We are developing compact space charge sensors that can be used in the space industry, using silicon photonic crystal elements.

In space, various space charges are flying around at high speeds and adversely affect electronic devices on spacecraft. Several cases of satellite abandonment caused by electronic equipment failure due to electrostatic discharge have been reported in large-scale projects in Japan. Detailed measurement data on space charge distribution in space is an indispensable piece in the new space age.

Real-time information on charged particles is essential. Our vision is to develop compact charged particle sensor that can be installed on a small satellite.

We've been studying silicon (Si) photonics and recently showed that it is possible to detect ionized air molecules in space by using a variety of Si photonic crystal (PC) devices; Raman Si lasers, high-Q nanocavities, and line-defect waveguides. When ionized molecules reach the surface of these devices, surplus charges are transferred to the inside of the PC and light is absorbed (free carrier absorption). Using these properties, we have developed sensors that can detect space charge.

The sensor we have developed does not require a PiN structure, so it is highly resistant to electrostatic discharge (ESD). Compared to existing detection methods, detection by PC devices is superior in terms of size, weight, and accessibility. Furthermore, they can be placed over a wide area and simultaneously detect charged particles in various locations by fiber connection.

・Control of the sensitivity of the detection of ionized air using photonic crystal waveguides

　Masanao Fujimoto, Yuki Takahashi, Kazuya Kikunaga, and Yasushi Takahashi

　Optics Continuum 2 (2) 349-360 (2023)

> https://opg.optica.org/optcon/fulltext.cfm?uri=optcon-2-2-349&id=525597

・Detection of ionized air using a photonic-crystal nanocavity excited by broadband light from a superluminescent diode

　Yuki Takahashi, Masanao Fujimoto, Kazuya Kikunaga, and Yasushi Takahashi

　Optics Express   30(7)  10694 - 10708 (2022)

> https://opg.optica.org/oe/fulltext.cfm?uri=oe-30-7-10694&id=470429

・Oscillation Interruption of a Raman Silicon Nanocavity Laser Induced by Positively Ionized-Air Irradiation

　Yuki Takahashi, Satoshi Yasuda, Masanao Fujimoto, Takashi Asano, Kazuya Kikunaga, Susumu Noda, and Yasushi Takahashi

　Nonlinear Optics 2021, NF2B.1

> https://opg.optica.org/abstract.cfm?uri=NLO-2021-NF2B.1

・Detection of negatively ionized air by using a Raman silicon nanocavity laser

　Satoshi Yasuda, Yuki Takahashi, Takashi Asano, Yuki Saito, Kazuya Kikunaga, Daiki Yamashita, Susumu Noda, and Yasushi Takahashi

　Optics Express 29(11), 16228-16240 (2021)

> https://opg.optica.org/oe/fulltext.cfm?uri=oe-29-11-16228&id=450959