This Issue 12(2) Photonics Letters of Poland contains 15 articles that have successfully undergone review processes and have been accepted for publication. The subjects of this issue concern mainly the problems of optoelectronic and photonic sensors. The group of papers includes works on the application of optical methods in medical engineering, including: eye examination, monitoring of the vortex chamber of the artificial heart, optical visualization of human tissues, detection of hemoglobin. Part of the works concern the subject of gas sensors, realized in integrated optics, planar optics as well as in systems using optical fibers. The issue also includes works on the use of photonic techniques in physico-chemical tests of materials, including graphene oxide and reduced graphene oxide. The utilitarian nature of most works is important. It should be expected that the research topics presented in Issue 12(2) PLP will be continued and developed by the Authors in the future.