Optical Trapping and Manipulating with a Silica Microring Resonator in a Self-Locked Scheme.

Victor W L Ho,Yang Liu,Guanghui Wang,Chi Zhang,Brent E Little,Roy R Davidson,Sai T Chu,Yuhua Li,Yao Chang

doi:10.3390/mi11020202

Abstract

Based on the gradient force of evanescent waves in silica waveguides and add-drop micro-ring resonators, the optical trapping and manipulation of micro size particles is demonstrated in a self-locked scheme that maintains the on-resonance system even if there is a change in the ambient temperature or environment. The proposed configuration allows the trapping of particles in the high Q resonator without the need for a precise wavelength adjustment of the input signal. On the one hand, a silicon dioxide waveguide having a lower refractive index and relatively larger dimensions facilitates the coupling of the laser with a single-mode fiber. Furthermore, the experimental design of the self-locked scheme reduces the sensitivity of the ring to the environment. This combination can trap the micro size particles with a high stability while manipulating them with high accuracy.

Highlights

Optical tweezers are widely used for capturing micro-particles or cells, due to the strong gradient force of highly focused laser beams [1,2]
To be able to trap the particles continually without interruption, it is vitally important to keep the input laser frequency aligned with the resonance frequency of the resonator, as the resonant frequency may shift during the operation from any changes in the ambient temperature and environment
The gap separation between the ring and the bus waveguide is 0.85 μm, so that the FWHM of the resonance peak is 21 pm at around 1550 nm. This corresponds to a Q factor of approximately 75,000 when the device is measured in air but the FWHM, Q factor, and free-spectral range (FSR) change to 27 pm, 65,000 and 572 GHz, respectively, when it is immersed in water

Summary

Introduction

Optical tweezers are widely used for capturing micro-particles or cells, due to the strong gradient force of highly focused laser beams [1,2]. Various demonstrations of optical trapping with planar microring resonators have previously been reported, e.g., the authors of [17] studied particles that are trapped and manipulated by adjusting the input tunable lasers both on and off resonance. The trapping and manipulation of micro particles on planar ring resonators have recently been demonstrated using silicon photonic crystal resonators [20]. This is especially important when applying optical trapping with high-Q ring resonators in highly precise measurements [17] and in biomedical [22,23], biochemical, and chemical sensing [24]. FFiigguurree 11.. ((aa))TThheeoopptitciaclatlrtarpappipnignsgyssytesmtemwitwhiathhiaghhliyg-hdloyp-deodpseildicasiglilcaassgrlainsgs rreinsognraetsoorninataorseilnf-laocskeelfdlcoocnkfiegducroatnifoing,uEraDtFioAn,isEaDnFeArbiisuamn-deorbpieudmfi-bdeorpaemd pfilbifieerra, manpdliPfiCeri,saandthPreCe-irsinagtphorelaer-rizinagtiopnoclaorniztraotliloenr. (cbo)nTtrhoellfears. t(bd)eTtehcetofrasotudtpetuetctforormoutthpeuttafprosmhotwheintgapQs-hswowiticnhginQg-isnwtihtcehfiinbgerinlotohpe cfiabveirtyl.oTophecarevpiteyt.itTiohne raepteeotiftitohne rQa-tsewoifttchheedQ-psuwlsitecshiesdappurlosexsimisaatpelpyr1o0x0imkaHtezlwy 1it0h0tkhHe hziwghithfrethqeuehnigchy fcroemqupeonnceyntcowmitphoinnethnet wQ-isthwinitcthedQp-suwlsietschaetd6.p6uMlsHesza, tw6h.6icMh cHozr,rewsphoicnhdcsotroreasfipboenrdlsotoopalefinbgetrhloof p30lemng. th of 30 m

32.. SMimatuerlaiatilosnand Methods

Simulation

Conclusions