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1、本科毕业设计外文翻译(原文) Real-time interactive optical micromanipulation of a mixture of high- and low-index particles Peter John Rodrigo, Vincent Ricardo Daria and Jesper Glckstad Optics and Plasma Research Department, Ris? National Laboratory, DK-4000 Roskilde, Denmark jesper.gluckstadrisoe.dk http:/www.ris
2、oe.dk/ofd/competence/ppo.htm Abstract: We demonstrate real-time interactive optical micromanipulation of a colloidal mixture consisting of particles with both lower (n L n0) refractive indices than that of the suspending medium (n0). Spherical high- and low-index particles are trapped in the transve
3、rse plane by an array of confining optical potentials created by trapping beams with top-hat and annular cross-sectional intensity profiles, respectively. The applied method offers extensive reconfigurability in the spatial distribution and individual geometry of the optical traps. We experimentally
4、 demonstrate this unique feature by simultaneously trapping and independently manipulating various sizes of spherical soda lime micro- shells (n L 1.2) and polystyrene micro-beads (n H = 1.57) suspended in water (n0 = 1.33). ?2022 Optical Society of America OCIS codes: (140.7010) Trapping, (170.4520
5、) Optical confinement and manipulation and (230.6120) Spatial Light Modulators. References and links 1. A. Ashkin, “Optical trapping and manipulation of neutral particles using lasers,” Proc. Natl. Acad. Sci. USA 94, 4853-4860 (1997). 2. K. Svoboda and S. M. Block, “Biological applications of optica
6、l forces,” Annu. Rev. Biophys. Biomol. Struct. 23, 247-285 (1994). 3. D. G. Grier, “A revolution in optical manipulation,” Nature 424, 810-816 (2022). 4. M. P. MacDonald, G. C. Spalding and K. Dholakia, “Microfluidic sorting in an optical lattice,” Nature 426, 421-424 (2022). 5. J. Glckstad, “Microf
7、luidics: Sorting particles with light,” Nature Materials 3, 9-10 (2022). 6. A. Ashkin, “Acceleration and trapping of particles by radiation-pressure,”Phys. Rev. Lett. 24, 156-159 (1970). 7. A. Ashkin, J. M. Dziedzic, J. E. Bjorkholm and S. Chu, “Observation of a single-beam gradient force optical tr
8、ap for dielectric particles,” Opt. Lett. 11, 288-290 (1986). 8. K. Sasaki, M. Koshioka, H. Misawa, N. Kitamura, and H. Masuhara, “Optical trapping of a metal particle and a water droplet by a scanning laser beam,” Appl. Phys. Lett. 60, 807-809 (1992). 9. K. T. Gahagan and G. A. Swartzlander, “Trappi
9、ng of low-index microparticles in an optical vortex,” J. Opt. Soc. Am. B 15, 524-533 (1998). 10. K. T. Gahagan and G. A. Swartzlander, “Simultaneous trapping of low-index and high-index microparticles observed with an optical-vortex trap,” J. Opt. Soc. Am. B 16, 533 (1999). 11. M. P. MacDonald, L. P
10、aterson, W. Sibbett, K. Dholakia, P. Bryant, “Trapping and manipulation of low-index particles in a two-dimensional interferometric optical trap,” Opt. Lett. 26, 863-865 (2022). 12. R. L. Eriksen, V. R. Daria and J. Glckstad, “Fully dynamic multiple-beam optical tweezers,” Opt. Express 10, 597-602 (
11、2022), /abstract.cfm?URI=OPEX-10-14-597. 13. P. J. Rodrigo, R. L. Eriksen, V. R. Daria and J. Glckstad, “Interactive light-driven and parallel manipulation of inhomogeneous particles,” Opt. Express 10, 1550-1556 (2022), /abstract.cfm?URI=OPEX-10-26-1550. 14. V. Daria, P. J. Rodrigo and J. Glckstad,
12、“Dynamic array of dark optical traps,” Appl. Phys. Lett. 84, 323-325 (2022). 15. J. Glckstad and P. C. Mogensen, “Optimal phase contrast in common-path interferometry,” Appl. Opt. 40, 268-282 (2022). 16. S. Maruo, K. Ikuta and H. Korogi, “Submicron manipulation tools driven by light in a liquid,” Ap
13、pl. Phys. Lett. 82, 133-135 (2022). #3781 - $15.00 US Received 4 February 2022; revised 29 March 2022; accepted 29 March 2022 (C) 2022 OSA 5 April 2022 / Vol. 12, No. 7 / OPTICS EXPRESS 1417 1. Introduction Light carries both linear and angular momenta. Momentum transfer that accompanies light-matte
14、r interaction has provided us means to trap and manipulate particles in the mesoscopic scale. Significant developments in the past decades have resulted in a variety of applications of conventional optical trapping in the biological and the physical fields and the emergence of a next-generation of o
15、ptical micromanipulation schemes 1-5. In 1970, Ashkin demonstrated that a transparent dielectric micro-sphere suspended in water is radially drawn towards the optical axis of a Gaussian laser beam where the intensity is strongest 6. He observed this behavior with latex spheres having relative refrac
16、tive index m greater than unity (m = n/n0 where n and n0 are the refractive indices of the particle and the suspending medium, respectively). Upon radial attraction towards the region of stronger intensity, the high-index particle accelerates in the direction of the Poynting vector due to an axial s
17、cattering force. On the other hand, Ashkin noted that for an air bubble (m 1) in water the sign of the radial force due to the intensity gradient is reversed; hence, the low-index particle is repelled away from the beam axis. Ashkin and co-workers later showed that by tightly focusing a Gaussian bea
18、m to a high-index particle an axial force due to an intensity gradient is also produced, strong enough to counteract the scattering force, resulting in a stable 3D confinement of the particle 7. However, a stationary tightly focused Gaussian beam does not provide a confining potential for low-index
19、particles. Optical trapping of a low-index microscopic particle requires a beam with an annular intensity profile. A straightforward approach is to apply high-speed deflectable mirrors that enable time multiplexing of a desired beam pattern at the trapping plane. Scanning the beam in a circular locu
20、s creates a ring of light that confines a low-index particle in its dark central spot 8. A low-index particle can also be trapped in an optical vortex produced from a focused TEM01* beam 9. An optical vortex has been used to trap a low-index sphere and a high-index sphere, at the same time, in two n
21、eighboring positions along the beam axis 10. Low-index particles were also trapped between bright interference fringes produced at the focal plane of an objective lens where two coherent plane waves converge 11. However, dynamic and parallel manipulation of a larger array of high- and low-index part
22、ic les has not been achieved with the above techniques. Here, we demonstrate real-time user-interactive manipulation of a mixture of high- and low-index particles by reading out 2D phase patterns encoded onto an input beam by a programmable spatial light mo dulator (SLM) using the generalized phase
23、contrast (GPC) approach to produce tailored light distributions that result in optical confinement of the mixed particles in the transverse plane. For spherical particles, trapping beams with radial symmetry are utilized. High-index micro-spheres were efficiently trapped and manipulated using trappi
24、ng beams with top-hat transverse profiles at the trapping plane 12, 13. On the other hand, low-index particles are trapped using beams with annular transverse profiles 14. We demonstrate that, unlike other methods, the GPC approach readily provides both the ability to create independently controllab
25、le optical traps for high- and low-index particles, and the flexibility to render, in real time, arbitrary dynamics for these two types of particles simultaneously. This exceptional functionality may facilitate particle encapsulation in air-bubbles or in water-in-oil emulsions applied in petroleum,
26、food, and drug processing. 2. Experiment Trapping and manipulation of colloidal particles is achieved using the experimental setup shown in Fig. 1. The system makes use of a continuous wave (CW) Titanium:Sapphire (Ti:S) laser (wavelength-tunable, Spectra Physics, 3900s) pumped with a CW frequency-do
27、ubled Neodymium:Yttrium Vanadate (Nd:YVO4) laser (532 nm, Spectra Physics, Millenia V). The Ti:S laser utilizes built-in birefringent quartz filter plates to select the operating wavelength within the near infrared (NIR) spectrum from 700 to 850 nm. In our experiments, the operation wavelength is se
28、t to = 830 nm. With a maximum pump power of 5.0 W from the Nd:YVO4, the Ti:S laser provides a maximum power of 1.5 W. The laser is expanded and #3781 - $15.00 US Received 4 February 2022; revised 29 March 2022; accepted 29 March 2022 (C) 2022 OSA 5 April 2022 / Vol. 12, No. 7 / OPTICS EXPRESS 1418 c
29、ollimated before incidence on a reflection-type phase-only SLM. The SLM, employing parallel-aligned nematic liquid crystals (Hamamatsu Photonics), is optically addressed by a VGA-resolution (480x480 pixels) liquid crystal projector element that is controlled from the video output of a computer. Fig.
30、 1. Experimental setup for simultaneous optical manipulation of high- and low-index particles at the trapping plane. The expanded beam ( = 830 nm) incident at the spatial light modulator (SLM) comes from a CW Ti:Sapphire (Ti:S) laser pumped by a visible CW Nd:YVO4 laser. Under computer control, arbi
31、trary 2D phase patterns are encoded onto the reflective SLM. A high-contrast intensity mapping of the phase pattern is formed at the image plane (IP) and is captured by a CCD camera via partial reflection from a pellicle. The intensity distribution is optically relayed to the trapping plane. Standar
32、d brightfield detection is used to observe the trapped particles. PCF: phase contrast filter, Ir: iris diaphragm, L1, L2 and L3: lenses, MO: microscope objective, DM: dichroic mirror, TL: tube lens. We use the SLM to imprint a programmable 2D binary phase pattern (0 or phase delays) to the wavefront
33、 of the 830 nm laser beam. The phase-modulated wavefront is directed into a 4-f filtering system composed of lenses L1 and L2, and a phase contrast filter (PCF) located at the Fourier plane. The PCF is constructed by deposi ting a 30-m-diameter circular transparent photoresist (Shipley, Microposit S
34、1818) structure on an optical flat. Centered at the Fourier plane, the PCF introduces a -phase shift between low and high spatial frequency components of the phase-encoded beam. The diameters of the SLM iris (Ir) and the on-axis PCF are adjusted to optimize the throughput and contrast of the output
35、intensity distribution 15. A high-contrast intensity distribution, which is geometrically identical to the phase-pattern at the SLM, is generated at the image plane (IP). To monitor the output intensity distribution, a pellicle is inserted in the path and directs a small fraction (3%) of the light t
36、owards a CCD camera. The intensity pattern at the IP is scaled and relayed by lens L3 and the microscope objective (MO) to a conjugate plane (trapping plane). The fluorescence port of the inverted microscope (Leica, DM-IRB) is used to direct the near-infrared laser light to the back-focal plane of t
37、he MO via a dichroic mirror. The same MO and a built-in microscope tube lens allow brightfield images to be captured by a second CCD camera. The quality of the intensity patterns synthesized at the image plane via the GPC approach is depicted in Fig. 2 where variably sized beams with top-hat and ann
38、ular transverse profiles are generated at different positions at the transverse x-y plane. The condition for achieving #3781 - $15.00 US Received 4 February 2022; revised 29 March 2022; accepted 29 March 2022 (C) 2022 OSA 5 April 2022 / Vol. 12, No. 7 / OPTICS EXPRESS 1419 optimal intensity contrast
39、 is described in the previous analysis of the GPC method 15. Optimum phase-to-intensity conversion requires that the ratio of the SLM area encoded with phase shift to that with 0 phase remains less than or equal to 0.25 for the operating diameters of the SLM iris and the PCF. When the condition is s
40、atisfied, the maximum intensity of the trapping pattern is approximately four times the average intensity of the SLM input beam. Fig. 2. (a) Measured high-contrast intensity pattern at the output plane IP. Corresponding surface intensity plots for the representative (b) top-hat (in yellow square) an
41、d (c) annular or doughnut (in green square) trapping beams. A trapping beam with a top-hat transverse intensity profile provides a radially symmetric potential well for a high-index particle as shown in Fig. 3(a). When a top-hat beam is positioned in the vicinity of a high-index particle, the partic
42、le gets attracted to the beam axis. We have observed previously that a beam with diameter slightly larger than that of the particle provides better transverse confinement especially when the trapped particle is moved along the horizontal plane 12. In contrast, a top-hat beam acts as a potential barr
43、ier for a low-index particle. Unstable at the beam center, the low-index particle gets repelled to either side of the optical potential as shown in Fig. 3(a). This is evident in the experiment we performed with spherical shells made of soda lime glass material (Polysciences) with de-ionized water as
44、 host medium. These air-filled hollow glass spheres have shell thickness of 1 m and outer diameters in the range of 2-20 m. The hollow glass spheres with outer diameters greater than 5 m effectively behave as low-index particles in water (n0 = 1.33). Similar hollow glass spheres where found to have
45、average density of 0.2 g/mL and effective refractive index n L = 1.2 9. A 6 m hollow sphere in the presence of a top-hat beam is shown in Fig. 4. The sequence of images shows the displacement of the low-index particle as a result of its repulsion from the region of stronger light intensity. A low-in
46、dex particle finds a minimum potential at the center of the beam with an annular transverse intensity profile as shown in Fig. 3(b). However, unlike the spontaneous attraction of a high-index particle towards the center of a top-hat beam, a low-index particle is not readily drawn to the dark central
47、 spot of the annular beam. From the outer region to the dark center of the annular beam, the low-index particle needs to overcome the potential barrier associated with the bright ring of light. #3781 - $15.00 US Received 4 February 2022; revised 29 March 2022; accepted 29 March 2022 (C) 2022 OSA 5 April 2022 / Vol. 12, No. 7 / OPTICS EXPRESS 1420 Fig. 3. Diagram of the optical potential (a) for a high-index (solid curve) and a low-index (dashed curve) particle due to a beam with top-hat transve