Abstract
Red VCSELs offer the benefits of improved performance and lower power consumption for medical and industrial sensing, faster printing and scanning, and lower cost, higher speed interconnects based upon plastic optical fiber (POF). However, materials challenges make it more difficult to achieve the desired performance than at the well-developed wavelength of 850 nm. This paper will describe the state of the art of red VCSEL performance and the results of development efforts to achieve improved output power and a broader temperature range of operation. It will also provide examples of the applications of red VCSELs and the benefits they offer. In addition, the packaging flexibility offered by VCSELs, and some examples of non-Hermetic package demonstrations will be discussed. Some of the red VCSEL performance demonstrations include output power of 14 mW CW at room temperature, a record maximum temperature of 115∘C for CW operation at an emission wavelength of 689 nm, time to 1% failure at room temperature of approximately 200,000 hours, lifetime in a 50∘C, 85% humidity environment in excess of 3500 hours, digital data rate of 3 Gbps, and peak pulsed array power of greater than 100 mW.
Highlights
Multimode 850 nm VCSELs based upon the AlGaAs materials system have been the standard optical source for glass fiber optic-based data communication links since the mid-1990s
The AlGaAs materials system which is used for 850 nm VCSELs provides good lattice matching over the full range of compositions, a reasonably good refractive index contrast between the high index (AlGaAs with approximately 15– 20% mole fraction AlAs) and low index (AlAs) materials used for the mirrors, and a high conduction band offset between the GaAs quantum wells and the AlGaAs compositions normally used as quantum well barriers
One of the most challenging aspects of designing red VCSELs has been achieving useable output power over the temperature ranges required by the applications of interest
Summary
Multimode 850 nm VCSELs based upon the AlGaAs materials system have been the standard optical source for glass fiber optic-based data communication links since the mid-1990s. The AlGaAs materials system is usually used for the mirrors Several limitations for these shorter wavelength VCSELs exist: (1) the available conduction band offset is smaller and ranges from approximately 0.17 eV at 650 nm to 0.23 eV at 700 nm [1]. (2) The requirement that the mirrors be nonabsorbing limits the mirror compositions available to AlGaAs materials with AlAs mole fraction greater than 0.4-0.5. This reduces the available range of refractive index, requiring more mirror periods to achieve the same reflectivity. Advances in Optical Technologies paper will first review the progress that has been made, will discuss recent developments, and discuss some applications of the technology
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