RESUMO
It is shown theoretically that optical bistability will exist in a material whose optical absorption is more than linearly proportional to the degree to which the material is excited. No cavity or external feedback is required. The underlying principle of this bistability appears to be a generalization of several previous independent discussions of mirrorless bistabilities in specific physical systems. This bistability and associated differential gain are demonstrated experimentally using a thermal nonlinearity in a GaAs/GaAlAs multiple-quantum-well semiconductor. Theory and experiment show good agreement.
RESUMO
We report results of cw degenerate four-wave mixing experiments on room-temperature GaAs-GaAlAs multiple quantum-well material using a commercial semiconductor diode laser as the sole light source. With cw powers of ~3 mW and intensities of ~13 W/cm(2), we observe diffraction efficiencies of ~10(-4), corresponding to an effective nonlinear coefficient of chi(3)~6 x 10(-2) esu.
RESUMO
By using a GaAs/GaAIAs multiple-quantum-well sample as a saturable absorber in an external resonator, we have passively mode locked a GaAs laser to obtain pulses as short as 1.6 psec, the shortest pulses ever observed to our knowledge from a mode-locked diode laser in a regulator pulse train.
RESUMO
We demonstrate the potential for all-optical processing of data transmitted over single-mode fibers using a bistable optical device (BOD). A stream of clock/bias pulses transmitted over a 1-km-long single-mode fiber (SMF) is processed by a pseudorandom data sequence of picosecond pulses transmitted over another 1-km SMF with the help of an optical bistable device. The processed signal from the BOD is transmitted over another kilometer of SMF and detected. The bistable device is an ~3-microm-thick molecular-beam epitaxially grown multiple-quantum-well structure of GaAs and GaAlAs. The clock pulses (at wavelength lambda = 870.0 nm) are just below the threshold for switching on the device, and the switching is accomplished by a pseudorandom data sequence of picosecond pulses (at lambda = 835.0 nm). The pulse width of the data transposed onto the clock stream by the BOD can be controlled by varying the phase of the switching data with respect to the clock, which may be of importance in interle aving data for time-division multiplexing. The experiment also demonstrates the potential of a BOD's capability of switching information from one wavelength to another. With optimized devices regeneration should be possible with reasonable gain.
RESUMO
We demonstrate an optical-level shifter and a modulator whose transmission varies linearly with drive current, both based on a new, negative-feedback mode of operation of the recently discovered quantum-well self-electro-optic effect device. The system is compatible with both laser diodes and low-power semiconductor electronics and is applicable in both analog and digital optical processing. An extension of the system gives inverted, linear modulation of a coherent beam by an incoherent light source.