MOBILITY ENGINEERING Produced by SAE Media Group
MOBILITY ENGINEERING
Magazines
Magazine cover

Current Issue

Archives

Magazine cover

Current Issue

Archives

Magazine cover

Current Issue

Archives

Magazine cover

Current Issue

Archives

Integrated Magneto-Optical Devices for On-Chip Photonic Systems

Development of magneto-optical (MO) materials could lead to a range of nonreciprocal optical devices for emerging standardized photonic integrated circuit (PIC) fabrication processes.

The magneto-optical (MO) oxide layer consists of (Bi,Y)3Fe5O12 or BiYIG, bismuth garnet. This material was selected because it has a better figure of merit than the CeYIG previously used, especially at lower wavelengths (1310 nm vs. 1550 nm). A top-down deposition process was developed in which BiYIG/YIG stacks are grown on the Si waveguide with YIG on top. The stack is annealed at 800°C/5 min to crystallize both layers, with the YIG templating the BiYIG leading to garnet phases rather than other oxides, and the BiYIG is directly on the Si waveguide. Initial attempts led to a film with Bi oxide phases, because the Bi was in excess and could not escape during the anneal as occurs in Si/YIG/BiYIG stacks. Hence the composition was adjusted to include slightly more Fe, which yielded films with only garnet peaks.

Conditions were also developed for growth of Bi-substituted iron garnet (BiYIG) on GGG garnet and Si substrates by combinatorial pulsed laser deposition.

Figure 1. Single Crystal BiYIG/GGG. Top left: XRD of two recent films on (111) GGG showing the effect of adding Fe. Right: Magnetometry data showing in plane (IP) and out of plane (OP) hysteresis loops for 100 nm thick Bi.97Y2.47Fe5O12 grown at 560oC, 20mTorr, 400mJ, on GGG (111). Lower left: OP Faraday loop of same film. Right: FR vs wavelength, in agreement with measurements on bulk BiYIG

For single crystal films on GGG (Figure 1), the conditions for growth that produced films with the best saturation magnetization (Ms) and surface topography were found to be at higher temperatures of 520-560°C and at oxygen pressures of 10 to 20 mTorr. Structural characterization revealed the growth of epitaxial BiYIG film on GGG without any secondary phases. This result was further confirmed by compositional analysis that showed the ratio of Bi+Y/Fe, as expected, was approximately 0.6 (in the range 0.62-0.65) suggesting no formation of secondary ferrous phases. The FR was 1.5 °/μm, which is comparable to other work considering the Bi content. The saturation field for out of plane hysteresis or Faraday loops is ~2 kOe which is close to that expected just from shape anisotropy, i.e. magne-tocrystalline or magnetoelastic contributions to anisotropy are probably small.

For polycrystalline films on Si (Figure 2) top-down crystallization of BiYIG using a YIG seed layer on topographical substrates was carried out to promote the crystallization of BiYIG on photonic substrates. A bilayer was grown (YIG/BiYIG/substrate) at 650°C, then annealed at 800°C. With the top seed layer, Bi escape during annealing was suppressed and the composition had to be adjusted (less Fe was added) to avoid secondary phases.

Figure 2. Polycrystalline Films on Si. Left: XRD of polycrystalline BiYIG film on Si grown with YIG bottom seed layer, showing the characteristic garnet peaks. Right: Scanning electron microscopy (SEM) of BiYIG grown on the sidewall of a SiN waveguide in a TE-mode isolator. The fabrication of the TE mode isolator is shown in the schematic.

X-ray diffraction (XRD) showed crystallization to the garnet structure and the saturation magnetization was consistent with the film thickness and the bulk magnetization of YIG and BiYIG (which are similar). However, films on Si had much weaker FR than expected.

During this work, the pulsed-laser deposition (PLD) system was reconfigured leading to a higher intensity of light incident on the target and higher growth rates, which led to a change in composition of most materials deposited by PLD. Compositional analysis showed that more recent BiYIG films contained less Bi than before, and this may account for the lower FR. The target, which contained Bi:Y:Fe = 0.8:2.2:5, yielded films of 0.5:2.5:3.8, or 0.5:1.9:4.2 when additional Fe oxide was code-posited. (In the latter case, Bi+Y/Fe = 0.57 which matches the stoichiometric ratio of 3/5 = 0.6.)

The results of growth experiments indicate that films grow with garnet crystal structure on GGG, even if the Bi+Y/Fe stoichiometry is not exactly correct. However, growth on Si is less forgiving, and making good quality garnet requires a closer control of stoichiometry. The Bi:Y ratio is controlled mainly by temperature, and the Bi+Y/Fe ratio is sensitive to laser power.

This work was done by Caroline Ross and Juejun Hu, Massachusetts Institute of Technology for the Air Force Research Laboratory. AFRL-0264

Topics:
Aeronautics Aerospace Aviation Electronic Components Electronic equipment Electronics Electronics & Computers Fabrication Heat treatment Integrated circuits Magnetic materials Manufacturing & Prototyping Manufacturing processes Materials Metallurgy Optical Components Optics Optics Photonics Semiconductors & ICs
This Brief includes a Technical Support Package (TSP).
Document cover
Integrated Magneto-Optical Devices for On-Chip Photonic Systems

(reference AFRL-0264) is currently available for download from the TSP library.

Don't have an account?

More From SAE Media Group

    Magazine cover
    Aerospace & Defense Technology Magazine

    This article first appeared in the September, 2018 issue of Aerospace & Defense Technology Magazine.

    Read more articles from this issue here.

    Read more articles from the archives here.

    Overview

    The document titled "Integrated Magneto-Optical Devices for On-Chip Photonic Systems" is a final report detailing research conducted under the sponsorship of the Air Force Research Laboratory (AFRL) and the Defense Advanced Research Projects Agency (DARPA). The research, carried out from May 3, 2016, to May 3, 2017, focuses on the development of magneto-optical (MO) materials aimed at enabling nonreciprocal optical devices for photonic integrated circuits (PICs).

    The primary objective of the program was to create MO materials that can be integrated into various optical and radio frequency (RF) photonic devices. These devices include low-loss interconnect waveguides, power splitters, filters, active amplifiers, lasers, optical modulators, and photodetectors. The report outlines the design of resonator and Mach-Zehnder interferometer (MZI) isolator devices, which were developed through optical modeling for both transverse-electric (TE) and transverse-magnetic (TM) polarization.

    The document is structured into several sections, beginning with a summary of key project results, followed by a detailed research description. It discusses the development of magneto-optical materials, the design of isolators, waveguide fabrication, and device characterization. The findings highlight the potential of these integrated magneto-optical devices to enhance the performance and functionality of on-chip photonic systems.

    The report emphasizes the significance of these advancements in the context of standardized PIC fabrication processes, which are crucial for the future of optical communication and signal processing technologies. The research contributes to the understanding of how magneto-optical materials can be utilized to create efficient and effective optical devices that can operate in various applications.

    Overall, the report serves as a comprehensive resource for researchers and professionals in the field of photonics, providing insights into the development and application of magneto-optical devices. It underscores the importance of continued research in this area to drive innovation in photonic systems, which are increasingly vital in modern communication and information technologies. The document is unclassified and approved for public release, making it accessible for further study and exploration by interested parties.

    Top Stories

    INSIDERWeapons Systems

    Feature Image AUSA 2025: The Army's New Anti-Vehicle Terrain Shaping Munition is Ready for...

    INSIDERUnmanned Systems

    Feature Image Meet Arc: Inversion's New Autonomous Space Vehicle for Logistics and Hypersonic...

    INSIDERAerospace

    Feature Image Mercury Signs Embedded Production Agreement for AeroVironment’s Satellite...

    INSIDERManned Systems

    Feature Image AUSA 2025: Secretary Driscoll Wants Army to Save Time and Money by 3D-Printing...

    INSIDERSoftware

    Feature Image Helsing Unveils New Autonomous Fighter Jet 'CA-1 Europa'

    PodcastsAerospace

    Feature Image Autonomous Targeting Systems for a New Autonomous Ground Vehicle

    Webcasts