Viewing a single comment thread. View all comments

Skeptical0ptimist t1_j7g5bw0 wrote

Most likely because development cost of red and green/blue semiconductor diode lasers have been paid for by other applications, and those devices are available cheap. Selling laser pointers probably does not generate enough profit to develop their own laser technology.

Optical data storage used to be pretty big, and paid for development of semiconductor lasers. CDROM used AlGaAs/GaAs/AlGaAs thin film 'stack' which emits in red spectrum. BlueRay uses GaN/InGaN/GaN stack, which emits green or blue depending on In content in the middle layer. So these lasers were/are produced in volume.

You can get yellow/orange LED (light emitting diodes), but not lasers. Old LEDs used to be doped GaP, which are pretty dim. More recent ones are AlInGaP layer wafer-bonded to GaP substrate. These are frequently used in traffic lights, and very bright.

The reason data storage lasers skipped yellow/orange is because timing of invention of green/blue lasers. Shorter the wavelength (red > yellow > green > blue), higher the data density on the storage disk. Green/blue lasers were invented before red-laser CDROM had gone obsolete. So when the time came for data storage industry to move to a shorter wavelength, they decided to put development money into green/blue.

16