Ultrafast all-optical switching with low saturation energy via intersubband transitions in GaN/AlN quantum-well waveguides (original) (raw)
2007, Optics express
A fiber-optic pump-probe setup is used to demonstrate all-optical switching based on intersubband cross-absorption modulation in GaN/AlN quantum-well waveguides, with record low values of the required control pulse energy. In particular, a signal modulation depth of 10 dB is obtained with control pulse energies as small as 38 pJ. Such low power requirements for this class of materials are mainly ascribed to an optimized design of the waveguide structure. At the same time, the intersubband absorption fully recovers from the control-pulse-induced saturation on a picosecond time scale, so that these nonlinear waveguide devices are suitable for all-optical switching at bit rates of several hundred Gb/s.
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Physica Status Solidi (a), 2008
We report the demonstration of intersubband modulators operating at telecommunication wavelengths at room temperature based on GaN/AlN quantum wells. We first investigate electro-optical modulators making use of electron tunneling in coupled quantum wells. Electro-absorption modulation with opposite sign induced by the electron tunneling between the reservoir and active quantum wells is observed at λ = 1.3–1.6 µm and λ = 2.2 µm. We show that by reducing the mesa size down to 15 × 15 µm2, optical modulation bandwidth as large as 3 GHz can be obtained. We then investigate waveguide intersubband modulators relying on the depletion of the ground electronic state of a 3 quantum well active region. Modulation depths as large as 14 dB in the wavelength range of 1.2–1.6 µm are obtained under –9 V/+7 V voltage swing. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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