Apparatus, methods, systems and devices for temperature independent or minimally temperature dependent narrow spectrum laser having an optimized output. The resonator includes at least one volume Bragg grating mirror that changes reflectance with temperature. The volume Bragg grating mirror in combination with a narrow spectrum laser optimizes the laser performance by being temperature tuned to the optimum reflectance. In an embodiment, the volume Bragg grating mirror has a temperature dependent reflectance that compensates for changes in the stimulated emission cross section of the gain medium and leads to a laser with output energy that is independent of temperature.