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Proceedings Paper

Frequency noise and lineshape of VCSELs
Author(s): Silvia Viciani; Francesco Marin
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Paper Abstract

The study of the lineshape of semiconductor lasers is very interesting, being related to phase and frequency noise sources which are usually hidden in other kinds of laser. The importance of this topic for Vertical Cavity Surface Emitting Lasers (VCSELs) is further increased by their large impact in communication applications, since frequency and phase noise limits the performances of different optical communication techniques. We have performed such a study on an air-post AlAs/AlGaAs VCSEL. We have recorded the lineshape at different injection current levels by heterodyne with a narrow linewidth extended-cavity laser, while the frequency noise spectrum is investigated using a Fabry-Perot cavity as frequency discriminator. In single-mode emission conditions, the lineshape is Lorentzian at low pump current, while a Gaussian contribution is evident for higher pump level. The Lorentzian linewidth is inversely proportional to the laser power and can be compared with the results of the Schawlow-Townes-Henry theory properly modified to consider the particular structure of VCSELs. The study of the frequency noise shows that a quasi-Gaussian lineshape is due to an excess low frequency noise. This contribution has a 1/f^n dependence, with n around 1, for frequencies higher than 20 kHz and is flat at lower frequencies. This peculiar power spectrum has been observed in the electric noise of AlGaAs Bragg reflectors. The current noise generated in the Bragg mirrors is the source of the frequency noise through the fluctuations of the cavity optical length. The results are extended to other kinds of VCSELs.

Paper Details

Date Published: 4 May 2001
PDF: 10 pages
Proc. SPIE 4286, Vertical-Cavity Surface-Emitting Lasers V, (4 May 2001); doi: 10.1117/12.424796
Show Author Affiliations
Silvia Viciani, Univ. degli Studi di Firenze (Italy) and LENS) (Italy)
Francesco Marin, Univ. degli Studi di Firenze (Italy) and LENS (Italy) (Italy)


Published in SPIE Proceedings Vol. 4286:
Vertical-Cavity Surface-Emitting Lasers V
Kent D. Choquette; Chun Lei, Editor(s)

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