Self-supporting　gold　nanowire　(AuNW)　gratings　with　a　thickness　of　about　200　nm　are　produced　by　solution-processing　and　flexible-transfer　techniques.　Such　an　ultrathin　structure　is　applied　as　an　ultrafast　optical　switch　that　enables　low-threshold　optical　modulation　with　a　high　signal　contrast　and　a　high　signal-to-noise　ratio.　Transient　energy-band　modification　in　gold　under　excitation　by　femtosecond　laser　pulses　is　the　main　responsible　mechanism.　For　a　pump　fluence　of　about　170　mu　J　cm(-2),　a　modulation　depth　of　about　10%　is　achieved　for　the　optical　switching　signal.　Self-supporting　metallic　plasmonic　photonic　thin　films　with　a　large　area　and　flexible　structures　are　important　for　applications　in　a　large　variety　of　circumstances　and　on　different　interfaces　for　optical　signal　processing,　optical　logic　circuits,　and　optical　communication　systems.