Aqiang Guo

Fixing multiple waveguides induced by photorefractive solitons: directional couplers and beam splitters

We show how to transform multiple real-time photorefractive solitons into permanent two-dimensional single-mode waveguides impressed into the crystalline lattice of the host material. We experimentally demonstrate two specific configurations of such fixed multiple waveguides: directional couplers and multiple beam splitters.

InGaAs Quantum Well Grown on High-Index Surfaces for Superluminescent Diode Applications

The morphological and optical properties of In0.2Ga0.8As/GaAs quantum wells grown on various substrates are investigated for possible application to superluminescent diodes. The In0.2Ga0.8As/GaAs quantum wells are grown by molecular beam epitaxy on GaAs (100), (210), (311), and (731) substrates. A broad photoluminescence emission peak (~950 nm) with a full width at half maximum (FWHM) of 48 nm is obtained from the sample grown on (210) substrate at room temperature, which is over four times wider than the quantum well simultaneously grown on (100) substrate. On the other hand, a very narrow photoluminescence spectrum is observed from the sample grown on (311) with FWHM = 7.8 nm. The results presented in this article demonstrate the potential of high-index GaAs substrates for superluminescent diode applications.

Electrically switched photoinduced waveguide in unpoled strontium barium niobate

The unpoled photorefractive strontium barium niobate crystal exhibiting quadratic electro-optic properties is characterized. It is used to form one-dimensional and two-dimensional bright photorefractive spatial solitons for either positive or negative low applied electric field. Solitons induce long-lived index changes in the medium which forms waveguides that can be tuned using an external voltage.

Fixing solitonic y junctions in photorefractive strontium-barium-niobate

Two-dimensional solitonic orbital waveguides as y junctions were formed in a strontium barium niobate crystal. The waveguides are 10–20 μm in diameter and propagate unpolarized light.

The photorefractive soliton as an electro-optic modulator

Summary form only given. We discuss how to fabricate an electro-optic modulator in SBN using a permanent two-dimensional single-mode waveguide impressed into a crystalline lattice by a real-time photorefractive soliton. After fixing the waveguide, we investigate the effect of the induced waveguide on the soliton polarization by using an 840 nm probe laser beam. An ordinary-polarized probe beam is launched to the SBN crystal. At the output side a polarizer at the crossing position is set so that the output beam is almost completely blocked without applying an external voltage. This configuration serves as the basis of the electro-optic amplitude modulation of light.