Utilize femtosecond laser on substrate of glass, to prepare the method for microfluid optical waveguide
Technical field
The present invention relates to microfluid optical waveguide, particularly a kind of method of utilizing femtosecond laser on substrate of glass, to prepare microfluid optical waveguide.This method is applicable at various glass and transparent polymer surface preparation microfluid optical waveguide.
Background technology
Learn device with all solid state micro-opto and compare, microfluidic device has unique advantage, for example can be by controlling the optical property that liquid mediums in the microchannel changes device, and two kinds of inconsistent fluids can also provide the high optical flat of flatness etc.Micro-optic and micro-fluidic technologies combined can prepare various novel microfluid optical device, it will be widely used in fields such as chip lab or micro-total analysis system.
Microfluid optical waveguide preparation method in the past comprises:
(1) use soft lithographic technique to go out the microchannel in transparent organic polymer material surface working, in passage, inject the fluid media (medium) of refractive index then a little more than polymkeric substance, this method need use expensive mother matrix and a series of such as pour into a mould, duplicate, subsequent operation such as transition diagram is (referring to document: O.J.A.Schueller, X.Zhao, et al., Advanced Materials, Vol.11, P 31,1999);
(2) fluid media (medium) of injection high index of refraction in hollow glass capillary, this type of glass capillary is to use the glass fibre of special-purpose drawing device stretching fusion to prepare, diameter capillaceous generally arrives between the hundreds of micrometer range (referring to document: A.Hanning tens, J.Westberg, et al., Electrophoresis, Vol.21, P 3290,2000).
Current, the femtosecond laser parallel micromachining technology with its machining precision height, thermal effect is little, damage threshold is low and can realize that advantages such as three-dimensional little processing are particularly useful for the preparation of various microstructures to transparent material.Utilize the femtosecond laser parallel micromachining technology in conjunction with supporting processes such as the thermal treatment in later stage and HF acid corrosions, people process three dimension microchannels that internal diameter is ten micron dimensions in the fotoceram inside of a kind of Foturan of being named as, and demonstrated its function of mixing two kinds of solution (referring to document: M.Masuda, K.Sugioka, et al., Applied Physics A, Vol.76, P 857,2003); Also there is the people directly to utilize the line focus femtosecond laser beam to process microchannel that live width is ten micron dimensions (referring to document: M.S.Giridhar in addition at the borosilicate glass chip surface, K.Seong, etal., Applied Optics, Vol.43, P 4584,2004), but only demonstrated its functional characteristic, and its optical function characteristic that is unrealized as microfluidic channel.
Summary of the invention
The technical problem to be solved in the present invention is to overcome soft in the past lithographic technique and the drawn glass kapillary prepares the shortcoming that optical waveguide needs complicated technology, a kind of method of utilizing femtosecond laser to prepare microfluid optical waveguide fast on substrate of glass is provided, further improve machining precision, thereby realize the single mode optical waveguide so that the microchannel internal diameter is reduced to below ten microns.
Technical solution of the present invention is as follows:
A kind of method of utilizing femtosecond laser to prepare microfluid optical waveguide on substrate of glass is characterised in that to comprise the following steps:
1. femtosecond etching: substrate of glass is fixed on the motorized precision translation stage, regulates femtosecond laser and focus on the back by microcobjective irradiation is carried out on the glass-chip surface, move motorized precision translation stage, make glass surface produce the ablation line, form sample by computing machine;
2. ultrasonic cleaning: after the completion of processing, take off sample and place the ultrasonic washing instrument that fills anhydrous alcohol to clean 15-20 minute, make the ablation line obtain the microchannel of inner wall smooth;
3. inject the liquid core: the fluid reagent that refractive index is higher than substrate of glass is injected in the microchannel of sample just make required optical waveguide.
The detailed process of described injection liquid core is: first allotment fluid reagent, will have the paraffin oil of different refractivity and α-a naphthalene bromide by volume the ratio mixing preparation form, the scope of the refractive index of this reagent is: 1.52~1.658; Use liquid-transfering gun that deployed reagent is injected the microchannel then, blow away microchannel residual reagent on every side with ear washing bulb then.
Utilize the refractive index of regulating described reagent, to obtain multimode lightguide or monomode optical waveguide.
Compare with technology in the past, the invention has the advantages that:
1, method simple and flexible: after putting up light path system, the microchannel that just can obtain required form of moving by the control translation stage, the post-processed process is also simpler, only need use ultrasonic washing instrument to clean, the machining chips of removing in the microchannel makes fluid communication, thereby has higher working (machining) efficiency.
2, machining precision height: the femtosecond laser parallel micromachining precision can break through diffraction limit in theory, and the gating pulse energy can obtain the optical waveguide of diameter in micron or even sub-micrometer scale, and they have important application in the nanophotonics field.
3, extensibility is good: use this technology not only can make optical waveguide, can also process a series of photonics devices such as light wave beam splitter based on fluid, coupling mechanism, micro-ring resonant cavity by programming Control translation stage mobile; Utilize the present technique also can be on same substrate of glass with integrated preparations of multiple function element such as microfluid, micro-optic, micromechanics and microelectronics.
4, the rapidoprint cost is low: the glass-chip of use is common microscope slide, and is cheap.
Description of drawings
Fig. 1 prepares the schematic flow sheet of microfluid optical waveguide for femtosecond laser of the present invention,
Fig. 2 is the used experimental provision synoptic diagram of waveguiding effect of demonstration microfluid optical waveguide.
Embodiment
See also Fig. 1 earlier, Fig. 1 is the preparation process synoptic diagram of microfluid optical waveguide of the present invention.
Utilize the present invention can prepare straight or crooked optical waveguide, but because when the leaded light performance of demonstration waveguide, can the coincidence phenomenon of coupled laser and output beam take place in the straight optical waveguide and cause the output mode resolution unclear, crooked waveguide then can be avoided this situation.Therefore will be example to prepare the one 90 crooked arc optical waveguide of degree, provide the scheme and the result that utilize femtosecond laser on substrate of glass, to prepare microfluid optical waveguide fast, specifically comprise following three steps:
(1) femtosecond etching: what we used in the preparation process is the titanium-doped sapphire fs-laser system that Spectra PhysicsSpitfire company produces, and pulsewidth is 40 ± 2fs, and centre wavelength is 800nm, and repetition frequency is 1kHz.Processing employed femtosecond laser single pulse energy is 7.1 μ J, and is that 0.46 microcobjective focuses on light beam with numerical aperture.With common microscope slide cut lengths is fritter and six mirror polish of 13mm * 5mm * 1mm, get a glass sample and be fixed on, simultaneously ccd video camera is connected on the computing machine so that the real-time monitored process by on computer-controlled D translation/universal stage.Translation stage translational speed by computer settings is 160 μ m/s, in order to make the inner wall smooth of microchannel, has adopted and has repeatedly scanned method for processing, comes flyback retrace along dotted line in the device synoptic diagram, is not less than 20 times.
(2) ultrasonic cleaning: after the completion of processing, take off sample and place the ultrasonic washing instrument that fills anhydrous alcohol to clean 15-20 minute.Be the optical waveguide of 90 ° of bendings making, the width at cross-sectional type top is about 7 μ m, and the degree of depth is 16 μ m.Can wait the cross-sectional type of controlling the microchannel by the pulse energy of control femtosecond laser, the numerical aperture and the scanning times of focusing objective len.
(3) inject the liquid core:, can use the reagent-paraffin oil (n=1.474) and α-a naphthalene bromide (n=1.658) of two kinds of different refractivities in order to form liquid core waveguide structure.Because the refractive index of the glass-chip that uses is 1.516, must mix above-mentioned two kinds of reagent by different volume ratios to make the range of adjustment of refractive index be 1.52~1.658 for this reason.Use the Eppendorf liquid-transfering gun of 10 μ L that deployed reagent is injected the microchannel,, also need use ear washing bulb to blow away residual reagent around the microchannel for fear of too much scattering loss.
After having prepared above-mentioned microfluid optical waveguide, demonstrate its waveguiding effect according to building device as shown in Figure 2: the He-Ne laser beam 1 after will collimating (wavelength is 632.8nm) adopts 20 * microcobjective 2 (numerical aperture is 0.46) be coupled to an end of waveguide 3, cooperate 5 pairs of ripple near fields of ccd video cameras mode imaging at this waveguide output terminal with object lens 4.We observe, and when the sandwich layer refractive index of fluid waveguide is 1.658, can obtain multimode output; Changing liquid core refractive index is 1.527 o'clock, can obtain single mode output.The light intensity space distribution of single mode field pattern also is approximately Gaussian distribution, and these are consistent with the conclusion of waveguide theory.