Although the low level laser therapy against tinnitus is known for more than 20 years, it is still a rather controversial treatment (and therefore usually not covered by health insurances). It is based on the theory that tinnitus is caused by damage or deterioration of the hair cells in the inner ear, and that this damage can be repaired by supplying radiative energy to the inner ear by means of the laser (although the laser can not directly reach the inner ear due to the amount of tissue that must be traversed, it is assumed that there is still sufficient energy being supplied to the inner ear). The low level laser therapy is either applied by a practitioner in special tinnitus clinics/practices (of which however there exist only very few) or one can buy or rent corresponding devices for home treatment. Whilst the latter are usually less expensive than a clinical treatment (which has to last for several sessions), they are also less powerful and therefore probably less effective.

Whether the above theory of the laser repairing the hair cell damage is correct is at least debatable since in many (if not the majority) of cases there is no reason to assume that the hair cells are damaged at all (the tinnitus is solely caused by by the nervous system). But there are a number of studies which seem to indicate that the low level leaser therapy is effective in at least significantly improving the condition, but these have usually been performed or sponsored by the institutions applying these treatments or selling lasers for home treatments. This is not to say that they should necessarily be questioned, but, as far as I am aware, independent studies have as yet not conclusively confirmed the effectiveness of the low level laser therapy.
Nonetheless, I know personally of people who have experienced a substantial improvement of the condition after having had a low level laser therapy treatment, so for anyone looking for a last resort it might still be worth checking out (even though it is a costly option).