Buried heterostructure lasers are formed by the regrowth of InP current blocking junctions around mesas etched in planar structures. Using metal organic vapor phase epitaxy (MOVPE) at atmospheric pressure, growth patterns were observed by inserting lattice matched 1.5 nm InGaAs or doping striations in the regrown layers. The conditions for planar regrowth are described using wet-etched mesas. With mesas formed by reactive ion etching, planar regrowth is easily achievable when Cl is added to the gas ambient using the pyrolysis of trichloroethane (TCA). When RIE mesas are cleaned and slightly etched (< 0.1 micrometers ), the laser properties are indistinguishable from those formed by wet etching, a result that has important implications for the processing of large area wafers (2 inch diameter) uniformly into lasers with controlled dimensional properties.
GaAs-based, edge-emitting diode lasers have become important light sources for numerous applications, e.g., in ophthalmology and dentistry, pumping of solid-state lasers, and printing on thermal media. The general performance requirements for these devices are high brightness, high reliability, stable optical-characteristics, and low system-cost to performance ratio. Device processing procedures such as dry etching, anodic oxidation, anti-reflection coatings, ion-implantation, and epitaxial growth on non-planar substrates impact the operation of the laser, both positively as well as negatively. The effect of these fabrication procedures on device reliability is discussed where applicable.
A simple and highly reliable processing technique for ridge waveguide InGaAs/GaAs SQW lasers is proposed. The comparison is made with other more conventional processing sequences and the measurements indicate that the characteristics of the lasers obtained by this simple method are at least as good and sometimes even better than those made by using the other processing sequences. It also is shown that the simplicity of the process guarantees a high yield. The high performances of these lasers can be further optimized by applying optical coatings.
A narrow spread of threshold currents from 10.8 to 12.8 mA across a wafer has been demonstrated. To the best of our knowledge, this is the narrowest spread of threshold currents that has ever been reported for non-broad-area semiconductor lasers. From experimental results, it seems that the active width is probably the most important parameter in controlling the spread of threshold currents.
Silicon is used as a packaging medium to integrate a laser, lenses, and a back facet monitor into a compact sub-assembly suitable for low-cost laser packages. The sub-assembly consists of separate laser and detector/optics submounts made of silicon. Only a single axis alignment is required during assembly to align the lenses (300 micrometers diameter sapphire spheres) with the laser active area. In a single lens configuration, the integrated sub-assembly had 25% coupling efficiency into single-mode fiber compared to 30% maximum coupling efficiency achieved on the optical bench. Coupling efficiencies of the integrated sub-assembly to 50 micrometers multi-mode fiber greater than 70% were achieved. The effective numerical aperture of the back facet monitor in the sub-assembly was greater than 0.7.
Commercial single heterojunction GaAs laser diode chips have been fiber pigtailed with a 100/140 micrometers fiber. These lasers, producing 5 ... 10 W peak pulse power, are used in time-of-flight distance measurement instruments. The laser chips were purchased mounted on a coaxial TO-5 base. Two different types of packaging constructions were tested: a sleeve construction and a butt construction. In the sleeve construction the fiber was aligned with the laser chip using a loose sleeve and a fiber ferrule. In the butt construction the fiber ferrule was butt coupled to the laser submount. The fiber ferrule was actively aligned with the laser and fixed with an adhesive or with an adhesive and laser welding. Silicone gel potting was tested to improve the module stability in outdoor applications. The pigtailed laser modules and commercial laser modules were temperature cycled and results were compared. The measurements show that the properties of the adhesive are crucial to the temperature stability of the module. The tests show that optical output variation of the module was 6 dB in the temperature range of -20 ... 55 degree(s)C when the peak power was 3.7 W at room temperature. The stability of poor adhesive joints can be improved utilizing laser welding. However, the drawback is the high investment cost of equipment required. The results show that simple and inexpensive fiber pigtailed modules can be made using properly selected adhesives.
Packaging technology is described for the DM-1062 gigabit optical module. This module is the IBM offering to comply with ANSI XT39.3 Fiber Channel Standard (FCS) for 1.0625 Gb/s optoelectronic transceiver with integrated serializer/deserializer functions. Performance data for this module is discussed as well as extensions of this technology to lower cost optical devices.
Diamond made by a dc arc-jet chemical vapor deposition (CVD) process is being successfully applied as a packaging material for semiconductor lasers. This CVD process is capable of making free-standing wafers up to 15 cm in diameter with thermal conductivity values similar to natural, type IIa diamond. A novel mathematical analysis using the surface element method was performed to predict the most cost effective size for a CVD diamond submount as a function of the laser size. A literature review of thermal modelling studies and performance testing indicates the outstanding performance benefits which can be realized with CVD diamond laser diode submounts.
There are many requirements for computer interconnects and local loop telecommunications for parallel fiber optic data channels. There have recently been many packaging approaches where a few channels have been cleverly packaged, using self-aligned approaches with silicon photolithographically etched rectangular or V-groove channels to achieve accurate alignment. Practical economical packaging of arrays must be developed, using conventional electronic packages for the interfacing optoelectronic arrays to fiber ribbon cables. In this way, optoelectronic arrays may be introduced which are compatible with conventional electronic packaging, and therefore readily acceptable to present system integrator and manufacturers. Depending on the application, single mode or multi-mode interconnects may be required. This paper proposes approaches to achieve both single mode and multi-mode array packaging which may be interfaced directly to existing electronic systems.
As one approach to retrofitting a reprographic writing engine with a higher-power laser for direct-to-plate imagesetting, we developed a single-mode-fiber delivery for a Nd:YAG laser. The writing process required 4 W cw in a high-quality beam capable of high-speed modulation. We developed a laser of adequate beam quality and a fiber-coupling system that met the requirement with emission of 4 W cw at 1064 nm wavelength from a 5 micrometers -core fiber that had a 950 nm wavelength cutoff for the second mode.
The applications for optoelectronic integrated circuits demand high performance optoelectronic devices or smart pixels. The stringent requirements on these smart pixels require that packaging technology be developed concurrently to the development of the optoelectronic components. We discuss the packaging requirements of smart pixels based on vertical-cavity microlasers. We present a novel microlens/macrolens combination which allows high power densities to be focused to a diffraction-limited spot using present VCSEL technology. Finally, we discuss the applications for microlaser-based spatial light source arrays.
The technology of vertical cavity surface emitting lasers (VCSELs) has grown dramatically in recent years. We have processed and packaged VCSELs, for various applications. The thermal, output coupling, and spectral characteristics for different devices and packages are shown. Practical single device and array packages, and the results of their coupling to optical fibers are presented.
Although semiconductor Bragg reflectors are widely used to realize vertical-cavity surface- emitting lasers, high-contrast dielectric stacks offer some advantages in terms of device flexibility and performance improvement. Here we discuss those advantages, and present data on both electrically driven and optically pumped vertical-cavity laser structures which incorporate ZnSe/CaF quarter-wave reflectors.
The selective area MBE deposition of InGaAs in InP substrates is reported. Successful selective growth of InGaAs in pre-ion etched windows of InP has been achieved utilizing a SILOX mask and lift-off techniques of polycrystalline InGaAs field layers. The optical quality of these epitaxial InGaAs windows was comparable to material deposited on non-patterned InP. An optimized pre-growth heat treatment of InP was very crucial in order to achieve the smooth InGaAs surface morphologies and excellent optical properties. Finally, no significant irregularities were observed at the InGaAs window edges, the alloy composition appeared uniform in the entire window areas and the incorporation of impurities from the SILOX was minimized.
A new type of flip-chip mounting method and a new type of optical plate have been developed. In addition, a new type of multi-chip direct contact-type image sensor has been developed, using the above mounting method and optical plate, for graphic image scanners used in office equipment such as high-speed facsimiles, intelligent photo-copy equipment, and computers. Furthermore, a next-generation multi-chip direct contact-type image sensor is now being developed.
The small optical user terminal (SOUT) is part of an experimental program of the European Space Agency, initiated by British Aerospace. One takes advantage of the high antenna gain obtainable at 830 nm to build a very small, lightweight, and comparatively low cost terminal, capable of communicating with SILEX, ESA's full scale optical telecommunication program. SPACEBEL is in charge of developing the transmitting chain of the SOUT, and demonstrating its performances on a breadboard model. In the first part of the paper, we describe the transmitting chain of SOUT, stressing the delicate optical link between the diode and the monomode fiber. In the second part of the paper, we report on the first measurement of the efficiency of the coupling between the laser diode and the fiber as measured on the engineering model of the flight design for the Silex Beacon.