Limits of Pulse Frequency..?

A bit of inchoherent light is just a side effect of semiconductor impurities, and will never yield an extra wavelength a diode could lase at.

Diode lasers are not tunable mostly because their wavelength is simply determined by the bandgap of the semiconductor they are made off, and this is not a property that can be changed on the fly. One factor that does affect this bandgap is the temperature of the laser, so in order to alter a diode lasers wavelength you can cool or heat it.

This effect isn't -very- big though, perhaps a few nm for every 10 degree temperature change. It is, however, useful when you need to match a 808 pump diode to a Nd:YVO solid state laser.

If you want to put a 100 Mhz FM carrier on a common small laser diode, no problem.
It will become AM, and a fast detector diode will translate it back to FM riding on a dc bias.

You need a "Bias T", its a inductor on one side, and lets the DC in to get the diode above threshold, but keeps the RF out of the bias supply. A capacitor couples in the RF with the modulation. The diode is in the third leg and one end is of course grounded.

Thorlabs.com - Laser Diode Bias-T PCB

Before you cringe at the price, consider whom their limited market is for the product.
Thats cheap if you don't have board fab skills and a way to insure you have a 50 ohm impedance.


Steve