Abstract

This paper describes a combination of photonic annealing and compression rolling to improve the conductive properties of printed binder‐based graphene inks. High‐density light pulses result in temperatures up to 500 °C that along with a decrease of resistivity lead to layer expansion. The structural integrity of the printed layers is restored using compression rolling resulting in smooth, dense, and highly conductive graphene films. The layers exhibit a sheet resistance of less than 1.4 Ω □−1 normalized to 25 µm thickness. The proposed approach can potentially be used in a roll‐to‐roll manner with common substrates, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and paper, paving thereby the road toward high‐volume graphene‐printed electronics.

The polarization properties of semiconductor vertical-cavity lasers ͑VCSELs͒ are generally described with a model introduced by San Miguel, Feng, and Moloney ͑SFM͒ in Phys. Rev. A 52, 1728 ͑1995͒. We have analyzed this SFM model from an experimentalist's point of view, using the idea that under certain conditions, which are satisfied by most practical VCSELs, the complicated spin dynamics can be adiabatically eliminated, leading to a managable analytical description. We hereby obtain new physical insight and intuitive pictures. One of the key results is the prediction that, via the spin dynamics, the presence of a strong lasing mode with a certain polarization will effectively lead to a broadening and frequency shift of the weak nonlasing mode with orthogonal polarization. This result gives a simple physical explanation for a polarization switch predicted by the model, and leads to further predictions that can be experimentally verified. The analysis also shows how the relaxation oscillations are related to the polarization dynamics and how they might be of crucial importance to experimentally determine the various parameters in the SFM model. We then discuss how the spin elimination reduces the SFM model to existing models for the polarization dynamics of class A ͑gas͒ lasers, with intuitive pictures of the polarization evolution on the Poincaré sphere. Finally we will show how, within the context of adiabatic elimination, the cubic crystalline symmetry plays a special role in possible generalizations of the SFM model. ͓S1050-2947͑98͒00703-3͔PACS number͑s͒: 42.55.Ϫf

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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.

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