Low-loss regrowth-free long wavelength quantum cascade lasers

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buir.contributor.authorGündoğdu, Sinan
buir.contributor.authorDemir, Abdullah
buir.contributor.authorPisheh, Hadi Sedaghat
buir.contributor.authorAydınlı, Atilla
dc.citation.epage2000en_US
dc.citation.issueNumber23en_US
dc.citation.spage1997en_US
dc.citation.volumeNumber30en_US
dc.contributor.authorGündoğdu, Sinanen_US
dc.contributor.authorDemir, Abdullahen_US
dc.contributor.authorPisheh, Hadi Sedaghaten_US
dc.contributor.authorAydınlı, Atillaen_US
dc.date.accessioned2019-02-21T16:04:40Z
dc.date.available2019-02-21T16:04:40Z
dc.date.issued2018-12-01en_US
dc.departmentDepartment of Physicsen_US
dc.departmentNanotechnology Research Center (NANOTAM)en_US
dc.departmentInstitute of Materials Science and Nanotechnology (UNAM)en_US
dc.departmentDepartment of Mechanical Engineeringen_US
dc.description.abstractOptical power output is the most sought-after quantity in laser engineering. This is also true for quantum cascade lasers operating especially at long wavelengths. Buried heterostructure cascade lasers with epitaxial regrowth have typically shown the lowest loss due to high current confinement as well as superior lateral thermal conductivity at the expense of complexity and cost. Among the many factors affecting optical output are the widely used passivating materials such as Si3N4 and SiO2. These materials have substantial optical absorption in the long wavelength infrared, which results in optical loss reducing the output of the laser. In this letter, we report on quantum cascade lasers with various waveguide widths and cavity lengths using both PECVD grown Si3N4 and e-beam evaporated HfO2 as passivating material on the same structure. Their slope efficiency was measured, and the cavity losses for the two lasers were calculated. We show that HfO2 passivated lasers have approximately 5.5 cm-1 lower cavity loss compared to Si3N4 passivated lasers. We observe up to 38% reduction in lasing threshold current, for lasers with HfO2 passivation. We model the losses of the cavity due to both insulator and metal contacts of the lasers using Comsol Multiphysics for various widths. We find that the loss due to absorption in the dielectric is a significant effect for Si3N4 passivated lasers and lasers in the 8-12-μm range may benefit from low loss passivation materials such as HfO2. Our results suggest that low-loss long wavelength quantum cascade lasers can be realized without epitaxial overgrowth.
dc.description.sponsorshipManuscript received May 28, 2018; revised September 22, 2018; accepted September 26, 2018. Date of publication October 4, 2018; date of current version November 20, 2018. This work was supported by the Republic of Turkey, Ministry of Science, Industry, and Technology, under Grant 573.STZ.2013-2. (Corresponding author: Sinan Gündog˘du.) S. Gündog˘du is with the Physics Department, Bilkent University, 06800 Ankara, Turkey (e-mail: gundogdu@fen.bilkent.edu.tr). A. Demir is with the UNAM—National Nanotechnology Research Center, Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey. H. Sedaghat Pisheh is with the Mechanical Engineering Department, Bilkent University, 06800 Ankara, Turkey. A. Aydınlı is with the Electrical and Electronics Engineering Department, Uludag University, 16059 Bursa, Turkey. Color versions of one or more of the figures in this letter are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/LPT.2018.2873827
dc.identifier.doi10.1109/LPT.2018.2873827
dc.identifier.eissn1941-0174en_US
dc.identifier.issn1041-1135
dc.identifier.urihttp://hdl.handle.net/11693/50202
dc.language.isoEnglish
dc.publisherInstitute of Electrical and Electronics Engineers
dc.relation.isversionofhttps://doi.org/10.1109/LPT.2018.2873827
dc.relation.projectKorea Institute of Materials Science, KIMS - Bilkent Üniversitesi - Ministry of Science, Technology and Space: 573.STZ.2013-2 - National Nanotechnology Center, NANOTEC
dc.source.titleIEEE Photonics Technology Lettersen_US
dc.subjectHafnium dioxideen_US
dc.subjectLossen_US
dc.subjectPassivationen_US
dc.subjectQuantum cascade lasersen_US
dc.subjectQuantum efficiencyen_US
dc.titleLow-loss regrowth-free long wavelength quantum cascade lasersen_US
dc.typeArticleen_US

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