Vertical-cavity surface-emitting lasers fabricated by vacuumintegrated processing

The authors report on the fabrication of vertical-cavity surface-emitting lasers (VCSELs) using vacuum processing techniques. The upper monolithic distributed Bragg reflector around the laser cavity is dry etched down to the top of the active region, followed by in situ contact deposition on the mesa sidewall, providing a short current path through the p-type mirror. These etched VCSELs exhibit lower series resistance, lower threshold voltage, greater thermal dissipation, and higher maximum output power than conventional planar VCSELs made from the same material     

Bow-tie surface-emitting lasers

We report a new design for surface emitting semiconductor lasers operating at 940 nm, incorporating a double-flare cavity, and distributed Bragg reflector (DBR) mirrors also providing surface emission. This design can take advantage of the modal behavior of the unstable resonator, and has shown very good mode control, with coherent emission from two facets in the same direction. We report preliminary performance results showing very promising characteristics including single-mode diffraction limited operation, and spectral behavior with 42 dB side-mode suppression. This design has exhibited promising results for increasing the current range between the lasing threshold and the filament threshold     

Vertical-cavity surface-emitting lasers with integrated refractivemicrolenses

The fabrication and performance of a vertical cavity surface emitting laser array integrated with microlenses are reported. The lasers emit at 967 nm through the substrate with integral polyimide microlenses. This design reduces beam divergence and provides an integrated device that emits a nearly collimated beam for applications such as optical interconnects     

Mid-IR vertical-cavity surface-emitting lasers

We theoretically investigate the feasibility and potential performance of optically and electrically pumped vertical-cavity surface-emitting lasers (VCSELs) emitting in the mid-IR spectral region. Our model includes spontaneous, stimulated, and nonradiative recombination, numerical dispersion relations and optical matrix elements from a multiband finite-element algorithm, carrier and lattice heating, three-dimensional heat flow, electrical injection, photon propagation, and diffraction. Each modeled structure consists of a distributed Bragg reflector (DBR) semiconductor bottom mirror, a λ, 2λ, or 3λ optical cavity incorporating the type-II active region, and a dielectric top mirror through which the output beam is emitted. The optically pumped VCSEL structure with a 10-μm-diameter spot is predicted to operate up to a heat-sink temperature of 250 K and to be capable of producing >2 mW of CW output power. Furthermore, by collimating the pump beam with a microlens array, gain-guided VCSEL arrays with output powers in the watt range should be attainable. Comparable powers and operating temperatures are predicted for patterned devices with electrical injection through annular contacts. By far the most attractive properties are expected for structures employing a type-II interband cascade active region with electron recycling. The simulation predicts single-element threshold currents of 150 μA at 200 K and 1.1 mA at 300 K and CW output powers of 4.7 and 1.2 mW, respectively     

Submilliamp vertical-cavity surface-emitting lasers with buriedlateral-current confinement

Lateral current confinement of intracavity contacted 0.98 μm vertical cavity surface emitting lasers has been achieved by inserting a 50 nm thick n-type GaAs current blocking layer into the p-doped cladding. Epitaxial regrowth by solid source MBE is used to bury the current confining layer in the cavities. Threshold currents of 0.78 mA, optical output powers of 1 mW and external quantum efficiencies of up to 15% are measured. The lateral current injection via the top p-type cladding leads to low voltages at threshold of 1.78 V     

Vertical-cavity surface-emitting lasers with lateral carrier confinement

A novel method to reduce threshold currents in vertical-cavity surface-emitting lasers (VCSELs) is proposed. By using selective quantum well intermixing, lateral heterobarriers are created that prevent carriers from diffusing away from the optical modes. Our devices show 40% reduction of threshold currents with the implementation of lateral carrier confinement     

Near-infrared vertical-cavity surface-emitting lasers with 3-MHzlinewidth

The linewidth of electrically pumped vertical-cavity surface-emitting lasers optimized for spectroscopic applications in the near-infrared has been examined in detail. Both a high-resolution scanning Fabry-Perot interferometer and a delayed self-homodyne technique were employed for high-resolution linewidth measurement. Record narrow spectral linewidths of 3 MWz were obtained at output powers near 0.8 mW     

Vertical-external-cavity surface-emitting lasers and quantum dot lasers

The use of cavity to manipulate photon emission of quantum dots (QDs) has been opening unprecedented opportunities for realizing quantum functional nanophotonic devices and quantum information devices....     

长波长GaInNAs垂直腔面发射激光器

新出现的直接跃迁GaInNAs与具有高反射率的AlAs／GaAs分布布拉格反射镜相结合构成了GaAs基长波长(1．3—1．6μm)垂直腔面发射激光器(VCSEL)，将成为光纤通信、光互联和光信息处理等的关键元件。本文从材料的选取、外延技术和GaInNAs VCSEL国外和国内的发展状况等方面对长波长GaInNAs VCSEL进行了综合阐述。     

Electrically gain-switched vertical-cavity surface-emitting lasers

The authors report electrical gain-switching of a packaged vertical-cavity surface-emitting laser (VCSEL). Pulse durations as short as 24 ps at repetition rates up to 2 GHz were obtained from a four-quantum-well GaAs/AlGaAs VCSEL, which emits 0.8 mW continuous wave power in a single mode at room temperature and has a current threshold of 5 mA. Simultaneous measurement of the optical spectrum showed an almost transform limited linewidth indicating ultralow chirp. Optical pumping with subpicosecond pulses of the same packaged devices, held at a constant electrical bias, yielded 22 ps pulses, in good agreement with the electrical pumping. Simple calculations show that the pulse duration obtained by gain-switching is limited by the design constraints necessary to operate the VCSEL continuous wave at room temperature with low-threshold current, high-quantum efficiency, and reasonable output power     

Polyimide-planarized vertical-cavity surface-emitting lasers with 17.0-GHz bandwidth

High-speed oxide-confined polyimide-planarized 850-nm vertical-cavity surface-emitting lasers exhibit -3-dB modulation bandwidths up to 17.0 GHz. The devices are fabricated using a reproducible, simple process incorporating polyimide with good adhesion that does not require implantation or semiinsulating substrates to achieve low capacitance.     

Vertical-cavity surface-emitting lasers with monolithically integrated horizontal waveguides

We present the development of novel 980-nm Ga/sub 0.8/In/sub 0.2/As-GaAs vertical-cavity surface-emitting lasers (VCSELs) with an internal waveguide structure. The monolithic integration of a horizontal waveguide in the top distributed Bragg reflector (DBR) creates the potential for achieving VCSEL-based photonic integrated circuits. In this work, an AlGaAs-GaAs-AlGaAs waveguide designed for horizontal propagation of light was monolithically integrated as part of the upper GaAs-AlGaAs DBR of the device. VCSELs with 9-/spl mu/m apertures emitted 3-mW single-mode power with both longitudinal and lateral mode suppression ratio of 40 dB under room-temperature continuous-wave operation.     

High-speed modulation of vertical-cavity surface-emitting lasers

The IM (intensity modulation) and FM (frequency modulation) characteristics of vertical-cavity surface-emitting lasers are studied. The laser has high FM efficiency and broad IM bandwidth (near 8 GHz) at a very low bias (4.5 mA). Five Gb/s pseudorandom direct intensity modulation of this laser with open eyes is demonstrated.<>     

Threshold analysis of vertical-cavity surface-emitting lasers with intracavity contacts

A numerical analysis of vertical-cavity surface-emitting lasers (VCSELs) incorporating intracavity contacts and distributed Bragg reflectors (DBRs) is presented. The model considers polarization dependent reflection at the DBRs, current spreading, and nonuniform carrier density distribution self consistently. Analytic expressions for the current spreading and the corresponding series resistance for VCSELs incorporating intracavity contacts are derived. It is shown that current spreading strongly affects the lateral gain profile, the threshold current density, the transverse mode shape and the transverse mode discrimination through the creation of intracavity optical phase and gain apertures. The series resistance and the depth of the dip in the current density distribution are used as figures-of-merit to provide guidelines for device optimization, as illustrated by means of two examples of long wavelength VCSEL designs.     

Small-dimension power-efficient high-speed vertical-cavity surface-emitting lasers

Small-dimension power-efficient high-speed oxide-confined 980 nm vertical-cavity surface-emitting lasers (VCSELs) with record-high bandwidth/power-dissipation ratio of 12.5 GHz/mW have been demonstrated. The devices show a modulation bandwidth of 15 GHz at a bias current 0.9 mA, corresponding to only 1.2 mW power dissipation     

Dynamic behavior of vertical-cavity surface-emitting lasers

A quasi-three-dimensional dynamic model of index-guided vertical-cavity surface-emitting lasers is developed. Detailed structure of Bragg reflectors and lateral optical confinement are considered into the model. A three-dimensional waveguide problem is reduced to one dimension by using the effective-index method. The dynamic response of optical field is solved by the time-domain algorithm. In addition, the lateral variation of carrier concentration, refractive index, and spontaneous-emission profile are also determined in a self consistent manner. Using this model, the influence of carrier transport and hot carriers on the dynamic behavior of vertical-cavity surface emitting lasers is studied. It is found that these nonlinearities have significant influence on the relaxation-oscillation frequency and modulation bandwidth of the devices     

Rate-equation model for coupled-cavity surface-emitting lasers

We present a detailed theoretical study of a vertical-cavity surface-emitting laser (VCSEL) with two optically coupled, active cavities. The study is based on a rate-equation model written for carriers and photons under steady-state conditions. The model allows one to determine all the relevant parameters-carrier densities, gains, and output powers-starting from two input parameters: the injection currents in each cavity. The system of equations is solved for different operating regimes of the device and the results provided by the model are shown to be in very good qualitative and quantitative agreement with the experimental data.     

Low threshold planarized vertical-cavity surface-emitting lasers

Vertical-cavity surface-emitting lasers fabricated utilizing a self-aligned process to provide planarized contacts are discussed. A single 80-Å In_0.2Ga_0.8As strained quantum well was used in the active region. Emission was at 963 nm. Threshold currents under continuous-wave room temperature operation of 1.1 mA, at 4.0-V bias, were measured for numerous 12-μm×12-μm devices. Corresponding threshold current densities were 800 A/cm² (600 A/cm² for broad area devices). These are the lowest figures yet reported for this type of device. It was found that grading of the mirror had a marked effect on mirror resistance     

Nonlinear dynamics of vertical-cavity surface-emitting lasers

The dependence of the transient response of a vertical-cavity surface-emitting laser (VCSEL) on its aperture size is investigated subject to direct current modulation and external optical feedback. It is shown that lasers with small aperture size suppress higher order bifurcations and chaos even under large-signal modulation and external optical feedback. Furthermore, the noise characteristics of VCSELs under the influence of external optical feedback are studied via the calculation of relative intensity noise. It is found that the level of external optical feedback for the onset of coherence collapse is high for devices with small aperture size. On the other hand, the small-signal response of lasers is also analyzed through the calculation of third-order harmonic distortion. It is shown that harmonic distortion is minimized in small devices. Therefore, VCSELs with small aperture size have better immunity to irregular response under direct current modulation and external optical feedback     

Polarization properties of vertical-cavity surface-emitting lasers

Polarization-state selection, polarization-state dynamics, and polarization switching of a quantum-well vertical-cavity surface-emitting laser (VCSEL) for the lowest order transverse spatial mode of the laser is explored using a recently developed model that incorporates material birefringence, the saturable dispersion characteristic of semiconductor physics, and the sensitivity of the transitions in the material to the vector character of the electric field amplitude. Three features contribute to the observed linearly polarized states of emission: linear birefringence, linear gain or loss anisotropies, and an intermediate relaxation rate for imbalances in the populations of the magnetic sublevels. In the absence of either birefringence or saturable dispersion, the gain or loss anisotropies dictate stability for the linearly polarized mode with higher net gain; hence, switching is only possible if the relative strength of the net gain for the two modes is reversed. When birefringence and saturable dispersion are both present, there are possibilities of bistability, monostability, and dynamical instability, including switching by destabilization of the mode with the higher gain to loss ratio in favor of the weaker mode. We compare our analytical and numerical results with recent experimental results on bistability and switchings caused by changes in the injection current and changes in the intensity of an injected optical signal