Optical modulators using semiconductor nano-structures: Difference between revisions

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A dc magnetic field Hdc is applied perpendicular to the light propagation direction to produce a single ___domain, transverse directed 4~Ms. The rf modulation field Hrf, applied by means of a coil along the light propagation direction, wobbles 4~Ms through an angle of @ and produces a time varying magnetization component in the longitudinal direction. This component then produces an ac variation in the plane of polarization via the longitudinal Faraday effect. Conversion to amplitude modulation is accomplished by the indicated analyzer.

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Micrometre-scale silicon electro-optic modulator<ref>Nature 435, 325-327 (19 May 2005)</ref>

This device was fabricated a shape of the p-i-n ring resonator on a silicon-on-insulator substrate with a 3-mm-thick buried oxide layer. Both the waveguide coupling to the ring and that forming the ring have awidth of 450 nm and a height of 250 nm. The diameter of the ring is 12 mm, and the spacing between the ring and the straight waveguide is 200 nm.

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Acoustic solitons in semiconductor nanostructures<ref>Journal of Physics: Conference Series 92 (PHONONS 2007)</ref>

Acoustic solitons strongly influence the electron states in a semiconductor nanostructure. The amplitude of soliton pulses is so high that the electron states in a quantum well make temporal excursions in energy up to 10 meV. The subpicosecond duration of the solitons is less than the coherence time of the optical transition between the electron states and a frequency modulation of emitted light during the coherence time (chirping effect) is observed. This system is for an ultrafast control of electron states in semiconductor nanostructures.

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A schematic diagram of the MO modulator is shown in Fig. 1. The MO active layer is a 4.5 μm (Y0.6Bi0.4LuPr)3(FeGa)5O12 film that has been grown on a 450-μm thick (1 1 1)-oriented gadolinium gallium garnet substrate by means of liquid-phase epitaxy. The MO film has an in-plane magnetization with a saturation value (μ0Ms) of 9 mT and a specific Faraday rotation of 5400°/cm at 800 nm. A linearly polarized optical beam from an 800 nm laser diode is focused and edge-coupled to the thin film waveguide. At this wavelength the optical absorption of the MO film is 400 cm−1 and, therefore, the length of the device is designed to be 60 μm. On the surface of the Bi-YIG film, a 50-Ω terminated microstrip transmission line is patterned and used to carry the high-speed electrical signals, I(t). The current transient creates a time-varying magnetic field that has a component, bz(t), along the direction of optical propagation. This component (underneath the microstrip line) acts to tip the magnetization, M, along the propagation direction of the optical beam. A static in-plane magnetic field, by, is applied perpendicular to the light propagation direction, thus ensuring the return of M to its initial orientation after the passage of the current transient. Depending on the component of the magnetization along the z-direction, Mz, the optical beam experiences a rotation of its polarization due to the Faraday effect. The polarization modulation is converted into an intensity modulation via a polarization analyzer, which is detected by a high-speed photodiode.

'''Other semiconductor nanostructures of optical modulator'''

MODULATION OF THz RADIATION BY SEMICONDUCTOR NANOSTRUCTURES<ref>MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 35, No. 5, December 5 2002</ref>

As a result of increased demand for bandwidth, wireless short-range communication systems are expected to extend into the THz frequency range. Therefore the fundamental interactions between THz radiation and semiconductors are receiving increasing attention. This new quantum structure is based on the well-established technology for producing high electron mobility transistors where an electron gas is confined at a GaAs/AlxGa1 xAs interface. The electron density at the hetero-interface can be controlled by the application of an external gate voltage, which in turn will alter the transmission/reflection characteristics of the device to an incident THz beam.