Will light therapy help bipolar-type disorder?

Not really. There is some thought that seasonal affective disorder is a variant of bipolar disorder. Light therapy can be effective food those who experience depression during the fall and winter. Outside of that, it would have no benefit.
Light therapy. has been used to treat: fatigue, jet lag, sleep disorders, seasonal affective disorder, depression, dementia and transitions to night work schedules. It would need to be used cautiously for bipolar disorder due to the possibility of becoming agitated or flipping into mania. See: http://www.mayoclinic.org/tests-procedures/light-therapy/home/ovc-20197416.