The　high　single　fundamental　mode　output　power　vertical　cavity　surface　emitting　laser　(VCSEL)　has　been　attracted　many　attention　due　to　its　important　applications　in　the　fields　of　optical　communications,　sensing,　atomic　frequency　standard　and　opto-electronic　hybrid　integration.　With　suitable　photonic　crystal　structure　and　distribution,　the　lateral　modes　of　VCSEL　can　be　effectively　controlled　by　introducing　the　photonic　crystal　structure　into　the　top　distribution　Bragg　reflector　(DBR).　In　this　paper,　square　array　photonic　crystal　structure　was　introduced　into　the　VCSEL　to　control　the　transverse　mode　and　single　fundamental　mode　output　power.　The　plane　wave　expansion　and　the　full-vector　three-dimensional　finite　difference　time　domain　method　(FDTD)　method　were　used　to　analyze　the　photonic　crystal　structure　and　arrangement.　The　important　parameters　such　as　the　period,　the　duty　cycle　and　the　etching　depth　of　the　square　arrangement　photonic　crystal　were　obtained　by　using　these　methods.　The　high　output　power　square　lattice　photonic　crystal　single　fundamental　mode　VCSEL　was　reported.　The　single　fundamental　mode　output　power　of　the　square　lattice　photonic　crystal　VCSEL　is　larger　than　3　mW　and　the　side　mode　suppression　ratios　(SMSRs)　is　more　than　40　dB.　©　2018,　Editorial　Board　of　Journal　of　Infrared　and　Laser　Engineering.　All　right　reserved.