A　3–5　µm　mid-infrared　(MIR)　laser　has　a　wide　range　of　applications　in　biological　tissue　ablation,　remote　spectral　fingerprint　recognition,　and　directional　infrared　countermeasures.　However,　the　performance　of　conventional　MIR　lasers　has　long　been　hindered　by　restricted　wavelength　radiation,　spectral　power　efficiency,　and　system　stability.　Here,　a　highly　efficient,　compact,　and　stable　MIR　light　source　is　reported,　which　is　directly　generated　from　a　supercontinuum　(SC)　laser　with　a　long　wavelength　edge　of　4.2　µm　in　a　7　µm　core　diameter　fluorotellurite　fiber.　Based　on　the　integration　of　a　high-peak-power　pump　light　source　and　a　small-core-diameter　nonlinear　medium,　efficient　nonlinear　frequency　conversion　from　traditional　near-infrared　laser　to　mid-infrared　laser　has　been　achieved,　resulting　in　a　significantly　enhanced　MIR　spectrum　of　3.7　µm,　exceeding　the　pump　peak　of　2　µm　by　more　than　12　dB.　The　pump　conversion　efficiency　is　50.8%,　with　94.3%　of　the　spectral　power　distributed　above　2.4　µm　and　71.4%　above　3　µm.　This　study　has　opened　up　a　feasible　avenue　for　obtaining　high-efficiency　mid-infrared　band　lasers　that　meet　practical　application　needs.　©　2025　Optica　Publishing　Group.　All　rights,　including　for　text　and　data　mining　(TDM),　Artificial　Intelligence　(AI)　training,　and　similar　technologies,　are　reserved.