Name: fabrication of nanopillar-based split ring resonators for displacement current mediated resonances in terahertz metamaterials
Uploaded: 2017-03-23T14:00:00.000+00:00
Duration: 10 min 28 s
Description: Watch this Scientific Journal Video about Fabrication of Nanopillar-Based Split Ring Resonators for Displacement Current Mediated Resonances in Terahertz Metamaterials at JoVE.com

この材料は、ミネソタ大学、ツインシティーズでのスタートアップ資金によってサポートされている作業に基づいています。この作業の一部はキャラ施設、ミネソタ州、MRSECプログラムを介して、NSFが資金を提供する材料研究施設ネットワーク（www.mrfn.org）のメンバーの大学で行いました。この作品の部分もNNCIプログラムを通じて、NSFからの部分的なサポートを受けるミネソタナノセンターで行われました。

注意：これらの合成に使用される化学物質のいくつかは非常に可燃性、毒性があり、そして触ったり吸入時の刺激や重度の臓器損傷を与える可能性があります。取り扱う際は、適切な個人用保護具（PPE）を着用してください。 まず、金（Au）ナノピラーアレイの層（図2A-C及び図2E-G）の調製<ol><li> 金電気めっきのための銅（Cu）のシード層の調製（図2a、b及び図2E、F） <ol><li> 4「高抵抗率のシリコン（Si）ウェハを使用します。： -基質として（抵抗560 840Ω・cm程度）をSiウェハはN型ドープされ、一方の側（ 図2a、e）の上に研磨します。 </li><li>後で使用するために2.5センチメートル個×2センチメートルにSiウエハをカット。 </li><li> SiとCuとの間の接着層として、電子ビーム（Eビーム）蒸着法を用いてシリコンサンプルの5 nmのクロム（Cr）層を堆積させます。 </li><li>使用して、既存のCr層の上に10nmのCu層を堆積させます金メッキのためのシード層として電子ビーム蒸着法（ 図2b、F）。 </li></ol></li><li> 金ナノピラーアレイ（図2c、g）を電気めっき <ol><li> ナノピラーアレイをパターニングします <ol><li> 60秒間、2000rpmでセクション1.1で調製した試料にスピンコートフォトレジスト。 </li><li> 60秒間115℃のホットプレート上のサンプルを焼きます。 </li><li> 22秒のためのナノピラーパターンの数千人が含まれているのCrフォトマスクを用いて紫外線（UV） -光（〜15ミリワット/ cm 2の電力）の下でフォトレジストを公開します。 </li><li>撹拌しながら90秒間現像液を用いて開発します。 </li><li>脱イオン（DI）水でサンプルをすすぎ、空気銃でサンプルをブロードライ。 </li></ol></li><li> 金ナノピラーアレイを電気めっき <ol><li>電極接続のためのCuシード層を露出させるためにアセトンでサンプル上のフォトレジストの上部を取り外します。 </li><li> SAMを接続しますクランプワイヤを使用して、ソースメータの負端子にPLE（Cuシード層）。この場合、サンプルは、電気めっきプロセス中のアノードです。 </li><li>ソースメータの正端子にプラチナのピース（Pt）からコーティングされたSi（サンプルと同じ大きさ）を接続します。 Ptが電気めっきプロセス中にカソードです。 </li><li>金めっき液中のPtカソードとCu陽極の両方を水没。約1センチの距離で互いに対向する2つの電極を保管してください。 </li><li>ソースメータをオンにして、8分間のサンプルに1.12 V.電気めっき金の一定の電圧を供給（蒸着速度：〜100ナノメートル/分）。 </li><li>フォトレジストを除去するためにアセトンに続いてDI水でサンプルを洗浄します。 </li><li>再びDI水でサンプルをすすぎ、ブロー乾燥空気銃で。 </li><li>顕微鏡下で電気めっきされた金ナノピラーアレイを点検します。 </li><li>プロフィル（の厚さのAuナノピラーの厚さを測定金ナノピラー）は〜800nmです。 注：定電流セットアップはまた、金ナノピラーを電気めっきするために使用することができます。定電圧定電流セット・アップの両方において、金電気めっきのために使用される理想的な電流及び電圧が試行錯誤することによって達成することができます。 </li></ol></li></ol></li></ol>金ナノピラー（図2d、h）の間のナノギャップの2作成<ol><li> Cr及びCuの層の除去 <ol><li>銅色が消えるまでのCuエッチング液にサンプルを沈めます。 </li><li> DI水でサンプルをすすぎ、ブロー乾燥空気銃で。 </li><li>顕微鏡下でのAuナノピラーを点検します。 </li><li> 10秒間Crマスクのエッチング液に試料を浸します。 </li><li> DI水でサンプルをすすぎ、ブロー乾燥空気銃で。 </li><li>顕微鏡下でのAuナノピラーを点検します。 </li></ol></li><li> ナノスケールの酸化アルミニウムの製造アルミニウム（Al 2 O 3）隙間 <ol><li> ALDシステムチャムを加熱200°CまでのBER。 </li><li>室内の中央にサンプルを置きます。 </li><li>真空チャンバーをポンプダウンし、100（蒸着速度：〜1Å/サイクル）にサイクル数を設定します。 </li><li>順次交互に均一に試料上にAl 2 O 3層を堆積させるためにチャンバ内に0.015秒の時間で0.015秒と水（H 2 O）蒸気の時間で、トリメチルアルミニウム（TMA）ガスをパルス。各パルス間の時間間隔は5秒です。 TMAパルスの間、チャンバ圧力は10トルであり、H 2 O蒸気パルスの間の圧力は2トルです。 </li><li>堆積の各サイクルの間のチャンバをパージし、真空。預金は100サイクルのための Al 2 O 3と、チャンバから試料を取り出します。 </li><li>エリプソメーターを用いて、ALD の Al 2 O 3の厚さを測定します。 </li></ol></li></ol> Au薄膜（図2I-l及び図2メートル-p）の第2層の調製<ol><li> 金電気めっきのためのCuシード層の調製（図2I、M） <ol><li>電子ビーム蒸発器のサンプルホルダーの中央にサンプルを置きます。 </li><li>電子ビーム蒸発器におけるサンプルの回転をオフにします。 </li><li> Al 2 O 3とCuとの間の接着層として作用するサンプルに5nmのCr層を堆積させます。試料回転することなく、電子ビーム蒸着法を使用してください。 </li><li>デポジット金電気めっきのためのシード層としてサンプル回転なしに電子ビーム蒸着法を使用して、既存のCr層の上に10nmの銅。 </li></ol></li><li> Au薄膜を電気めっき（図2J、n）は、 <ol><li>クランプワイヤを使用して、ソースメータの負端子に試料（Cuシード層）を接続します。この場合、サンプルは、電気めっきプロセス中のアノードです。 </li><li>ソースメータの正端子に白金カソードを接続します。 </li><li>白金カソードとCu anod両方を水没金めっき液の電子。約1センチの距離で互いに対向する2つの電極を保管してください。 </li><li>ソースメータをオンにして、1.35 Vの定電圧を設定し、16分間のサンプル上にAuを電気メッキ。 </li><li> DI水でサンプルをすすぎ、ブロー乾燥空気銃で。 </li><li>電気メッキ、Auと顕微鏡下で以前に電気メッキされたAuナノピラーアレイを点検します。 </li><li>プロフィルで金ナノピラーの厚さを測定（金ナノピラーの厚さは〜400 nmです）。 注：セクション1.2.2におけるAuメッキと同様に、定電流のセットアップは、Au薄膜を電気めっきするためにも使用することができます。定電圧定電流セット・アップの両方において、金電気めっきのために使用される理想的な電流及び電圧が試行錯誤することによって達成することができます。 </li></ol></li><li> Cr及びCuの層の除去（図2K、O） <ol><li> 10秒間のCuエッチング液にサンプルを沈めます。 </li><li> DI水ANとサンプルをすすぎますDブロー乾燥空気銃を持ちます。 </li><li>顕微鏡下でのAuナノピラーを点検します。 </li><li> 10秒間Crマスクのエッチング液に試料を浸します。 </li><li> DI水でサンプルをすすぎ、ブロー乾燥空気銃で。 </li><li>顕微鏡下でのAuナノピラーを点検します。 注：別の方法として、Cr及びCuの（ステップ3.3）を除去した後に、第2の電気メッキAu層の上に金の余分な層を堆積させるために、再び金めっき液中にサンプルを沈めます。この追加のAu層は、第2のAu層の合計の厚さを増加させ、Au層とAl 2 O 3層（ 図2I、P）との間の良好な接触を確実にします。 </li></ol></li></ol> C字型SRR（図2Q-sおよび図2U-W）の4定義<ol><li> C字型SRRをパターニングする（図2Q、U） <ol><li> 60秒間2000rpmでコートをサンプル上にフォトレジストをスピン。 </li><li> 60秒間115℃のホットプレート上のサンプルを焼きます。 </li><li&gt;は、UV光の下でフォトレジスト22秒のためのCrフォトマスクと（〜15ミリワット/ cm 2の出力）を公開します。 </li><li>撹拌しながら90秒間現像液を用いて開発します。 </li><li> DI水でサンプルをすすぎ、空気銃でサンプルをブロードライ。 </li></ol></li><li> イオンミル（図2R、Vおよび図2S、W）を用いて、C-形状定義 <ol><li>両面にCu導電性テープを用いたイオンミル試料ホルダー上の試料を取り付けます。 </li><li> 6°Cにイオンミル室をクールダウン。 </li><li>イオンミル300 Vのビーム電圧と30分間〜125ミリアンペアのビーム電流を有するサンプル。 </li><li>サンプルを取り出し、C字型の外側金ナノピラーを検査します。 </li><li> AuをC字型の外にまだ表示されている場合、ステップ4.2.3と4.2.4を繰り返します。 </li><li>フォトレジストを除去するためにアセトン中で試料を超音波処理。 </li><li> DI水でサンプルをすすぎ、ブロー乾燥空気銃で。 </li><li>顕微鏡下でサンプルを検査します。 </li><li>繰り返しステップ4.2.6と4.2。7フォトレジストが完全に除去されない場合。 注：別の方法として、酸素を適用するフォトレジストを除去する前に、フォトレジストに軟化手順に耐えます。しかし、超音波処理浴が該当する場合、フォトレジストを除去するための最も効果的な方法です。 </li></ol></li></ol>エアナノギャップのための Al 2 O 3の5の取り外し（図2トン、x）は、 <ol><li> Al 2 O 3を除去するために5分間、5％フッ化水素（HF）溶液中にサンプルを浸します。 </li><li> DI水でサンプルをすすぎ、ブロー乾燥空気銃で。 </li></ol>

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Commun. 4 (2361), (2013).</li><li>Nam, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sub-10-nm+nanochannels+by+self-sealing+and+self-limiting+atomic+layer+deposition.">Sub-10-nm nanochannels by self-sealing and self-limiting atomic layer deposition.</a> Nano Lett. 10 (9), 3324-3329 (2010).</li></ol>

著者らは、開示することは何もありません。

この製造技術は、電子ビームリソグラフィと自己組織化などの既存の方法を介して、ナノスケールの構造体を作成するための重要な利点を有します。まず、ナノスケールの構造体は、電子ビームリソグラフィプロセスでは実用的ではないナノピラーアレイを備えたフォトマスクを用いて大面積（ウェハ全体）にわたって実現することができます。第二に、製造プロセスは、電子ビームリソグ?...

テラヘルツ（テラヘルツ）メタマテリアル（MMS）は、生物医学的センサーと周波数アジャイル装置1、2、3、4、5、6、7、8、9、10、11のために開発されています。テラヘルツMMセンサの感度と周波数選択性を向上させるために、ナノピラーベースのスプリットリング共振器（SRR）は、（超高品質因子を有するテラヘルツ共鳴を励起するためにナノピラーアレイを金（Au）の内部で発生する変位電流を使用して設計されていますQ因子）（〜450）（ 図1）12。ナノピラーベースのSRRは、高Q値および有望なセンシング能力、そのようなnanostructurの製造を示しているにもかかわらず大面積にわたって高アスペクト比（40以上）とナノスケールのギャップ（サブ10 nm）を持つESが困難な13のまま。 ナノスケール構造体を製造するために最も一般的に使用される技術は、電子ビームリソグラフィ（EBL）14、15、16、17です。しかしながら、EBLの解像度静止によるビームスポットサイズ、電子散乱、レジストの特性、及び現像工程18、19に限定されます。また、原因遅い処理時間に大きな面積にわたってEBLを用いてナノ構造体を作製するのは実用的ではなく、大規模なプロセス20がかかり。ナノ構造を達成するための別の戦略は、自己組織化技術21,22を使用することです。溶液と、utilの中で自己集合金属ナノキューブ（NCS）によります静電相互作用とのNC間のポリマーリガンドの結合をizing、ナノスケールのギャップをきちんと整理1次元NCアレイは、23を達成することができます。ナノギャップの大きさは、NCの間にポリマーリガンドに依存し、異なる分子量24、25、26と異なるポリマー材料を適用することによって制御することができます。自己組織化は、スケーラブルでコスト効率の高いナノ構造体23を実現するための強力な手法です。しかし、製造プロセスは、従来のマイクロ及びナノ製造工程に比べて複雑であり、ナノギャップの大きさの制御は、電子デバイス用途のために十分に正確ではありません。 ⅰ）製造プロセスを適用することが容易であり、慣例と互換性があります正常にナノピラーベースのSRRを製造するためには、新規の製造方法は、以下の目標を達成するために考案されるべきですアルマイクロおよびナノ製造プロセス。 ⅱ）大面積にわたって製作が適用されます。 iii）は、ナノギャップの大きさを容易かつ正確に0.1 nmの分解能で制御することができ、10nm以下に縮小することができます。 新規な製造方法はナノピラーベースのSRRを製造するために電気めっきプロセスの組み合わせと原子層堆積（ALD）プロセスを用いて実証されます。電気めっきは、低コストの自己充填プロセスであるため、大面積にわたって構造を作製することは容易です。 ALDは、正確に処理中の反応サイクルにより制御することができる化学蒸着（CVD）プロセスです。 ALD薄膜の分解能は0.1nmであることができ、薄膜は、ナノスケールのギャップ27、28を作成するのに適した高品質で均一にコーティングされます。 10ナノメートルのギャップ以下でナノピラーベースSRRアレイが正常に6 mmの×6mmの領域上に製造することができます。両方のimulatedと測定されたテラヘルツ透過スペクトルは、変位電流によって媒介ナノピラーベースSRRの実行可能性を証明する、Q値と大きな周波数シフト超で共振挙動を示します。詳細な製造プロセスは、プロトコルセクションに説明されており、ビデオプロトコルは、開業医が、製造プロセスを理解し、ナノピラーベースSRRの製造に関連する一般的なミスを回避するのに役立つことができます。

<table><tbody><tr><td>Silicon Wafer</td><td>Siltronic AG</td><td>N/A</td><td>100 mm diameter, N-type, one-side polish, resitivity: 560-840 &amp;Omega;&amp;bull;cm</td></tr><tr><td>Chromium</td><td>Kurt J. Lesker Company</td><td>EVMCR35J</td><td>99.95% pure</td></tr><tr><td>Copper</td><td>Kurt J. Lesker Company</td><td>EVMCU40QXQJ</td><td>99.99% pure</td></tr><tr><td>E-Beam Evaporator System</td><td>Rocky Mountain Vacuum Tech.</td><td>N/A</td><td>RME-2000</td></tr><tr><td>S1813 Positive Photoresist</td><td>Microposit</td><td>10018348</td><td>N/A</td></tr><tr><td>Spinner</td><td>Best Tools</td><td>S0114031123</td><td>SMART COATER 100</td></tr><tr><td>Mask Aligner</td><td>Midas</td><td>MDA-400LJ</td><td>N/A</td></tr><tr><td>Digital Hot Plate</td><td>Thermo Scientific</td><td>HP131725</td><td>Super-Nuvoa series, maximum temperature: 370 &amp;deg;C</td></tr><tr><td>MF319 Developer</td><td>Microposit</td><td>10018042</td><td>N/A</td></tr><tr><td>Acetone</td><td>Fisher Chemical</td><td>A18P-4</td><td>N/A</td></tr><tr><td>Isopropyl Alcohol</td><td>Fisher Chemical</td><td>A416-4</td><td>N/A</td></tr><tr><td>Gold 25 ES RTU</td><td>Technic Inc.</td><td>391427</td><td>N/A</td></tr><tr><td>Source Meter</td><td>Keithley</td><td>N/A</td><td>2612 System SourceMeter</td></tr><tr><td>Microscope</td><td>Omax</td><td>NJF-120A</td><td>N/A</td></tr><tr><td>Profilometer</td><td>Tencor Instruments</td><td>N/A</td><td>Alpha-Step 200</td></tr><tr><td>APS Copper Etchant 100</td><td>Transfene Company, Inc.</td><td>N/A</td><td>N/A</td></tr><tr><td>CE-5 M Chromium Mask Etchant</td><td>Transfene Company, Inc.</td><td>N/A</td><td>N/A</td></tr><tr><td>Atomic Layer Deposition System</td><td>Cambridge Nano Tech inc.</td><td>N/A</td><td>Savannah series</td></tr><tr><td>Ion Mill Etching System</td><td>Intlvac Thin Film</td><td>N/A</td><td>Nanoquest series</td></tr><tr><td>Ultrasonic Cleaner</td><td>Crest Ultrasonics</td><td>N/A</td><td>Powersonic series</td></tr><tr><td>Hydrofluoric Acid</td><td>Sigma-Aldrich</td><td>244279</td><td>Diluted to 5%</td></tr><tr><td>Field Emission Gun Scanning Electron Microscope</td><td>Jeol Ltd.</td><td>N/A</td><td>JEOL 6700 series</td></tr></tbody></table>

fabrication of nanopillar-based split ring resonators for displacement current mediated resonances in terahertz metamaterials

SRRは、このような共振器を周囲温度および圧力などの環境の特性に影響されないので、テラヘルツ（テラヘルツ）スプリットリング共振器（SRR）メタマテリアル（MMS）は、ガス、化学物質、および生体分子センシング応用のために研究されてきました。テラヘルツ周波数の電磁放射が、特に生体分子センシングの応用のための重要な条件である、生体適合性です。しかし、品質係数（Q値）と従来の薄膜ベースのスプリットリング共振器の周波数応答は、（SRR）MMSは、センサーとしての感度及び選択性を制限する、非常に低いです。この作業、新規ナノピラーベースのSRRのMMでは、変位電流を利用して、従来の薄膜系のMMよりも約45倍である450 Qファクタアップを強化するように設計されています。強化されたQファクタの他に、ナノピラーベースMMSは伝統により得られるシフトと比較し（17倍より大きい周波数シフトを誘発しますアル薄膜ベースMMS）。そのため大幅に強化されたQ値と周波数シフトだけでなく、生体適合性の放射線の特性の、テラヘルツナノピラーベースのSRRは、生体材料への損傷や歪みを誘発することなく、高感度と選択性を有する生体分子センサーの開発のための理想的なのMMです。新規の製造プロセスは、変位電流媒介テラヘルツのMM用ナノピラーベースのSRRを構築することが実証されています。二段階の金（Au）、電気めっき法、原子層堆積（ALD）プロセスは、金ナノピラーの間にサブ10nmのスケールのギャップを作成するために使用されます。 ALDプロセスは、コンフォーマルコーティングプロセスであるので、ナノメートルスケールの厚さの均一な酸化アルミニウム（Al 2 O 3）層を実現することができます。順次の Al 2 O 3とAu、最密充填のAu- の Al 2 O 3 -Auナノスケールの Al 2 O 3ギャップを有する構造がすることができます間のスペースを埋めるために別のAu薄膜を電気めっきすることにより、製作。ナノギャップの大きさが十分に正確に0.1ナノメートルの精度を有するALDプロセスの堆積サイクルを制御することによって定義することができます。

<html>製造方式は、各ステップ（ 図2a-X）を示します。光学像（ 図2Y-AC）及び走査型電子顕微鏡（SEM）画像（ 図2AD-AG）は、異なる製造工程におけるナノピラーベースのSRRのために収集しました。アニメーション（ 図2a-c）は、電気メッキ金ナノピラーの第1層と電気めっきAu膜の第二の層だけでなく、それらの間に作成さ...

Watch this Scientific Journal Video about Fabrication of Nanopillar-Based Split Ring Resonators for Displacement Current Mediated Resonances in Terahertz Metamaterials at JoVE.com

Fabrication of Nanopillar-Based Split Ring Resonators for Displacement Current Mediated Resonances in Terahertz Metamaterials

設計および新規ナノピラーベースのスプリットリング共振器（SRR）の製造のためのプロトコルが提供されます。

テラヘルツメタマテリアルにおける変位電流仲介共鳴のためのナノピラーベースのスプリットリング共振器の作製

Terahertz (THz) split ring resonator (SRR) metamaterials (MMs) has been studied for gas, chemical, and biomolecular sensing applications because the SRR ...

fabrication-nanopillar-based-split-ring-resonators-for-displacement

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Unit 1

Electromagnetic Induction

SCIENTISTS IN ACTION

7.7K ビュー.  University of Minnesota. 設計および新規ナノピラーベースのスプリットリング共振器（SRR）の製造のためのプロトコルが提供されます。 

ビデオ: Fabrication of Nanopillar-Based Split Ring Resonators for Displacement Current Mediated Resonances in Terahertz Metamaterials

Fabrication of Silica Ultra High Quality Factor Microresonators

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the quality factor (Q) of the cavity, can be in excess of 500ns for cavities with Q factors above 100 million. As a result of their low material losses, silica microcavities have demonstrated some of the longest photon lifetimes to date1-2. Since a portion of the circulating light extends outside the resonator, these devices can also be used to probe the surroundings. This interaction has enabled numerous experiments in biology, such as single molecule biodetection and antibody-antigen kinetics, as well as discoveries in other fields, such as development of ultra-low-threshold microlasers, characterization of thin films, and cavity quantum electrodynamics studies.3-7
The two primary silica resonant cavity geometries are the microsphere and the microtoroid. Both devices rely on a carbon dioxide laser reflow step to achieve their ultra-high-Q factors (Q&gt;100 million).1-2,8-9 However, there are several notable differences between the two structures. Silica microspheres are free-standing, supported by a single optical fiber, whereas silica microtoroids can be fabricated on a silicon wafer in large arrays using a combination of lithography and etching steps. These differences influence which device is optimal for a given experiment.
Here, we present detailed fabrication protocols for both types of resonant cavities. While the fabrication of microsphere resonant cavities is fairly straightforward, the fabrication of microtoroid resonant cavities requires additional specialized equipment and facilities (cleanroom). Therefore, this additional requirement may also influence which device is selected for a given experiment.
Introduction
An optical resonator efficiently confines light at specific wavelengths, known as the resonant wavelengths of the device. 1-2 The common figure of merit for these optical resonators is the quality factor or Q. This term describes the photon lifetime (&tau;o) within the resonator, which is directly related to the resonator's optical losses. Therefore, an optical resonator with a high Q factor has low optical losses, long photon lifetimes, and very low photon decay rates (1/&tau;o). As a result of the long photon lifetimes, it is possible to build-up extremely large circulating optical field intensities in these devices. This very unique property has allowed these devices to be used as laser sources and integrated biosensors.10
A unique sub-class of resonators is the whispering gallery mode optical microcavity. In these devices, the light is confined in circular orbits at the periphery. Therefore, the field is not completely confined within the device, but evanesces into the environment. Whispering gallery mode optical cavities have demonstrated some of the highest quality factors of any optical resonant cavity to date.9,11 Therefore, these devices are used throughout science and engineering, including in fundamental physics studies and in telecommunications as well as in biodetection experiments. 3-7,12
Optical microcavities can be fabricated from a wide range of materials and in a wide variety of geometries. A few examples include silica and silicon microtoroids, silicon, silicon nitride, and silica microdisks, micropillars, and silica and polymer microrings.13-17 The range in quality factor (Q) varies as dramatically as the geometry. Although both geometry and high Q are important considerations in any field, in many applications, there is far greater leverage in boosting device performance through Q enhancement. Among the numerous options detailed previously, the silica microsphere and the silica microtoroid resonator have achieved some of the highest Q factors to date.1,9 Additionally, as a result of the extremely low optical loss of silica from the visible through the near-IR, both microspheres and microtoroids are able to maintain their Q factors over a wide range of testing wavelengths.18 Finally, because silica is inherently biocompatible, it is routinely used in biodetection experiments.
In addition to high material absorption, there are several other potential loss mechanisms, including surface roughness, radiation loss, and contamination loss.2 Through an optimization of the device size, it is possible to eliminate radiation losses, which arise from poor optical field confinement within the device. Similarly, by storing a device in an appropriately clean environment, contamination of the surface can be minimized. Therefore, in addition to material loss, surface scattering is the primary loss mechanism of concern.2,8
In silica devices, surface scattering is minimized by using a laser reflow technique, which melts the silica through surface tension induced reflow. While spherical optical resonators have been studied for many years, it is only with recent advances in fabrication technologies that researchers been able to fabricate high quality silica optical toroidal microresonators (Q&gt;100 million) on a silicon substrate, thus paving the way for integration with microfluidics.1
The present series of protocols details how to fabricate both silica microsphere and microtoroid resonant cavities. While silica microsphere resonant cavities are well-established, microtoroid resonant cavities were only recently invented.1 As many of the fundamental methods used to fabricate the microsphere are also used in the more complex microtoroid fabrication procedure, by including both in a single protocol it will enable researchers to more easily trouble-shoot their experiments.

We describe the use of a carbon dioxide laser reflow technique to fabricate silica resonant cavities, including free-standing microspheres and on-chip microtoroids. The reflow method removes surface imperfections, allowing long photon lifetimes within both devices. The resulting devices have ultra high quality factors, enabling applications ranging from telecommunications to biodetection.

シリカ超高品質ファクターMicroresonatorsの作製

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the ...

工学

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

ファイバー描画法を用いたメタマテリアルの作製

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic samples with a wide range of possible sensor designs such as interferometers and resonators 1,2. Most of the existing RI sensing applications focus on biological materials in aqueous solutions in visible and IR frequencies, such as DNA hybridization and genome sequencing. At terahertz frequencies, applications include quality control, monitoring of industrial processes and sensing and detection applications involving nonpolar materials.
Several potential designs for refractive index sensors in the terahertz regime exist, including photonic crystal waveguides 3, asymmetric split-ring resonators 4, and photonic band gap structures integrated into parallel-plate waveguides 5. Many of these designs are based on optical resonators such as rings or cavities. The resonant frequencies of these structures are dependent on the refractive index of the material in or around the resonator. By monitoring the shifts in resonant frequency the refractive index of a sample can be accurately measured and this in turn can be used to identify a material, monitor contamination or dilution, etc.
The sensor design we use here is based on a simple parallel-plate waveguide 6,7. A rectangular groove machined into one face acts as a resonant cavity (Figures 1 and 2). When terahertz radiation is coupled into the waveguide and propagates in the lowest-order transverse-electric (TE1) mode, the result is a single strong resonant feature with a tunable resonant frequency that is dependent on the geometry of the groove 6,8. This groove can be filled with nonpolar liquid microfluidic samples which cause a shift in the observed resonant frequency that depends on the amount of liquid in the groove and its refractive index 9.
Our technique has an advantage over other terahertz techniques in its simplicity, both in fabrication and implementation, since the procedure can be accomplished with standard laboratory equipment without the need for a clean room or any special fabrication or experimental techniques. It can also be easily expanded to multichannel operation by the incorporation of multiple grooves 10. In this video we will describe our complete experimental procedure, from the design of the sensor to the data analysis and determination of the sample refractive index.

The procedure for implementing a refractive index sensor for terahertz frequencies based on a grooved parallel-plate waveguide geometry is described here. The method yields a measurement of the refractive index of a small volume of liquid through monitoring of the shift in the resonant frequency of the waveguide structure

平行平板導波センサを用いたテラヘルツマイクロ流体センシング

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic ...

Simulation, Fabrication and Characterization of THz Metamaterial Absorbers

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical1 and experimental demonstration2 of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical3, near IR4, mid IR5 , THz6 , mm-wave7 , microwave8 and radio9 bands. Applications include perfect lenses10, sensors11, telecommunications12, invisibility cloaks13 and filters14,15. We have recently developed single band16, dual band17 and broadband18 THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers19. In our MM absorber the THz radiation is absorbed in a thickness of ~ &lambda;/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems.

This protocol outlines the simulation, fabrication and characterization of THz metamaterial absorbers. Such absorbers, when coupled with an appropriate sensor, have applications in THz imaging and spectroscopy.

テラヘルツメタマテリアルアブソーバのシミュレーション、作製と評価

Metamaterials (MM),  artificial materials engineered to have properties that may not be found in  nature, have been widely explored since the first ...

Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on photoconduction, which has been one of the most commonly used techniques for terahertz generation 1-8. Terahertz generation in a photoconductive emitter is achieved by pumping an ultrafast photoconductor with a pulsed or heterodyned laser illumination. The induced photocurrent, which follows the envelope of the pump laser, is routed to a terahertz radiating antenna connected to the photoconductor contact electrodes to generate terahertz radiation. Although the quantum efficiency of a photoconductive emitter can theoretically reach 100%, the relatively long transport path lengths of photo-generated carriers to the contact electrodes of conventional photoconductors have severely limited their quantum efficiency. Additionally, the carrier screening effect and thermal breakdown strictly limit the maximum output power of conventional photoconductive terahertz sources. To address the quantum efficiency limitations of conventional photoconductive terahertz emitters, we have developed a new photoconductive emitter concept which incorporates a plasmonic contact electrode configuration to offer high quantum-efficiency and ultrafast operation simultaneously. By using nano-scale plasmonic contact electrodes, we significantly reduce the average photo-generated carrier transport path to photoconductor contact electrodes compared to conventional photoconductors 9. Our method also allows increasing photoconductor active area without a considerable increase in the capacitive loading to the antenna, boosting the maximum terahertz radiation power by preventing the carrier screening effect and thermal breakdown at high optical pump powers. By incorporating plasmonic contact electrodes, we demonstrate enhancing the optical-to-terahertz power conversion efficiency of a conventional photoconductive terahertz emitter by a factor of 50 10.

We describe methods for the design, fabrication, and experimental characterization of plasmonic photoconductive emitters, which offer two orders of magnitude higher terahertz power levels compared to conventional photoconductive emitters.

プラズモニック光伝導テラヘルツエミッターの設計、製作、および実験特性

In this video article we present a detailed demonstration of a highly efficient method for generating terahertz waves. Our technique is based on ...

Implementation of a Reference Interferometer for Nanodetection

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing its free spectral range (FSR), the module is put in parallel with a fiber taper-microcavity system and then calibrated through isolating and eliminating random shifts in the laser frequency (i.e. laser jitter noise). To realize the taper-microcavity junction and to maximize the optical power that is transferred to the resonator, a single-mode optical fiber waveguide is pulled. Solutions containing polystyrene nanobeads are then prepared and flown to the microcavity in order to demonstrate the system&#8217;s ability to sense binding to the surface of the microcavity. Data is post-processed via adaptive curve fitting, which allows for high-resolution measurements of the quality factor as well as the plotting of time-dependent parameters, such as resonant wavelength and split frequency shifts. By carefully inspecting steps in the time-domain response and shifting in the frequency-domain response, this instrument can quantify discrete binding events.

A reference interferometer technique, which is designed to remove undesirable laser jitter noise for nanodetection, is utilized for probing an ultra-high quality factor microcavity. Instructions for assembly, setup, and data acquisition are provided, alongside the measurement process for specifying the cavity quality factor.

Nanodetectionのリファレンス干渉計の実装

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing ...

Utilization of Plasmonic and Photonic Crystal Nanostructures for Enhanced Micro- and Nanoparticle Manipulation

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological research. Perhaps the most widely used physical force to achieve noninvasive manipulation of small particles has been dielectrophoresis(DEP).1 However, DEP on its own lacks the versatility and precision that are desired when manipulating cells since it is traditionally done with stationary electrodes. Optical tweezers, which utilize a three dimensional electromagnetic field gradient to exert forces on small particles, achieve this desired versatility and precision.2 However, a major drawback of this approach is the high radiation intensity required to achieve the necessary force to trap a particle which can damage biological samples.3 A solution that allows trapping and sorting with lower optical intensities are optoelectronic tweezers (OET) but OET's have limitations with fine manipulation of small particles; being DEP-based technology also puts constraint on the property of the solution.4,5
This video article will describe two methods that decrease the intensity of the radiation needed for optical manipulation of living cells and also describe a method for orientation control. The first method is plasmonic tweezers which use a random gold nanoparticle (AuNP) array as a substrate for the sample as shown in Figure 1. The AuNP array converts the incident photons into localized surface plasmons (LSP) which consist of resonant dipole moments that radiate and generate a patterned radiation field with a large gradient in the cell solution. Initial work on surface plasmon enhanced trapping by Righini et al and our own modeling have shown the fields generated by the plasmonic substrate reduce the initial intensity required by enhancing the gradient field that traps the particle.6,7,8 The plasmonic approach allows for fine orientation control of ellipsoidal particles and cells with low optical intensities because of more efficient optical energy conversion into mechanical energy and a dipole-dependent radiation field. These fields are shown in figure 2 and the low trapping intensities are detailed in figures 4 and 5. The main problems with plasmonic tweezers are that the LSP's generate a considerable amount of heat and the trapping is only two dimensional. This heat generates convective flows and thermophoresis which can be powerful enough to expel submicron particles from the trap.9,10 The second approach that we will describe is utilizing periodic dielectric nanostructures to scatter incident light very efficiently into diffraction modes, as shown in figure 6.11 Ideally, one would make this structure out of a dielectric material to avoid the same heating problems experienced with the plasmonic tweezers but in our approach an aluminum-coated diffraction grating is used as a one-dimensional periodic dielectric nanostructure. Although it is not a semiconductor, it did not experience significant heating and effectively trapped small particles with low trapping intensities, as shown in figure 7. Alignment of particles with the grating substrate conceptually validates the proposition that a 2-D photonic crystal could allow precise rotation of non-spherical micron sized particles.10 The efficiencies of these optical traps are increased due to the enhanced fields produced by the nanostructures described in this paper.

Plasmonic tweezers and photonic crystal nanostructures are shown to produce useful enhancements in the efficiency and orientation control of optically trapping micro- and nano-particles.

強化されたマイクロおよびナノ操作のためのプラズモニックとフォトニック結晶ナノ構造の利用

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological ...

生物工学

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

超伝導共振器の作製と評価

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using femtosecond laser-induced ablation. We show that thousands of periodic nano-craters are fabricated on an optical nanofiber by irradiating with just a single femtosecond laser pulse. For a typical sample, periodic nano-craters with a period of 350 nm and with diameter gradually varying from 50 - 250 nm over a length of 1 mm are fabricated on a nanofiber with diameter around 450 - 550 nm. A key aspect of such a nanofabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. Moreover, the single-shot fabrication makes it immune to mechanical instabilities and other fabrication imperfections. Such periodic nano-craters on nanofiber, act as a 1-D PhC and enable strong and broadband reflection while maintaining the high transmission out of the stopband. We also present a method to control the profile of the nano-crater array to fabricate apodized and defect-induced PhC cavities on the nanofiber. The strong confinement of the field, both transverse and longitudinal, in the nanofiber-based PhC cavities and the efficient integration to the fiber networks, may open new possibilities for nanophotonic applications and quantum information science.

We present a protocol for fabricating 1-D photonic crystal cavities on subwavelength diameter silica fibers (optical nanofibers) using femtosecond laser-induced ablation.

フェムト秒レーザー誘起アブレーションを用いたナノファイバー上の1次元フォトニック結晶共振器の作製

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.