מחקר זה מומן על ידי סוכנות ההגנה האמריקנית לפרויקטי מחקר המתקדם תחת מרכזים בחקר הנדסה משולבת פוטוניקס (צופן) תכנית עם ד&quot;ר ג&#39;יי סקוט רוג&#39;רס כמנהל פרויקט. המידע הכלול בדוח זה אינו משקף בהכרח את העמדה או המדיניות של ממשלת ארה&quot;ב ואין אישור רשמי צריכה להיות מוסקת.

1. הכנת PDMS microsphere (כדור ש) <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> בסיס polydimethylsiloxane (PDMS) וסוכן הריפוי מעורבב עם יחס נפח של 60:1. </li><li style=";text-align:right;direction:rtl"> גדיל של סיבים אופטיים סיליקה, באורך 2 סנטימטר, המנוער הראשון של חיפוי הפלסטיק שלה באמצעות חשפנית אופטית. </li><li style=";text-align:right;direction:rtl"> קצה אחד של הסיב מחומם ונמתח כדי לספק קצה גבעול שהוא ~ 25-50 מיקרומטר בקוטר בקצה. </li><li style=";text-align:right;direction:rtl"> הסוף המתוח של הסיבים הוא שקוע לתוך תערובת PDMS על ידי אורך של כ 2-4 מ&quot;מ ולאחר מכן הוא שלף. </li><li style=";text-align:right;direction:rtl"> מתח פנים ומשקל של תערובת PDMS לאפשר היווצרות של כדור בקצה סיב סיליקה. הגודל של הכדור הוא נשלט על ידי טבילת האורך ומהירות חילוץ. על ידי שינוי שני הפרמטרים הללו, קטרי כדור בטווח 100 מיקרומטר - 1000 מיקרומטר ניתן להשיג. </li><li style=";text-align:right;direction:rtl"> אז הרכבת microsphere / גזע ממוקמת בתנור ב ~ 90 מעלות צלזיוס למשך 4 שעות כדי לאפשר ריפוי תקין של פוליחומרי mer (ליצור שרשרות צולבות). האיור 1 א הם סכמטי של הכדור ראשון </li></ol> 2. הכנת PDMS מבוסס טריפל Layer כדור (כדור השני) <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> Microsphere PDMS 60:1 משמש ליבה הפנימית. באותם שלבים המתוארים ב1) לעיל הם בעקבות לתהליך הזה. </li><li style=";text-align:right;direction:rtl"> תערובת של titanate בריום (3 BaTiO) ננו חלקיקים ו60:1 PDMS משמש כשכבה אמצעית. תערובת PDMS, שהוכנה באותה הדרך שתוארה ב1.1) לעיל, הוא מעורבב עם titanate בריום חלקיקי ננו. </li><li style=";text-align:right;direction:rtl"> ליבת microsphere PDMS המתוארת ב2.1) לאחר מכן טבלה את תערובת PDMS titanate-הבריום למעיילו (בעובי נומינלי שכבה ~ 10 מיקרומטר). </li><li style=";text-align:right;direction:rtl"> בשלב בא, המרחב דו שכבתי ממוקם בתנור ב ~ 90 מעלות צלזיוס למשך 4 שעות כדי לאפשר ריפוי תקין של השכבה השנייה. </li><li style=";text-align:right;direction:rtl"> ברגע שכדור 2 השכבה הוא נרפא, הוא שקוע שוב בתערובת של 60:1 PDMS לספק ציפוי חיצוני (שכבה 3). זה חיצונישכבה משמשת כמדריך אופטי כדורי (~ 10 עובי מיקרומטר). האיור 1b הוא סכמטי של כדור השני. </li></ol> 3. סיליקה / הכנת microsphere PDMS (כדור שלישי) <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> ~ 3 סנטימטר קטע ארוך של סיבים אופטיים בודדים מצב סיליקה הוא הפשט הראשון של חיצה (פלסטיק) ציפוי ולאחר מכן קצו הוא נמס באמצעות מייקרו לפיד (יחד עם החיפוי וליבה). מתח פנים וכוח הכביד פועלים יחד כדי לעצב את הקצה המומס לכדור. כדורים בקטרים ​​הנעים 200-500 מיקרומטר ניתן להשיג עם תהליך זה. </li><li style=";text-align:right;direction:rtl"> אז microsphere סיליקה הוא שקוע באמבט של PDMS בסיס (ללא סוכן הריפוי) כדי לכסות אותו עם מעייל של ~ 50 מיקרומטר. שכבה חיצונית זו נשארת כמו נוזל צמיג מאוד בינגהאם (תשואת לחץ). האיור 1c הוא סכמטי של כדור שלישי. </li></ol> 4. הכנת סיב אופטית <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> קטע של סיב אופטי במצב יחיד הוא פשט של CLA הפלסטיק שלהdding באמצעות חשפנית אופטית. שימוש בסעיף פסי מייקר לפיד של הסיבים הוא מחומם עד שהוא מותך (שניהם החיפוי וסיבי ליבה). </li><li style=";text-align:right;direction:rtl"> בעוד שהחלק האמצעי הוא מותך, קצה אחד של הסיב האופטי הוא משך לאורך הציר עד יוצר סעיף מחודד של הסיב שאורכו כ 1 סנטימטר. משך החימום, מהירות והמרחק מושך לקבוע את קוטרו של סעיף הקונים הנע בין 10 ל 20 מיקרומטר. האור מליזר DFB מצמיד אל הזירה דרך הסעיף המחודד של הסיב. תרשים 2 מציג את צימוד תחום הסיבים. </li></ol> 5. אופטו התקנה <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> הפלט של ליזר DFB מתכונן מצמיד לסיב אופטי במצב יחיד בקצה אחד והסתיים בphotodiode מהיר בצד השני, כפי שמוצג באיור 3. </li><li style=";text-align:right;direction:rtl"> הפלט הוא photodiode דיגיטציה באמצעות ממיר אנלוגי לדיגיטלי (A / D) ומאוחסן במחשב אישי (PC). </li><li&gt; שימוש שלב תרגום המייקר microsphere (סוג I, II או III) הוא הביא במגע עם החלק המחודד של הסיב האופטי (איורים 2 ו 3) לספק צימוד אופטי בין שני אלמנטים. </li><li style=";text-align:right;direction:rtl"> ליזר DFB מכוון על ידי בקר ליזר. בקר הליזר, בתורו הוא מונע על ידי גנרטור פונקציה המספק מתח קלט משונן. </li></ol> 6. דור שדה חשמלי <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> שתי צלחות נחושת מרובעות (2 2 סנטימטר) בעובי של 1 מ&quot;מ משמשות ליצירת שדה החשמלי האחיד. הצלחות מחוברות לאספקת מתח ואת חיישני הכדור מונחים בפער בין שתי צלחות (איור 4). </li><li style=";text-align:right;direction:rtl"> על מנת להגביר את רגישות המדידה, הם כיוונו את התחומים ראשונים בשדה חשמלי של 1 MV / מ &#39;ל2 שעות. </li></ol>

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אין לנו מה למסור.

התחומים לראשונה דרכו על ידי חיבור אלקטרודות לאספקת מתח גבוהה DC. בסוף תקופת poling, המוביל אלקטרודה מנותק מאספקת מתח DC ומחובר לגנרטור פונקציה כמצוין באיור 4. התוצאות מוצגות באיורים 5 עד 8 ​​תכנית ששדות חשמליים חיוביים ושליליים (ביחס לכיוון של ?...

<table border="1" style=";text-align:right;direction:rtl"><tbody><tr><td></td><td> חברה </td><td> מספר קטלוגים </td><td> תגובות (אופציונלי) </td></tr><tr><td> PDMS </td><td> Dow Corning </td><td> Sylgard 184 </td><td></td></tr><tr><td> סיבי סיליקה </td><td> מכירות כלי סיבים </td><td> דואר 37AP15-FIS </td><td></td></tr><tr><td> Titanate הבריום (3 BaTiO) חלקיקים </td><td> סיגמה אולדריץ </td><td> 467634-100G </td><td></td></tr><tr><td> ליזר בקר </td><td> ILX Lightwave </td><td> LDC-3724B </td><td></td></tr><tr><td> DFB ליזר </td><td> Agere </td><td> Agere 2300 </td><td> 1.310 אורך גל מרכזי מיקרומטר </td></tr><tr><td> Photodiode </td><td> Thorlabs </td><td> PDA10CS </td><td></td></tr><tr><td> כרטיס / D </td><td> מכשירים הלאומיים </td><td> PXI 6115 </td><td></td>
 </tr>
 </tbody>
</table>

development of whispering gallery mode polymeric micro-optical electric field sensors

מצבים אופטיים של מייקרו חללים דיאלקטרי זכו לתשומת לב משמעותית בשנים האחרונות לפוטנציאל שלהם במגוון רחב של יישומים. המצבים האופטיים לעתים קרובות מכונים &quot;לוחש מצבי גלריה&quot; (WGM) או &quot;תהודות תלויות מורפולוגיה&quot; (MDR) ומפגינים גורמי איכות אופטיות גבוהים. החלק מהיישומים מוצעים של תהודה האופטית מייקרו החלל נמצאים ב1 ספקטרוסקופיה, טכנולוגיית מייקרו חריר ליזר 2, 3-6 תקשורת האופטית, כמו גם טכנולוגיית חיישן. היישומים מבוססי חיישני WGM כוללים את אלה ב7 ביולוגיה, גילוי גז עקבות 8, וזיהוי טומאה ב9 נוזלים. חיישנים מכאניים המבוססים על תהודת microsphere גם הוצעו, כוללים אלה של כוח 10,11, לחץ 12, תאוצה 13 ולחץ קיר גזירת 14. בהווה, אנחנו מדגימים את חיישן WGM מבוסס שדה חשמלי, אשר מבוסס על Studi הקודם שלנוes 15,16. יישום מועמד של חיישן זה הוא בזיהוי של פוטנציאל פעולה עצבי. חיישן השדה החשמלי המבוסס על דיאלקטרי microspheres פולימרים רבים שכבתי. השדה החשמלי החיצוני גורם לכוחות הגוף ושטח בתחומים (השפעת electrostriction) שמובילים לעיוות אלסטי. שינוי זה במורפולוגיה של הספירות, מוביל לשינויים בWGM. משמרות WGM השדה החשמלי מושרות חקירה על ידי מרגשים המצבים האופטיים של התחומים על ידי אור ליזר. אור ממשוב שיחולק (DFB) ליזר (אורך גל נומינלי של 1.3 ~ מיקרומטר) הוא צד מצמיד לmicrospheres באמצעות סעיף מחודד של סיב אופטי במצב יחיד. חומר הבסיס של הספירות הוא polydimethylsiloxane (PDMS). שלוש גיאומטריות microsphere משמשות: (1) תחום PDMS עם יחס נפח של 60:1 לבסיס ריפוי תערובת סוכן, (2) כדור רב שכבתי עם 60:1 PDMS ליבה, במטרה להגדיל את דיאלקטרי הקבוע של התחום דואר, שכבה אמצעית של 60:1 PDMS שמעורבב עם כמויות משתנות (2% עד 10% בנפח) של titanate בריום ושכבה חיצונית של 60:1 PDMS ו( 3) כדור סיליקה מוצק מצופה בשכבה דקה בסיס של PDMS דפוק. בכל סוג של חיישן ליזר, אור מהסיב המחודד מצמיד אל השכבה החיצונית המספקת איכות גורם WGM האופטי גבוהה (ש ~ 10 6). הם כיוונו את microspheres במשך כמה שעות בשדות חשמליים של MV ~ 1 / מ &#39;כדי להגדיל את רגישותם לשדה חשמלי.

מצב אופטי (WGM) של המרחב מתלהב מאור הליזר, כאשר אורך הנתיב אופטי נסע באור הוא מספר מרובה של הליזר באורך הגל. להסדר שמוצג באיור 3, אורך הנתיב האופטי הוא 2πrn, כאשר n ו R הוא מקדם שבירה ורדיוס הכדור, בהתאמה. באמצעות קירוב האופטיקה גיאומטרי, מצב WGM הוא מרו?...

Watch this Scientific Journal Video about Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors at JoVE.com

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

חיישן מייקרו רגישות גבוהה פוטוניים פותח לגילוי שדה חשמלי. החיישן מנצל את המצבים האופטיים של מרחב דיאלקטרי. שינויים בשדה החשמלי החיצוני מטריד את מורפולוגיה הכדור שהובילה לשינויים במצבים האופטיים שלה. עוצמת השדה החשמלית שנמדדה על ידי ניטור אופטיים המשמרות האלה.

פיתוח של חיישני Whispering גלרית Mode פולימריים מייקר אופטי שדה חשמליים

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

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13.1K Views.  Southern Methodist University. חיישן מייקרו רגישות גבוהה פוטוניים פותח לגילוי שדה חשמלי. החיישן מנצל את המצבים האופטיים של מרחב דיאלקטרי. שינויים בשדה החשמלי החיצוני מטריד את מורפולוגיה הכדור שהובילה לשינויים במצבים האופטיים שלה. עוצמת השדה החשמלית שנמדדה על ידי ניטור אופטיים המשמרות האלה.

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

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.

ייצור של אולטרה סיליקה Microresonators באיכות גבוהה פקטור

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

Synthesis and Operation of Fluorescent-core Microcavities for Refractometric Sensing

This paper discusses fluorescent core microcavity-based sensors that can operate in a microfluidic analysis setup. These structures are based on the formation of a fluorescent quantum-dot (QD) coating on the channel surface of a conventional microcapillary. Silicon QDs are especially attractive for this application, owing in part to their negligible toxicity compared to the II-VI and II-VI compound QDs, which are legislatively controlled substances in many countries. While the ensemble emission spectrum is broad and featureless, an Si-QD film on the channel wall of a capillary features a set of sharp, narrow peaks in the fluorescence spectrum, corresponding to the electromagnetic resonances for light trapped within the film. The peak wavelength of these resonances is sensitive to the external medium, thus permitting the device to function as a refractometric sensor in which the QDs never come into physical contact with the analyte. The experimental methods associated with the fabrication of the fluorescent-core microcapillaries are discussed in detail, as well as the analysis methods. Finally, a comparison is made between these structures and the more widely investigated liquid-core optical ring resonators, in terms of microfluidic sensing capabilities.

Fluorescent-core microcavity sensors employ a high-index quantum-dot coating in the channel of silica microcapillaries. Changes in the refractive index of fluids pumped into the capillary channel cause shifts in the microcavity fluorescence spectrum that can be used to analyze the channel medium.

סינתזה והפעלה של microcavities פלורסנט ליבות לחישת Refractometric

This paper discusses  fluorescent core microcavity-based sensors that can operate in a microfluidic  analysis setup. These structures are based on 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.

מיקרוגל Photonics מערכות המבוססות על מהודי לחישות-גלריה של מצב

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

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.

יישום של אינטרפרומטר הפניה לNanodetection

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

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

ייצור ובדיקה של מתנדים optomechanical Microfluidic

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Attaching Biological Probes to Silica Optical Biosensors Using Silane Coupling Agents

In order to interface with biological environments, biosensor platforms, such as the popular Biacore system (based on the Surface Plasmon Resonance (SPR) technique), make use of various surface modification techniques, that can, for example, prevent surface fouling, tune the hydrophobicity / hydrophilicity of the surface, adapt to a variety of electronic environments, and most frequently, induce specificity towards a target of interest.1-5 These techniques extend the functionality of otherwise highly sensitive biosensors to real-world applications in complex environments, such as blood, urine, and wastewater analysis.2,6-7 While commercial biosensing platforms, such as Biacore, have well-understood, standard techniques for performing such surface modifications, these techniques have not been translated in a standardized fashion to other label-free biosensing platforms, such as Whispering Gallery Mode (WGM) optical resonators.8-9
WGM optical resonators represent a promising technology for performing label-free detection of a wide variety of species at ultra-low concentrations.6,10-12 The high sensitivity of these platforms is a result of their unique geometric optics: WGM optical resonators confine circulating light at specific, integral resonance frequencies.13 Like the SPR platforms, the optical field is not totally confined to the sensor device, but evanesces; this "evanescent tail" can then interact with species in the surrounding environment. This interaction causes the effective refractive index of the optical field to change, resulting in a slight, but detectable, shift in the resonance frequency of the device. Because the optical field circulates, it can interact many times with the environment, resulting in an inherent amplification of the signal, and very high sensitivities to minor changes in the environment.2,14-15
To perform targeted detection in complex environments, these platforms must be paired with a probe molecule (usually one half of a binding pair, e.g. antibodies / antigens) through surface modification.2 Although WGM optical resonators can be fabricated in several geometries from a variety of material systems, the silica microsphere is the most common. These microspheres are generally fabricated on the end of an optical fiber, which provides a "stem" by which the microspheres can be handled during functionalization and detection experiments. Silica surface chemistries may be applied to attach probe molecules to their surfaces; however, traditional techniques generated for planar substrates are often not adequate for these three-dimensional structures, as any changes to the surface of the microspheres (dust, contamination, surface defects, and uneven coatings) can have severe, negative consequences on their detection capabilities. Here, we demonstrate a facile approach for the surface functionalization of silica microsphere WGM optical resonators using silane coupling agents to bridge the inorganic surface and the biological environment, by attaching biotin to the silica surface.8,16 Although we use silica microsphere WGM resonators as the sensor system in this report, the protocols are general and can be used to functionalize the surface of any silica device with biotin.

Biosensors interface with complex, biological environments and perform targeted detection by combining highly sensitive sensors with highly specific probes attached to the sensor via surface modification. Here, we demonstrate the surface functionalization of silica optical sensors with biotin using silane coupling agents to bridge the sensor and the biological environment.

הוספת בדיקות ביולוגיות Biosensors סיליקה אופטי באמצעות סוכני צימוד silane

In order to interface with biological environments, biosensor platforms, such as the popular Biacore system (based on the Surface Plasmon Resonance (SPR) ...

Bioengineering

Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres can be thought as a store of energy with a huge variety of applications: compact laser sources, highly sensitive biochemical sensors and nonlinear phenomena. A protocol for the fabrication of both the microspheres and coupling system is given. The couplers described here are tapered fibers. Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility &#935;(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS). A proof of the cavity-enhanced phenomenon is given by the lack of correlation among the pump, signal and idler: a resonant mode has to exist in order to obtain the pair of signal and idler. In the case of hyperparametric oscillations (four wave mixing and stimulated anti-stokes Raman scattering), the modes must fulfill the energy and momentum conservation and, last but not least, have a good spatial overlap.

Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility &#935;(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS).

המאולץ סטוקס Antistokes פיזור ראמאן ב Microspherical Whispering גלרית מצב מההודים

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres ...

Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces

Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. Optical property evaluation of thin films and the surfaces of bulk materials is an important step in understanding new optical material systems and their applications. The method presented can estimate thickness, refractive index, and use absorptive properties of materials for detection. This metrology system uses evanescent field-based photoacoustics (EFPA), a field of research based upon the interaction of an evanescent field with the photoacoustic effect. This interaction and its resulting family of techniques allow the technique to probe optical properties within a few hundred nanometers of the sample surface. This optical near field allows for the highly accurate estimation of material properties on the same scale as the field itself such as refractive index and film thickness. With the use of EFPA and its sub techniques such as total internal reflection photoacoustic spectroscopy (TIRPAS) and optical tunneling photoacoustic spectroscopy (OTPAS), it is possible to evaluate a material at the nanoscale in a consolidated instrument without the need for many instruments and experiments that may be cost prohibitive.

Here we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. This technique evanescent field-based photoacoustics can be used to create a photoacoustic metrology system to estimate materials&#39; thicknesses, bulk and thin film refractive indices, and explore their optical properties.

חלוף שדה בהתבסס Photoacoustics: הערכת נכס אופטית על משטחים

Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. ...

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.

ייצור של פולימרים microspheres עבור מהוד אופטי ויישומי לייזר

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

A Silicon-tipped Fiber-optic Sensing Platform with High Resolution and Fast Response

In this article, we introduce an innovative and practically promising fiber-optic sensing platform (FOSP) that we proposed and demonstrated recently. This FOSP relies on a silicon Fabry-Perot interferometer (FPI) attached to the fiber end, referred to as Si-FOSP in this work. The Si-FOSP generates an interferogram determined by the optical path length (OPL) of the silicon cavity. Measurand alters the OPL and thus shifts the interferogram. Due to the unique optical and thermal properties of the silicon material, this Si-FOSP exhibits an advantageous performance in terms of sensitivity and speed. Furthermore, the mature silicon fabrication industry endows the Si-FOSP with excellent reproducibility and low cost toward practical applications. Depending on the specific applications, either a low-finesse or high-finesse version will be utilized, and two different data demodulation methods will be adopted accordingly. Detailed protocols for fabricating both versions of the Si-FOSP will be provided. Three representative applications and their according results will be shown. The first one is a prototype underwater thermometer for profiling the ocean thermoclines, the second one is a flow meter to measure flow speed in the ocean, and the last one is a bolometer used for monitoring exhaust radiation from magnetically confined high-temperature plasma.

This work reports an innovative silicon-tipped fiber-optic sensing platform (Si-FOSP) for high-resolution and fast-response measurement of a variety of physical parameters, such as temperature, flow, and radiation. Applications of this Si-FOSP span from oceanographic research, mechanical industry, to fusion energy research.

פלטפורמה משופעת סיליקון סיבים אופטיים חישה עם רזולוציה גבוהה ותגובה מהירה

In this article, we introduce an innovative and practically promising fiber-optic sensing platform (FOSP) that we proposed and demonstrated recently. This ...