Generally the evidence for any electrophysical agent in these sorts of problems is disappointing. However There is some evidence for a beneficial effect of laser at the right dosage for a number of tendon problems around the body. Here is a look on PEDro for evidence for laser:

PEDro - Search Results

However I would interpret the benefit from laser as most likely some form of pain modulation and therefore is very much a symptomatic treatment - rather than doing a lot for the tendon. What really is going to count is the appropriate sort of exercise which it sounds like you are already doing. To get the beneficial effects of eccentric muscle training, it can take quite some time. So you could throw laser in the mix so to speak (to get some pain relief so you can do more) but keep persisting and progressing with the eccentric training. Tendons take time to remodel. If you don't get any improvements in your symptoms at 3 months then it is time to get it reviewed.

Here are some questions
What exercise are you actually doing and how do you progress the exercise as the muscle gets stronger?
Is your exercise being supervised by a PT?
Did the PT really check your back and hip? You want to be sure there isn't a referred pain component to your problem - this may be unlikely but it is worth getting it ruled out.