The dynamic behavior of the light output from aluminum-free 980nm ridge waveguide GaInAs/GaInAsP/GaInP pump lasers is studied in the high power regime on a picosecond time scale. Three types of the temporal evolution of the turn-on emission dynamics measured by a single-shot streak-camera can be distinguished in the near field, according to the injection current. First, at moderate pumping, the laser emission evolves through a regime of relaxation oscillations, which can be modelled by rate equations incorporating nonlinear gain. Second, at a higher current, high frequency switching between the left and right part of the active region is observed. The frequency of the switching increases proportional to the excitation current amplitude and is in the order of 10GHz. The third regime shows highly complex spatio-temporal dynamics with the coexistence of low and high frequency spatial switching and temporal pulsations. Finally, consequences of the results for applications will be discussed.
Aluminum-free material has proved to be very promising for lasers of 800 - 1000 nm wavelength range. Up to now the most widely used growth method of GaInAsP quaternary alloys was Metal-Organic Chemical Vapor Deposition (MOCVD) technique. Gas Source Molecular Beam Epitaxy (GSMBE) is also able to produce high-quality Al-free material for optoelectronics. This paper aims to present the direct comparison of laser material quality grown by MOCVD and GSMBE. The easiness of composition control, flexibility of the deposition process and composition uniformity in GSMBE-grown material allowed us to further improve the performance of laser diodes operating at 800 nm wavelength range.
InGaAs/GaInAsP/GaInP ridge waveguide 980-nm laser diodes for pumping light into erbium doped fiber amplifiers are reviewed. These lasers have very good performance characteristics. They exhibit kink-free, single mode emission up to a power of 250 mW with a slope efficiency of 0.7 to 0.95 W/A, a thermally limited maximum power of 450 - 500 mW, and the threshold current density of about 150 A/cm2. They are relatively stable against temperature variations. A 100 mW power from a fiber-pigtail module has been demonstrated. The lasers withstand severe thermal roll-over tests without showing degradation effects. Preliminary lifetime tests indicate that their mean-time-to-failure may be very high if not limited by sudden failure, from several hundred thousand to one million hours.
The fabrication of epitaxial compound semiconductors and optoelectronic devices at Tampere University of Technology is described. First, we determine the bandgap energies of technologically important quaternary alloys GaxIn1-xAsyP1-y, grown by gas-source molecular beam epitaxy, which are lattice-matched to InP and GaAs throughout the entire composition ranges. Second, we discuss state-of-the art aluminum-free laser diodes intended for pumping light at λ = 980 nm into erbium-doped optical fiber amplifiers. Third, principles of a new kind of avalanche photodetector (APD), a "unipolar" APD, are discussed. Our attempt is to develop a compound semiconductor detector that could detect an event of single-photon absorption. Finally, we present a photovoltaic fiber optical power converter. This device is comprised of a series of photovoltaic cells and an integrated 980-nm data laser. It is designed to convert the fiber-coupled optical power launched by a transmitter laser at 780<λ<850 nm into electrical power.
We review state-of-the-art aluminum-free GaInP-GaInAsP-GaInAs laser diodes which emit at the wavelength of 980 nm. These lasers are intended for pumping light into erbium-doped optical fiber amplifiers. We discuss the preparing of the layer structure, using the gas-source molecular beam epitaxy growth method, the lasing characteristics, fiber coupling efficiency, and reliability issues.
This paper describes state-of-the-art aluminum-free 980-nm laser diodes which are intended for pumping erbium doped optical fiber amplifiers (EDFA's). There are three principal issues for these laser diodes to be considered for the EDFA applications: light output power, efficiency of coupling the power into a fiber, and reliability. It has been shown that the lasers can launch 400 mW in single transverse mode of operation into free space. A coupling efficiency of 53% and a fiber-coupled power of 58 mW have been demonstrated. Because the Al-free 980-nm lasers are new, their lifetimes have not yet been thoroughly studied. However, some tentative experiments indicate that extrapolated lifetimes may be several hundred thousand hours at reasonable power levels. Thermal roll-over tests prove that the lasers withstand high currents and temperatures without any sign of degradation.
The planar doped barrier diode being majority carrier semiconductor device has promising application areas in high-frequency and microwave circuits. The paper reviews the main features of diode structures. The different current conducting processes as the thermionic emission, the diffusion, and the tunneling are treated. The design rules for the barrier height also are given, and our own experimental results reported. Microwave diodes and zero bias detectors have been fabricated in RITP on layer structures grown in TUT.
This paper deals with growth of GaAs InP and their ternaries quaternaries and heterostructures by the gas-source molecular beam epitaxy (GSMBE) method. Epilayer qualities are discussed and compared with those obtained by other methods. Some problems related to growth of layers and interfaces are discussed in detail. Properties of lasers photodetectors and optical modulators fabricated by GSMBE are presented.