{"id":48747,"date":"2021-12-03T12:25:14","date_gmt":"2021-12-03T10:25:14","guid":{"rendered":"https:\/\/www.iemn.fr\/articles-temporaires-anglais\/48633-2.html"},"modified":"2022-01-06T11:03:52","modified_gmt":"2022-01-06T09:03:52","slug":"48633-2","status":"publish","type":"post","link":"https:\/\/www.iemn.fr\/en\/newsletter\/48633-2.html","title":{"rendered":"A promising photomixer developed at IEMN"},"content":{"rendered":"<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-w15dyx-15466484a3d4402aa8d84b50166ba59d\">\n.flex_column.av-w15dyx-15466484a3d4402aa8d84b50166ba59d{\nborder-radius:0px 0px 0px 0px;\npadding:0px 0px 0px 0px;\n}\n<\/style>\n<div  class='flex_column av-w15dyx-15466484a3d4402aa8d84b50166ba59d av_one_full  avia-builder-el-0  avia-builder-el-no-sibling  first flex_column_div av-zero-column-padding'     ><section  class='av_textblock_section av-kwq8qaf4-a99f03fd889e186bee01ffd51afc3a82'   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/BlogPosting\" itemprop=\"blogPost\" ><div class='avia_textblock'  itemprop=\"text\" ><h2 style=\"text-align: center;\">A promising photomixer developed at IEMN<\/h2>\n<p align=\"justify\"><a href=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photo1.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignleft wp-image-48653\" src=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photo1-300x171.png\" alt=\"\" width=\"350\" height=\"200\" srcset=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photo1-300x171.png 300w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photo1-18x10.png 18w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photo1.png 700w\" sizes=\"auto, (max-width: 350px) 100vw, 350px\" \/><\/a>THz <strong>sources based on the photodetection of an optical beat of two laser lines by an ultrafast photodetector<\/strong>also called <strong>photomixer<\/strong>, <strong>coupled to a THz broadband antenna are very promising<\/strong> because they operate at room temperature, are compact, and above all, can be tuned over frequency ranges reaching several THz. They are therefore perfectly adapted to THz molecular spectroscopy systems <strong>for the study of materials<\/strong>, <strong>the earth, the sciences of the universe<\/strong> or <strong>biological systems<\/strong>. <strong>The THz Photonics group has developed a photomixer allowing to reach powers from mW to 1 THz.<\/strong><\/p>\n<h4 style=\"text-align: center;\"><\/h4>\n<p>THz sources based on the photomixing of two laser lines in an ultrafast photodetector are very promising because they operate at room temperature, are potentially compact, low cost, most importantly, broadly tunable in frequency. However, their use is currently limited due to an available power level that remains in the \u03bcW range beyond 1 THz.<\/p>\n<blockquote>\n<p>We have developed a millimeter-length traveling-wave structure paving the way for large active-area (~4000 \u03bcm2) photomixing devices capable of sustaining optical pump power in excess of 1 W well beyond the capabilities of standard localized-element devices using small active areas (&lt;50 \u03bcm2) required to maintain a level of capacitance (&lt;10 fF) compatible with THz operation.<\/p>\n<\/blockquote>\n<div id=\"attachment_48647\" style=\"width: 166px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photomelangeur-a-ondes-progr..png\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-48647\" class=\"wp-image-48647\" src=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photomelangeur-a-ondes-progr.-300x166.png\" alt=\"\" width=\"156\" height=\"86\" srcset=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photomelangeur-a-ondes-progr.-300x166.png 300w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photomelangeur-a-ondes-progr.-768x425.png 768w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photomelangeur-a-ondes-progr.-18x10.png 18w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photomelangeur-a-ondes-progr.-705x390.png 705w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Photomelangeur-a-ondes-progr..png 899w\" sizes=\"auto, (max-width: 156px) 100vw, 156px\" \/><\/a><p id=\"caption-attachment-48647\" class=\"wp-caption-text\">Fig. 1 : Travelling wave photomixer<\/p><\/div>\n<p>This type of traveling wave photomixer is not limited by an RC cutoff frequency, but it requires <strong>a perfect agreement between the propagation speed of the optical beat (group speed) and the propagation speed of the generated THz waves<\/strong> so that they all have identical phases and interfere constructively. In addition, the THz guide must also have contained propagation losses over distances of the order of a millimeter. Finally, it is necessary to have a photoconductor integrated into the guide with an intrinsic cut-off frequency close to 1 THz.<\/p>\n<div id=\"attachment_48645\" style=\"width: 217px\" class=\"wp-caption alignright\"><a href=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Image-Meb.png\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-48645\" class=\"wp-image-48645\" src=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Image-Meb-300x158.png\" alt=\"\" width=\"207\" height=\"109\" srcset=\"https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Image-Meb-300x158.png 300w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Image-Meb-18x9.png 18w, https:\/\/www.iemn.fr\/wp-content\/uploads\/2021\/12\/Image-Meb.png 538w\" sizes=\"auto, (max-width: 207px) 100vw, 207px\" \/><\/a><p id=\"caption-attachment-48645\" class=\"wp-caption-text\">Fig. 2 : SEM image of the final device<\/p><\/div>\n<p>We present in Fig. 1 <strong>the original structure<\/strong> studied here that potentially meets all these challenges. It consists of <strong>a dielectric guide<\/strong> (silicon nitride core and silicon oxide cladding) <strong>carrying the optical pump beat <\/strong>that is<strong> evanescently coupled to a photoconductor <\/strong>composed of<strong> a membrane of a sub-picosecond response time photoconductive material<\/strong> (low temperature epitaxial GaAs) and <strong>contact electrodes<\/strong> that form a coplanar THz waveguide (THz CPW). Experimentally, the frequency response of a 1 mm long structure, measured using the optical beat produced by two 780 nm-DFB lasers, <strong>clearly shows the expected traveling wave signature<\/strong> consisting of a 6 dB decay ending at ~50 GHz when the contra-propagating traveling wave contribution is fully cancelled, followed by a plateau.<br \/>\nThe experimental demonstration of traveling wave operation is <strong>a first step towards realizing the initial promise of this concept in terms of power level and bandwidth<\/strong>.<\/p>\n<p><em>Fuanki Bavedila, Charbel Tannoury, Quyang Lin, Sylvie Lepilliet, Vanessa Avramovic, Etienne Okada, Dmitri Yarekha, Marc Faucher, David Troadec, Jean-Francois Lampin, Guillaume Ducournau, Goulchen Loas, Vincent Magnin, and Emilien Peytavit, Development of a Millimeter-Long Travelling Wave THz Photomixer, JOURNAL OF LIGHTWAVE TECHNOLOGY 39, 4700-4709 (2021). https:\/\/doi.org\/10.1109\/JLT.2021.3078226<\/em><\/p>\n<div  class='avia-button-wrap av-rpqvoq-e0784838a3b9930372ca90556be3d406-wrap avia-button-left  avia-builder-el-2  avia-builder-el-no-sibling'><a href='mailto:emilien.peytavit@univ-lille.fr'  class='avia-button av-rpqvoq-e0784838a3b9930372ca90556be3d406 av-link-btn avia-icon_select-yes-left-icon avia-size-small avia-position-left avia-color-silver'   aria-label=\"emilien.peytavit@univ-lille.fr\"><span class='avia_button_icon avia_button_icon_left' aria-hidden='true' data-av_icon='\ue805' data-av_iconfont='entypo-fontello'><\/span><span class='avia_iconbox_title' >emilien.peytavit@univ-lille.fr<\/span><\/a><\/div>\n<\/div><\/section><\/div>","protected":false},"excerpt":{"rendered":"","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[297],"tags":[],"class_list":["post-48747","post","type-post","status-publish","format-standard","hentry","category-newsletter"],"_links":{"self":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts\/48747","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\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/comments?post=48747"}],"version-history":[{"count":0,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts\/48747\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/media?parent=48747"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/categories?post=48747"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/tags?post=48747"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}