{"id":71663,"date":"2025-01-07T15:10:12","date_gmt":"2025-01-07T13:10:12","guid":{"rendered":"https:\/\/www.iemn.fr\/?p=71663"},"modified":"2025-01-07T17:15:09","modified_gmt":"2025-01-07T15:15:09","slug":"these-alexandra-khabbaz","status":"publish","type":"post","link":"https:\/\/www.iemn.fr\/en\/a-la-une\/these-alexandra-khabbaz.html","title":{"rendered":"Alexandra Khabbaz's thesis: \"High Resolution THz Spectroscopy Based on Frequency Combs and Optically Pumped Molecular Lasers\" 13\/01 at 14:00 MERI1 Dunkerque"},"content":{"rendered":"<div id='layer_slider_1'  class='avia-layerslider main_color avia-shadow  avia-builder-el-0  el_before_av_heading  avia-builder-el-first  container_wrap sidebar_right'  style='height: 261px;'  ><div id=\"layerslider_58_ue1cvg2z17q8\" data-ls-slug=\"homepageslider\" class=\"ls-wp-container fitvidsignore ls-selectable\" style=\"width:1140px;height:260px;margin:0 auto;margin-bottom: 0px;\"><div class=\"ls-slide\" data-ls=\"duration:6000;transition2d:5;\"><img loading=\"lazy\" decoding=\"async\" width=\"2600\" height=\"270\" src=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2019\/01\/sliders_news1.jpg\" class=\"ls-bg\" alt=\"\" srcset=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2019\/01\/sliders_news1.jpg 2600w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2019\/01\/sliders_news1-300x31.jpg 300w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2019\/01\/sliders_news1-768x80.jpg 768w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2019\/01\/sliders_news1-1030x107.jpg 1030w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2019\/01\/sliders_news1-1500x156.jpg 1500w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2019\/01\/sliders_news1-705x73.jpg 705w\" sizes=\"auto, (max-width: 2600px) 100vw, 2600px\" \/><ls-layer style=\"font-size:14px;text-align:left;font-style:normal;text-decoration:none;text-transform:none;font-weight:700;letter-spacing:0px;border-style:solid;border-color:#000;background-position:0% 0%;background-repeat:no-repeat;width:180px;height:30px;left:0px;top:231px;line-height:32px;color:#ffffff;border-radius:6px 6px 6px 6px;padding-left:50px;background-color:rgba(0, 0, 0, 0.57);\" class=\"ls-l ls-ib-icon ls-text-layer\" data-ls=\"minfontsize:0;minmobilefontsize:0;\"><i class=\"fa fa-quote-right\" style=\"color:#ffffff;margin-right:0.8em;font-size:1em;transform:translateY( -0.125em );\"><\/i>ACTUALITES<\/ls-layer><\/div><\/div><\/div><div id='after_layer_slider_1'  class='main_color av_default_container_wrap container_wrap sidebar_right'  ><div class='container av-section-cont-open' ><div class='template-page content  av-content-small alpha units'><div class='post-entry post-entry-type-page post-entry-71663'><div class='entry-content-wrapper clearfix'>\n\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-k5dohoxw-114dc3106577fd47524bb080b39b92c7\">\n#top .av-special-heading.av-k5dohoxw-114dc3106577fd47524bb080b39b92c7{\nmargin:0 0 10px 0;\npadding-bottom:4px;\n}\nbody .av-special-heading.av-k5dohoxw-114dc3106577fd47524bb080b39b92c7 .av-special-heading-tag .heading-char{\nfont-size:25px;\n}\n.av-special-heading.av-k5dohoxw-114dc3106577fd47524bb080b39b92c7 .av-subheading{\nfont-size:15px;\n}\n<\/style>\n<div  class='av-special-heading av-k5dohoxw-114dc3106577fd47524bb080b39b92c7 av-special-heading-h4  avia-builder-el-1  el_after_av_layerslider  el_before_av_hr  avia-builder-el-first  av-linked-heading'><h4 class='av-special-heading-tag'  itemprop=\"headline\"  >Alexandra Khabbaz's thesis: \"High Resolution THz Spectroscopy Based on Frequency Combs and Optically Pumped Molecular Lasers\" 13\/01 at 14:00 MERI1 Dunkerque<\/h4><div class=\"special-heading-border\"><div class=\"special-heading-inner-border\"><\/div><\/div><\/div>\n\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-18u73nj-dad6a947580930e400fc42ba200e80f1\">\n#top .hr.av-18u73nj-dad6a947580930e400fc42ba200e80f1{\nmargin-top:5px;\nmargin-bottom:5px;\n}\n.hr.av-18u73nj-dad6a947580930e400fc42ba200e80f1 .hr-inner{\nwidth:100%;\n}\n<\/style>\n<div  class='hr av-18u73nj-dad6a947580930e400fc42ba200e80f1 hr-custom  avia-builder-el-2  el_after_av_heading  el_before_av_textblock  hr-left hr-icon-no'><span class='hr-inner inner-border-av-border-thin'><span class=\"hr-inner-style\"><\/span><\/span><\/div>\n<section  class='av_textblock_section av-jriy64i8-fd5f2e9d63bf552d6910d12f255eb26e'   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/BlogPosting\" itemprop=\"blogPost\" ><div class='avia_textblock'  itemprop=\"text\" >\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-13ewzjw-68e036126b913e5028f77311dc66b825\">\n.av_font_icon.av-13ewzjw-68e036126b913e5028f77311dc66b825{\ncolor:#bfbfbf;\nborder-color:#bfbfbf;\n}\n.av_font_icon.av-13ewzjw-68e036126b913e5028f77311dc66b825 .av-icon-char{\nfont-size:60px;\nline-height:60px;\n}\n<\/style>\n<span  class='av_font_icon av-13ewzjw-68e036126b913e5028f77311dc66b825 avia_animate_when_visible av-icon-style- avia-icon-pos-left avia-icon-animate'><span class='av-icon-char' aria-hidden='true' data-av_icon='\ue8c9' data-av_iconfont='entypo-fontello' ><\/span><\/span>\n<p><strong>Thesis Thesis Alexandra Khabbaz<br \/>\n<\/strong><\/p>\n<p>Defence: 13 January 2025 14:00<strong><br \/>\n<\/strong>A<span class=\"\">mphith\u00e9\u00e2tre de la <span id=\"DWT261\" class=\"ZmSearchResult\">MREI1<\/span>in Dunkirk<\/span><\/p>\n<\/div><\/section>\n\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-jtefqx33-6db969b2e204313ebd62331ed4fc69ec\">\n#top .av_textblock_section.av-jtefqx33-6db969b2e204313ebd62331ed4fc69ec .avia_textblock{\nfont-size:15px;\n}\n<\/style>\n<section  class='av_textblock_section av-jtefqx33-6db969b2e204313ebd62331ed4fc69ec'   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/BlogPosting\" itemprop=\"blogPost\" ><div class='avia_textblock'  itemprop=\"text\" ><div  class='hr av-kjh3zw-4dff888f744b728a1aca9b3a0971493a hr-default  avia-builder-el-6  avia-builder-el-no-sibling'><span class='hr-inner'><span class=\"hr-inner-style\"><\/span><\/span><\/div>\n<h5><strong>\u00a0<\/strong>Summary:<\/h5>\n<p>The aim of this thesis is to study the use of frequency combs for high-resolution molecular spectroscopy in the terahertz (THz) region of the electromagnetic spectrum. This approach is based on the conversion of a comb in the optical domain to the THz domain. However, the state of the art of these sources requires a very sensitive heterodyne THz receiver in order to measure the amplitude of each tooth of the comb separately. We demonstrate the effectiveness of this approach at frequencies below 1 THz using Schottky diode-based receivers. Commercial mixers exist for higher frequencies, but there is the problem of the local oscillator (LO). We explored the use of optically pumped molecular lasers (OPML). Several active media were considered: ammonia (NH3), hydrogen cyanide (HCN), water vapour (H2O) and heavy water vapour (D2O). Experimental results show significant gains, but these are limited by the power of the quantum cascade lasers (QCLs) available. Sufficient power to pump a mixer was nevertheless obtained, paving the way for more advanced OPML designs. Lastly, the OPML was used as a LO in a molecular spectroscopy experiment involving the use of a quantum cascade laser.<span id=\"OBJ_PREFIX_DWT866_com_zimbra_date\" class=\"Object\" role=\"link\"><span id=\"OBJ_PREFIX_DWT872_com_zimbra_date\" class=\"Object\" role=\"link\">game<\/span><\/span>synchrotron radiation. The experimental set-up and the techniques used for signal acquisition enable high-precision measurements in a range (1 - 4 THz) where few solutions exist. This work should eventually lead to the development of a compact spectrometer with high performance throughout this range.<\/p>\n<div>\n<div><\/div>\n<div><\/div>\n<\/div>\n<h5>Abstract:<\/h5>\n<div class=\"\"><span class=\"size\">The objective of this thesis is to study the use of frequency combs for high-resolution molecular spectroscopy in the terahertz (THz) region of the electromagnetic spectrum. This approach is based on the conversion of an optical frequency comb into the THz domain. Nevertheless, the state of the art of these sources requires a highly sensitive THz heterodyne receiver to measure the amplitude of each comb tooth separately. We demonstrate the effectiveness of this approach at frequencies below 1 THz using Schottky diode-based heterodyne receivers. For higher frequencies, commercial mixers exist, but the challenge lies with the local oscillator (LO). We explored the use of optically pumped molecular lasers (OPML). Several active media were considered: ammonia (NH3), hydrogen cyanide (HCN), water vapor (H2O), and heavy water vapor (D2O). The experimental results show significant gains, though limited by the power of the available quantum cascade lasers (QCL) used to pump the gas. Sufficient THz power for pumping a mixer is nevertheless achieved, paving the way for more advanced OPML designs. Finally, the OPML is used as an LO in a molecular spectroscopy experiment involving synchrotron radiation. The experimental setup and techniques used for signal acquisition allow for high-precision measurements in the 1 - 4 THz range, where few solutions exist. This work ultimately envisions a compact and high-performance spectrometer for this entire range.<\/span><\/div>\n<div class=\"\"><\/div>\n<div class=\"\"><span class=\"\"><span class=\"size\">Keywords: Terahertz (THz), optically pumped molecular lasers (OPML), molecular gas lasers, quantum cascade lasers (QCL), molecular spectroscopy, frequency comb (FC), heterodyne receiver, local oscillator (LO)<br \/>\n<\/span><\/span><\/div>\n<div><\/div>\n<div><\/div>\n<div>\n<p><strong>Take part in the Zoom meeting<\/strong><\/p>\n<p><a href=\"https:\/\/univ-littoral-fr.zoom.us\/j\/98697343543?pwd=WcLsIieg1Ib7Da03szlE2ihITIJk3T.1\">https:\/\/univ-littoral-fr.zoom.us\/j\/98697343543?pwd=WcLsIieg1Ib7Da03szlE2ihITIJk3T.1<\/a><\/p>\n<p>Meeting ID:<a href=\"callto:986%209734%203543\">986 9734 3543<\/a><\/p>\n<p>Secret code: 734020<\/p>\n<p>&#8212;<\/p>\n<p>One touch on the mobile device<\/p>\n<p>+33186995831,,98697343543#,,,,*734020# France<\/p>\n<p>+33170372246,,98697343543#,,,,*734020# France<\/p>\n<p>&#8212;<\/p>\n<p>Dial a number based on your location<\/p>\n<ul>\n<li><a href=\"callto:+33%201%208699%205831\">+33 1 8699 5831<\/a>France<\/li>\n<li><a href=\"callto:+33%201%207037%202246\">+33 1 7037 2246<\/a>France<\/li>\n<li><a href=\"callto:+33%201%207095%200103\">+33 1 7095 0103<\/a>France<\/li>\n<\/ul>\n<p>Meeting ID:<a href=\"callto:986%209734%203543\">986 9734 3543<\/a><\/p>\n<p>Secret code: 734020<\/p>\n<p>Find your local number :<a href=\"https:\/\/univ-littoral-fr.zoom.us\/u\/aefaxiq7qi\">https:\/\/univ-littoral-fr.zoom.us\/u\/aefaxiq7qi<\/a><\/p>\n<p>&#8212;<\/p>\n<p>Participate using SIP protocol<\/p>\n<ul>\n<li><a href=\"mailto:98697343543@zoomcrc.com\">98697343543@zoomcrc.com<\/a><\/li>\n<\/ul>\n<p>&#8212;<\/p>\n<p>Participate using an H.323 protocol<\/p>\n<ul>\n<li><a href=\"callto:144.195.19.161\">144.195.19.161<\/a>(United States (West))<\/li>\n<li><a href=\"callto:206.247.11.121\">206.247.11.121<\/a>(United States (East))<\/li>\n<li><a href=\"callto:159.124.15.191\">159.124.15.191<\/a>(Amsterdam, Netherlands)<\/li>\n<li><a href=\"callto:159.124.47.249\">159.124.47.249<\/a>(Germany)<\/li>\n<\/ul>\n<p>Meeting ID:<a href=\"callto:986%209734%203543\">986 9734 3543<\/a><\/p>\n<p>Secret code: 734020<\/p>\n<\/div>\n<\/div><\/section>","protected":false},"excerpt":{"rendered":"","protected":false},"author":20,"featured_media":71447,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,8,319,87,65,84],"tags":[],"class_list":["post-71663","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-a-la-une","category-actualites","category-actualites2022","category-agenda-en","category-agenda","category-agenda-en-en"],"_links":{"self":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts\/71663","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/users\/20"}],"replies":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/comments?post=71663"}],"version-history":[{"count":0,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts\/71663\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/media\/71447"}],"wp:attachment":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/media?parent=71663"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/categories?post=71663"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/tags?post=71663"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}