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- Cardinali, G., et al.
(författare)
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Low-Threshold AlGaN-based UVB VCSELs enabled by post-growth cavity detuning
- 2022
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 121:10
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Tidskriftsartikel (refereegranskat)abstract
- The performance of vertical-cavity surface-emitting lasers (VCSELs) is strongly dependent on the spectral detuning between the gain peak and the resonance wavelength. Here, we use angle-resolved photoluminescence spectroscopy to investigate the emission properties of AlGaN-based VCSELs emitting in the ultraviolet-B spectral range with different detuning between the photoluminescence peak of the quantum-wells and the resonance wavelength. Accurate setting of the cavity length, and thereby the resonance wavelength, is accomplished by using doping-selective electrochemical etching of AlGaN sacrificial layers for substrate removal combined with deposition of dielectric spacer layers. By matching the resonance wavelength to the quantum-wells photoluminescence peak, a threshold power density of 0.4 MW/cm2 was achieved, and this was possible only for smooth etched surfaces with a root mean square roughness below 2 nm. These results demonstrate the importance of accurate cavity length control and surface smoothness to achieve low-Threshold AlGaN-based ultraviolet VCSELs.
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| 4. |
- Haglund, Åsa, 1976, et al.
(författare)
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Are blue and ultraviolet VCSELs a reality or just a dream?
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Blue-emitting vertical-cavity surface-emitting lasers (VCSELs) with high optical output powers and decent threshold current densities have recently been demonstrated, but the power efficiency is still below 10%. We will give an overview of the challenges to realize high-performing devices and summarize state-of-the-art results, including our schemes for optically guided devices that are used in the best blue VCSELs today. In addition, we will present our method to simultaneously achieve high-reflectivity mirrors and good control over the cavity length for ultraviolet VCSELs. This has resulted in, to the best of our knowledge, the shortest VCSEL emission wavelength around 310 nm.
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| 8. |
- Haglund, Åsa, 1976, et al.
(författare)
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Out of the blue: UV VCSELs
- 2022
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - 0277-786X .- 1996-756X. ; PC12001
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Konferensbidrag (refereegranskat)abstract
- In recent years, there has been tremendous improvement in the performance of blue-emitting vertical-cavity surface-emitting lasers (VCSELs) and they are now on the cusp of commercialization. We will summarize state-of-the-art results and outline the main challenges in extending the emission wavelength into the ultraviolet (UV). Our method to simultaneously achieve high-reflectivity mirrors and good cavity length control by selective electrochemical etching has been essential to demonstrate the world’s first UV-B VCSEL. The use of dielectric mirrors, where one material has a negative thermo-optical coefficient, counteracts the inherent red-shift of the resonance wavelength, enabling a temperature-stable emission.
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| 9. |
- Haglund, Åsa, 1976, et al.
(författare)
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Recent progress for blue VCSELs and challenges to move to UV
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We will summarize state-of-the-art results in III-nitride-based vertical-cavity surface-emitting lasers (VCSELs) and the main challenges in going from blue to ultraviolet-emitting devices. In particular we will highlight how to reduce threshold current densities by using optically guided cavities and our method to simultaneously achieve high-reflectivity mirrors and good control over the cavity length for AlGaN-based ultraviolet VCSELs. The latter has resulted in the shortest emission wavelength from a VCSEL at around 310 nm. This claim of lasing is supported by a nonlinear increase in output power versus pump power and a simultaneous beam width and spectral narrowing around threshold.
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| 10. |
- Haglund, Åsa, 1976, et al.
(författare)
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The quest for ultraviolet vertical-cavity surface-emitting lasers
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023.
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Konferensbidrag (refereegranskat)abstract
- We daily rely upon vertical-cavity surface-emitting lasers (VCSELs) for facial recognition and data communication. These lasers are now experiencing exponential growth and serves in other applications as well such as oxygen monitoring in combustion processes and in anesthetized patients in hospitals and as a source of heating in industry in the form of a large-sized array. The large interest for this laser class is linked to its beneficial qualities such as low threshold current, circular-symmetric low-divergent output beam, high efficiency, compactness, and low fabrication cost due to on-wafer testing. Due to these advantages, there is a strong push to realize VCSELs in other wavelength regimes, beyond the commercially available infrared and red. This would open completely new markets such as flood lights, projectors, sterilization, and medical diagnosis and treatment.
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