High quality carbon nanochains or carbon nanotubes are produced by methods that include mixing a carbon-containing feedstock with a catalyst to form a feedstock/catalyst mixture, or coating a catalyst with a carbon-containing feedstock, and subjecting the feedstock/catalyst mixture or feedstock-coated catalyst to irradiation with a laser to convert the feedstock into carbon nanochains or carbon nanotubes in the presence of the catalyst. In some instances, the feedstock is converted to a char by pyrolysis and the char is instead subjected to laser irradiation. The carbon-containing feedstock can be a biomass or a carbonaceous material. In some instances, the catalyst is a metal salt, preferably a transition metal salt. In some instances, the catalyst is an elemental metal, an alloy, or a combination thereof.