This work was funded by Startup funding from the University of Illinois at Urbana-Champaign, DARPA ORCHID program through a grant from AFOSR, the National Science Foundation through grant CMMI-1265164, and the National Science Foundation Graduate Research Fellowship program. We acknowledge enlightening discussions with Prof. Jack Harris, Prof. Pierre Meystre, Dr. Matt Eichenfield, Prof. Taher Saif, and Prof. Rashid Bashir.

1. Fabrication of Ultra-high-Q Microfluidic Resonators
<ol>
	<li>Preparation of capillary manufacturing setup
	<ol>
		<li>Fabricate the microfluidic optomechanical resonator in the following way &#8211; Heat a glass capillary preform with approximately 10 W of CO2 laser radiation at 10.6 microns wavelength, and draw out the heated capillary linearly using motorized translation stages. Figure 1 shows the arrangement of the linear translation stages, the lasers, and the location of the capilla...

<ol>
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We have fabricated and tested a new device that bridges between cavity optomechanics and microfluidics by employing high-Q optical resonances to excite (and interrogate) mechanical vibration. It is surprising that multiple excitation mechanisms are available in the very same device, which generate a variety of mechanical vibrational modes at rates spanning 2 MHz to 11,300 MHz. Centrifugal radiation pressure supports both wineglass modes and breathing modes in the 2-200 MHz span, Forward stimulated Brillouin scattering al...

Cavity optomechanics studies the parametric coupling between phonon modes and photon modes in microresonators by means of radiation pressure (RP)1-3 and stimulated Brillouin scattering (SBS)4-6. SBS and RP mechanisms have been demonstrated in many different optical systems, such as fibers7, microspheres4,6,8, toroids1,9, and crystalline resonators5,10. Through this photon-phonon coupling, both cooling11 and excitation6,10 of mechanical modes have been demonstrated. However, almost all reported optomechanics experiments are with solid phases of matter. This is because direct liquid immersion of the optomechanical devices results in greatly increased radiative acoustic loss because of the higher impedance of liquids compared against air. In addition, in some situations dissipative loss mechanisms in liquids may exceed the radiative acoustic losses.
Recently, a new type of hollow optomechanical oscillator with a microcapillary geometry was introduced12-15, and which by design is equipped for microfluidic experiments. The diameter of this capillary is modulated along its length to form multiple &#8216;bottle resonators&#8217; that simultaneously confine optical whispering-gallery resonances16 as well as mechanical resonant modes17. Multiple families of mechanical resonant modes participate, including breathing modes, wine-glass modes, and whispering-gallery acoustic modes. The wine-glass (standing-wave) and whispering-gallery acoustic (traveling-wave) resonances are formed when a vibration with integer multiple of acoustic wavelengths occurs around the device circumference. Light is evanescently coupled into the optical whispering-gallery modes of these &#8216;bottles&#8217; by means of a tapered optical fiber18. Confinement of the liquid inside19,20 the capillary resonator, as opposed to outside it, enables high mechanical- and optical- quality factors simultaneously, which allows the optical excitation of mechanical modes by means of both RP and SBS. As has been shown, these mechanical excitations are able to penetrate into the fluid within the device12,13, forming a shared solid-liquid resonant mode, thus enabling an opto-mechanical interface to the fluidic environment within.
In this paper we describe fabrication, RP and SBS actuation, and representative measurement results for this novel optomechanical system. Specific material and tool lists are also provided.

<table border="0" cellpadding="0" cellspacing="0" style="width:647px;" width="647">
	<tbody>
		<tr>
			<td>Tunable IR laser</td>
			<td>Newfocus</td>
			<td>TLB-6328</td>
			<td></td>
		</tr>
		<tr>
			<td>Photodetectors</td>
			<td>Newfocus</td>
			<td>1811-FC (Low speed 125MHz) / 1611-FC-AC (High speed 1GHz)</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical fiber</td>
			<td>Corning</td>
			<td>SMF28</td>
			<td></td>
		</tr>
		<tr>
			<td>Silica capillary</td>
			<td>PolyMicro</td>
			<td>TSP700850</td>
			<td></td>
		</tr>
		<tr>
			<td>10.6 um wavelength CO2 laser</td>
			<td>Synrad</td>
			<td>48-1KWM and 48-2KWM</td>
			<td></td>
		</tr>
		<tr>
			<td>UV-curing optical adhesive</td>
			<td>Thorlabs</td>
			<td>NOA81</td>
			<td></td>
		</tr>
		<tr>
			<td>Tubing</td>
			<td>Tygon</td>
			<td>EW-06418-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringes</td>
			<td>B-D</td>
			<td>YO-07940-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Needles</td>
			<td>Weller</td>
			<td>KDS201P</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrical spectrum analyzer</td>
			<td>Agilent Technologies</td>
			<td>N9010A (EXA Signal Analyzer)</td>
			<td></td>
		</tr>
		<tr>
		</tr>
		<tr>
			<td>Tektronix</td>
			<td>6114A (RSA, Real-time spectrum analyzer)</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical spectrum analyzer</td>
			<td>Advantest</td>
			<td>Q8384</td>
			<td></td>
		</tr>
		<tr>
			<td>Oscilloscope</td>
			<td>Tektronix</td>
			<td>DPO 4104B-L</td>
			<td></td>
		</tr>
		<tr>
			<td>Gold mirrors</td>
			<td>II-VI Infrared</td>
			<td>836627</td>
			<td></td>
		</tr>
		<tr>
			<td>Linear stage (slow)</td>
			<td>DryLin</td>
			<td>H1W1150</td>
			<td></td>
		</tr>
		<tr>
			<td>Linear stage (fast)</td>
			<td>PBC Linear</td>
			<td>MTB055D-0902-14F12</td>
			<td></td>
		</tr>
		<tr>
			<td>Fabry Perot optical spectrum analyser</td>
			<td>Thorlabs</td>
			<td>SA 200-14A (FSR: 1.5 GHz)</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

The capillaries produced by this method are thin (between 30 &#181;m and 200 &#181;m), clear, and very flexible, but are sufficiently robust for direct handling. It is important to protect the outer surface of the capillary device against dust and water (moisture) in order to maintain a high optical quality factor (Q). By dipping one end of the capillary in water and blowing air through the capillary by means of a syringe, it can be verified whether the capillary is through or whether was sealed off during fabrication du...

Watch this Scientific Journal Video about Fabrication and Testing of Microfluidic Optomechanical Oscillators at JoVE.com

Fabrication and Testing of Microfluidic Optomechanical Oscillators

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.

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

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12.0K vistas.  University of Illinois at Urbana-Champaign. 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. 