A reflection filter is disposed on a solid state laser so as to preferentially reflect TE or TM modes and to suppress oscillation within the resonator of the non-reflected modes. In one embodiment, the filter includes a layer having a plurality of grooves which may be straight and parallel or curved...http://www.google.com.au/patents/US4870649?utm_source=gb-gplus-sharePatent US4870649 - Tranverse mode control in solid state lasers
