Fibre-Channel and Gigabit Ethernet (GbE) standardization opened the first significant VCSEL commercial market, accelerating development, and sealing 850nm as the standard VCSEL wavelength for a couple decades. In succession, 10-Gigabit Ethernet (10GbE) accelerated oxide VCSEL development. Standards continue to shape VCSEL technological developments, e.g. to today’s 4-level 50 Gigabit/sec devices and 2-4-wavelength WDM.
This article outlines development work at JDSU on InGaNAs based vertical cavity surface emitting lasers (VCSELs)
operating at 1270nm and their use in 10Gbps SFP+ modules. DC and AC performance of die and transmit optical
subassemblies (TOSAs) will be described. Due to their low power consumption, LW VCSELs are ideal for use in
SFP+; module performance will be described as well.
Beginning with 4 Gigabit/sec Fibre-Channel, 1310nm vertical-cavity surface-emitting lasers (VCSELs) are now entering the marketplace. Such VCSELs perform like distributed feedback lasers but have drive currents and heat dissipation like 850nm VCSELs, making them ideal for today's high-performance interconnects and the only choice for the next step in increased interconnection density. Transceiver performances at 4 and 10 Gigabits/sec over fiber lengths 10-40km are presented. The active material is extremely robust, resulting in excellent reliability.
Vertical-cavity surface-emitting lasers (VCSELs) emitting in the 1530-1565 nm region of flat gain in Er-doped fibers offer the potential for low-cost transmitters for wavelength division multiplexing (WDM). Methods are described to produce precisely-defined vertical-cavity surface-emitting laser arrays which: 1) efficiently utilize wafer real estate; 2) have precise and uniform wavelength distributions despite wafer thickness nonuniformity and wafer-to-wafer thickness variation; 3) are compatible with known multiplexing technologies; 4) have minimum wavelength variation with temperature. Epitaxial growth on patterned substrates with varying-size mesas has been shown to produce multiple-wavelength VCSEL arrays by Iga's group at the Tokyo Institute of Technology. This can be combined with additional refinements to fine tune the wavelengths, increase yield, and to maximize VCSEL efficiency, manufacturability and performance. Multi-wavelength VCSEL arrays represent a much lower cost, more controllable alternative to distributed-feedback laser arrays for WDM sources. The difference in laser output powers can be largely compensated via use of an Er-doped fiber amplifier within the transmitter. Reports such as that by ElectroniCast point to transmitters and receivers as being the most vital WDM components, in terms of both cost and technology.
Arrays of 8 X 8 of GaAs/AlGaAs vertical cavity surface emitting lasers (VCSELs), which operate at approximately 850 nm, are being fabricated for integration with low power, optoelectronic integrated circuits. These high performance optoelectronic computing modules are being developed for high speed switching and data processing applications. The VCSEL array is a gain-guided, top-surface emitting device. It is fabricated from a GaAs/AlGaAs p-i-n distributed Bragg reflector structure, which is grown by metal organic chemical vapor deposition. The VCSEL fabrication process involves two stages of hydrogen ion implantation and three stages of metallization. A set of five photolithography masks has ben developed for VCSEL fabrication.
Optics will soon established as the mainstay for data-intensive communications at distances about 100 meters or less between workstations, displays and peripherals. The datacom hardware includes of arrays of multi-mode vertical-cavity surface-emitting lasers (VCSELs) emitting in the 650-1000 nm range and parallel channels of multi-mode optical fiber, which are major departures from the already-established long-distance optical fiber communications for telecom. These radical departures are brought about by two major forces. (1) They are forced by the driving need to reduce costs for datacom links to the consumer affordability level, as opposed to the network provider level in telecom links. (2) They are allowed by the different requirements of the shorter communication distances. In the future, optics is expected to replace traditional communication links at even shorter distances. If optical communications extends down to the inter-chip level, it is likely that the “chipcom” links will require technologies as different from datacom technologies as VCSEL arrays and fiber ribbons are from distributed feedback lasers and single-mode fibers. In this paper are reviewed the forces which shape the emerging datacom hardware, current state of datacom links, and a cmde forecast of what will be required for chipcom links.
Military aviators have a need for lightweight Helmet Mounted Display (HMD) systems capable of displaying Night Vision (NV) imagery (which has been collected at the O.665m-O.93Optm portion of the spectrum), Forward Looking Infrared (FLIR) imagery (which has been collected at the 3-5im and 8-l2im waveband portions of the spectrum) and/or Heads-Up Display (HUD) information. Present HMD systems have excessive head—supported weights and poor centers of gravity (CG), inducing fatigue and creating an unsafe ejection condition. These problems are created mostly by the weight of the optics and optics support structure attached to the side and front of the aviator's helmet. The optics are necessary to redirect the imagery output of a phosphor screen to the aviator's eyes with as much fidelity as possible. An alternative approach to present HMD systems involves the use of a microlaser based image output array. The micro—lasers would be an array of Vertical Cavity Surface Emitting Laser (VCSEL) diodes. VCSELs have circular output beams, as opposed to edge emitting laser diodes which have astigmatic output beams. The VCSEL circular output beam geometry lends itself to the use of micro-lenses. The micro-lenses allow for f/number modulation with a significantly reduced number of optical elements in the optical path during the redirection of the output image to the user's eyes. Reduced optical elements equate to reduced weight and better CG. In addition, this approach may allow for significantly greater fields-of-view (FOV), possibly in excess of 100 degrees. This paper addresses the attributes and drawbacks of current HMD systems (especially NV systems) and the attributes, drawbacks, and technical challenges associated with realization of a HMD utilizing VCSELs as a display illumination source.
We have reduced the threshold voltages and currents of vertical cavity surface emitting lasers by using dielectric high reflectivity mirrors which were deposited after the diode fabrication step. This device fabrication sequence is able to correct for inaccuracies in the crystal growth and allows the future development of more complex laser structures. The quantum- well based laser diodes were demonstrated at 0.72 micrometers , 0.85 micrometers , and 1.55 micrometers . Threshold currents and voltages of our 0.85 micrometers lasers were 2.8 mA at 1.7 V pulsed, and 4 mA when cw- pumped. The threshold currents of 5x7 micrometers <SUP>2</SUP> area 1.55 micrometers devices were 17 mA.
Optoelectronic integrated circuits based on arrays of vertical- cavity surface emitting lasers (VCSELs) are evolving into functional chips enhancing the performance of fiber optic networks, optical data storage, laser printing and scanning, visual displays, and optoelectronic computing and other systems. This evolution involves the development of advanced manufacturing technology germane to packaged arrays of VCSELs comprising micro- optic lens arrays and interface electronics. In this paper we describe Photonics Research's LASE-ARRAY commercial manufacturing efforts. Specifically we will discuss commercial manufacturing advancements in molecular beam epitaxial growth, full-wafer processing, interface electronics, microoptic lens arrays, packaging and implementation of statistical process control. Yield and reliability will also be discussed. Last we discuss emerging applications for the LASE-ARRAY technology.
The monolithic and hybrid integration of vertical-cavity surface-emitting lasers to phototransistors, heterojunction bipolar transistors, and field-effect transistors is presented. The integrated devices or `microlaser smart pixels' exhibit a high level of performance. For example, Boolean logic functions, high gain and speed are demonstrated. These `microlaser smart pixels' integrated with micro-optics have numerous applications.
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.
In the future optoelectronic integrated circuits (OEICs) are destined to evolve into sophisticated functional circuitry upon which a multiplicity of applications will be based, such as: optical communications, optical interconnects, optical computing, optical memory, laser printing and scanning, visual displays, pattern recognition, and neural networks. This evolution of OEICs involves the integration of phototransmitters (semiconductor lasers and light-emitting diodes), photoreceivers (photodetectors and phototransistors), spatial-light modulators, transistors (bipolar and field-effect), diodes, resistors and capacitors, and micro- optic components (e.g., micro lenses). We describe our efforts to date and future directions which are concentrated on the integration of vertical-cavity surface-emitting laser diodes (VCSELs) with transistors, photoreceivers, and micro-optic components. VCSELs, which may be patterned in high densities (over a million in a square cm) and emit light perpendicular to the plane of the substrate, have an ideal light-emitting geometry for the above mentioned applications and for integration with micro-optic components. We describe our efforts to develop monolithic surface-emitting laser logic devices, which we refer to as CELLs, consisting of phototransistors, current controlled bipolar transistors, and voltage-controlled field-effect transistors integrated with a VCSEL to form optically and electrically addressable photonic switching devices having high contrast. We also discuss the integration of micro- optics with VCSELs. Finally, we describe combinations of OEIC components and subassemblies and their applications to several of the above mentioned photonic switching applications.
We report batch-processed, totally planar, vertical-cavity top surface emitting GaAs/AlGaAs laser devices and arrays. Different size devices are studied experimentally. We measure continuous-wave threshold currents down to 1.7 mA and output powers > 3.7 mW at room temperature. We also discuss interesting characteristics such as differential quantum efficiencies exceeding unity and multi-transverse mode behavior. An array having 64 X 1 individually-accessed elements is characterized and shown to have uniform room-temperature continuous-wave operating characteristics in threshold current approximately equals 2.1 +/- 0.1 mA, wavelength approximately equals 849.4 +/- 0.8 nm, and output power approximately equals 0.5 +/- 0.1 mW.
Vertical-cavity surface-emitting lasers1 are generating much interest due to their geometric suitability for two-dimensional array fabrication and their potential for achieving ultra-low thresholds. Here we report on optically- and electrically-pumped microlaser devices. having transverse dimensions of a few microns and active material lengths of a few hundred A. The very small volumes are a key factor in achieving low thresholds. So far however surface recombination has prevented us from achieving thresholds much below 1 mA.
Vertical-cavity, surface-emitting lasers have great potential owing to their inherent two-dimensional geometry
and very small gain nedium volumes which are essential to low threshold currents. Possible applications are
optical switching/computing, photonic interconnection, high/low power laser sources, image processing,
optical neural networks, etc. Driven by these high promises, there have been numerous reports on vertical
cavity surface emitting laser diodes using InGaAs/GaAs/A1As, GaAs/AlGaAs structures16. In this paper, we
report characteristics of discrete InGaAs microlasers and monolithic two-dimensional arrays of microlasers.
The advantages of optics for communications of data over distances longer than nearby gates have been argued
previously7. We proposed and demonstrated a photonic interconnect scheme using microlasers with planar
optics which will be robust, accurate, and easily alignable.
Vertical-cavity electrically pumped surface-emitting microlasers are formed on GaAs substrates at densities greater than two million per square centimeter. Two wafers were grown with ln02Ga0As active material composing three 80 A thick quantum wells in one and a single quantum well (SQW) 100 A thick in the other. Lasing was seen in devices as small as 1 .5 jim diameter with <0.05 pm3 active material. SQW microlasers 5 x 5 m square had room-temperature cw current thresholds as low as 1.5 mA with 983 nm output wavelength. 10 x 10 m square SQW
microlasers were modulated by a pseudorandom bit generator at 1 Gb/s with less than 10_b bit error rate. Pulsed output >170 mW was obtained from a 100 .tm square device. The laser output passes through the nominally transparent substrate and out its back side, a configuration well suited for micro-optic integration and photonic switching and interchip connections.