Softening hairline after HT using laser with low energy, is it possible ?

You cannot use lasers to achieve a better hair line. You need a better doctor to achieve a better hair line.  In general if you have very coarse donor hair your hair line may look harsh.  However a good doctor with good surgical technique and artistic skills can make a hair line look soft and natural.

I'm not aware of this being helpful.  If single hair follicles are used in the front of the hairline and packed in an appropriate density and orientation the results should look very natural. Hairs at the name of the neck may provide "thinner" hairs than mid post scalp.

Dear houssam23,True that laser and other technique can decrease the caliber of transplanted coarser hair. Sorry but I have to disagree that even with the best surgeons hair lines do not look natural. Modern hair restoration techniques have made possible completely natural looking results, even in highly visible areas like beards, eyebrows and eyelashes. Please do your research well,finding the results that you are looking for are well worth the effort!Good luck,B. Arocha, MD

An interesting idea, but a better idea to achieve a natural hairline is to dense pack it with true single hair grafts. If there is an unnatural look to the hairlines you've been looking at it is most likely due to the spaces between the hairs, not the caliber of the hairs themselves. Even patients with course fat hairs can have a natural looking hairline if built with pure single packed tightly. In fact, that's how we fix plug hairlines. 

This does not work for that purpose. The key to creating a soft hairline is to take the smallest single hairs and place them in the front of the transplanted hairline. This is done at the time of the surgery. Experienced doctors know how to do this. Doctors should NEVER use neck hair for this purpose because neck hair is not permanent hair in many people and neck donor areas scar more than scalp hair extractions do.