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Journal of the Optical Society of America B

Reflective vertical cavity quantum-well saturable absorber as an all-optical nonlinear phase-shifting element

Rajib Pradhan, S. Saha, Prasanta Kumar Datta

Published Nov 5, 2014• 4 citations

Abstract

A scheme of an all-optical nonlinear phase-shifting element is proposed, based on a reflective vertical cavity semiconductor (quantum-well) saturable absorber (R-VCSSA). The nonlinear round-trip phase shift in a low-intensity resonant VCSSA is obtained at an input intensity due to the saturating nonlinearity in index change and optically induced thermal effects. An enhanced large nonlinear positive or negative phase shift incurred in a reflected signal is investigated analytically with the wavelength tuning of the probe signal around the low-intensity resonant wavelength of a Fabry–Perot cavity. The device may be useful in compensating the phase of an input signal, either positive or negative, in long-haul fiber communications. A representative InGaAs/InP quantum-well-based VCSSA is considered to demonstrate the phase shift in the pump–probe configuration. With a device speed of 10 GHz, maximum phase shifts of −0.24 and +0.14 rad at pump power of 19.2 mW are observed for the operations at probe wavelengths of 1555.6 and 1557.8 nm, respectively.

DOI: 10.1364/josab.31.002956

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A scheme of an all-optical nonlinear phase-shifting element is proposed, based on a reflective vertical cavity semiconductor (quantum-well) saturable absorber (R-VCSSA). The nonlinear round-trip phase shift in a low-intensity resonant VCSSA is obtained at an input intensity due to the saturating nonlinearity in index change and optically induced thermal effects. An enhanced large nonlinear positive or negative phase shift incurred in a reflected signal is investigated analytically with the wavelength tuning of the probe signal around the low-intensity resonant wavelength of a Fabry–Perot cavity. The device may be useful in compensating the phase of an input signal, either positive or negative, in long-haul fiber communications. A representative InGaAs/InP quantum-well-based VCSSA is considered to demonstrate the phase shift in the pump–probe configuration. With a device speed of 10 GHz, maximum phase shifts of −0.24 and +0.14 rad at pump power of 19.2 mW are observed for the operations at probe wavelengths of 1555.6 and 1557.8 nm, respectively.

The phase response of a commercial saturable absorber based on semiconductor quantum wells embedded in a resonant cavity is investigated. The nonlinear absorption change is accompanied by a variation of the spectral phase characteristic. Also, a nonlinear change in the refractive index of the material, induced by the modified carrier density, produces a weak shift in the resonant wavelength of the cavity. These effects can be exploited to realize an optically-controllable phase shifter. Simulations based on a nonlinear model are also carried out in order to investigate the effect of the various cavity parameters and phase response of the device under different operating conditions. The results from this characterization and numerical analysis show that such device can have the potential for practical applications in telecom systems, including dynamic dispersion compensation, tunable nonlinear effects compensation, and nonlinear signal processing and all-optical regeneration of phase-modulated optical signals.

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