Saturable absorption by carbon nanotubes on silica microtoroids

Tsutaru Kumagai, Naoya Hirota, Katsuya Sato, Koki Namiki, Hideyuki Maki, Takasumi Tanabe

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Saturable absorption is a key technology for shaping the waveform of light such as in passive mode-locking. The combination of high-Q optical microcavities with a saturable absorber allows stable lasing and soliton formation. This work describes saturable absorption by carbon nanotubes (CNTs) on silica microtoroids. CNTs, which are saturable absorbers capable of a fast response time and broadband absorption, were grown on silica microtoroids by chemical vapor deposition (CVD). Raman spectroscopy revealed that the CNTs are in good quality (G/D ratio ∼ 7) and about 1.0 nm in diameter, thus confirming that a sample for use in the telecommunication band can be prepared by CVD. A counter-propagating pump-probe experiment enabled us to investigate the characteristics of CNTs as saturable absorbers while suppressing thermo-optic bistability in a microcavity system. The results revealed a saturable absorption coefficient of 0.042 cm-1, a saturable intensity of 25.9 MW/cm2, and a modulation depth of 28%. This is the first step toward the demonstration of the robust mode-locking in a silica microtoroid consisting of CNTs.

Original languageEnglish
Article number233104
JournalJournal of Applied Physics
Volume123
Issue number23
DOIs
Publication statusPublished - 2018 Jun 21

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carbon nanotubes
silicon dioxide
absorbers
locking
vapor deposition
lasing
telecommunication
Q factors
absorptivity
waveforms
counters
Raman spectroscopy
solitary waves
optics
pumps
broadband
modulation
probes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Saturable absorption by carbon nanotubes on silica microtoroids. / Kumagai, Tsutaru; Hirota, Naoya; Sato, Katsuya; Namiki, Koki; Maki, Hideyuki; Tanabe, Takasumi.

In: Journal of Applied Physics, Vol. 123, No. 23, 233104, 21.06.2018.

Research output: Contribution to journalArticle

Kumagai, Tsutaru ; Hirota, Naoya ; Sato, Katsuya ; Namiki, Koki ; Maki, Hideyuki ; Tanabe, Takasumi. / Saturable absorption by carbon nanotubes on silica microtoroids. In: Journal of Applied Physics. 2018 ; Vol. 123, No. 23.
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