The mode of heat transfer is very important for applications like this. Higher mass flow means you need a hotter heater which can get tricky for long term usage

The mode of heat transfer is very important for applications like this. Higher mass flow means you need a hotter heater which can get tricky for long term usage or you'll have to use some sort of refractory or ceramic based heater. Also with conduction, the biggest problem is heat loss either due to the environment of the system . It is almost impossible to direct all your energy towards a single source with conduction. Radiation on the other hand works really well for this type of application. Especially for lasers since the energy sources is highly polarized and condensed. The other method might be to use induction heaters or microwave, but plastics do not play well with that.