The best treatment for PIH on darker skin is to allow for gradual spontaneous clearance over several to many months and avoiding further skin injury/inflammation that will make the PIH worse. The use of lightening creams makes help hasten the process.
Q-switched 1064nm lasers have been used with variable success in treating PIH. If used, I have found it safer to use a low fluence toning technique rather than a high fluence blasting technique which tends to worsen the PIH instead of improving it.
I have not found fractional radiofrequency (e.g. Venus Viva) useful in treating PIH. Venus Viva remains primarily a skin resurfacing procedure.