Er-implanted silica lasers based on Si nanobeam cavities

by Daiki Yamashita (Quantum Optoelectronics Research Team)

Thursday 27 Feb 2020, 13:30 → 15:00 Asia/Tokyo

210 (Nishina building)

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Joint Seminar of the 30th Nuclear Spectroscopy Lab. & Quantum Beam Application Research (B03)

第 30 回 核分光研 & 新学術領域研究「量子ビーム応用」合同セミナー

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Lecturer: Daiki Yamashita (Quantum Optoelectronics Research Team)

Title: Er-implanted silica lasers based on Si nanobeam cavities

Language: Japanese

Date: February 27 (Thu.), 2020, 13:30-

Place: Nishina building #210

Abstract: 

Silicon (Si) photonics is a promising technology for integrating optical and electronic components onto a single microchip, which utilizes standard semiconductor processes. Various key elements such as waveguides, demultiplexers, modulators, and photodetectors have already been integrated on chips. In comparison, the development of practical Si-based lasers has been very challenging, because Si has an indirect band gap, which results in low light emission efficiency. In the last half a century, numerous studies have been made to increase light emission from Si. Among such studies, erbium (Er) ion doping has been found to generate radiative transitions around 1.5 mm optical communication wavelength. Nevertheless, light emission from Er-doped Si at room-temperature is too weak to achieve lasing operation. To overcome the problem, light emission has thus focused on the use of SiO2 as a host material for doping Er ions and microcavities with high-qulity (Q) factor to enhance light emissions. The Er-implanted silica lasers have been demonstrated by using high-Q toroidal cavities [1] and microdisk cavities [2]. These achievements are important steps towards practical Si-based lasers, however, these device fabrication seem to be difficult in terms of connections to waveguides and etching conditions. Moreover, due to the small emission cross section of Er at 1.55 mm (s = 4E−21 cm^2), lasing operation requires cavities with Q > 1E5. Therefore, more robust device and fabrication designs are desirable.

Here, we propose the Er-implanted silica lasers based on Si nanobeam cavities. We utilize photonic crystal (PC) nanobeam cavities [3] to enhance light emission from Er ions. PC nanobeam cavities have the advantages of high-Q factor (~1E5) and ultrasmall mode volume (0.02 (λ/n)^3, λ: wavelength, n: refractive index), which can further improve the performance through the Purcell effect that accelerates the radiative decay into the cavity mode. The device design and laser operation principles are explained in the following. The devices are fabricated from silicon-on-insulator wafers and Er ions are implanted into the buried oxide layer. The Er ions are excited by external excitation laser and the generated light is coupled to the nanobeam cavity designed on the top Si layer. The light emission is enhanced in the nanobeam cavity and lasing begins. Using finite difference time domain simulations, we design cavities that enable efficient coupling to Er ions light emission and calculate lasing threshold conditions with two types of nanobeam cavities.

This work is supported in part by MIC (SCOPE 191503001), MEXT (Nanotechnology Platform) and RIKEN (Incentive Research Project). Simulations are performed by HOKUSAI at RIKEN.

References

[1] B. Min, T. J. Kippenberg, L. Yang, K. J. Vahala, J. Kalkman, and A. Polman, Phys. Rev. A 70, 033803 (2004).

[2] T. J. Kippenberg, J. Kalkman, A. Polman, and K. J. Vahala, Phys. Rev. A 74, 051802(R) (2006).

[3] R. Miura, S. Imamura, R. Ohta, A. Ishii, X. Liu, T. Shimada, S. Iwamoto, Y. Arakawa, and Y. K. Kato, Nat. Commun. 5, 5580 (2014).

 

Host laboratory: Nuclear spectroscopy laboratory