Fabrication Of Innovative Tunable Miro/Nano Optical Device Based On Liquid Features

Micro-and nano-optical device is widely used in fluorescence detection,Raman enhancement,biological and chemical detection and metal surface plasmon resonance enhancement,and so on.The designed micro-and nano-structural parameters are the key to the achievement of functionality.For micro/nano fabrication,it is reasonably mature for the processing technology,however,the fabrication error is inescapable.Consequently,an increasing number of researchers have tried best to fabricate the tunable micro/nano optical device which increases the fabrication tolerance and decreases the fabrication cost.Meanwhile,some functionalities are demonstrated.Based on the importance of tunability,some tunable micro/nano optical devices are theoretically designed and experimentally fabricated and characterized.The specific contents of this paper are as follow:1.An optofluidic device with tunable optical limiting property is proposed and demonstrated.The optofluidic device is designed for adjusting the concentration of graphene oxide(GO)in the ethanol solution and fabricated by photolithography technique.By controlling the flow rate ratio of the injection,the concentration of GO can be precisely adjusted so that the optical nonlinearity can be changed.The nonlinear optical properties and dynamic excitation relaxation of the GO/ethanol solution are investigated by using Z-scan and pump-probe measurements in the femtosecond regime within the 1.5?m telecom band.The GO/ethanol solution presents ultrafast recovery time.Besides,the optical limiting property is in proportion to the concentration of the solution.Thus,the threshold power and the saturated power of the optical limiting property can be simply and efficiently manipulated by controlling the flow rate ratio of the injection.Furthermore,the amplitude regeneration is demonstrated by employing the proposed optofluidic device.The signal quality of intensity-impaired femtosecond pulse is significantly improved.The optofluidic device is compact and has long interaction length of optical field and nonlinear material.Heat can be dissipated in the solution and nonlinear material is isolated from other optical components,efficiently avoiding thermal damage and mechanical damage.2.This chapter presents an in-plane hydrodynamically reconfigurable optofluidic microlens,which is formed by the laminar flow of two streams of a low-refractive-index fluid and two streams of a high-refractive-index fluid in the two microchannels connecting to an expansion chamber where the microlens finally forms.In the expansion chamber,the stream of high-refractive-index fluid,acting as core,is sandwiched by the two streams of lowrefractive-index fluid,acting as cladding.The interfaces between the streams can be flexibly manipulated by controlling the flow rate ratio between the two fluids in real time.Thus,the biconvex and biconcave microlens with different curvatures can be formed.By adjusting the microlens,the light beam can be continuously manipulated from focusing to collimation and then to divergence.In the experiment,a wide focus tuning range from 2.75(focusing)to-1.21 mm(diverging)via collimation is achieved.3.A liquid plano-convex lens with focal length tuning is proposed,which is formed by sinking an oil droplet onto the bottom of an elastomer.A simple and low-cost fabrication method is presented.The lens aperture and initial focal length can be controlled during the fabrication.Furthermore,focal length tuning is demonstrated.The lens made of a 40 mg oil droplet can achieve the tuning range from 12 to 17 mm.The effective aperture of the lens is about 2.8 mm.In the demonstration of an imaging system,the lens assists in focusing and a clear image can be observed.4.A compact,tunable guided-mode resonant filter(GMRF)is experimentally demonstrated whose spectral reflectance wavelength varies as a function of the illumination position on the device.The GMRF consists of a grating of gradient-varying period ranging from 402.5 to 466.6 nm,which is obtained by casting a stretched polydimethylsiloxane(PDMS)grating wedge.By spatially changing the illumination position on the GMRF over 11 mm,a spectral reflectance peak with low sidelobes varies from 596.8 to 684.1 nm.The influence on the resonance efficiency and the limitation of the wavelength tuning range are discussed in depth.5.A compact,tunable linear optofluidic Bragg filter is simulated,designed,fabricated,and characterized.The device consists of a nanocavity sandwiched by two symmetrical film stacks made of high-and low-refractive-index dielectric materials.The fabrication parameters are simulated by using the commercial software Essentical Macleod.The resonant wavelength can be linearly shifted by up to 34.8 nm when the refractive index of the liquid injected into the Bragg nanocavity varies from 1.333 to 1.51.Meanwhile,the filter has a narrow bandwidth of 1.1 nm and a very high extinction ratio with the sensitivity(??/?n)of 374 nm/RIU.6.A rapid method is developed for fabricating low-cost and high-numerical-aperture photosensitive-gel microlens arrays(MLAs)with well controllable curvatures.The interface of UV-curable photosensitive gel film beneath microholes of a silicon mold can be flexibly deformed by thermally manipulating the surface tension of the photosensitive gel.Then,the concave interface is solidified by UV curing,forming a MLA with concave curvature.The MLAs of focal length ranging from 51.4 ?m to 71.9 ?m and NA of 0.49 are fabricated.The photocured MLA has high mechanical and thermal strength and is suitable for a master mold for further producing convex MLAs.The high-quality imaging and focusing performances of the MLAs are also demonstrated in this work.