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1.
Jiu H  Tang H  Zhou J  Xu J  Zhang Q  Xing H  Huang W  Xia A 《Optics letters》2005,30(7):774-776
We report on the formation of submicrometer voids within Sm(DBM)3Phen-doped poly(methyl methacrylate) (PMMA) under multiphoton absorption excited by an infrared laser beam. An ultrashort-pulsed laser beam with a pulse width of 200 fs at a wavelength of 800 nm is focused into doped PMMA. The large changes in refractive index and the fluorescence associated with a void allow conventional optical microscopy and reflection-type confocal microscopy to be used as detection methods. Voids can be arranged in a three-dimensional multilayered structure for high-density optical data storage.  相似文献   

2.
We address shock waves generated upon the interaction of tilted plane waves with negative refractive index defects in defocusing media with linear gain and two-photon absorption. We found that, in contrast to conservative media where one-dimensional dispersive shock waves usually exist only as nonstationary objects expanding away from a defect or generating beam, the competition between gain and two-photon absorption in a dissipative medium results in the formation of localized stationary dispersive shock waves, whose transverse extent may considerably exceed that of the refractive index defect. One-dimensional dispersive shock waves are stable if the defect strength does not exceed a certain critical value.  相似文献   

3.
The field distribution of the surface plasmon (SP) around a silver nanowire greatly influences its applications for both spectrum enhancement and nano-waveguide. This paper demonstrates the change of the SP local field distribution of a silver nanowire on glass substrate with the refractive index of the covering medium by numerical simulation. The hot energy site is observed focusing on the interface between the nanowire and the surround material of larger refractive index. Moreover, we also find that the surface plasmon field becomes more confined as the refractive index between the substrate and medium has a larger gap, while a homogeneous distribution of the surrounding dielectric material around the nanowire shows a uniform local field distribution with a larger surface plasmon propagation length. The change of related parameters, such as effective index, mode area, and propagation length are also comprehensively investigated against the refractive index for nanowires with 100, 200, 300 nm diameter. Considering the wide use of polymethyl methacrylate (PMMA) material, the field distribution of silver nanowire partially imbedded in PMMA against the PMMA thickness is also studied.  相似文献   

4.
This paper reports changes in refractive index and thickness of spin-coated poly(methyl methacrylate) (PMMA) thin films upon irradiation by a conventional high-pressure mercury UV lamp. Significant increase in refractive index and reduction in thickness are detected. Index modulations of greater than 0.01 are achieved in the thin films after 4 min of irradiation. The thickness reduction of an irradiated PMMA film is consistent with its weight loss. This is caused by the escape of the volatile molecules generated during the irradiation process. A slight increase in the refractive index is also found in the film, heat-treated above its glass transition temperature (Tg). This thermal effect is detected in the UV irradiation process. We propose three possible aliphatic structures that are formed during the photochemical reaction and may exist in the main chain of irradiated PMMA after the irradiation. Their refractive indices in aggregate state are greater than that of PMMA based on an evaluation using the Lorentz-Lorenz equation. This is suggested to be an important reason for the refractive index increase in the UV-irradiated PMMA films. A UV-irradiated film, heat-treated above its Tg, has a rough surface with many tiny holes as illustrated by atomic force microscopy. These holes are attributed to the evaporation of the small molecules generated during the irradiation process.  相似文献   

5.
The third order nonlinear optical properties of Rhodamine6G (Rh6G) doped silica and polymeric samples have been investigated using single beam z-scan technique under excitation by the second harmonic of Nd:YAG laser beam (532 nm). The nonlinear refractive index, nonlinear absorption coefficient, real and imaginary parts of third order nonlinear susceptibility in the samples of silica and poly-methylmethacrylate (PMMA) matrices are measured. Thermal contribution to the nonlinear refractive index in case of undoped silica samples has been calculated in order to have better accuracy of the material response contribution to third order nonlinearity. The comparative study of the optical limiting performance of Rh6G doped silica and polymeric samples show that Rh6G doped silica is relatively superior for optical limiting applications.  相似文献   

6.
The thickness and refractive index of a thick transparent plate are measured by using an unexpanded HeNe laser beam. The laser beam is incident at different angles onto the plate; and then two reflected beams; from the front and back surfaces; are received on a distant screen: the corresponding separations between them are measured. A theoretical relation between the refractive index; thickness; angle of incidence and separation is derived. This relation is experimentally verified and shows good agreement. The errors in the measured thickness and refractive index are analysed. The method is non-contact; non-destructive and low cost.  相似文献   

7.
We describe a Mach–Zehnder interferometer (MZI) method for measuring the refractive index (RI) of polymethyl-methacrylate (PMMA) solution in both acetone and methyl-ethyl-ketone (MEK). The measurements are made as a function of concentration values 4, 8, 12, 16 and 20 g/l at a wavelength of 488 nm with a high degree of accuracy tends to 1.4×10−5. The refractive index increments (RIIs) dn/dc of PMMA in both investigated solvents are determined too. In addition, the RIIs Δn as a function of concentration and the RIIs at zero concentration (dn/dc)c=0 are determined for both solvents accurately. The PMMA solutions in acetone and MEK solvents are chosen for laser light scattering investigations.  相似文献   

8.
The possibilities of improving the optical characteristics of spherical lenses with an axial refractive index gradient are analyzed. The refractive index profile obtained as a result of the Fickian-diffusion exchange of molecules through a flat boundary of the medium is considered. It is shown for the specific polymer system polydiallyl isophthalate plus polymethyl methacrylate (PMMA) that the spherical aberrations can be reduced by almost an order of magnitude in comparison to the aberrations of a homogeneous lens of the same geometric shape made from PMMA. Zh. Tekh. Fiz. 68, 70–73 (October 1998)  相似文献   

9.
Gaba  V. M.  Stadnyk  V. I.  Kushnir  O. S.  Chizh  O. Z. 《Optics and Spectroscopy》2011,111(6):967-972
Average and fluctuation parameters of a shock wave that arises in a supersonic air flow around bodies are studied based on numerical simulation using FLUENT 6.0 models of computational fluid dynamics. A series of closed numerical experiments show that distributions of the structural characteristic of the refractive index and average air density in the region of shock wave localization can be reconstructed from measurements of parameters of the laser beam intersecting the flow.  相似文献   

10.
Analytical propagation expression of a super Lorentz-Gauss(SLG) 01 mode in uniaxial crystal orthogonal to the optical axis is derived.The SLG 01 mode propagating in uniaxial crystal orthogonal to the optical axis mainly depends on the ratio of the extraordinary refractive index to the ordinary refractive index.The SLG 01 mode propagating in uniaxial crystals becomes an astigmatic beam.The beam spot of the SLG 01 mode in the uniaxial crystal is elongated in the x-or y-direction,which is determined by the ratio of the extraordinary refractive index to the ordinary refractive index.With the increase of the deviation of the ratio of the extraordinary refractive index to the ordinary refractive index from unity,the elongation of the beam spot also augments.In different observation planes,the phase distribution of an SLG 01 mode in the uniaxial crystal takes on different shapes.With the variation of the ratio of the extraordinary refractive index to the ordinary refractive index,the phase distribution is elongated in one transversal direction and is contracted in the other perpendicular direction.This research is beneficial to the practical applications of an SLG mode.  相似文献   

11.
It is known that deep ultraviolet (UV) radiation induces a refractive index increase in the surface layer of polymethylmethacrylate (PMMA) samples. This effect can be used for the fabrication of integrated optical waveguides. PMMA is of considerable interest for bio and chemical sensing applications because it is biocompatible and can be micromachined by several methods, e.g. structuring by photolithography, ablation and hot embossing. In the presented work direct UV irradiation of a common PMMA substrate by a krypton fluoride excimer laser beam through a contact mask has been used to write integrated optical Mach-Zehnder interferometers (MZI). MZI are used as sensitive bio and chemical sensors. The aim was to determine contact mask design and laser irradiation parameters for fabricating single-mode MZI for the infrared region from 1.30 μm to 1.62 μm. Straight and curved waveguides have been generated and characterized to determine the optical losses. The generation of channel waveguide structures has been optimized by a two step irradiation process to minimize the lithographic writing time and optical loss. By flood exposure to UV laser radiation in the first step the optical absorption of PMMA can be increased in the irradiated region. The required refractive index profile is then achieved with a second lithographic irradiation. The spectral behaviour of an unbalanced, integrated optical MZI fabricated by this excimer laser based contact mask method is shown for the first time. Further the optical intensity at the output port of a MZI has been measured while the optical path length difference was tuned by creating a temperature difference between the two arms of the MZI.  相似文献   

12.
周国泉 《中国物理 B》2012,21(5):54104-054104
Analytical propagation expression of a super Lorentz-Gauss(SLG) 01 mode in uniaxial crystal orthogonal to the optical axis is derived.The SLG 01 mode propagating in uniaxial crystal orthogonal to the optical axis mainly depends on the ratio of the extraordinary refractive index to the ordinary refractive index.The SLG 01 mode propagating in uniaxial crystals becomes an astigmatic beam.The beam spot of the SLG 01 mode in the uniaxial crystal is elongated in the x-or y-direction,which is determined by the ratio of the extraordinary refractive index to the ordinary refractive index.With the increase of the deviation of the ratio of the extraordinary refractive index to the ordinary refractive index from unity,the elongation of the beam spot also augments.In different observation planes,the phase distribution of an SLG 01 mode in the uniaxial crystal takes on different shapes.With the variation of the ratio of the extraordinary refractive index to the ordinary refractive index,the phase distribution is elongated in one transversal direction and is contracted in the other perpendicular direction.This research is beneficial to the practical applications of an SLG mode.  相似文献   

13.
A polarization interferometer is described which has prisms made of Iceland spar and of glass. The refractive index of glass is approximately equal to that of Iceland spar for the ordinary beam. Interferograms are presented showing the supersonic flow around a sphere and the flow behind a shock wave diffracting around the edge of a nozzle.  相似文献   

14.
阶变折射率轴棱锥产生局域空心光束   总被引:4,自引:0,他引:4       下载免费PDF全文
马亮  吴逢铁 《物理学报》2010,59(9):6096-6100
提出利用折射率成阶跃性变化的轴棱锥产生局域空心光束(bottlebeam).讨论了折射率沿径向成阶跃式减小或增加两种模型,从几何光学角度分析了它们产生bottle beam的原理,利用衍射积分理论数值模拟两种轴棱锥光传输的光场分布和不同距离处的二维光斑图,研究结果表明折射率沿径向阶跃减小的轴棱锥产生单个bottle beam,而折射率沿径向阶跃增加的轴棱锥产生具有周期再现的bottle beams.bottle beam在原子引导和囚禁、光学俘获及光镊等方面有广泛的应用,因此本文的研究对bottlebeam的产生和实际应用具有指导意义.  相似文献   

15.
The manufacturing of test diffractive refractive intraocular lenses is illustrated by means of LIGA (deep X-ray LIthography and GAlvanoplastics and polymer forming). Dynamic X-ray lithography used while rotating the substrate versus an X-ray mask fixed in a beam of synchrotron radiation (SR) yields smooth optical 3D surfaces with roughnesses of 10–30 nm rms in polymethylmethacrylate (PMMA) layers. The axisymmetric diffractive refractive profile of a lens is predetermined by the radial angular function of the X-ray mask topology. The quality of the optical surface is reproduced for the nickel master form, which is electroplated onto a gold layer atop the PMMA relief. The optical quality also remains high for replicated lenses synthesized in this manner during silicon polymerization.  相似文献   

16.
The refractive index profile of an axially symmetric fiber preform is determined by using the transport of intensity equation. In this method the preform is immersed in an index-matching liquid, and a collimated light beam impinges on it laterally. The intensity distributions of the transmitted light are measured on two close parallel planes inside the preform core. From the recorded intensity distributions, the deflection function is calculated by the transport of intensity equation. The refractive index profile is obtained by means of Abel inversion. Also, for comparison, the refractive index profile of the preform is measured by the focusing method and the results are in agreement with less than 3% error.  相似文献   

17.
Variations in the profile and shift of a Gaussian light beam upon reflection from a plane interface between a transparent dielectric and a medium with a complex refractive index are studied. The beam is assumed to be incident at angles close to the Brewster’s angle, where the effects of transformation of the beam profile are most substantial. Based on numerical analysis, the reflected beam profiles are obtained for different properties of the media, parameters of the incident beam, and positions of the plane of observation.  相似文献   

18.
Insensitive bulk samples of poly-(methyl methacrylate) (PMMA) may be sensitized by in-diffusion of monomers and photoinitiators. Different methods for the fabrication of refractive index profiles in the PMMA surface for lightguiding are demonstrated. The photolocking procedures are suitable for recording 2 dimensional patterns as well.  相似文献   

19.
The photo-induced effects in 9,10-phenanthrenequinone-doped (PQ-doped) poly(methyl methacrylate) (PMMA) photopolymer were studied by phase-modulated ellipsometry and polarimetry in real time. The PQ-doped PMMA was exposed to an Ar/Kr tunable laser at the wavelength of 488 nm and measured by a HeNe laser (632.8 nm). We measured the induced birefringence and the variation of the refractive index separately during exposure; there was a difference of three orders of magnitude between these two effects. This suggested that the physical mechanism of holographic recording in PQ-doped PMMA is mainly due to the photo-induced variation in the refractive index.  相似文献   

20.
Ao X  He S 《Optics letters》2005,30(16):2152-2154
A two-dimensional metallo-dielectric photonic crystal of negative refraction was designed for the application of polarization beam splitters. To match the refractive index of air, the effective refractive index of the designed photonic crystal is -1 for TE polarization and +1 for TM polarization. Two types of polarization beam splitter are presented.  相似文献   

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