Ulm Photonics VCSEL Fab, Ulm

ULM photonics has opened a new manufacturing facility in Ulm, Germany. The fab has new 5 x 4in MBE (Molecular Beam Epitaxy) equipment for growing single crystal VCSELs (Vertical Cavity Surface Emitting Lasers) on GaAs wafers.

The Ulm site has a 120m² epitaxial growth cleanroom, a 200m² device production cleanroom and 150m² of office space. The expansion brings a 240m² VCSEL cleanroom and a 100m² MBE cleanroom (both class 100 to 1,000).

EDGE EMITTING DIODES AND VERTICAL CAVITY SURFACE EMITTING LASERS (VCSEL)

Communication systems designers are facing rapid increases in equipment functions, processing requirements and data rates, all against the background of rapidly falling costs. ULM manufactures high speed VCSELs for communication, printing and sensor markets.

VCSELs are replacing edge emitting diodes. They cost less to make and their faster operation and higher efficiencies boost the speed and reach of fiberoptic networks. Edge emitting diodes emit their energy in a direction parallel to the boundaries between semiconductor layers. VCSELs instead emit energy perpendicular to the layer boundaries (hence ‘vertically’, since semiconductor layers are normally illustrated as horizontal).

The diodes emit a narrow circular beam which makes for easier interfacing to optical fibers. Devices use GaAs and similar materials. For data communications, they are commonly produced in one of two (infrared) wavelengths: 850nm and 1,300nm. Devices for sensing and printing have similar, but more varied frequencies.

850nm VCSEL DIODE MARKET

ULM offers devices in die TO46/56 packages and optical subassemblies for serial configurations and die form for 1×4, 1×12 and other parallel configurations. Multimode devices aim at low cost telecoms networks that use multimode fibers. These have shorter transmission distances than single mode fibers. Single mode fibers are used in high-speed / long distance links and are finer than multimode fibers. They allow only one mode of light to propagate which reduces the number of times the light bounces off the walls of the fiber. ULM also supplies single mode and 12mW VCSELs for use in sensing and processing.

ULM expects the 850nm VCSEL diode market to increase to $180 million in 2005, up to $560 million in 2010. To help take advantage in the US, ULM is increasing cooperation with optical company Schott. The company has become lead investor with the partnership allying ULM’s VCSELs with Schott’s fiber management products for Very Short Reach (VSR) optical interconnects.

MOLECULAR BEAM EPITAXY (MBE)

ULM photonics is using MBE to produce the VCSELs, which is a form of PVD for compound semiconductors. The substrate is held in high vacuum and bombarded with ions. The substrate acts as a seed crystal and the epitaxial film copies the structure of the crystal. MBE allows precise control of complex doping profiles.

The main stress for accelerating device failure mechanisms is temperature and ULM performs intensive accelerated device lifetime testing. Lifetime is related to the junction or internal temperature of the device, which is itself determined by ambient temperature, dissipated power and thermal resistance. ULM plots lognormal MTTF (Mean Time To Failure) against the junction temperature to find the activation energy of the failure mode. ULM-photonics’ VCSELs are reliability tested and 85%RH/85°C tested without hermetic sealing.

120Gbit/s MULTIMODAL OPTICAL FIBER LINK

ULM recently demonstrated a 120Gbit/s link together with IC company Primarion, semiconductor manufacturer Microsemi and fiber optic producer OFS. The Parallel Optics Interconnect has twelve 10Gb/s channels for Enterprise, Telco and Datacenter networking equipment.

The demonstration used 850nm wavelength over 300m of multimode optical fiber ribbon. It trebles the previous fastest demonstrated speeds and shows that component interoperability is ready for the next generation of short reach, ultra high bandwidth optical links.

CONTRACTORS

LUWA (Uster, Switzerland) installed the 240m² VCSEL cleanroom and ASYS (Dornstatt, Germany) installed the 100m² MBE cleanroom (both class 100 to 1000). Riber (Paris, France) supplied an MBE 49 (multi 4in) Molecular Beam Epitaxy system.