A　novel　high-power　semiconductor　laser　diode　(LD)　with　very　large　cavity　using　multi-active-layer　cascaded　by　tunnel-junction　was　developed.　The　window　size　of　the　LD　was　enlarged　extremely　and　less　than　20　degree　of　the　lasing　beam　divergency　was　obtained,which　benefits　the　coupling　between　the　LD　and　the　optical　fiber.　Many　types　of　lensed　fibers　were　used　to　test　with　the　LD　and　the　coupling　efficiencies　were　increased　over　30%　compared　with　the　conventional　LD.