Polarization switching and dynamics induced by optical injection in VCSELs

Abstract

Brussels (Belgium).The vertical-cavity surface-emitting laser (VCSEL) has attracted much attention due to its numerous advantages with respect to the conventional edge-emitting lasers. The VCSEL generally emits a linear polarization but its direction is not fixed a priori since polarization switching may occur as the operating conditions, i.e. the injection current or the temperature, are modified [1]. The optical injection from an external source of light may help to control or stabilize the VCSEL polarization and its study is interesting both from the point of view of dynamical instabilities and for applications in high density optical storage and optical signal processing [2].We report on an experimental and theoretical study of the polarization dynamics of a VCSEL submitted to optical injection. In our configuration, the linearly polarized injected light is orthogonal to the light emitted by the free running VCSEL [2]. The optical injection leads to a bistable polarization switching with or without injection locking, the switching power being strongly dependent on the frequency detuning (Fig. 1). For large positive detunings, we observe the locking of the first order transverse mode to the master laser and the suppression of the fundamental transverse mode. The polarization switching induced by optical injection may be furthermore accompanied by a mode hopping regime, i.e. a random hopping between the two linearly polarized modes. The statistical properties of the residence time are influenced by the optical injection strength and frequency detuning. On the other hand, the optical injection may stabilize an otherwise mode hopping VCSEL. Our experiment unveils a rich nonlinear polarization dynamics, which we map in detail in the plane of the injection parameters (injection strength, frequency detuning). Several different time-periodic dynamics are observed as a result of multiwave mixing or Hopf bifurcation. These timeperiodic instabilities may further bifurcate to a period doubling route to chaos, as shown in Fig. 2: an increase of the injected power leads first to a polarization switching with injection locking (b). The stationary state then undergoes a

Analysis of nonlinear dynamics and spin-flip parameters on elliptically polarized injection-locked VCSELs

“…In addition regions of nearly degenerate four-wave mixing, limit cycle, period doubling and chaotic behavior have been reported [12][13][14] and it has been shown that optical injection can stabilize the polarization of a VCSEL operating in regimes of pulsation [13] or mode hopping [14]. A number of theoretical accounts of polarized optical injection in VCSELs has appeared, including models that take account of electron spin as described by the SFM approach [15][16][17] and treatments that focus on spatial overlap of the optical fields and the carrier distributions [18][19].…”

“…The fundamental transverse mode of a VCSEL can possess two orthogonal polarizations with corresponding effective refractive indices (propagation constants) whose difference in magnitudes can be defined by a birefringence rate. PS between the two linearly polarized (LP) modes can be achieved either by changing the pumping current (see [20] and references therein) or introducing polarized optical injection [10,14], both of which can be described by the spin-flip model (SFM) [15,16].Several groups have started their experimental and theoretical research in optical injection in VCSELs by taking account of the SFM; mostly their work concerned polarization switching by inducing an optical injection. Hence, we focused our research on optical injection nonlinear dynamics by taking account of the SFM and different polarization behavior in VCSELs.…”

Polarization Instabilities in Vertical-Cavity Surface-Emitting Lasers

“…Polarization mode hopping features demonstrated for SL based VCSEL are similar to QW VCSELs in case of switching between the two orthogonal modes [8][9][10][11][12], but in contrast there is no abrupt polarization switching point -power of LP1 mode gradually decreases after passing a fixed current value. In polarization mode hopping dynamics gradual LP1 mode suppression is observed for 9.8-11 mA current region.…”

“…The research results of the dynamics of polarization switching for VCSELs based on quantum wells (QWs) for solitary VCSELs were previously analyzed in Refs. [8][9][10][11]. In Ref.…”