Embodiments of the present invention provide improved laser systems and methods for endoscopic laser treatment of abnormal tissue such as abnormal mucosal tissue, for example esophageal dysplasia that is also referred to as Barretts esophagus (BE). The systems and methods described here can also be used in many applications where treatment of shallow surface layers with minimal damage to the tissue beneath is desirable, for example BE tissue comprising hemoglobin. In many embodiments, the system is configured to emit light energy having an optical wavelength to treat tissue having oxygenated hemoglobin.
