Stable Dissipative Solitons in Semiconductor Optical Amplifiers

We have observed for the first time stable spatial solitons in semiconductor optical amplifiers. Soliton destabilization due to the growth of background noise was suppressed by using patterned electrodes on the device. Numerical simulations fit very well with the experiment results. We show that it is possible to excite these solitons with about 60 mW input power.

Figure 1

Plot of peak field level ( $\sqrt{\mathrm{m}\mathrm{W}/\mu \mathrm{m}}$) of soliton solutions versus small signal gain $\delta G$. The dashed line shows the unstable solutions, and the dark line shows the stable solitons. Current values ($x$ axis-top scale) are calculated assuming $300\mathrm{\mu }\mathrm{m}$ width contact patterns on a 1 cm long device. (Current $I=\pi qd{N}_{\mathrm{t}\mathrm{r}}{A}_{\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{t}\mathrm{a}\mathrm{c}\mathrm{t}}/\eta$, where $A_{\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{t}\mathrm{a}\mathrm{c}\mathrm{t}}=300\mu \mathrm{m}\times 1\mathrm{c}\mathrm{m}\times 0.5$). The inset shows a sample device with propagation direction along the arrow.

Figure 2

(Top) Input beam profile at $\lambda =965\mathrm{n}\mathrm{m}$, Gaussian fitted $\mathrm{F}\mathrm{W}\mathrm{H}\mathrm{M}=16.5\mathrm{\mu }\mathrm{m}$. (Middle) Diffracted beam ($62.5\mathrm{\mu }\mathrm{m}$ FWHM) at the output facet. (Bottom) Output beam profile at $\lambda =950\mathrm{n}\mathrm{m}$, and $4A$ current injection.

Figure 3

(a) Images from output facet when the measured input at the focus of the microscope objective is $160\mathrm{m}\mathrm{W}$ and $16.5\mathrm{m}\mathrm{m}$ FWHM. Note that losses due to Fresnel reflection and mismatch between the Gaussian input beam and the waveguide mode reduce the power coupled into the waveguide. (b) Numerical simulation of the output profile with a 55 mW, 17.5 mm FWHM Gaussian assumed just inside the input facet of the waveguide.

Figure 4

(a) Images from the output facet with $4A$ pumping. (b) Numerical simulation of solitons at $4A$ pumping when the input intensity at the front facet is increased (50% coupling is assumed).

Figure 5

Output beam waist versus the waist of a Gaussian input beam with 160 mW input power at front facet, and $4A$ current injection.