Ultrafast　injection-locked　amplification　is　achieved　by　sending　femtosecond　supercontinuum　pulses　into　a　polymeric　thin　film　coated　on　a　distributed　feedback　(DFB)　microcavity　consisting　of　chirped　gratings.　The　spatial　variation　of　the　grating　period　led　to　the　resonance　of　the　DFB　microcavity　at　different　wavelengths　for　injection　at　different　locations.　This　enables　convenient　and　continuous　tuning　of　the　amplification　spectrum　by　displacing　the　grating　structures.　The　large　area　of　the　grating　structures　enabled　large　tuning　range.　The　amplified　spectrum　can　be　continuously　tuned　from　545　to　580　nm　through　sliding　the　grating　structures　by　about　3.5　mm.　Sub-1　ps　lifetime　has　been　measured　for　the　amplification　process　with　a　net　amplification　factor　as　large　as　33.　Injection　locking　enabled　high-quality　control　of　the　divergence　and　transverse　mode　of　the　output　laser　beam.