Using Quantum Dots (QDs) as active region for a semiconductor laser can be preferable for various laser properties. However, the internal strain and the fabrication of an active region membrane can alter the structure properties and, consequently, the laser emission properties as well. In this contribution, we present the emission characteristics of a MECSEL based on InP QDs and emitting in the red spectral range. We discuss the influence of different membrane fabrication methods on the laser emission and the composition of the gain region.
Vertical External Cavity Surface Emitting Laser (VECSEL) and Membrane External Surface Emitting Laser (MECSEL) have demonstrated their superior performance due to the flexibility in cavity design as well as power scalability. The epitaxy of different materials and band gap engineering allows the coverage of a wide spread of emission wavelength.
We present in this contribution strategies for different gain regions for devices from the red to the near-infrared spectral range, fabricated by Metal-Organic Vapor-Phase Epitaxy (MOVPE) and show the optical properties of the different gain chips and the laser performances of produced VECSEL and MECSEL.
While vertical external-cavity surface-emitting lasers (VECSELs) provide several superior laser properties, the heat generated by the pump laser within the active region proves to be a limiting factor for achieving higher output powers.
We present our recent progress in the development of an AlGaInP-VECSEL based on a grating waveguide structure. The heat spreader is placed below the active region membrane while a grating structure is etched into the top layer of the active region. This improves the heat removal from the membrane, while the guided-mode resonances should provide good coupling of the pump and laser field as well as a high reflectivity. The VECSEL cavity is completed with an external mirror, serving also as an output coupler.
Membrane External-Cavity Surface-Emitting Lasers (MECSELs) are a new kind of vertically emitting semiconductor laser with enormous potential and versatility for tailoring the laser parameters. Part of their benefits is related to the fact that they do not need to employ integrated Distributed Bragg Reflectors (DBRs), which are known to hamper the heat transfer and limit wavelength versatility via strain and band-gap engineering constraints. Furthermore, the substrate on which the active region is grown on is removed and the resulting thin active region membrane is sandwiched between transparent Intra Cavity (IC) heat spreaders for improved thermal management. Initial characterization of room temperature operation of a new red emitting AlGaInP-based structure design containing 40 Quantum Wells (QWs) will be presented. Further, the main aspects of the design of active region membranes will be reviewed with respect to double-side pumping possibilities enabled by the absence of a DBR and the substrate. The comparably high cavity losses show future potential of a properly double-side pumped gain structure.
We present a nanoscopic investigation of the carrier transport into individual single InP quantum dots (QDs) of a membrane external-cavity surface-emitting laser structure (MECSEL) by means of highly spatially resolved cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope (STEM-CL). The lateral STEM-CL spectrum linescans across a single InP QD exhibit a characteristic change of excitonic transitions during this linescan. This gives direct access to the QD population by the generated excess carriers and the renormalization of the QD ground state while the electron beam approaches and subsequently recedes the QD position.
This Conference Presentation Generation of ultrashort pulses by saturable absorbers with and without DBR in a red-emitting VECSEL was recorded at Photonics Europe held in Strasbourg France.
For wavelengths deviating from 1µm, a SESAM can be limited by the underlying DBR design. Using substrate-removal, it is possible to isolate the active region and circumvent restrictions due to a DBR.
Only lately, the dynamics of SESAM mode-locked VECSELs, producing different multi-pulse emission, was investigated by several groups and motivated numerical modeling of mode-locking VECSELs.
We present the fabrication, characterization and mode-locking of our red-emitting AlGaInP active regions. This includes a comparison of mode-locking dynamics of DBR-free saturable absorber and SESAM-based mode-locking approaches in the red spectral range and the nonlinear reflectivity of a set of GaInP QW SESAMs.
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