The optical injection-locking technique has been demonstrated to enhance the microwave performance of fiber-optic links based on vertical-cavity surface-emitting lasers (VCSELs). We report recent advances of a comprehensive study on VCSELs under ultrahigh injection-locking conditions. The performance improvements include /spl sim/20-dB increase of both spur-free dynamic range and RF link gain, a factor of 5-10 increase in resonance frequency, as well as /spl sim/20-dB reduction in laser noise.

/pdf/microwave-performance-of-optically-injection-locked-vcsels-51pmfy5d7i.pdf

Microwave performance of optically injection-locked VCSELs

In this paper, the output characteristics of an oxide-confined AlGaAs-As quantum well vertical-cavity surface-emitting laser (VCSEL) under orthogonal optical injection are mapped as a function of the strength of the optical injection and the detuning between the injection frequency and the free-running frequency of the solitary laser, for a very large range of frequency detuning (from -82 to 89 GHz). The injection light is polarized orthogonally with respect to the solitary VCSEL output light. As the injection strength increases the VCSEL switches to the master laser polarization. Polarization switching is accompanied by a rich nonlinear dynamics, including limit cycle, wave mixing, subharmonic resonance and period doubling route to chaos. Polarization switching is found with but also without injection locking. Injection locking occurs with the slave fundamental transverse mode or, for large positive detunings, with the first-order transverse mode.

Mapping of the dynamics induced by orthogonal optical injection in vertical-cavity surface-emitting lasers

In this paper, we report on theoretical and experimental investigation on polarization and transverse mode behavior of vertical-cavity surface-emitting lasers (VCSELs) under orthogonal optical injection as a function of the injection strength and of the detuning between the injection frequency and the free-running frequency of the solitary laser. As the injection strength increases the VCSEL switches to the master laser polarization. We find that the injection power necessary to obtain such polarization switching is minimum at two different values of the frequency detuning: the first one corresponds to the frequency splitting between the two linearly polarized fundamental transverse modes, and the second one appears at a larger positive frequency detuning, close to the frequency difference between the first-order and the fundamental transverse modes of the solitary VCSEL. We show theoretically that both the depth and the frequency corresponding to the second minimum increase when the relative losses between the two transverse modes decrease. Bistability of the polarization switching is obtained for the whole frequency detuning range. Such a bistability is found for the fundamental mode only or for both transverse modes, depending on the value of the detuning. The theoretical and experimental optical spectra are in good agreement showing that the first-order transverse mode appears locked to the external injection

/pdf/transverse-mode-switching-and-locking-in-vertical-cavity-1gj4r0knot.pdf

Transverse Mode Switching and Locking in Vertical-Cavity Surface-Emitting Lasers Subject to Orthogonal Optical Injection

We investigate both analytically and numerically the switching, locking and stability properties of a bistable semiconductor ring laser subject to an external optical injection. Minimum optical power required for the injected signal at certain frequency to switch the lasing direction of a bistable semiconductor ring laser from its initially lasing direction to initially nonlasing direction is determined. Locking to the injected signal and stability of the switched laser are investigated to give an area of reliable switching operation. Correspondingly, numerical simulation has been carried out to find successful switching and stable locking region with variable injection power and frequency, and is compared with the analytical results. The region obtained from simulation coincides well with the intersection of switching, locking and stable locking regions. The relation between switching speed and parameters of injected source is also studied numerically.

Bistability and Switching Properties of Semiconductor Ring Lasers With External Optical Injection

We investigate theoretically the static and dynamic characteristics of an optically injected vertical-cavity surface-emitting laser (VCSEL), under both single- and two-mode operation. Our model includes the spatial dependence of both the carrier density and the optical field. We find that within the locking range, a two-mode VCSEL can be forced to operate in a single transverse mode under appropriate conditions. Outside the locking range, the VCSEL shows a rich variety of nonlinear dynamics. Results show that the static and dynamic behaviours depend strongly on the frequency detuning, the injection power and the strength of the intermodal coupling induced by spatial hole burning. In particular, strong intermodal coupling can reduce the sensitivity of the VCSEL toward external injection, in terms of both static (locking) and dynamic (nonlocking) behaviours.

http://iopscience.iop.org/article/10.1088/1355-5111/9/5/007/pdf

Effects of transverse-mode competition on the injection dynamics of vertical-cavity surface-emitting lasers

Stable phase locking of an electrically pumped vertical cavity surface-emitting semiconductor laser (VCSEL) was demonstrated experimentally by injecting light from an edge-emitting master laser into the slave laser VCSEL cavity within a large detuning range (/spl sim/80 GHz). By varying the injected power and frequency detuning, a variety of interesting nonlinear behavior was observed. A theoretical model based on two-field rate equations is presented and compared with experiment, showing good agreement.

M.W. Wright

Papers

Injection locking dynamics of vertical cavity semiconductor lasers under conventional and phase conjugate injection