Methods and apparatus for improved heat spreading in solid state lighting systems

A solid state lighting subassembly or fixture includes an anisotropic heat spreading material. A heat spreading layer may be placed between a light emitting diode (LED) and luminaire or reflector and serves to spread heat laterally away from the LED. Low profile, low weight heat spreading may be utilized both to retrofit existing light fixtures with LEDs or to replace existing incandescent and fluorescent fixtures with LED based fixtures.