J. R. Hayes

Fabrication of a Two-Dimensional Phased Array of Vertical-Cavity Surface-Emitting Lasers

We report the successful fabrication of a two‐dimensional phase‐locked array of vertical‐cavity surface‐emitting lasers. The array was comprised of more than 160 vertical‐cavity surface‐emitting lasers of 1.3 μm diameter with a separation of less than 0.1 μm between each lasing element. The array had a 25 μm diameter and each of the elemental lasers was located on a two‐dimensional rectangular lattice. The threshold current of the two‐dimensional array 45 mA yields a threshold current of 280 μA for an elemental laser. The far‐field beam angle of the array was as narrow as 7°, and the spectral purity was found to be good enough to allow for a clear holographic image reconstruction of a holographic memory.

Wavelength‐selectable laser emission from a multistripe array grating integrated cavity laser

We report laser operation of a multistripe array grating integrated cavity (MAGIC) laser in which the wavelength of the emission from a single output stripe is chosen by selectively injection pumping a second stripe. We demonstrate a device that lases in the 1.5 μm fiber band at 15 wavelengths, evenly spaced by ∼2 nm. The single‐output/wavelength‐selectable operation, together with the accurate predefinition of the lasing wavelengths, makes the MAGIC laser a very attractive candidate for use in multiwavelength networks.

Array mode analysis of two-dimension phased arrays of vertical cavity surface emitting lasers

The modal properties of two-dimensional phase-locked arrays of vertical cavity surface emitting (VCSE) lasers where the spatial coherency across the aperture comes from the evanescent coupling of the optical fields of the lasers were investigated. Typical two-dimensional arrays can be separated into three categories: the periodic array, the circular array and the centered polygonal array (or concentric circular array). It is shown that symmetry plays an important role in determining the array mode, and that the use of VCSE lasers gives a good longitudinal mode selection leading to dynamic single-mode operation. These results can be extended to a quantum box laser array to give better optical beam control. >

DC, RF, and noise characteristics of carbon-doped base InP/InGaAs heterojunction bipolar transistors

The first successful demonstration of high-performance InP/InGaAs heterojunction bipolar transistors utilizing a highly carbon-doped base is reported. The detailed device characteristics including dc, RF, and noise performance have been investigated. For the first time base layers free of hydrogen passivation have been obtained using chemical beam epitaxy. The HBTs showed almost ideal dc characteristics; a gain independent of collector current, a near unity ideality factor, a very small offset-voltage, and a high breakdown voltage. Devices having two 1.5 /spl mu/m/spl times/15 /spl mu/m emitter fingers exhibited a maximum f/sub T/ of 115 GHz and f/sub max/ of 52 GHz. The device also exhibited a minimum noise figure of 3.6 dB and associated gain of 13.2 dB at a collector current level of 2 mA where a f/sub T/ of 29 GHz and f/sub max/ of 23 GHz were measured. The nearly ideal dc characteristics, excellent speed performance, and RF noise performance demonstrate the great potential of the carbon-doped base InP/InGaAs HBTs. >

Low series resistance vertical‐cavity front‐surface‐emitting laser diode

We have fabricated a front‐surface‐emitting laser diode (FSELD) using a technique which relies on a double ion implant of oxygen and beryllium. The laser had a low operating voltage at the lasing threshold, a low series resistance, and a relatively small threshold current of 6 mA for a 25‐μm‐diam device. The lasing wavelength was 971 nm and the spectral width above threshold was 5 A. Since the light comes from the front surface of the wafer, the fabrication technique described here for realizing a FSELD can be used for the fabrication of vertical‐cavity visible surface‐emitting lasers.

Anisotropic transport in a modulation‐doped GaAs quantum well microstructured by growth on a submicron grating

We report on the transport properties of quantum wire‐like GaAs/AlGaAs heterostructures, obtained by organometallic chemical vapor deposition of a modulation‐doped quantum well structure on a submicron grating, etched in the substrate prior to growth. Shubnikov–deHaas and mobility measurements show that the electron gas is preserved in the grating areas and that transport parallel to the grating is not severely degraded as compared to an unpatterned control sample. Perpendicular to the grating the mobility strongly decreases at low temperatures, leading to an anisotropy ratio of 1:200. The temperature dependence of the perpendicular mobility indicates strong boundary scattering at the GaAs/AlGaAs interfaces.

A MAGIC laser for WDM applications

Summary form only given. The authors report the realization of a new form of semiconductor laser that has excellent potential for use as a multiwavelength source in multiwavelength networks. The MAGIC (multi-stripe array grating integrated cavity) laser is a single-chip injection laser that is capable of providing addressable single- and multiple-wavelength laser radiation from a single-output port at precisely predetermined wavelengths over a broad spectral range. The monolithic laser source is expected to be robust and the fabrication technology employed suggests high yield and low cost of manufacture. The laser comprises an array of active stripes, monolithically integrated with a planar waveguide that contains a dispersive diffraction grating. This wavelength dispersing grating provides the optical feedback required for wavelength-specific operation. >

Fabrication Of Top Electrode Front Surface Emitting Laser Diode (FSELD) Using HBT Process

In this talk we will discuss the process compatibility between HBTsrref. 23 and VC-SELD in order to study its optoelectronic integrated circuit and optical computing applications. In addition, we will demonstrate succesful fabrication of a new SELD in which both the p-electrode and n-electrode, of the laser diode, are placed on the top surface and the total step height of the device is less than lpm. It has a low series resistance and the potential advantage of less absorption because the multilayer semiconductor mirror can be undoped. Its laser light emits from the front surface leading to the possibility of having emission wavelength that are not restricted by the bandgap of the substrate. If a semi-insulating wafer is used as the substrate, device isolation can be easily obtained without deep groove etching. The semiconductor layers that were used to form the top electrode FSELDrref.31 were grown by MBE and comprised a stack of AIAs/GaAs bottom DBR mirrors doped n-type, an AlGaAs lower cavity layer, an InGaAs strained quantum well active region, an AlGaAs upper cavity layer and a p-type GaAs/AlAs top DBR mirror. The top electrode FSELD was fabricated by performing a double ion implant into the device epi-layer that was patterned with 25pm diameter dots of a Si/Al2O3 dielectric stack using the emitter mask of an HBT. The dielectric stack initially functions as the implant mask but will eventually act as the top DBR mirror. An O+-implant was first perfomed to create a buried insulating layer. Following this, a heavy Be-implant was undertaken to form a low resistance p-ohmic side contact to the active region. The p-electrode was patterned using the base mask. After revealing n-DBR layers by wet chemical etching, Ni/Ge/Au/Ag/Au was deposited on the n-DBR layers to make an n-ohmic contact. The top electrode FSELD had a current/voltage characteristic that showed significantly less series resistance than a device fabricated from the same wafer having both top and bottom semiconductor mirror/contact stacks. In addition, the threshold current of the top electrode FSELD was 6mA for a 25pm diameter device which compares favorably with the mesa etched SELD that had a threshold current of 15mA.The top electrode FSELD had an emission wavelength of 971nm and a spectral width above threshold of 581. Only single mode operation was observed because the mode spacing is large in these short cavity lasers. The top electrode FSELD has a low operating voltage, small series resistance and low threshold current. In addition, since both the n-electrode and p-electrode are on the top surface of the wafer and the total step height of the device is relatively low, this structure is attractive for optoelectronic integrated circuit applications.

Phase-Locked Two-Dimensional Arrays of Vertical Cavity Surface Emitting Lasers

We report the characteristics of two-dimensional phase-locked arrays of vertical cavity surface emitting lasers. Three different two-dimensional array structures have been realized, they are a 2×3 periodic array of 10 µm squares, a hexagonal array and a centered hexagonal array of 5 µm hexagons. All arrays were fabricated using the same technique which was a combination of mesa etching and oxygen implantation isolation. The threshold current of 2×3 periodic array was 24 mA, hexagonal array was 30 mA and centered hexagonal array was 22 mA. The far field beam angle was about 2°. The centered hexagonal array has the most circularly symmetric far field beam pattern.