Disclosed herein are optical assemblies having thin, low profile shapes. These optical assemblies may be used with
fiber coupled lasers and other light sources, including high power sources, to irradiate tissue at a
wavelength suitable for inducing
ablation or coagulation to a target depth, denaturation, thermal modification of a tissue, and / or preferential injury to a
target tissue structure. Example optical assemblies can produce substantially uniform illumination patterns that are useful for treating superficial tissue, including the internal or luminal (e.g., esophageal) tissue. Some examples may have capability for cooling superficial tissue or
skin, such as a detachable, reusable
heat sink for
active cooling without
consumables, fluid pumps, or other cooling equipment.