While time-of-flight applications have led to VCSEL arrays operating at currents measured in the amperes and producing very high aggregate powers, the current through each individual VCSEL aperture is not substantially higher than in many other applications. Driving a single VCSEL emitter of moderate size to extremely high currents requires specialized circuits and operation in a regime where thermal effects will not destroy it, meaning low duty cycles and pulse on-times measured in single-digit nanoseconds. In that regime traditional VCSEL performance and geometry scaling rules no longer apply and surprising behaviors emerge. We describe results for small area single-emitter 850-nm VCSELs designed for high power extraction operating at peak currents of several amperes. The electrooptical behaviors observed afford opportunities for VCSELs in nontraditional areas, but they may also indicate some previously unsuspected limitations.
Finisar has developed a line of high power, high efficiency VCSEL arrays. They are fabricated at 860nm as traditional P side up top emitting devices, leveraging Finisar’s existing VCSEL fab and test processes for low cost, high volume capability. A thermal camera is used to accurately measure temperature profiles across the arrays at a variety of operating conditions and further allowing development of a full reliability model. The arrays are shown to demonstrate wear out reliability suitable for a wide range of applications. Typical 1/e^2 beam divergence is near 16 degrees under CW operating conditions at peak wall plug efficiency, narrowing further under pulsed drive conditions.
Over the last 20 years, nearly 1 billion VCSELs have been shipped, the vast majority of them emitting at 850nm using GaAs active regions, and primarily used in data communications and optical tracking applications. Looking to the future, the ever increasing speed of data communications is driving the VCSEL to evolve with more complex active regions, optical mode control, and alternate wavelengths to meet the more stringent requirements. We will discuss the current state of VCSELs for 28Gbps, and higher speeds, focusing on evolution to more complex active regions and alternate wavelength approaches, particularly as the market evolves to more active optical cables. Other high volume applications for VCSELs are driving improvements in single mode and optical power characteristics. We will present several evolving market trends and applications, and the specific VCSEL requirements that are imposed. The ubiquitous 850nm, GaAs active region VCSEL is evolving in multiple ways, and will continue to be a viable optical source well in to the future.
For nearly twenty years most models of VCSEL wearout reliability have incorporated Arrhenius activation energy near
0.7 eV, usually with a modest current exponent in addition. As VCSEL production extends into more wavelength, power, and speed regimes new active regions, mirror designs, and growth conditions have become necessary. Even at
more traditional VCSEL 850-nm wavelengths instances of very different reliability acceleration factors have arisen. In
some cases these have profound effects on the expected reliability under normal use conditions, resulting in wearout
lifetimes that can vary more than an order of magnitude. These differences enable the extension of VCSELs in
communications applications to even greater speeds with reliability equal to or even greater than the previous lowerspeed devices. This paper discusses some of the new applications, different wearout behaviors, and their implications in real-life operation. The effect of different acceleration behaviors on reliability testing is also addressed.
Commercial demand for optical transceivers operating at 14Gbps is now a reality. It is further expected that
communications standards utilizing 850nm VCSELs at speeds up to 28Gbps will be ratified in the near future. We report
on the development and productization of 850nm VCSELs for several applications, including high speed (both 14Gbps
and 28Gbps) operation to support the continued fulfillment of data communication demand.
VCSELs continue to be widely deployed in data communication networks. The total bandwidth requirements continue to
grow, resulting in higher data rates and utilization of both spatial and wavelength multiplexing. This paper will discuss
recent results on VCSELs operating at aggregate speeds up to 1000Gbps as well as the prospects and results on
extending to higher serial data rates.
In this paper we will discuss recent results on high speed VCSELs targeted for the emerging 16GFC (Fibre Channel)
standard as well as the now forming 25Gbps PCI express standard. Significant challenges in designing for reliability and
speed have been overcome to demonstrate VCSELs with bandwidth in excess of 20Gbps.
In 2007 Finisar® completed the transfer of an entire epitaxial and fabrication line from one facility to another. During
this period, reliability models had to be re-validated and product continuity maintained. In this paper we describe the
activities necessary to support such a transition, and we extend previously published VCSEL failure atlases.
Since the commercialization of Vertical Cavity Surface Emitting Lasers (VCSELs) in 1996, Finisar's Advanced Optical
Components Division has shipped well over 50 Million VCSELs. The vast majority of these were shipped into the data
communications industry, which was essentially the only volume application until 2005. The driver for VCSEL
manufacturing might well shift to the increasingly popular laser based optical mouse. The advantages of the laser based
mouse over traditional LED mice include operation on a wider range of surfaces, higher resolution, and increased
battery lifetime. What is the next application that will drive growth in VCSELs? This paper will offer a historical
perspective on the emergence of VCSELs from the laboratory to reality, and the companies that have played key roles
in VCSEL commercialization. Furthermore, a perspective on the market needs of future VCSEL development and
applications is described.
After some thirty years of materials analyses into the failure behavior of III-V semiconductor lasers, manufacturers of these devices still regularly encounter new failure mechanisms. This is due mainly to the implementation of progressively more complex and refined designs in devices that are, moreover, often subjected to increasingly more stressful operating or environmental conditions. It is therefore incumbent upon commercial laser manufacturers to maintain a persistent effort to search out and understand these new failure mechanisms, preferably before they are uncovered by an unhappy customer. Below, we describe our pursuit of a thorough materials-level understanding of VCSEL behaviors and illustrate some of the positive effects of these efforts.
During a year of substantial consolidation in the VCSEL industry, Honeywell sold their VCSEL Optical Products Division, which has now officially changed its name to Advanced Optical Components (AOC). Both manufacture and applied research continue, however. Some of the developments of the past year are discussed in this paper. They include advances in the understanding of VCSEL degradation physics, substantial improvements in long-wavelength VCSEL performance, and continuing progress in manufacturing technology. In addition, higher speed serial communications products, at 10 gigabits and particularly at 4 gigabits per second, have shown faster than predicted growth. We place these technologies and AOC's approach to them in a market perspective, along with other emerging applications.
Honeywell continues to be the world’s leading supplier of VCSELs operating at 850 nm. This paper will cover new commercial application areas for 850-nm VCSELs, and will present new findings in VCSEL reliability science. In particular, newly-developing applications drive requirements for ever more reliable VCSEL design and fabrication, and for improvements in controls for ESD (electrostatic discharge) and EOS (electrical overstress) at manufacturing facilities both for VCSEL components and for higher-level assemblies employing VCSEL components. Honeywell efforts toward improvement of reliability and toward reduction of ESD exposure are described, as is an alternative approach to improving reliability of systems containing VCSELs without compromising their performance.
Vertical Cavity Surface Emitting Lasers (VCSELs) are now essentially the only source used in short distance high bit rate data communications over multimode optical fiber. First commercially realized in 1996 by Honeywell, the primary application has been single channel links operating Ethernet or Fibre Channel protocols in the LAN and SAN environments. Today, the total bandwidth throughput is being raised to more than 10Gbps per channel, with the potential of several channel operation to yield more than 100Gbps. 850nm VCSELs are beginning to emerge in relatively new application arenas and wavelengths. This paper describes the market readiness for VCSELS in a wide variety of optical networking applications.
In this paper we describe both the 1310 and 1550 nm VCSEL development work at Honeywell using both InP and GaAs substrates, and using both MOCVD and MBE. We describe the material systems, the designs, the growth techniques, and the promising results obtained and compare them to the needs of the communications industry. InGaAsN quantum well based VCSELs have been demonstrated to 1338 nm lasing at temperatures up to 90 C. Continuous wave InP based 1550 nm VCSELs have also been demonstrated.
The paper addresses the current status of 850nm VCSELs in data communications systems, and the outlook for adoption of VCSELs in other applications. In particular, recent experimental results obtained by research and development activities at Honeywell are discussed.
Born of necessity of application, the Vertical Cavity Surface Emitting Laser (VCSEL) is now found in nearly all optical networking systems based on standards such as the IEEE 802.3z and ANSI X3.t11. Reliability continues to be the hallmark of the technology, and the volume manufacturing aspects are now realized. While VCSEls satisfying optical networking standards continue to provide the highest volume applications, the advantages of the technology are beginning to enable novel optical equipment. This paper explores development of VCSELs at wavelengths from 650 to 850nm, and the commercial applications of these devices in both the data communications and optical sensing arenas. VCSELs operating at longer wavelengths are also being developed, but are not at a stage of commercialization to be discussed in this forum.
Each year, more VCSEL technologies make the transition from research curiosities to commercially available products. In this paper we describe several such technologies at Honeywell, each at a different stage of that transition. Oxide-confined devices are already past the transition stage. We describe the generally excellent reliability of oxide-confined devices already in high-volume production, and compare it to results of the most recent-and possibly last-long-term reliability study of proton-implanted VCSELs. We report on detailed package-VCSEL interaction modeling, which is being used to improve performance and extend the life of common form-factor packages. We also note Honeywell's progress toward commercialization of VCSELs and allied products at wavelengths other than 850 nm.
In 1996, Honeywell was the first company to commercialize VCSEL technology, and today it is the world's largest VCSEL component supplier. This paper will focus on the aspects of VCSEL manufacture that are important to maintain highly reliable and producible components. For current VCSEL products, we will address the evolution of VCSEL reliability and its effect on performance in data communications systems. New applications in both the data communications and sensor markets are being enabled by the VCSEL technology. This paper will also discuss new VCSEL structures, packages and wavelengths that are being commercialized by Honeywell to address these emerging markets.
Proc. SPIE. 3004, Fabrication, Testing, and Reliability of Semiconductor Lasers II
KEYWORDS: Signal to noise ratio, Modulation, Polarization, Signal attenuation, Resistance, Polarizers, Vertical cavity surface emitting lasers, Circuit switching, Charged particle optics, Near field optics
The high speed characteristics of Vertical Cavity Surface Emitting Lasers (VCSELs) for use in modern high bandwidth fiber optical networks is presented. An equivalent circuit model based on microwave network analyzer S11 measurements is developed. The dynamic operation of multi- transverse mode VCSELs is also investigated. Experimentally, a laser with two orthogonally polarized modes is examined. We show that each of the transverse laser modes may have significantly different rise and fall times. A multimode rate equation model is used to predict the exact pulseshape for each mode. The laser gain is saturated by the total optical intensity, and the sum of the modal powers is shown to have a constant rise and fall time. The system performance in terms of the bit error rate is also investigated. We demonstrate that selective attenuation of the optical modes can lead to an increase in the bit error rate due to polarization partitioning noise.
Ultrafast gain recovery dynamics of a diode laser are explored when a picosecond pulse propagates through a semiconductor amplifying medium. Theoretical modelling employs a set of nonlinear dynamical equations to predict the temporal dependence of the population difference and the diode laser output intensity in the wake of an applied signal pulse. Experimentally, this system of study is a cw-pumped 670 nm InGaAlP diode laser probed by a tunable train of 10 psec pulses emitted from a synchronously pumped mode-locked pyridine 1 dye laser. In addition to discussing the details of the gain, the authors also report the phase locking of the diode laser to the applied signal over a broad range of wavelengths.
We study the output of a gain switched diode laser as a function of the pumping parameters. Experimentally we look at the output pulse shape height and width timing conditions and stability. Theoretically we calculate the conditions under which a gain switched diode laser is optimized with respect to the width of the injection current pump pulse. We find for both biased and unbiased operations that a current pulse of approximately 20 psec corresponds to a Dirac delta function a situation which yields the shortest most intense output pulses. A sensitivity analysis performed on an analytic distillation of the model gives us design considerations for diode lasers with improved stability.