Is a long-pulsed diode laser machine with the 1064-nm handpiece safe to treat Skin Type V and VI?

The only laser that should be used on the darker skin types is a 1064 laser. It still needs to be operated appropriately with proper settings and cooling. I don't think that diode lasers emit a 1064 wavelength, they are generally Nd:YAG lasers. 

As long as the wavelength is 1064 nm, whether it is emitted by Diode or Nd:YAG, it should be safer on darker skin types. Also its important to remember that safety does not equate to efficacy. However diodes do not give much control over the pulse widths like the Nd;YAG machines do. Beam emitting Nd YAG also allows for more precise targeting.