Impedance characteristics and parasitic speed limitations of high speed 850 nm VCSELs

• Abstract—The impedance characteristics of high-speed oxideconfined 850-nm vertical-cavity surface-emitting lasers have been studied with the aim of identifying the importance of device parasitics for the modulation bandwidth. Through equivalent circuit modeling, it is confirmed that device parasitics have a major impact on the bandwidth and the importance of each individual circuit element has been investigated. According to the extrapolation of the parameters derived from S11 measurements below 20 GHz towards higher frequencies and assuming that the mesa capacitance can be reduced by adding a few extra oxide layers without significantly affecting series resistance, our model predicts that the 3-dB parasitic frequency can be increased from 22 to above 30 GHz. Accounting also for bandwidth limitations due to thermal effects, we expect an increase of the modulation bandwidth of several gigahertz which may enable direct current modulation at 40 Gb/s.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Annan teknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Other Engineering and Technologies (hsv//eng)

NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)

NATURVETENSKAP  -- Fysik -- Annan fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Other Physics Topics (hsv//eng)

Nyckelord

vertical-cavity surface-emitting laser

high speed

VCSEL

modulation bandwidth

Electrical parasitics

impedance

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