Optical injection locking of polarization modes and spatial modes in single-aperture VCSELs and VCSEL arrays emitting at 1.3 mu m

We report the injection locking of specific spatial modes and polarization modes of 1.3 mu m wavelength vertical surface emitting lasers (VCSELs) in single-aperture devices and phase-coupled arrays. The optical injection is realized using a master laser (ML) VCSEL, the beam of which is directed onto the output facet of the slave laser (SL) VCSEL or VCSEL array. We measured the emission spectra of the SL as the ML operating conditions (frequency, power) were varied systematically, and present the results on two-dimensional stability maps of power versus detuning of the ML from the injected modes. In single-aperture devices, the high degree of circular symmetry allows the support of two modes with orthogonal polarizations with similar to 75 GHz frequency difference. With optical injection, we could induce a polarization mode switching and decrease the power of the free running mode by 25 dB. Model calculations confirm injection locking and specify the stability region. In a 1x2 VCSEL array defined by tunnel junction patterning and biased below threshold, we injection locked the fundamental mode (1x2 mode) and a "broad area" mode (1x3 mode). The spatial overlap between the ML spot and the array mode is shown to be a key factor in injection locking. Locking of the non-lasing 1x3 mode results in suppressed output power of the free running 1x2 mode. These studies are useful for understanding the mode structure of these VCSELs and suggesting ways for their discrimination.