Fabrication and Testing of Microfluidic Optomechanical Oscillators

Summary

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.

Abstract

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.

Introduction

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, microspheres^4,6,8, toroids^1,9, and crystalline resonators^5,10. Through this photon-phonon coupling, both cooling¹¹ and excitation^6,10 of mechanical modes have been demonstrated. However, almost all reported optomechanics experiments are with solid phases of matter. This is because direct liquid ....

Protocol

1. Fabrication of Ultra-high-Q Microfluidic Resonators

1. Preparation of capillary manufacturing setup
   1. Fabricate the microfluidic optomechanical resonator in the following way – 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 capillary preform before the pulling process.
   2. Program suitable automation software to simultaneously control the two CO₂ lasers (for he....

Results

The capillaries produced by this method are thin (between 30 µm and 200 µm), 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 due to overh.......

Discussion

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.......

Materials

List of materials used in this article

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