Appendix H: Red VCSELs

Vertical‐cavity surface‐emitting laser (VCSEL) operating in the visible wavelengths has been commercialized in several applications such as blood oximetry, photodynamic therapy, and communications using plastic optical fiber. Plastic optical fiber has long been touted as an attractive economical alternative to glass optical fiber. The emitter definition is left to the implementor and can be a VCSEL, EEL, or LED, as appropriate. Single‐use measurement of the oxygen content in blood is an area of considerable interest in the medical community, particularly in the oxygen measurement of venous or capillary vessels. The use of lasers in medicine has been growing dramatically in the last decade and in particular the use of low‐level photodynamic therapy for home use. One particular example for red VCSELs is in regrowth of hair. Several companies have commercialized helmet‐ or hat‐type devices with many tens of VCSELs in the device.