VCSELs (Vertical Cavity Surface Emitting Lasers ) provide a very versatile optical source for Low Light Therapy
applications. This talk will discuss performance characteristics and packaging demonstrations for VCSELs primarily
operating in the 680nm and 850nm regimes. At 680nm individual VCSELs produce >10mW, while >0.35W can be
provided from a 0.4mm2 emission area. Spectral width is typically 1-2nm even for a multi-mode or array device. At
850nm these numbers increase to >30mW and >0.8W. Even higher powers can be achieved under pulsed modulation,
i.e. 0.55W for a 680nm VCSEL or 1.2W for an 850nm VCSEL. While we report on results achieved at 680nm and
850nm, extension to wavelengths ranging from 660nm to 1000nm is easily achieved.
The packaging flexibility of VCSELs also makes them of significant interest to the Low Light Therapy community. We
will report on the incorporation of VCSELs into surface mount packages, including typical LED packages such as the
PLCC, or ceramic chip carriers. VCSELs in PLCC packages have been attached to flexible circuits to provide a broad
area illumination. We will also report on a unique chip on board package which easily allows for the addition of optical
elements such as diffusers, diffraction gratings or lenses. This package is 2mm on a side, sufficiently small for
incorporation into catheters or implantation.
Vixar has been developing VCSELs at both shorter (680nm) and longer (1850nm) wavelengths. This paper reports on
advances in technology at both of these wavelengths. 680nm VCSELs based upon the AlGaAs/AlGaInP materials
system were designed and fabricated for high speed operation for plastic optical fiber (POF) based links for industrial,
automotive and consumer applications. High speed testing was performed in a “back-to-back” configuration over short
lengths of glass fiber, over 42 meters of POF, with and without I.C. drivers and preamps, and over temperature.
Performance to 90°C, 10 Gbps and over 40 meters of plastic optical fiber has been demonstrated. Reliability testing has
been performed over a range of temperatures and currents. Preliminary results predict a TT1% failure of at least 240,000
hours at 40°C and an average current modulation of 4mA. In addition, the VCSELs survive 1000 hours at 85% humidity
85°C in a non-hermetic package. 1850nm InP based VCSELs are being developed for optical neurostimulation. The
goals are to optimize the output power and power conversion efficiency. 7mW of DC output power has been
demonstrated at room temperature, as well as a power conversion efficiency of 12%. Devices operate to 85°C. Over
70mW of pulsed power has been achieved from a 35 VCSEL array, with a pulse width of 10μsec.
Vixar has recently developed VCSELs at 1850nm, a wavelength of interest for neural stimulation applications. This
paper discusses the design and fabrication of these new long-wavelength lasers, and reports on the most recent
performance results. The VCSELs are based on InP-compatible materials and incorporate highly strained InGaAs
quantum wells to achieve 1850nm emission. Current confinement in the VCSEL is achieved by ion implantation,
resulting in a planar fabrication process with a single epitaxial growth step. Continuous wave lasing is demonstrated
for aperture sizes varying from 8 to 50μm with threshold currents of 1-17mA. The devices demonstrate peak power
of 7mW at room temperature and CW operation up to 85°C.
Red VCSELs are of interest for medical and industrial sensing, printing, scanning, and consumer electronics
applications. This paper will describe the optimization of red VCSEL design to achieve improved output power and a
broader temperature range of operation. We will also discuss alternative packaging approaches and in particular will
describe non-hermetic packages and performance of the VCSELs in a humid environment.
Record output power of 14mW CW and a record maximum temperature of operation of 105°C have been achieved at an
emission wavelength of 680nm. The achievement is the result of attention to many details including resonance cavitygain
peak offset, material choices, current and mode confinement approaches, and metal aperture design. We have also
demonstrated lifetimes >1000 hours for non-hermetic packages in an 85% humidity environment. A chip on board
approach has been used to create a large scale linear array of VCSELs for a scanning application.
Although vertical cavity surface emitting lasers (VCSELs) have traditionally found their place in high-speed
communication links, the recent advancements of VCSELs emitting in the visible spectrum has sparked interest
for new applications in scanning and imaging. Compared to other lasers, VCSELs have many advantageous
characteristics including compact size, low power requirements, low cost, and high reliability. VCSELs also offer
the unique ability to be fabricated in one- or two-dimensional arrays, making it possible for multiple VCSELs on
a single chip to perform the same function as a mechanically scanned beam. One such application is computed
radiography (CR), which provides an efficient solution for digitizing and electronically storing x-ray images. In
this work, we demonstrate a 1-inch prototype CR scanner based on high-density VCSEL arrays. The device is
capable of generating very fast scans with no moving parts, and has the potential to increase throughput, stability,
and image quality. In this paper, we discuss the design and performance of this scanner and demonstrate X-ray
image acquisition with resolution exceeding 5 line pairs per millimeter (lp/mm).