This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 within the LDRD program.

1. Vorbereitung der Polierer und Gülle Bereiten Sie zuerst die Convergent Poliersystem (genauer gesagt mit dem Namen C onvergent, ich nitial Oberflächen Independent, S ingle Iteration, R ogue partikelfreie Polierer oder CISR (ausgesprochen &#39;Schere&#39;)) 7,17 durch die Installation des Pad &amp; Septum, Anlage das Pad, Verdünnen und chemischen Stabilisierung der Aufschlämmung und Einbeziehung der Aufschlämmung innerhalb des Filtrationssystems. <ol><li> Auf der CISR Polierer, sich ein Polyurethan-Pad auf den Granit Runde Basis. Halten Sie Pad eine Kante zuerst und Druck in Richtung auf die gegenüberliegende Kante Luftspalte zu minimieren. Schneiden Sie die überstehenden Unterlage und verwenden Sie dann eine Rasierklinge und Rollendurchstoßen und Luftblasen entfernen, wenn nötig. </li><li> Bei der ersten Inbetriebnahme und nach jeder ~ 100 hr von Polieren, Diamant Zustand des Pads unter Verwendung eines CMP Diamantkonditionierer (50 mm Durchmesser, 0,6 psi aufgebrachte Druck, 5 min Verweilzeit an jeder radialen Runde Lage mit Abstand 25 mm-Schritten; Runde Dreh 25 rpm) mit fließenden DI-Wasser. </li><li> Zwischen Polieren Iterationen, entfernen Sie alle Restschlamm und Glaswaren aus dem Pad mit einem in-situ-Ultraschall-Reiniger (~ 2 min Verweilzeit an jeder radialen Position; Runde Dreh 5 rpm) mit fließenden DI-Wasser. </li><li> Auf der einzigartig geformten Septum Gewicht, sich Doppelklebeband und dann das Septum Material (zB Pre-Cut Glas oder anderen verschleißfreie Material). Schneiden Sie überhängende Schaumstoffband, um die Form der Nasenscheidewand Material und Gewicht entsprechen. Notieren Sie sich die Scheidewand-Design (beide Form und Gewicht) ändert für verschiedene Größen des Werkstücks und Runden 7,17. </li><li> Bereiten Polieraufschlämmung Baume 4 Konzentration (genauer Mischungsvolumen ~ 1 Teil Ceroxid Polieraufschlämmung und ~ 9 Teile entionisiertes (DI) Wasser in einem 11 L bucket). Überprüfen Baume mit einem Baume Schwimmer. Hinzufügen ~ 5 ml KOH (10 M) auf pH-Wert auf 9,5 einzustellen, und fügen ~ 120 ml (1 Vol%) des proprietären Tensid 19. Nachstellen pH und Baume alle 24 Stunden des Polierens. </li><li> Installieren Eimer mit der hergestellten Aufschlämmung in Filtersystem. Dann die gewünschten CMP Partikelfilter zu installieren in Filtersystem. Lassen Aufschlämmung Rezirkulat im Filtrationssystem für mehrere Stunden. </li><li> Messen Sie Partikelgrößenverteilung von Gülle (zB mit Einzelpartikel optische Messtechniken), um das hintere Ende der Verteilung zu gewährleisten ist ausreichend Schurkenpartikelfrei 9,20. </li></ol> 2. Herstellung von Werkstück (Radierung und Blocking) Vor dem Polieren chemisch zu ätzen, die, wie er erhalten feingeschliffenen Werkstück, um die Menge der Materialentfernung benötigt, um den Untergrund Schleifen Schäden 21 entfernen zu reduzieren. Dann blockieren die Werkstück (wenn das Seitenverhältnis (dh Länge / Dicke)&gt; 10) unter Verwendung eines neuen Pitch-Taste Sperr (PBB) Technik, um das Werkstück während der Sperrung und Polieren 22 Biegen zu verhindern. <ol><li> Ätzen der feingeschliffenen Werkstücks (insbesondere eine 265 x 265 x 8 mm 3 Quarzglas flach) in einem Behälter mit HF gefüllt: NH 4 F (6: 1 gepufferten Oxidätzung (BOE) 3x verdünnt mit DI-Wasser) für 6 Stunden entfernt 10 &amp; mgr; m von Glas von der Oberfläche des Werkstücks. VORSICHT! BOE ist extrem gefährlich; Tragen Sie geeignete Schutzausrüstung (PSA). Entfernen Sie Werkstück von Ätztank und das Werkstück mit VE-Wasser spülen aggressiv und lassen Sie das Werkstück in die Luft vertikal trocknen. </li><li> Untersuchen Sie das Werkstück für tiefe Beschädigungen während des Schleifvorgangs mit einem hellen Licht Inspektion in einem dunklen Raum. Wenn keine tiefen Schäden festgestellt werden, mit dem nächsten Schritt fortfahren, sonst schicken Werkstück zurück zum Nachschleifen. </li><li> Heizen Sie blockieren Abstand in einer Klebepistole, um ~ 95 ° C und Ort Tröpfchen (auch als Tasten) der Tonhöhe (~ 0,06 g) auf das Gesicht derPrägeplatte in einem 9 x 9-Array (81 Tasten mit 26 mm Abstand). Für unterschiedlich große Werkstücke, siehe Regeln für die ideale Anzahl, Größe und Abstände der Pitch-Taste 22 zu entwerfen. Legen Sie die blockierende Platte mit dem aufgebrachten Tasten Seite nach oben in den vorgeheizten Ofen bei 70 ºC. </li><li> Das Band auf der Seite des Werkstücks, die nicht poliert werden sollen. Vermeiden Sie die Erzeugung von Luftblasen oder übermäßig das Band dehnen. </li><li> Legen Sie das Werkstück mit der Bandseite nach unten, auf Tasten auf der Sperrplatte in den Ofen. Decken Sie die Werkstück-Tasten-Block, um konvektive Strömung zu minimieren. Nach 1,5 Stunden, eingestellt Ofen auf Raumtemperatur abkühlen 10 ºC / h. Nach dem Erkalten sollen die Tonhöhenstärke am Werkstück blockiert ~ 1 mm. </li></ol> 3. Konvergente Polieren <ol><li> Schalten Sie Feuchtigkeitssystem der Umweltkammer CISR Polierschlamm auf dem Austrocknen beim Polieren zu verhindern und die Rogue-Partikel Kratzen Sie das Werkstück zu minimieren. </li><li> Insgroß und montieren Sie die speziell entwickelt und vorbereitet Septum in Polierer. Installieren PBB Werkstück in CISR Polierer und Untergurt, das Werkstück zu halten. </li><li> Polish Werkstück auf CISR 4 h bei einer angepaßten Schoß und Werkstückdrehgeschwindigkeit von 25 Umdrehungen pro Minute mit einem radialen Hub von ~ 75 mm und mit einer Aufschlämmung von Strömungsfiltrationssystem von 1 gal / min. HINWEIS: Die Sperrplatte dient auch als das Belastungsgewicht an dem Werkstück entspricht, 0,6 psi Druck aufgebracht. </li><li> Schalten Schoß und Werkstückdrehung und Schlammstrom. Entfernen PBB Werkstück von CISR Polierer und tauchen sie in DI-Wasser gefüllt Badewanne. Wischen Werkstückoberfläche mit Reinraum-Tuch, während unter Wasser. Entfernen PBB Werkstück von Bad und sprühen gründlich mit VE-Wasser. </li><li> Deblock Werkstück, indem Sie einen Shim am Werkstück-Block-Schnittstelle. Entfernen Sie das Klebeband von der Werkstückoberfläche. Aggressiv spülen Werkstück mit VE-Wasser und der Luft trocknen. </li><li> PBB die gegenüberliegende Fläche des Werkstücks, wie in Abschnitt 2 beschrieben Wiederholen poGründung Vorgehensweise wie in Kapitel 3 beschrieben. </li></ol> 4. Messtechnik und Inspektion <ol><li> Messen reflektierten Wellenfront (dh Oberflächen Abbildung) auf beiden Seiten des Werkstücks sowie Wellenfront- Verwendung eines Interferometers. </li><li> Berg Werkstück auf helles Licht Prüfstation und messen die Kratzer / dig Eigenschaften mit Hilfe der optischen Fertigung von Standardmethoden. Ein kurzer BOE Ätzung des Werkstücks, wie in Schritt 2.1 beschrieben, kann verwendet werden, um versteckte Kratzer für Werkstücke in hohen Einfluss Laseranwendungen freizulegen. Zur Messung von feinen Kratzern oder Rauheit auf dem Werkstück können Standardlichtmikroskopie oder Weißlicht-Interferometrie verwendet werden. </li><li> Speicher abgeschlossen Werkstückes in einem Behälter Minimierung des Kontakts mit dem Gesicht des Werkstücks. </li></ol>

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The authors have nothing to disclose.

Wie in der Einleitung erwähnt, erfolgreiche Umsetzung von Convergent Polieren auf Oberflächen- Abbildung beinhaltet beseitigt oder minimiert alle Phänomene, die räumliche Material Ungleichmäßigkeit der Ausnahme, dass der Werkstück-Runden-Fehlanpassung aufgrund der Werkstückform beeinflussen. Wenn eines dieser Phänomene nicht entsprechend vermindert, sei es durch Prozesssteuerung oder durch entsprechende Konstruktion des Polierer, dann kann der gewünschte Konvergenzpunkt nicht erreicht oder beibehalten werden k...

Die wichtigsten Schritte in einem typischen optischen Herstellungsprozess gehören Formung, Schleifen, Polieren voller Öffnung, und manchmal kleine Werkzeugpolier 1-3. Mit zunehmender Nachfrage nach qualitativ hochwertigen optischen Komponenten für die Bildgebung und Lasersysteme, gab es bedeutende Fortschritte in der optischen Fertigung in den letzten Jahrzehnten. Zum Beispiel, Präzision, ist deterministisch Materialabtrag möglich bei der Formgebung und Schleifprozesse mit Fortschritten in der Computer Numerical Controlled (CNC) Glasformmaschinen. Ebenso kleines Tool Polieren Technologien (zB computergesteuerte optische Oberflächen (CCOS), Ionen herauszufinden, und magneto-rheologischen Endbearbeitung (MRF)) haben, um determinis Materialabtrag und Oberflächen mit Kontroll-LED, so stark beeinflussen die optische Fertigungsindustrie. Doch der Zwischenschritt des Fertigungsprozesses, voller Öffnung Polieren, fehlt immer noch hohen Determinismus erfordern in der Regel Fach opticians für die Durchführung mehrerer, oft lang, iterativen Zyklen mit mehreren Prozessänderungen auf die gewünschte Oberfläche Abbildung 1-3 zu erreichen. Die große Anzahl von Polierverfahren, Prozessvariablen und die komplexen chemischen und mechanischen Wechselwirkungen zwischen dem Werkstück, Runden- und Gülle 4.3 machen es schwierig, optische Polieren von einer &quot;Kunst&quot; zu einer Wissenschaft zu verwandeln. Deterministische voller Öffnung Polieren erreichen, muss die Abtragsleistung gut verstanden werden. Historisch gesehen hat Abtragsleistung durch die weit verbreitete Preston Gleichung 5 beschrieben worden <img alt="Gleichung 1" fo:content-width="1in" fo:src="/files/ftp_upload/51965/51965eqn1.jpg" src="/files/ftp_upload/51965/51965eqn1.jpg" width="100px" /> (1) wo dh / dt ist die durchschnittliche Dicke Abtragsleistung ist, k p die Preston Konstante σ o ISder ausgeübte Druck und V r der durchschnittliche Relativgeschwindigkeit zwischen dem Werkstück und dem Schoß. Abbildung 1 zeigt schematisch die physikalischen Konzepte, die Abtragsleistung beeinflussen, wie beschrieben, die Preston-Gleichung, einschließlich räumlichen und zeitlichen Schwankungen in Geschwindigkeit und Druck, Unterschiede zwischen den aufgebrachten Druck und die Druckverteilung, die der Werkstück Erfahrungen und Reibungseffekte 8.6. Insbesondere wird die tatsächliche Druckverteilung durch das Werkstück erfahrene durch eine Reihe von Phänomenen, die stark beeinflussen resultierende Oberfläche Gestalt des Werkstücks (an anderer Stelle ausführlich beschrieben 6-8) geregelt. Auch in der Preston-Gleichung, die mikroskopische und molekularNiveauEffekte weitgehend in die makroskopische Preston Konstante (k p), welche die Gesamt Abtragsleistung Mikrorauhigkeit und sogar Kratzer an dem Werkstück beeinflußt gefaltet. Verschiedene Studien haben Prestons Modell erweitert, um Konto<html> zur mikroskopischen Partikelschlamm-pad-Werkstück-Interaktionen zu erklären, Abtragsleistung und Mikrorauhigkeit 9-16. Deterministische Kontrolle der Oberflächenfigur bei voller Öffnung Polieren zu erreichen, jede der oben beschriebenen Phänomene verstanden werden muss, quantifiziert und gesteuert. Die Strategie hinter Convergent Polieren zu beseitigen oder die unerwünschten Ursachen ungleichmäßigen Abtrag minimieren, entweder durch technische Polierer Entwurf oder durch Prozesssteuerung, so dass das Entfernen nur von dem Werkstück-Lap Fehlanpassung aufgrund der Werkstückform angetrieben 7,17- 18. 2 zeigt, wie Werkstückform, um die Konvergenz auf der Basis des Werkstück-Lap Mismatch Konzept führen. Stellen Sie sich eine flache Schoß und eine hypothetische Werkstück von oben links gezeigt komplexe Form. Die Schnittstelle Höhenübereinstimmung (die als die Lücke &amp; Dgr; h oL genannt) beeinflusst die Schnittstelle Druckverteilung (σ) als: Inhalt &quot;fo: keep-together.within-page =&quot; always &quot;&gt; <img alt="Gleichung 2" fo:content-width="1in" fo:src="/files/ftp_upload/51965/51965eqn2.jpg" src="/files/ftp_upload/51965/51965eqn2.jpg" width="100px" /> (2) wobei H eine Konstante beschreibt die Geschwindigkeit, mit der der Druck nimmt mit einer Zunahme der Spalt &amp; Delta; h oL 6. In diesem Beispiel hat das Werkstück die höchste lokale Druck in der Mitte (siehe unten links in 2), und damit diese Stelle die höchste anfängliche Abtrag während des Polierens zu beobachten. Als Material entfernt wird, wird die Druckdifferenz über das Werkstück zu einer Abnahme in dem Werkstück-Lap Fehlanpassung zu verringern durch, und das Werkstück wird an die Form des Überlappungs konvergieren. Bei der Konvergenz, dem Werkstück Druckverteilung und damit Materialentfernung wird über das Werkstück gleichmäßig sein (siehe rechte Seite der Abbildung 2). Dieses Beispiel ist für eine flache Runde dargestellt, however gilt das gleiche Konzept für ein Kugelrunde (entweder konkav oder konvex). Auch hier funktioniert diese Konvergenzprozess nur dann, wenn alle anderen Phänomene beeinflussen räumliche Material Ungleichmäßigkeit wurden eliminiert. Die spezifische Verfahrenstechnik und Minderungen in der Convergent Polieren Protokoll implementiert werden in der Diskussion beschrieben. Die in der folgenden Studie beschriebenen Protokoll ist die konvergente Polierprozess, der speziell für eine 26,5 cm im Quadrat Quarzglas Werkstück ausgehend von einem fein geschliffenen Oberfläche. In 8 Stunden Polieren (4 Stunden / Oberfläche), kann dieses Werkstück eine Flachheit der polierten ~ λ / 2 mit einer sehr hohen Oberflächenqualität (dh geringe Kratzdichte) zu erzielen.

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convergent polishing: a simple, rapid, full aperture polishing process of high quality optical flats &amp; spheres

Convergent Polieren ist eine neue Poliersystem und ein Verfahren zur Veredelung flacher und sphärischer Glasoptik in dem ein Werkstück unabhängig von seiner ursprünglichen Form (dh Oberfläche Abbildung), werden bis zur endgültigen Oberflächenfigur mit exzellenter Oberflächenqualität unter einer festen, unveränderlichen Satz konvergieren Polierparameter in einer einzigen Polier Iteration. Im Gegensatz dazu herkömmliche voller Öffnung Polierverfahren benötigen mehrere, oft lang, iterativen Zyklen mit Polieren, Messtechnik und Prozessänderungen, um die gewünschte Oberflächenfigur zu erreichen. Die konvergente Poliervorgang basiert auf dem Konzept der Werkstück-Rundenhöhe Missverhältnis, was zu Druckdifferenz, die mit der Entfernung und führt zu dem Werkstück zusammenlaufen, um die Form der Runde sinkt basiert. Die erfolgreiche Durchführung der Convergent Polierverfahren ist ein Ergebnis der Kombination einer Anzahl von Technologien, alle Quellen von ungleichmäßigen räumlichen Materialabtrag (außer Werkstück-Runde zu entfernenMismatch) für Oberflächen mit Konvergenz und um die Anzahl der Schurken Teilchen im System für geringe Kratzdichten und geringe Rauigkeit zu reduzieren. Die konvergente Polierprozess ist für die Herstellung der beiden Wohnungen und Kugeln in verschiedenen Formen, Größen und Seitenverhältnissen auf verschiedenen Glasmaterialien nachgewiesen. Die praktischen Auswirkungen ist, dass qualitativ hochwertige optische Komponenten können schneller mehr wiederholt hergestellt werden, mit weniger Messtechnik, und mit weniger Arbeit, was zu geringeren Stückkosten. In dieser Studie wird die Convergent Polieren Protokoll speziell für die Herstellung von 26,5 cm im Quadrat zu einem poliert ~ λ / 2 Oberflächenfigur nach dem Polieren von 4 Stunden pro Fläche auf einem 81 cm Durchmesser Polier Quarzglas Wohnungen von einem feinen Bodenoberfläche beschrieben.

Die oben beschriebene Polierung Convergent-Protokoll ermöglicht eine Masse Quarzglas Werkstück (in diesem Fall eine 26,5 cm im Quadrat) poliert werden, in einem einzigen Durchlauf von 4 h pro Fläche auf eine Spitze-zu-Tal-Ebenheit von ~ λ / 2 (~ 330 nm) mit niedrigem Seitenverhältnis Werkstücke und ~ 1λ (~ 633 nm) für hohen Aspektverhältnis von Werkstücken (siehe Abbildung 3). Auch hier wiederholt konvergiert dieses Verfahren Werkstücke auf die gleiche endgültige Oberflächen Figur ohne Änd...

Watch this Scientific Journal Video about Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats & Spheres at JoVE.com

Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats & Spheres

A novel optical polishing process, called &#8220;Convergent Polishing&#8221;, which enables faster, lower cost polishing, is described. Unlike conventional polishing processes, Convergent Polishing allows a glass workpiece to be polished in a single iteration and with high surface quality to its final surface figure without requiring changes to polishing parameters.

Convergent Polieren: Eine einfache und schnelle, Schmalrandpolierprozess der Hochwertiges optisches Wohnungen &amp; Spheres

Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial ...

convergent-polishing-simple-rapid-full-aperture-polishing-process

Research

JoVE Journal

Engineering

Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats &amp; Spheres

11.0K Aufrufe.  Lawrence Livermore National Laboratory. A novel optical polishing process, called “Convergent Polishing”, which enables faster, lower cost polishing, is described. Unlike conventional polishing processes, Convergent Polishing allows a glass workpiece to be polished in a single iteration and with high surface quality to its final surface figure without requiring changes to polishing parameters.

Serie: Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats & Spheres

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.

Herstellung von Silica Ultra High Quality Factor Mikroresonatoren

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

Forschung

Ingenieurwesen

Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The optical modes are frequently referred to as "whispering gallery modes" (WGM) or "morphology dependent resonances" (MDR) and exhibit high optical quality factors. Some proposed applications of micro-cavity optical resonators are in spectroscopy1, micro-cavity laser technology2, optical communications3-6 as well as sensor technology. The WGM-based sensor applications include those in biology7, trace gas detection8, and impurity detection in liquids9. Mechanical sensors based on microsphere resonators have also been proposed, including those for force10,11, pressure12, acceleration13 and wall shear stress14. In the present, we demonstrate a WGM-based electric field sensor, which builds on our previous studies15,16. A candidate application of this sensor is in the detection of neuronal action potential.
The electric field sensor is based on polymeric multi-layered dielectric microspheres. The external electric field induces surface and body forces on the spheres (electrostriction effect) leading to elastic deformation. This change in the morphology of the spheres, leads to shifts in the WGM. The electric field-induced WGM shifts are interrogated by exciting the optical modes of the spheres by laser light. Light from a distributed feedback (DFB) laser (nominal wavelength of ~ 1.3 &mu;m) is side-coupled into the microspheres using a tapered section of a single mode optical fiber. The base material of the spheres is polydimethylsiloxane (PDMS). Three microsphere geometries are used: (1) PDMS sphere with a 60:1 volumetric ratio of base-to-curing agent mixture, (2) multi layer sphere with 60:1 PDMS core, in order to increase the dielectric constant of the sphere, a middle layer of 60:1 PDMS that is mixed with varying amounts (2% to 10% by volume) of barium titanate and an outer layer of 60:1 PDMS and (3) solid silica sphere coated with a thin layer of uncured PDMS base. In each type of sensor, laser light from the tapered fiber is coupled into the outermost layer that provides high optical quality factor WGM (Q ~ 106). The microspheres are poled for several hours at electric fields of ~ 1 MV/m to increase their sensitivity to electric field.

A high-sensitivity photonic micro sensor was developed for electric field detection. The sensor exploits the optical modes of a dielectric sphere. Changes in the external electric field perturb the sphere morphology leading to shifts in its optical modes. The electric field strength is measured by monitoring these optical shifts.

Entwicklung von Whispering Gallery-Modus polymeren Mikro-optische Electric Field Sensoren

Optical modes of dielectric micro-cavities have received significant attention in recent years for their potential in a broad range of applications. The ...

Microwave Photonics Systems Based on Whispering-gallery-mode Resonators

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various areas of technology and applied science, such as aerospace and communication engineering, sensing, metrology, nonlinear photonics, and quantum optics. In this article, we present the principal techniques used in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators. First detailed in this article is the protocol for resonator polishing, which is based on a grind-and-polish technique close to the ones used to polish optical components such as lenses or telescope mirrors. Then, a white light interferometric profilometer measures surface roughness, which is a key parameter to characterize the quality of the polishing. In order to launch light in the resonator, a tapered silica fiber with diameter in the micrometer range is used. To reach such small diameters, we adopt the "flame-brushing" technique, using simultaneously computer-controlled motors to pull the fiber apart, and a blowtorch to heat the fiber area to be tapered. The resonator and the tapered fiber are later approached to one another to visualize the resonance signal of the whispering gallery modes using a wavelength-scanning laser. By increasing the optical power in the resonator, nonlinear phenomena are triggered until the formation of a Kerr optical frequency comb is observed with a spectrum made of equidistant spectral lines. These Kerr comb spectra have exceptional characteristics that are suitable for several applications in science and technology. We consider the application related to ultra-stable microwave frequency synthesis and demonstrate the generation of a Kerr comb with GHz intermodal frequency.

The customized techniques developed in our lab to build microwave photonics systems based on ultra-high Q whispering gallery mode resonators are presented. The protocols to obtain and characterize these resonators are detailed, and an explanation of some of their applications in microwave photonics is given.

Mikrowelle Photonics Systems on Whispering-Gallery-Mode-Resonatoren Grundlage

Microwave photonics systems rely fundamentally on the interaction between microwave and optical signals. These systems are extremely promising for various ...

The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry

Thermal noise in high-reflectivity mirrors is a major impediment for several types of high-precision interferometric experiments that aim to reach the standard quantum limit or to cool mechanical systems to their quantum ground state. This is for example the case of future gravitational wave observatories, whose sensitivity to gravitational wave signals is expected to be limited in the most sensitive frequency band, by atomic vibration of their mirror masses. One promising approach being pursued to overcome this limitation is to employ higher-order Laguerre-Gauss (LG) optical beams in place of the conventionally used fundamental mode. Owing to their more homogeneous light intensity distribution these beams average more effectively over the thermally driven fluctuations of the mirror surface, which in turn reduces the uncertainty in the mirror position sensed by the laser light.
We demonstrate a promising method to generate higher-order LG beams by shaping a fundamental Gaussian beam with the help of diffractive optical elements. We show that with conventional sensing and control techniques that are known for stabilizing fundamental laser beams, higher-order LG modes can be purified and stabilized just as well at a comparably high level. A set of diagnostic tools allows us to control and tailor the properties of generated LG beams. This enabled us to produce an LG beam with the highest purity reported to date. The demonstrated compatibility of higher-order LG modes with standard interferometry techniques and with the use of standard spherical optics makes them an ideal candidate for application in a future generation of high-precision interferometry.

Large laser-interferometers are being constructed to create a new type of astronomy based on gravitational waves. Their sensitivities, as for many other high-precision experiments, are approaching fundamental noise limits such as the atomic vibration of their components. We are pioneering technologies to overcome these limits using novel laser beam shapes.

Die Generation von höherer Ordnung Laguerre-Gauss optischen Strahlen für Präzisions-Interferometrie

Thermal noise in high-reflectivity mirrors is a major impediment for several  types of high-precision interferometric experiments that aim to reach the  ...

High-speed Continuous-wave Stimulated Brillouin Scattering Spectrometer for Material Analysis

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as aqueous solutions and biomaterials, with fast acquisition times. Here, we discuss the assembly and operation of a Brillouin spectrometer that uses stimulated Brillouin scattering (SBS) to measure stimulated Brillouin gain (SBG) spectra of water and lipid emulsion-based tissue-like samples in transmission mode with &lt;10 MHz spectral-resolution and &lt;35 MHz Brillouin-shift measurement precision at &lt;100 ms. The spectrometer consists of two nearly counter-propagating continuous-wave (CW) narrow-linewidth lasers at 780 nm whose frequency detuning is scanned through the material Brillouin shift. By using an ultra-narrowband hot rubidium-85 vapor notch filter and a phase-sensitive detector, the signal-to-noise-ratio of the SBG signal is significantly enhanced compared to that obtained with existing CW-SBS spectrometers. This improvement enables measurement of SBG spectra with up to 100-fold faster acquisition times, thereby facilitating high spectral-resolution and high-precision Brillouin analysis of soft materials at high speed.

We describe the construction of a rapid continuous-wave-stimulated-Brillouin-scattering (CW-SBS) spectrometer. The spectrometer employs single-frequency diode-lasers and an atomic vapor notch-filter to acquire transmission spectra of turbid/non-turbid samples with high spectral-resolution at speeds up to 100-fold faster than those of existing CW-SBS spectrometers. This improvement enables high-speed Brillouin material analysis.

High-Speed-Dauerstrich-stimulierten Brillouin-Streuung Spektrometer für Materialanalyse

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as ...

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.

Herstellung von Polymer-Mikrosphären für optische Resonator- und Laseranwendungen

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Demonstration of a Hyperlens-integrated Microscope and Super-resolution Imaging

The use of super-resolution imaging to overcome the diffraction limit of conventional microscopy has attracted the interest of researchers in biology and nanotechnology. Although near-field scanning microscopy and superlenses have improved the resolution in the near-field region, far-field imaging in real-time remains a significant challenge. Recently, the hyperlens, which magnifies and converts evanescent waves into propagating waves, has emerged as a novel approach to far-field imaging. Here, we report the fabrication of a spherical hyperlens composed of alternating silver (Ag) and titanium oxide (TiO2) thin layers. Unlike a conventional cylindrical hyperlens, the spherical hyperlens allows for two-dimensional magnification. Thus, incorporation into conventional microscopy is straightforward. A new optical system integrated with the hyperlens is proposed, allowing for a sub-wavelength image to be obtained in the far-field region in real time. In this study, the fabrication and imaging setup methods are explained in detail. This work also describes the accessibility and possibility of the hyperlens, as well as practical applications of real-time imaging in living cells, which can lead to a revolution in biology and nanotechnology.

The use of a hyperlens has been regarded as a novel super-resolution imaging technique due to its advantages in real-time imaging and its simple implementation with conventional optics. Here, we present a protocol describing the fabrication and imaging applications of a spherical hyperlens.

Demonstration eines Hyperlens integriert Mikroskop und super-Resolution Imaging

The use of super-resolution imaging to overcome the diffraction limit of conventional microscopy has attracted the interest of researchers in biology and ...

Rapid Optical Clearing for Semi-High-Throughput Analysis of Tumor Spheroids

Tumor spheroids are fast becoming commonplace in basic cancer research and drug development. Obtaining data regarding protein expression within the spheroid at the cellular level is important for analysis, yet existing techniques are often expensive, laborious, use non-standard equipment, cause significant size distortion, or are limited to relatively small spheroids. This protocol presents a new method of mounting and clearing spheroids that address these issues while allowing for confocal analysis of the inner structure of spheroids. In contrast to existing approaches, this protocol provides for rapid mounting and clearing of a large number of spheroids using standard equipment and laboratory supplies. Mounting spheroids in a pH-neutral agarose-PBS gel solution before introducing a refractive-index-matched clearing solution minimizes size distortion common to other similar techniques. This allows for detailed quantitative and statistical analysis where the accuracy of size measurements is paramount. Furthermore, compared to liquid clearing solutions, the agarose gel technique keeps spheroids fixed in place, allowing for the collection of three-dimensional (3D) confocal images. The present article elaborates how the method yields high-quality two- and 3D images that provide information about inter-cell variability and inner spheroid structure.

Tumor spheroids are becoming increasingly utilized to assess tumor cell-microenvironment interactions and therapy response. The present protocol describes a robust but simple method for semi-high-throughput imaging of 3D tumor spheroids using rapid optical clearing.

Rapid Optical Clearing für die Semi-Hochdurchsatzanalyse von Tumorsphäroiden

Tumor spheroids are fast becoming commonplace in basic cancer research and drug development. Obtaining data regarding protein expression within the ...

Krebsforschung

Plasma Polishing as a New Polishing Option to Reduce the Surface Roughness of Porous Titanium Alloy for 3D Printing

Porous titanium alloy implants with simulated trabecular bone fabricated by 3D printing technology have broad prospects. However, due to the fact that some powder adheres to the surface of the workpiece during the manufacturing process, the surface roughness in direct printing pieces is relatively high. At the same time, since the internal pores of the porous structure cannot be polished by conventional mechanical polishing, an alternative method needs to be found. As a surface technology, plasma polishing technology is especially suitable for parts with complex shapes that are difficult to polish mechanically. It can effectively remove particles and fine splash residues attached to the surface of 3D printed porous titanium alloy workpieces. Therefore, it can reduce surface roughness. Firstly, titanium alloy powder is used to print the porous structure of the simulated trabecular bone with a metal 3D printer. After printing, heat treatment, removal of the supporting structure, and ultrasonic cleaning is carried out. Then, plasma polishing is performed, consisting of adding a polishing electrolyte with the pH set to 5.7, preheating the machine to 101.6 &#176;C, fixing the workpiece on the polishing fixture, and setting the voltage (313 V), current (59 A), and polishing time (3 min). After polishing, the surface of the porous titanium alloy workpiece is analyzed by a confocal microscope, and the surface roughness is measured. Scanning electron microscopy is used to characterize the surface condition of porous titanium. The results show that the surface roughness of the whole porous titanium alloy workpiece changed from Ra (average roughness) = 126.9 &#181;m to Ra = 56.28 &#181;m, and the surface roughness of the trabecular structure changed from Ra = 42.61 &#181;m to Ra = 26.25 &#181;m. Meanwhile, semi-molten powders and ablative oxide layers are removed, and surface quality is improved.

Plasma polishing is a promising surface processing technology, especially suitable for 3D printing of porous titanium alloy workpieces. It can remove semi-molten powders and ablative oxide layers, thereby effectively reducing surface roughness and improving surface quality.

Plasmapolieren als neue Polieroption zur Reduzierung der Oberflächenrauheit poröser Titanlegierungen für den 3D-Druck

Porous titanium alloy implants with simulated trabecular bone fabricated by 3D printing technology have broad prospects. However, due to the fact that ...

Medizin

Impact of Fabrication Techniques and Polishing Procedures on Surface Roughness of Denture Base Resins

This study aimed to assess the impact of various fabrication techniques and polishing procedures on the surface roughness (Ra) of resin-based materials used in the fabrication of complete dentures. A total of 90 specimens were produced from three different resin materials: heat-polymerized polymethyl methacrylate (PMMA) resin, CAD-CAM milled PMMA resin, and 3D-printed resin (n = 30). Each specimen measured 10 mm in diameter and 2 mm in height. The surface roughness (Ra) values of the specimens were initially determined using a contact profilometer following fabrication. Subsequently, each group of specimens was polished with 600-, 800-, and 1000-grit silicon carbide abrasive papers under running water. A second measurement of the surface roughness (Ra) values was then performed. The data were analyzed statistically using the Kruskal-Wallis test, Mann-Whitney U test, Wilcoxon signed-rank test, and paired samples t-test (p = 0.05). A statistically significant difference was identified between the groups in terms of surface roughness (Ra) prior to the polishing process (p &#60; 0.001). However, no statistically significant difference was observed between the milled and heat-polymerized PMMA base materials following the polishing process. The 3D-printed specimens showed the most notable improvement in surface roughness due to the polishing process. Nevertheless, their surface roughness remained statistically significantly higher compared to the other samples, both before and after polishing (p &#60; 0.001). The fabrication method of complete denture base materials was observed to influence surface roughness. The surface roughness values of the base materials fabricated using the 3D printing method were higher compared to those fabricated with milled and heat-polymerized PMMA resin, both before and after polishing.

This article presents a protocol to evaluate the effects of different manufacturing methods (heat-polymerized PMMA, CAD-CAM milled PMMA, and 3D-printed resin) and polishing techniques (600, 800, and 1000 grit silicon carbide abrasive papers) on the surface roughness (Ra) of resin base materials used for complete dentures.

Einfluss von Fertigungstechniken und Polierverfahren auf die Oberflächenrauheit von Prothesenbasiskunststoffen

This study aimed to assess the impact of various fabrication techniques and polishing procedures on the surface roughness (Ra) of resin-based materials ...

Convergent Polieren: Eine einfache und schnelle, Schmalrandpolierprozess der Hochwertiges optisches Wohnungen & Spheres

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