Objective　The　significance　of　deep-ultraviolet　(DUV)　band　light　is　its　unique　sterilization　and　disinfection　ability,　environmental　performance,　and　wide　application　in　other　fields.　Specifically,　deep　ultraviolet　light　can　destroy　the　deoxyribonucleic　acid　(DNA)　or　ribonucleic　acid　(RNA)　structure　of　microorganisms,　such　as　bacteria　and　viruses,　thereby　achieving　efficient　sterilization　and　disinfection.　In　addition,　DUV　technology　has　been　applied　in　multiple　fields　such　as　water　purification,　air　purification,　medical　treatment,　biological　research,　national　defense　security,　and　ultraviolet　communication,　demonstrating　broad　application　prospects.　Therefore,　the　DUV　bands　are　crucial　in　improving　the　quality　of　human　life　and　promoting　technological　progress.　Deep-ultraviolet　vertical-external-cavity　surface-emitting　laser　(VECSEL)　can　achieve　high　output　power,　excellent　beam　quality,　and　tunable　wavelength　by　optimizing　the　resonant　cavity　structure　to　meet　the　urgent　demand　for　DUV　laser　sources　in　scientific　research　and　industrial　fields.　Stable　and　efficient　DUV　VECSELs　provide　advanced　analytical　tools　and　technical　means　in　fields　such　as　materials　science,　biomedicine,　and　environmental　monitoring.　In　addition,　research　on　DUV　VECSEL　will　promote　the　development　of　nonlinear　optical　frequency　conversion　and　quantum　frequency　conversion　technologies,　providing　key　technical　support　for　cutting-edge　fields　such　as　quantum　communication　and　quantum　computing.　Overall,　research　on　DUV　VECSEL　aims　to　expand　the　application　boundaries　of　laser　technology　and　promote　technological　progress　and　industrial　development.　Methods　First　a　gain　chip　with　a　center　wavelength　of　980　nm　is　designed.　A　high-Al-composition　Al0.6GaAs　etch　stop　layer　is　grown　on　a　GaAs　substrate　to　block　selective　corrosion.　Subsequently,　a　GaAs　cap　layer　is　grown,　and　after　the　etch-stop　layer　is　corroded,　this　layer　becomes　the　outermost　layer　of　the　gain　chip,　providing　protection　for　the　chip.　Next,　the　active　region　is　grown,　which　is　mainly　composed　of　12　pairs　of　In0.2GaAs/GaAsP0.02　multiple　quantum　wells　(MQWs).　The　content　of　In　in　the　In0.2GaAs　quantum-well　material　corresponds　to　a　design　wavelength　of　980　nm,　but　epitaxial　growth　on　the　GaAs　substrate　introduces　a　compressive　strain　of　approximately　1.4%,　which　affects　the　quality　of　epitaxial　growth.　To　minimize　the　frequent　replacement　of　material　types　during　epitaxial　growth　and　better　ensure　the　quality　of　epitaxial　growth,　this　chip　design　specifically　uses　the　GaAsP　layer　not　only　as　a　stress　compensation　layer　but　also　as　a　barrier　layer　for　quantum　wells.　Therefore,　the　content　of　P　in　GaAsP　needs　to　be　finely　and　reasonably　designed　to　be　sufficiently　high　to　compensate　for　the　stress　introduced　by　multiple　quantum　wells.　However,　if　the　content　of　P　is　too　high,　InGaP　cannot　absorb　pump　photons.　The　final　growth　part　of　the　gain　chip　is　the　distributed　Bragg　reflector　(DBR),　which　is　composed　of　30　pairs　of　alternating　GaAs/AlAs,　with　each　layer　having　an　optical　thickness　of　1/4　laser　wavelength,　which　is　980　nm.　Next　is　the　performance　testing　of　the　gain　chips,　especially　temperature　and　power　testing,　which　directly　affects　the　quality　and　efficiency　of　the　final　output　light.　Temperature　and　power　testing　are　particularly　important,　because　they　can　intuitively　reflect　the　stability　and　output　power　of　chips　in　different　working　environments.　It　is　particularly　noteworthy　to　observe　the　redshift　phenomenon　between　the　chip　design　wavelength　and　the　actual　output　wavelength.　Subsequently,　the　design　of　optical　resonant　cavities　and　the　optimization　of　crystal　selection　are　also　key　steps　in　improving　optical　conversion　efficiency.　When　using　a　flat　concave　cavity　structure,　it　is　necessary　to　accurately　match　the　core　diameter　of　the　pump　with　the　laser　spot　inside　the　resonant　cavity　and　calculate　the　waist　position　of　the　laser　inside　the　cavity　through　simulation.　This　is　directly　related　to　the　placement　and　length　selection　of　the　subsequent　crystals.　Based　on　the　waist　size,　the　optimal　crystal　length　can　be　calculated,　and　the　crystal　can　be　accurately　placed　at　the　position　of　the　laser　waist　to　achieve　high-　frequency　doubling　conversion　efficiency　and　high-power　blue　light　output.　Finally,　the　high-　power　blue　light　obtained　is　further　converted　into　245　nm　deep　ultraviolet　light　through　barium　metaborate　(BBO)　crystals.　Results　and　Discussions　We　use　a　specially　designed　semiconductor　gain　chip　(Fig.　1).　The　characteristics　and　advantages　of　the　flat　concave　V-　shaped　cavity　frequency-　doubled　blue　light　combined　with　the　generated　frequency-　doubled　blue　light　for　fourthharmonic　generation　result　in　a　DUV　output　at　246.8　nm.　The　results　indicate　that　the　frequency-　doubled　blue　light　obtained　using　this　cavity　structure　has　excellent　beam　quality,　close　to　the　diffraction　limit,　a　small　beam　divergence　angle,　and　a　more　stable　output　mode　while　producing　high　power.　In　this　study,　a　type-　I　phase-　matched　lithium　triborate　(LBO)　crystal　is　selected　as　the　frequency-doubling　crystal.　At　an　operating　temperature　of　15　℃　using　thermoelectric　cooler　(TEC),　a　0.5　mm　thick　birefringent　filter　is　inserted　into　the　cavity.　Using　a　5　mm　long　LBO,　we　obtain　a　high-　power　blue　light　output　of　4.5　W　at　a　wavelength　of　493　nm　(Fig.　4).　After　passing　through　the　type-　I　phase-　matched　BBO　crystal,　a　DUV　output　of　29.2　mW　at　a　wavelength　of　246.8　nm　is　obtained　(Fig.　7).　This　frequency-　quadrupled　VECSEL　has　advantages　such　as　excellent　beam　quality,　easy　implementation,　and　a　compact　structure.　Conclusions　This　paper　presents　the　output　of　a　compact　frequency-　quadrupled　vertical　external　cavity　surface　that　emits　a　DUV　laser.　A　V-　type　laser　resonant　cavity　is　constructed　using　specially　designed　semiconductor　gain　chips,　folding　mirrors,　and　rear-　end　mirrors.　Under　a　working　temperature　of　15　℃,　a　high-　power　blue　light　output　of　4.5　W　is　obtained　by　inserting　a　5　mm　long　LBO　crystal.　A　single-　pass　four-　fold　structure　is　formed　by　combining　the　rear　reflection　mirror,　ultraviolet　folding　mirror,　and　ultraviolet　output　mirror　of　the　frequency-　doubling　blue　resonant　cavity.　The　obtained　blue　light　passes　through　a　3　mm　long　type　I　phase-matched　BBO　crystal,　resulting　in　a　246.8　nm　DUV　laser　output　with　a　power　of　29.2　mW　through　an　output　mirror　with　a　transmittance　of　50%　at　a　wavelength　of　245　nm.　The　aforementioned　experimental　results　are　limited　by　the　pump　power　and　coating　of　each　optical　lens.　The　DUV　laser　in　this　band　can　play　a　significant　role　in　sterilization,　disinfection,　formaldehyde　treatment,　and　other　fields.　©　2025　Science　Press.　All　rights　reserved.