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This presentation described the construction of neural networks using light; it was an introduction to three papers that have been submitted on optical neural networks since 2018. In recent years, many attempts have been made to reproduce neural networks with light to increase speed and reduce power. In constructing a network, optimization is essential to generate appropriate outputs from inputs. Matrix computation in optical neural networks is based on the principle of Mach-Zehnder interferometry, and is represented by the intensity of light intensity due to phase shift. Optimization requires measurement of the gradient. While previous studies have used computer models for optimization, a new approach, called the associated transformation, is used to obtain the gradient by measuring the light intensity of the device. This allows the gradient to be acquired in the optical domain, shortening the procedure used in conventional methods.
Article: https://www.osapublishing.org/optica/abstract.cfm?uri=optica-5-7-864
: https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-8-12138
: https://advances.sciencemag.org/content/5/12/eaay6946
CLEO 2020 Takumasa Kodama
Research
CLEO 2020 Participation Report
11-15 May 2020, Online
Takumasa Kodama, 1st year master's student
About CLEO2020
CLEO (The Optical Society OSA) is the largest international photonics conference sponsored by the American Physical Society (APS) and the IEEE Photonics Society. The conference is usually held in San Jose, but this year, due to the spread of the new coronavirus (COVID-19), all presentations were made online. Although the situation was unprecedented, presenters from a total of 75 countries gathered, and more than 2000 presentations and 248 posters were made. As the presenter also participated in the conference, I would like to introduce some of the presentations I attended, including my impressions through my own presentation.
2. Presentation by the presenter
Title: High-resolution Spectrometer with Random Photonic Crystals
Presenter: Takumasa Kodama
Affiliation: Keio University
Presentation No.: FM2R.4 (Mon, May 11th)
幅変化型の線欠陥フォトニック結晶導波路と深層学習アルゴリズムを用いた微小サイズの分光器についての発表を行った．フォトニクスと深層学習をマージした研究は本会議でも見られ，深層学習は近年の流行りであることを再確認できたと同時に，我々の研究の様に，データ解析に用いている研究は見当たらなかったため，新たな深層学習の利用を発表できたのでは，と考えている．発表形式はLive形式で行い，質疑ではQ&A欄に届いた質問を座長が読む，というものであった．英語の聞き取りに不安があったが，届いた質問を自身でも読むことが出来るため，乗り越えることが出来た．質問の内容は，データ解析に用いた深層学習と最適化アルゴリズムの差異について，また何故そのようなアルゴリズムを適用することで分解能を向上させることが出来るかなどのコンセプトに関係があるものが多かった．自身の発表に際して，プレゼン資料を画面に共有するのだが，やり方を間違えると発表者ツールが聴講者に見えるというアクシデントが起こる．これを回避するには，パワーポイントを共有した後に，スライドショーを開始すれば良い．
3. presentations attended
Title: Lasing up to T = 339K in Subwavelength Nanowire-Induced Photonic Crystal Nanocavities
Presenter: Sylvain Sergent
Affiliation: NTT Nanophotnics Center
Presentation No.: SM1J.6 (Mon, May 11th)
Low-threshold lasing using silicon-nitride photonic crystals and group III-V nanowires The photonics group at NTT has been actively working on photonic crystals and plasmonics in recent years. In this presentation, nanowires are placed in a photonic crystal waveguide, which serves as a gain medium, and excitation up to T = 360 K is confirmed. Many combinations of nanowire length, radius, and lattice constant were tested, and their Q-values and threshold values were measured, showing their relationship. The photonic crystals are used to directly insert light into the nanowires, making them compatible with integrated circuits, room temperature, and low power input (3.5 MW/cm2). The silicon substrate is very small in size, so there is little loss of light. The silicon substrate is very small in size, and can be operated at room temperature, resulting in very low power consumption. The presenters also mentioned the advantage of using various nanowires to control the laser wavelength and flexibility in design, although ZnO was used in this presentation.
Paper: https://pubs.acs.org/doi/pdf/10.1021/acsphotonics.0c00166
Title: Photonic neural networks: training, nonlinearity, and recurrent systems
Presenter: Shanhui Fan
Affiliation: Stanford University
Presentation No.: JF2A.3 (Fri, May 15th)
