) 38745-38761, doi: 10.1364/OE.404684

The results of the research were presented on the following conferences:

• Conference "SPIE Photonics West 2021 Digital Forum OPTO", Comparison of planar focusing reflectors based on monolithic HCGs with parabolic mirrors, 6-11 March 2021, online.
• Conference "SPIE Photonics West 2021 Digital Forum OPTO", Experimental demonstration of light focusing achieved by monolithic high-contrast grating mirrors, 6-11 March 2021, online.
• Conference "SPIE Photonics West OPTO 2020", Monolithic high-contrast gratings as planar focusing reflectors for VCSELs, 1-6 February 2020, San Francisco (USA).
• Conference "8th Workshop on Physics and Technology of Semiconductor Lasers", Long focal-length planar focusing reflectors based on monolithic high contrast gratings, 13-16 October 2019, Kraków (Poland).
• Conference "SPIE Photonics West OPTO 2019", Long focal-length planar focusing reflectors based on high-contrast gratings, 2-7 February 2019, San Francisco (USA).
• Conference "Nanophotonics and Micro/Nano Optics International Conference2018", Planar focusing reflectors based on high contrast gratings, 1-3 October 2018, Rome (Italy).

The following conference proceedings were published within the project:

• Paulina Komar, Marcin Gębski, Maciej Dems, Tomasz Czyszanowski, Michał Wasiak, "Monolithic high-contrast gratings as planar focusing reflectors for VCSELs", Proc. SPIE 11290, High Contrast Metastructures IX, 1129015F; doi: 10.1117/12.2545565
• Paulina Komar, Marcin Gębski, Maciej Dems, Tomasz Czyszanowski, Michał Wasiak, Long focal-length planar focusing reflectors based on high-contrast gratings, Proc. SPIE 10928, High Contrast Metastructures VIII, 109281F; doi: 10.1117/12.2511028

The following presentations (along with recorded audio) show the research results obtained during the realization of the project. The results have been divided thematically, and in some cases a summary description of the presentation content has been listed under the link to the video.

1. Basic information on the structures used in this project.
   • Introduction to parabolic mirrors.
   • Definition of a subwavelength monolithic high contrast grating.
   • Description of the algorithm to design a focusing grating based on MHCG.
2. Does the phase reconstruction of the designed planar MHCG focusing mirror have to be perfect?
3. Comparison of the focusing properties of conventional (curved) parabolic mirrors with planar MHCG focusing mirrors.
4. Experimental observation of light focusing obtained by the MHCG planar focusing mirror.
5. Chromatic aberration of the MHCG planar focusing mirror (coming soon).