IEEE Photonics Conference Tomohiro Tetsumoto

As mentioned above, there were many reports related to microcavities at the conference, so there were many topics that I was familiar with. SNAP by Kobatake and fluid sensing by opto-mechanics by Kobayashi, both of which I supported in Spring Coro, were presented. There were also several researchers who used IMEC for metamaterials and spot-size converters, which are difficult to fabricate, and I felt that the hurdle for fabrication is getting lower thanks to the spread of foundries and improved accuracy.
Below are some of the presentations that were of particular interest to me at the conference.

[TuF3.1: X. Jiang, et al., Ultrahigh-Q microcavities with highly directional emission].Presentation by Prof. Xiao's group at Peking University. I had heard that toroids can be made elliptical to allow directional spatial input/output, but this time I listened to a thorough explanation of the principle again. It seems that chaos is involved at a deep level, but in the end, it seems that the toroidal structure is made in such a way that only a part of the total reflection condition is not satisfied. However, I was surprised at the high precision of the fabrication. I wonder if it is possible to control the resonance wavelength of the toroid with high precision by using it as a reference. I think this technology is necessary for packaging. One of the advantages of spatial coupling is that the coupling Q-value is stable, and they are trying to use this to achieve ultra-high precision sensing from mode broadening rather than mode splitting of the resonance spectrum. After hearing it again, I thought it sounded reasonable.

[WH.4.3: B. Oner, et al., Broadband one way propagation via dielectric waveguides with unequal effective index].
This is a story about the numerical analysis of an MZI type interferometer structure isolator. The principle is simple and is presented here. The device configuration is, for example, as follows. A single waveguide extends from the left and is designed to propagate only the fundamental mode. The two waveguides have different widths. The separated waveguides connect on the right side to a waveguide that can propagate both first- and second-order modes.
The two separate waveguides have different propagation constants due to their different widths, and are set to lengths that invert the phase by exactly π. Therefore, light input to the two waveguides simultaneously forms a mode with second-order odd symmetry when the two waveguides meet again. In this case, light input from the right cannot be guided through the tapered structure to the left waveguide because it cannot shift to the first-order mode on its way to the left waveguide, while light input from the left can propagate through the right waveguide as a mode with second-order odd symmetry. In this way, it works like an isolator. The two split waveguides are almost the same width, which allows for a wider operating bandwidth.

[WH.4. 4: R. Van Laer, et al., Observation of 4.4 dB brillouin gain in a silicon photonic wire].
The contents of this paper show that high gain Brillouin scattering was excited inductively using a silicon wire. To reduce mechanical vibration loss, the silica layer under the silicon layer was cut to about 10 nm, and by increasing the photon-phonon interaction distance (about several centimeters), a gain-loss ratio of nine times higher than that of conventional devices could be obtained. The concept is exactly the same as the design of photonic-phononic resonators. In a waveguide type resonator, it seems that there are equal amounts of traveling wave and backward wave in the optical resonator, but can both Raman light be emitted? I had a prejudice that the excitation of Brillouin scattering is not easy to see, but it seems that it can be seen in the same way as other nonlinearities if the light is injected at high intensity. I thought that it would be possible to excite it by careful consideration of the design. I am interested in this field, so I would like to check it out. In Nature Physics 5, 276-280 (2009), something similar to the generation of optical kerr combs in modulation by optomechanics, which I discussed with Dr. Kato before, was found via Brillouin scattering.