Objective　Vertical　external　cavity　surface-emitting　lasers　(VECSELs)　combine　the　advantages　of　both　disc　and　semiconductor　lasers,　such　as　high　beam　quality,　low　cost,　and　compact　packaging,　making　them　suitable　for　a　wide　range　of　applications.　The　outer　cavity　structure　of　a　VECSEL　enables　convenient　control　of　the　transverse　mode　size　and　optical　gain　region　of　the　laser,　resulting　in　a　high-power　Gaussian　beam　near　the　diffraction　limit.　This　feature　significantly　improves　the　efficiency　of　applications　in　space　laser　communication,　laser　lighting,　and　beyond.　Similar　to　traditional　lasers,　VECSELs　can　also　employ　acousto-optic　or　electro-optic　modulation　technology　for　space　laser　communication;　however,　achieving　both　high　power　and　high　speed　simultaneously　remains　challenging,　and　the　addition　of　a　modulation　system　compromises　compact　packaging.　Unlike　solid　gain　media,　which　have　excessively　long　fluorescence　lifetimes,　the　VECSEL　gain　chip　possesses　a　nanosecond-scale　energy-level　lifetime,　supporting　high-speed　direct　modulation　within　the　cavity.　Nevertheless,　due　to　the　limitations　of　current　drive　circuit　performance,　direct　modulation　of　this　type　of　laser　has　not　yet　been　reported,　highlighting　the　need　to　explore　its　high-speed　modulation　characteristics.　Methods　In　this　study,　we　design　a　high-current,　high-frequency　drive　circuit　to　achieve　high-power　and　high-speed　direct　modulation　of　high-power　pumped　laser　diodes　operating　at　several　megahertz.　The　frequency　response　of　electro-optical　and　opto-optical　conversion　in　the　modulation　system　is　experimentally　analyzed.　Based　on　this,　a　directly　modulated　VECSEL　system　with　a　double-pump　structure　is　constructed,　and　the　influence　of　the　VECSEL　cavity　structure　on　the　high-speed　direct　modulation　characteristics　of　this　type　of　laser　is　further　examined.　Results　and　Discussions　First,　as　shown　in　Figs.　3　and　4,　optimizing　the　modulation　drive　circuit　enables　direct　modulation　of　the　high-power　laser,　enhancing　the　modulation　amplitude　of　the　output　pump　light　signal.　With　this　optimization,　the　3　dB　response　bandwidth　achieved　by　sine　wave　modulation　is　approximately　9.5　MHz.　Building　on　this,　the　VECSEL　system　is　directly　modulated　using　a　double-pump　structure,　and　the　modulation　bandwidth　is　further　improved　by　adjusting　the　VECSEL　resonator　length　and　the　transmittance　coefficient　of　the　output　mirror　to　increase　cavity　losses.　As　shown　in　Figs.　7　and　8,　a　VECSEL　laser　with　an　80　mm　cavity　length　and　a　2%　transmittance　output　mirror　exhibits　optimal　modulation　bandwidth,　reaching　approximately　6.3　MHz.　With　a　pump　power　of　5.27　W　and　the　removal　of　direct-current　bias　power,　the　output　modulation　laser　power　reaches　approximately　2　W.　Due　to　the　low　one-way　gain　of　the　VECSEL,　increasing　the　output　mirror　transmittance　leads　to　a　rapid　reduction　in　output　optical　power.　Conclusions　VECSEL　technology,　with　its　excellent　beam　quality　and　flexible　wavelength　design　capability,　holds　promising　applications　in　space　optical　communication.　The　VECSEL　direct　modulation　system　comprises　a　drive　circuit,　pump　source,　gain　chip,　and　laser　resonator,　with　its　high-frequency　characteristics　determined　by　the　module　with　the　lowest　upper-frequency　response.　To　simplify　the　modulation　drive　circuit　design,　the　laser　diode　(LD)　pump　source　should　operate　in　high-voltage,　low-current　mode,　with　further　hardware　optimizations　achieved　through　a　dual-pump　structure　to　enhance　laser　modulation　power.　Addressing　baseband　signal　modulation　requirements,　this　study　employs　a　high-power,　high-frequency　transistor　as　the　core　switching　device,　achieving　an　LD　pump　light　modulation　frequency　of　nearly　10　MHz　with　high　modulation　depth　by　optimizing　circuit　parameters.　A　VECSEL　direct　modulation　system　is　developed　based　on　these　parameters,　and　the　high-frequency　modulation　characteristics　of　the　VECSEL　laser　are　studied　by　adjusting　the　cavity　length　and　end　mirror　transmittance.　Results　indicate　that　the　VECSEL　modulation　bandwidth　is　significantly　influenced　by　cavity　losses.　When　the　cavity　length　is　80　mm　and　the　output　mirror　transmittance　is　2%,　the　system　achieves　a　3　dB　bandwidth　of　6.3　MHz.　With　further　advancements　in　drive　circuit　performance　and　selection　of　LD　pump　sources　with　lower　capacitance　effects,　combined　with　resonator　structure　optimization,　the　modulation　bandwidth　of　the　VECSEL　direct　modulation　system　can　potentially　exceed　10　MHz.　Additionally,　integration　with　VECSEL　frequency-doubling　blue　light　technology　can　extend　the　system　applications　to　underwater　laser　communication　and　other　fields.　©　2025　Science　Press.　All　rights　reserved.