Design and modeling of a transistor vertical-cavity surface-emitting laser

A multiple quantum well (MQW) transistor vertical-cavity surface-emitting laser (T-VCSEL) is designed and numerically modeled. The important physical models and parameters are discussed and validated by modeling a conventional VCSEL and comparing the results with the experiment. The quantum capture/escape process is simulated using the quantum-trap model and shows a significant effect on the electrical output of the T-VCSEL. The parameters extracted from the numerical simulation are imported into the analytic modeling to predict the frequency response and simulate the large-signal modulation up to 40 Gbps

Development of high speed vertical cavity surface-emitting semiconductor diode laser and transistor laser

High speed semiconductor lasers are used in optical transceivers for short-reach data links. With fast-growing data capacity and traffic in the data centers around the globe, faster optical transceivers are demanded. A microcavity vertical cavity surface-emitting laser (VCSEL) is able to show a high modulation bandwidth as well as single-mode operation; however, because of the small oxide aperture (< 3 µm), a microcavity VCSEL shows high resistance and low optical power. An 850 nm oxide-confined VCSEL with an aperture ~4 µm is able to show error-free transmission at 40 Gb/s. With an advanced DBR design for parasitic reduction as well as better thermal conduction and a short 0.5-λ cavity with five quantum wells, an 850 nm VCSEL is able to demonstrate 57 Gb/s error-free transmission at 25 °C and 50 Gb/s error-free transmission at 85 °C. The dynamic carrier profile in the base of a transistor laser makes it possible to have a shorter carrier lifetime than in a diode laser. The first oxide-confined vertical cavity transistor laser (VCTL) is realized with a trench oxidation process and a lateral-feeding base metal design. To further reduce the excessive emitter series resistance, a VCTL with AlGaAs and dielectric distributed Bragg reflector (DBR) is fabricated. Because of the mismatch between the cavity design and the quantum well emission, the VCTL is only able to show stimulated emission at low temperatures

All epitaxial mode and current confined semiconductor laser using selective fermi level pinning

textThis dissertation presents a new lithographically defined approach to form self-aligned mode- and current-confined all-epitaxial GaAs-based VCSELs and quantum dot lasers. The mode confinement mechanism by intracavity phase shifting mesa is verified by a specially designed mode confined VCSEL, which shows the lasing peaks only on the phase shifting mesa with relatively low threshold current density. The current-confining mechanism, which is self aligned with mode confining phase shifting mesa using selective Fermi-level pinning is verified with the test structure with the same active layers in the cavity by substantially increasing the turn on voltage of the region outside mesa. The mode- and current-confined VCSEL also shows improved slope efficiency and lasing spectrum which indicate the only lasing on the mesa region throughout the entire operation range. All-epitaxial, fully planarized mode- and current-confined VCSELs, which have only single phase shifting mesa and surrounding current blocking regions are successfully demonstrated with considerably improved efficiency and threshold current density. As an important application of this technology, all- epitaxial index- and current-confined quantum dot laser is demonstrated. The performances of quantum dot laser shows ground state lasing and stable operation up to high input current of 1.5 A. Extracted waveguide loss indicates additional loss is coming from the current blocking hetero-interfaces which can be reduced by optimization of regrowth condition.Electrical and Computer Engineerin

Long Wavelength VCSELs and VCSEL-Based Processing of Microwave Signals

We address the challenge of decreasing the size, cost and power consumption for practical applications of next generation microwave photonics systems by using long-wavelength vertical cavity surface emitting lasers. Several demonstrations of new concepts of microwave photonics devices are presented and discussed

Microwave characterization of vertical cavity surface emitting diode laser and transistor laser

Semiconductor lasers are widely deployed in optical transceivers for optical fiber based short-reach (< 100m) data links. With increasingly growing data traffic worldwide in data centers, developments of faster optical transceivers, hence high-speed semiconductor lasers, are highly demanded. The vertical cavity surface-emitting laser (VCSEL) is the most commercially popular choice. With high reflectivity DBR mirrors and oxide-confinement for emission mode control and leakage current reduction, VCSELs are able to achieve a low laser threshold and high modulation bandwidth. Currently in published research results, the highest data transmission rate demonstrated for an 850 nm VCSEL is 57 Gb/s error-free at 25 °C and 50 Gb/s error-free at 85 °C. Nevertheless, the bandwidth and data transmission performance of diode lasers, such as VCSELs, are fundamentally limited by the slow spontaneous recombination lifetime. Therefore, a new kind of semiconductor laser, the transistor laser (TL), is proposed to break the bandwidth bottleneck as the dynamic carrier transport in the base of a TL drastically reduces the spontaneous recombination lifetime. Ultimately to reach low threshold and high energy per bit efficiency, the first oxide-confined vertical cavity transistor laser (VCTL) is realized with a trench oxidation process and a lateral-feeding base metal design. To further reduce the excessive emitter series resistance, a VCTL with partially etched mesa is developed and fabricated. The tunneling modulation aspect and possible application of the TL is also explored in this dissertation

1300nm optically pumped quantum dot spin vertical external-cavity surface-emitting laser

We report a room temperature optically pumped Quantum Dot-based Spin-Vertical-External-Cavity Surface-Emitting laser (QD Spin-VECSEL) operating at the telecom wavelength of 1.3μm. The active medium was composed of 5 × 3 QD layers; each threefold group was positioned at an antinode of the standing wave of the optical field. Circularly polarized lasing in the QD-VECSEL under Continuous-Wave optical pumping has been realized with a threshold pump power of 11mW. We further demonstrate at room temperature control of the QD-VECSEL output polarization ellipticity via the pump polarization

Sandia`s photonic program and its changing national role

Photonics activities at Sandia National Laboratories are founded on an extensive materials research program. In 1988, the Compound Semiconductor Research Laboratory (CSRL) was established at Sandia to bring together device and materials research and development, in support of Sandia`s role in weapons technologies. Recently, industrial competitiveness has been added as a major mission for the national laboratories. As a result, present photonics programs are not only directed towards internal applications-driven projects, but are increasingly tied to the Department Of Energy`s (DOE`s) Technology Transfer Initiatives (TTIs), Cooperative Research and Development Agreements (CRADAs), and participation in partnerships and consortia. This evolution yields a full range of photonics programs, ranging from materials synthesis and device fabrication to packaging, test, and subsystem development. This paper presents an overview of Sandia`s photonics-program directions, using three applications as examples

Fabrication Techniques for III-V Micro-Opto-Electro-Mechanical Systems

This thesis studies selective etching techniques for the development of AlxGa1-xAs micro-opto-electro-mechanical systems (MOEMS). New MEMS technology based on materials such as AlxGa1-xAs enables the development of micro-systems with embedded active micro-optical devices. Tunable micro-lasers and optical switching based on MOEMS technology will improve future wavelength division multiplexing (WDM) systems. WDM vastly increases the speed of military communications and sensor data processing. From my designs, structures are prepared by molecular beam epitaxy. I design a mask set for studies of crystal plane selectivity. I perform a series of experiments on the selective removal of GaAs and AlAs. I convert AlAs and Al0.98Ga0.02As layers within the test structures to AlOx and Al0.98Ga0.02Ox and perform selective etching experiments on these sacrificial oxide layers. The etchants and materials studied showed high selectivity for removal of all materials studied. Results suggest that any of these material layers are useful as sacrificial layers for general MOEMS technology. I design, fabricate, and characterize prototype III-V MOEMS. Using AlOx sacrificial layers, I investigate a new technique for transplanting microcavity light-emitting devices. I successfully transplant arrays of light-emitting diodes. Finally, I discuss ideas on how this work forms the basis for nano-electro-mechanical systems (NEMS) fabrication in III-V materials