R.F.M. Hendriks

Electro-optic birefringence in semiconductor vertical-cavity lasers

Birefringence induced by the electro-optic effect is demonstrated in vertical-cavity surface-emitting lasers (VCSEL). This is done by comparing two types of optically pumped VCSELs: VCSELs with standard pin-doping and VCSELs with symmetrical pip-doping. The observed birefringence in these VCSELs differs by an order of magnitude, a difference that we ascribe to the presence and absence, respectively, of electro-optic birefringence.

Memory effect for polarization of pump light in optically pumped vertical-cavity semiconductor lasers

We report that the polarization of the emission of an optically pumped vertical-cavity surface-emitting laser (VCSEL) is sensitive to the polarization state of the pump light. By measuring this memory effect for circularly polarized pump light, we determine the normalized relaxation rate of the carrier spin, /spl Gamma//sub s/, which is a vital parameter in current theoretical models of VCSEL polarization. We find /spl Gamma//sub s/=300/spl plusmn/150, a value which is significantly larger than previously estimated. We also observe a memory effect for the orientation of linearly polarized pump light. This signals that, apart from the carrier spin, the VCSEL polarization is also determined by the carrier momentum.

Spontaneous emission spectra of optically pumped vertical-cavity surface-emitting lasers

Abstract We study the spontaneous emission spectra of optically pumped vertical-cavity surface-emitting lasers (VCSELs) operating below threshold. By spatial and angular filtering of the spontaneous emission spectra we can relate the observed asymmetrical shape of these spectra to the subthreshold guiding properties of the VCSELs. We find a substantial difference between VCSELs with a thin gain medium, consisting of quantum wells, and VCSELs with a thick gain medium, consisting of bulk GaAs; this difference is explained by analyzing the relative weights of thermal index guiding and carrier-induced index anti-guiding.

Explanation of double-peaked intensity noise spectrum of an external-cavity semiconductor laser

Abstract We give a quantitative explanation for the intriguing double-peaked structure in the intensity noise spectrum of an external-cavity semiconductor laser. We find strong suppression of the intensity noise due to coupling between the subthreshold modes (FM-locking). The measured power dependence of the shift and broadening of the double-peaked structure allows detailed diagnostic of the laser.

Transverse anisotropy and mode structure in VCSELs

Vertical-cavity surface-emitting lasers (VCSELs) are a new type of semiconductor laser with intriguing properties. As the small cavity ensures single longitudinal mode operation, the VCSEL mode structure is fully determined by the transverse spatial profile combined with the polarization behavior. After discussing some general ideas behind mode formation in VCSELs, we present a number of experiments performed to obtain the relevant numbers for practical AlGaAs-GaAs devices. These include measurements of: the (polarization-resolved) light output-versus-current characteristic, far-field patterns, the wavefront curvature inside a VCSEL, a spectral analysis of spontaneous emission below and above threshold, and a study of the influence of an axial magnetic field. This article contains a relatively large number of equations and experimental and literature values to make it more useful for later reference. Of course it is difficult to tell how specific some of these numbers are related to the particular planar VCSELs we have investigated.

Phase coupling of two optically pumped vertical‐cavity surface‐emitting lasers

We have studied the interaction between two optically pumped vertical‐cavity surface‐emitting lasers (VCSELs) on a wafer as a function of their separation d. The VCSELs are strongly coupled for d⩽13 μm, leading to the appearance of higher‐order lateral modes. For d⩾13 μm the VCSELs are weakly coupled, leading to phase locking of the individual emitters.

Birefringence in TEM01 optically-pumped VCSELs

Abstract We study the polarization properties of optically-pumped vertical-cavity semiconductor lasers (VCSELs) pumped with a TEM01 beam and which also oscillate in this mode. When the two-lobed pump pattern is rotated, the birefringence of the laser changes periodically by ± 3.8 GHz accompanied by polarization rotation. We attribute these effects to stress-induced birefringence.

Engineering the polarization-dependent saturation in quantum-well surface-emitting semiconductor lasers

We discuss how the polarization dependence of the saturation in vertical-cavity surface emitting lasers (VCSELs) can be influenced by the design of the quantum-well (QW) gain medium. As an important concept in our discussion, we use carrier reservoirs, i.e., we separate the carrier population into a number of subpopulations. Specifically, we treat VCSELs in which the carriers are separated on the basis of their spin, their momentum, or on the basis of their spatial position. By numerically analyzing the rate equations for one specific case, we show how a properly chosen polarization dependence of the saturation leads to polarization self-modulation.

Optical versus electrical pumping in VCSELs

We present a detailed device characterization of a series of optically pumped VCSELs, emphasizing in particular a comparison with electrically pumped devices. We conclude that fundamental device parameters such as threshold pump power, input-output efficiency and polarization behavior do not depend on the pumping scheme.