Abstract:We report the first room temperature optical spin-injection of a dilute nitride 1300 nm vertical-cavity surface-emitting laser (VCSEL) under continuous-wave optical pumping. We also present a novel experimental protocol for the investigation of optical spin-injection with a fiber setup. The experimental results indicate that the VCSEL polarization can be controlled by the pump polarization, and the measured behavior is in excellent agreement with theoretical predictions using the spin flip model. The ability to control the polarization of a long-wavelength VCSEL at room temperature emitting at the wavelength of 1.3 µm opens up a new exciting research avenue for novel uses in disparate fields of technology ranging from spintronics to optical telecommunication networks. ©2012 Optical Society of America

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Atomic-scale understanding and processing of the oxidation of III-V compound-semiconductor surfaces are essential for developing materials for various devices (e.g., transistors, solar cells, and light emitting diodes). The oxidation-induced defect-rich phases at the interfaces of oxide/III-V junctions significantly affect the electrical performance of devices. In this study, a method to control the GaAs oxidation and interfacial defect density at the prototypical Al2O3/GaAs junction grown via atomic layer deposition (ALD) is demonstrated. Namely, pre-oxidation of GaAs(100) with an In-induced c(8 × 2) surface reconstruction, leading to a crystalline c(4 × 2)-O interface oxide before ALD of Al2O3, decreases band-gap defect density at the Al2O3/GaAs interface. Concomitantly, X-ray photoelectron spectroscopy (XPS) from these Al2O3/GaAs interfaces shows that the high oxidation state of Ga (Ga2O3 type) decreases, and the corresponding In2O3 type phase forms when employing the c(4 × 2)-O interface layer. Detailed synchrotron-radiation XPS of the counterpart c(4 × 2)-O oxide of InAs(100) has been utilized to elucidate the atomic structure of the useful c(4 × 2)-O interface layer and its oxidation process. The spectral analysis reveals that three different oxygen sites, five oxidation-induced group-III atomic sites with core-level shifts between -0.2 eV and +1.0 eV, and hardly any oxygen-induced changes at the As sites form during the oxidation. These results, discussed within the current atomic model of the c(4 × 2)-O interface, provide insight into the atomic structures of oxide/III-V interfaces and a way to control the semiconductor oxidation.

IntroductionSpin-VCSELs can be produced by injecting spin polarized electrons either via suitable electrical contacts or by optical pumping with polarized light, in order to control its output polarization [1]. Such devices in particular promise a number of advantages over conventional VCSELs including improved light and polarization stability, polarization control and a reduced threshold current [2]. It was found that spin-VCSELs can exhibit rich dynamics due to the competition of spinflip processes and birefringence [3][4]. Gahl et al [3] have used the spin flip model (SFM) [5] to study the behaviour of optically-pumped VCSELs. They found that various forms of oscillatory behaviour can be induced by different excitation processes causing self-sustained oscillations in the polarization of the emitted light even for VCSELs subject to CW pumping. Recently, a comprehensive theoretical analysis of optically-pumped spin-VCSELs has been reported by combining the SFM with the largest Lyapunov exponent method to determine the regions of stability and instability in spin-VCSELs [4]. This work also highlighted the importance of the linewidth enhancement factor and birefringence rate when engineering a device for high frequency applications. Damped periodic oscillations with an 850 nm spin-VCSEL under both CW electrical pumping and pulsed optical excitation have also recently been reported by Gerhardt et al. [6]. Here, we present a novel experimental investigation of the dependence of the sustained oscillatory behaviour of a spin-VCSEL on the polarisation of the optical pump. The experiments were performed for the first time to our knowledge with a long-wavelength device, a 1300 nm dilute nitride VCSEL operated at room temperature and under CW optical pumping. With this device, we report the first observation of self-sustained 10 GHz periodic oscillations that can be tuned with the pump polarisation. Theoretical simulations were carried out using the SFM [5] providing excellent agreement with the experimental findings.

We report on a GaInNAs/GaAs semiconductor disk laser frequency-doubled to produce orange-red radiation. The disk laser operates at a fundamental wavelength of 1224 nm and delivers an output power of 2.68 W in the visible region with an optical-to-optical conversion efficiency of 7.4%. The frequency-converted signal could be launched into a singlemode optical fiber with 70-78% coupling efficiency, demonstrating good beam quality for the visible radiation. Using a Fabry-Pérot glass etalon the emission wavelength could be tuned over an 8 nm spectral range.