Paper
19 June 2003 Quantum dots: a new approach to low Vπ optical modulators
Elizabeth Twyford Kunkee, Peter M. Livingston, Steve Holm
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Abstract
Preliminary analysis has shown that quantum dots enable tens of millivolt-range operation of phase-shifters in a semiconductor Mach-Zehnder interferometer modulator. Our methodology based upon the quantum dot experimental work of Hse et al, makes use of his measured exciton line shapes to estimate refractive index changes in a PIN structure in which the intrinsic laser is loaded with self-organizing quantum dots and their associated wetting layers. We consider both forward and reversed bias cases; in the former, the interferometer phase shift sections become DFB lasers, and in the latter, the phase shift is caused by the quantum-confined Stark effect (QCSE). With the latter, we found a trade-off between low operating voltage and modulating bandwidth. For a phase shifter insertion loss of 5 dB, a 250-micron long phase section will yield a pi/2 control voltage of 50 mV at a bandwidth of around 18 GHz. Ifi 90 mV control voltage swing can be tolerated, the modulator bandwidth increases to 30 GHz. If a resonant tunneling diode (RTD) is made part of the assembly, the local E-field is enhanced by a factor of 5 to 10, thereby reducing the drive requirements even further. Similar, though narrower bandwidth results were noted for the DFB laser phase modulator concept.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Elizabeth Twyford Kunkee, Peter M. Livingston, and Steve Holm "Quantum dots: a new approach to low Vπ optical modulators", Proc. SPIE 4987, Integrated Optics: Devices, Materials, and Technologies VII, (19 June 2003); https://doi.org/10.1117/12.478330
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KEYWORDS
Modulators

Phase shifts

Quantum dots

Modulation

Refractive index

Excitons

Absorption

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