Michael S. Lebby

Long wavelength VCSEL

Long wavelength VCSELs at 1300 nm have been developed to serve 10-Gigabit enterprise networks over FDDI grade multimode fibers up to 300 m in distance. The long wavelength VCSELs operate CW at temperatures over 100 °C. They are ideal low cost alternatives to DFB lasers for transceivers and transponders compatible with IEEE 10GBASE-LX4 or 10GBASE-LRM standards over multimode fibers.

A low cost, high performance optical interconnect

Optobus is a ten channel parallel bi-directional datalink based on multimode fiber ribbons. The design represents a series of tradeoffs between cost and performance to produce a low cost interconnect solution with a minimum of 1.5 Gbit/s of aggregate throughput.

Characteristics of VCSEL arrays for parallel optical interconnects

The use of vertical cavity surface emitting lasers (VCSELs)in a parallel optical interconnect for Motorolas OPTOBUS/sup TM/ interconnect was made public over 1 year ago. This was the first time VCSELs were introduced into a product which took advantage of the excellent qualities of VCSELs over edge-emitting lasers. Motorolas OPTOBUS/sup TM/ interconnect is a ten channel parallel bi-directional data link based on two 10 channel multimode fiber ribbons. One of the key differences in this type of interconnect compared with previous data link designs is the use of the VCSELs as the optical source for the links fiber optic transmitter. A single 1/spl times/10 VCSEL array from a GaAs wafer is die attached to a 10 channel GUIDECAST/sup TM/ optical interface unit which couples the emission from each laser device to its corresponding fiber ribbon channel and thus negates the use of expensive manufacturing techniques such as active alignment and pigtailing. The OPTOBUS/sup TM/ interconnect achieves its performance goals (which include low cost) via the unique characteristics of the GaAs VCSELs arrays. For example, the 850 nm devices produce a circular symmetric beam with a half angle of about 10 degrees allowing the coupling loss into the waveguide to be less than 3 dB. In addition, to maintain low manufacturing costs, each VCSEL array is individually and automatically probe tested (just as in the silicon industry) to verify that each VCSEL achieves the OPTOBUS/sup TM/ interconnects stringent electrical, optical, thermal and mechanical specifications. Typical computer generated wafer maps from automated production tooling and statistical parametric results are discussed. The combination of low threshold currents with superior thermal and optical performance allow the devices to be modulated under fixed bias conditions. Typical drive currents of 3X threshold are used to obtain nominal FDA Class 1 safety optical power levels from the GUIDECAST/sup TM/ optical interface unit.

Use of VCSEL arrays for parallel optical interconnects

The use of vertical cavity surface emitting lasers (VCSELs) in a parallel optical interconnect for Motorolas OPTOBUSTM interconnect was made public over 1 year ago. This was the first time VCSELs were introduced into a product which took advantage of the excellent qualities of VCSELs over edge-emitting lasers. Motorolas OPTOBUSTM interconnect is a ten channel parallel bi-directional data link based on two 10 channel multimode fiber ribbons. One of the key differences in this type of interconnect compared with previous data link designs is the use of the VCSELs as the optical source for the links fiber optic transmitter. A single 1 X 10 VCSEL array from a GaAs wafer is die attached to a 10 channel GUIDECASTTM optical interface unit which couples the emission from each laser device to its corresponding fiber ribbon channel and thus negates the use of expensive manufacturing techniques such as active alignment and pig-tailing. The OPTOBUSTM interconnect achieves its performance goals (which include low cost) via the unique characteristics of the GaAs VCSELs arrays. For example, the 850 nm devices produce a circular symmetric beam with a half angle of about 10 degrees allowing the coupling loss into the waveguide to be less than 3 dB. In addition, to maintain low manufacturing costs, each VCSEL array is individually and automatically probe tested (just as in the silicon industry) to verify that each VCSEL achieves the OPTOBUSTM interconnects stringent electrical, optical, thermal and mechanical specifications. Typical computer generated wafer maps from automated production tooling and statistical parametric results are discussed. The combination of low threshold currents with superior thermal and optical performance allow the devices to be modulated under fixed bias conditions. Typical drive currents of 3X threshold are used to obtain nominal FDA Class 1 safety optical power levels from the GUIDECASTTM optical interface unit.

Low-cost high-performance optical interconnect

Summary form only given. The optical waveguides have a uniformity of 1 dB. The resulting optical links have a jitter of no more than 150 ps not including pulse-width distortion, static skew between channels of less than 200 ps and dissipate 1.5 W. A representative multichannel eye pattern at 400 Mbit/s is shown. In this presentation we focus on the design approach and subsystem requirements that make this performance possible without sacrificing manufacturability or cost.

Automatic power control of a VCSEL using an angled lid TO56 package

Many applications of semiconductor lasers require that the output power from the laser is maintained at a fixed level independent of temperature and aging, this is typically accomplished with edge emitting lasers using a back facet monitor photodiode which is incorporated into the laser package. The signal from the photodiode is used to drive the feedback control circuit. In the absence of a back facet it is necessary to develop an alternate packaging scheme for VCSELs that allows for the generation of a signal for use in maintaining a fixed output power. In this paper we present a VCSEL packaged in a TO56 can with a silicon pin photodetector. A portion of the emitted beam from the VCSEL is reflected from the lid onto the photodetector. Results demonstrating an auto-power control capability of /spl plusmn/3 percent are presented.

Vertical cavity surface emitting laser packaging with auto power control

We will discuss a discrete VCSEL packaging method using a monitoring photodiode for auto power control. We have demonstrated a VCSEL package with an output power variation within /spl plusmn/1% over a temperature range from 0 to 65/spl deg/C.

Semiconductor Laser and Light-Emitting Diode Fabrication

This chapter focuses on the manufacturing issues of the optical sources: light-emitting diodes (LEDs), edge-emitting lasers, and vertical cavity surface-emitting laser (VCSEL) sources. In particular, the chapter concentrates on the fabrication of these laser sources. It is noted that edge-emitting laser diodes are extensively used for CD/DVD data storage, laser printing, bar code scanners, pointers, optical communications, and solid-state laser pumping sources. The chapter describes VCSEL manufacturing in detail, as it is an emerging field having potentially great impact on the data communication industry. However, it is noted that manufacturability and manufacturing cost relative to VCSELs are the two factors that often hinders their commercialization. Edge-emitting lasers are grown by liquid phase epitaxy (LPE), molecular beam epitaxy (MBE), or metal organic chemical vapor deposition (MOCVD) techniques; whereas, VCSELs are generally grown by MBE or MOCVD techniques. Because, MOCVD offers the best growth throughput and excellent material quality, so it is predominantly used by all the commercial VCSEL manufacturers. Many edge-emitting laser manufacturers are also relying on the MOCVD technology for the high-volume production.

Packaging of Optical Components and Systems

The sections in this article are 1 Optical Components 2 Packaging 3 Packaging Philosophy and Roadmap

Vertical cavity surface emitting laser-based parallel optical data link

Vertical cavity surface emitting laser (VCSEL) arrays are designed and used for 10-channel parallel optical data links, OPTOBUS™, to transmit data at a speed of up to 800 Mbits/s per channel. The interface between the VCSELs and the optical fiber ribbons is based on molded plastic waveguide technology. A bit error rate of 10-15 is demonstrated.