共查询到20条相似文献,搜索用时 156 毫秒
1.
利用二维结构薄膜构建了具有偏振选择特性的新型相位光栅,借助严格耦合波分析(RCWA)方法计算了光栅各级衍射强度随入射光波长及入射角的变化,发现在垂直入射情况下,波长600—640 nm范围内,相位光栅对横向电学(TE)模主要产生0级衍射,而对横向磁学(TM)模产生±1级衍射,在波长633nm处,0级衍射光的偏振消光比为109.8,±1级衍射光的偏振消光比为334.6.利用时域有限差分方法对这种相位光栅的偏振分束现象进行了模拟,偏振分离角在玻璃基板内可以达到10°左右,最后模拟了入射角为23°时光栅对不同偏 相似文献
2.
《Photonics and Nanostructures》2014,12(3):252-258
Optical Tamm (OT) modes formed at the interface of distributed-Bragg reflector (DBR) and low-index dielectric material, exhibit strong dispersive features at optical frequencies which gives rise to the possibility of designing refractometer with improved sensitivity. Using this idea, we design a TiO2/SiO2 based DBR configuration for sensing refractive-index changes around 1.33 using spectral-interrogation as well as angular-interrogation method. Dispersion characteristics of OT modes in the DBR configuration are tailored to obtain spectral sensitivity ∼1200 nm/RIU and angular sensitivity ∼40°/RIU for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. We also show that the sensitivity could be substantially tuned over a wide range by appropriately choosing the thicknesses of DBR constituent layer. An all-dielectric DBR configuration gives rise to the possibility of realizing refractometer in any desired spectral region by linearly translating the dispersive behavior of photonic bandgap (PBG) guided OT modes. 相似文献
3.
In this paper, we report and analyze the large blue shift in the optical band-gap of sol-gel derived Ba0.5Sr0.5TiO3 (BST) thin films. BST films of different thickness (150 nm, 320 nm and 480 nm respectively) were deposited layer by layer onto fused quartz substrates by a spin coating technique. The drying temperature for individual layers (pre-sintering temperature) was varied as 400, 500 and 600 °C. A large blue shift in the band-gap was observed (with a value 4.70 eV compared to the bulk value of 3.60 eV) for films pre-sintered at 400 °C, which decreased with increase in the pre-sintering temperature. To date such blue shifts have been attributed to grain size reduction, stress and the amorphous nature of the films. Here, the blue shift has been correlated with the presence of charge carriers generated by oxygen vacancies and explained on the basis of the Burstein-Moss effect. 相似文献
4.
5.
High-power distributed-feedback (DFB) lasers for the wavelength range near 940 nm (i.e. about 10,600 cm−1) were used for line-broadening measurements of individual rotational-vibrational absorption lines of water vapour at atmospheric
pressure using a minimalist set-up. The laser has a maximum output power larger than 500 mW. Over the whole power range from
threshold to maximum power, it operates in single mode operation with a tuning range of 4.7 nm, i.e. 50 cm−1, at 20°C. With an emission line-width ≤2 MHz (0.66×10−4 cm−1), the device is well suited for high-resolution spectroscopy. 相似文献
6.
P. Karasiński 《Opto-Electronics Review》2007,15(3):168-178
The paper presents the results of theoretical analysis as well as the results of experimental research involving planar sensor
structures with input grating couplers of the period Λ = 800 nm. In the theoretical part of the paper we discussed the influence
of the parameters of a sensor structure on it sensitivities. The experimental part of the work presents the results of experimental
research involving the influence of refractive index of the cover on the coupling characteristics of sensor structures with
grating couplers. The full widths at half maximum (FWHM) were from 0.023° to 0.029°. For the investigated structures we estimated
detection thresholds for the changes of refractive index of the cover and the changes of sensitive film thickness. It has
been demonstrated that by the application of the elaborated structures we can detect minimal changes of the refractive index
(Δnc)min = 2.1×10−6 when the refractive index of the cover nc = 1.333 and (Δnc)min = 1.0×10−6 when nc = 1515. For sensitive films of the thickness w < 100 nm, by using the elaborated structures, we can detect mean changes of
the thickness along the values lower than 10−3 nm. 相似文献
7.
We describe the application of a long-wavelength vertical-cavity surface-emitting laser (VCSEL) with extended tuning range
to the detection of benzene vapor at atmospheric pressure. A benzene absorption feature centered at 1684.24 nm was accessed
by reducing the heat sink temperature of a VCSEL designed for room-temperature operation to −55°C. This allowed us to increase
the injection current and thus to extend a single-scan tuning interval up to 46.4 cm−1 or 13.2 nm around a central wavelength of 1687.4 nm. Five absorption lines of methane in the 5903–5950 cm−1 range could be acquired within single laser scans at a repetition rate of 500 Hz. A benzene absorption feature between 5926
and 5948 cm−1 was recorded for concentration measurements at atmospheric pressure using a single-pass 1.2 m absorption cell. A 50 ppmv
mixture of CH4 in N2 was introduced into the cell along with benzene vapor to calibrate benzene concentration measurements. Benzene mixing ratios
down to ∼90 ppmv were measured using a direct absorption technique. The minimum detectable absorbance and detection limit
of benzene were estimated to be ∼10−4 and 30 ppmv, respectively. Using the wavelength modulation technique, we measured a second harmonic sensor response to benzene
vapor absorption in air at atmospheric pressure as a function of modulation index. We conclude that a low-temperature monolithic
VCSEL operating near 1684 nm can be employed in compact benzene sensors with a detection limit in the sub-ppm range. 相似文献
8.
The synthesis of aqueous dispersion of spherical, underivatized silver nanoparticles (Ag-NPs) stabilized by macrocyclic polyammonium
chlorides (MCPAC), [28]ane-(NH2
+)6O2·6Cl− (28-MCPAC) and [32]ane-(NH2
+)8·8Cl− (32-MCPAC), which are evidently anion receptors, is reported. As-synthesized Ag-NPs are characterized by UV-vis spectroscopy
and transmission electron microscopy (TEM). The 28/32-MCPAC-stabilized Ag-NPs show the surface plasmon band around 400 nm.
The TEM-images show that the particles are spherical and well-dispersed. By tuning the 28/32-MCPAC:Ag-OAc (silver acetate)
ratio, nanoparticles with different core diameters ranging from 13 to 8 nm for 28-MCPAC and from 10 to 6 nm for 32-MCPAC can
be obtained. The advantage of using MCPAC as stabilizers is that they make the particles functionalized for sensing anions.
Thus, the potential of the as-synthesized Ag-NPs for sensing phosphates: H2PO4
− (monobasic phosphate, MBP), HPO4
2− (dibasic phosphate, DBP) and PO4
3− (tribasic phosphate, TBP) is investigated spectroscopically. Interaction of phosphate ions with macrocyclic polyammonium
cations makes the Ag-NPs bare, leading agglomeration. The phosphate-assisted agglomeration of 32-MCPAC-Ag-NPs follow the order
TBP > DBP ≫ MBP.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
9.
We discuss the transmission characteristics of a microscale dielectric waveguide device with a deep groove and an embedded metallodielectric grating illuminated by a continuous wave of TM and TE modes at low terahertz frequency. To study its performance we solve numerically the corresponding Maxwell equations by means of finite difference time domain method with uniaxial perfectly match layer as its boundary condition. By varying the angle of incident, grating filling factor and refractive index of analyte in the deep groove, it is found that the device exhibits a significant transmission enhancement for the TM mode due to the existence of surface plasmon interaction. We also demonstrate its potential application as a biosensor device. 相似文献
10.
Mingfu Zhang Hengzhi Chen Bin Yang Wenwu Cao 《Applied Physics A: Materials Science & Processing》2009,97(4):741-744
Layered-perovskite ferroelectric Bi2.85La0.15TiNbO9 (LBTN) optical waveguiding thin films were grown on fused silica substrates by pulsed laser deposition (PLD). X-ray diffraction
(XRD) revealed that the film is highly (00l) textured. We observed sharp and distinct transverse electric (TE) and transverse magnetic (TM) multimodes and measured the
refractive indices of LBTN thin films at 632.8 nm. The ordinary and extraordinary refractive indices were calculated to be
n
TE=2.358 and n
TM=2.464, respectively. The film homogeneity and the film-substrate interface were analyzed using an improved version of the
inverse Wentzel–Kramer–Brillouin (iWKB) method. The refractive index of the film remains constant at n
0 within the waveguiding layer. The average transmittance of the film is 70% in the wavelength range of 400–1400 nm and the
optical waveguiding properties were evaluated by the optical prism coupling method. Our results showed that the LBTN films
are very good electro-optical active material. 相似文献
11.
S. D. Liu J. F. Yang J. L. He B. T. Zhang X. Q. Yang F. Q. Liu H. W. Yang J. L. Xu H. T. Huang 《Laser Physics》2011,21(2):327-330
This paper reported a broadband tuning intracavity optical parametric oscillator (IOPO), based on the multiple grating periodical
poled lithium niobate (PPLN) pumped by a acoustic-optical (AO) Q-switched Nd:YVO4 laser. The widely tunable OPO output signal wavelength range from 1390 to 1605 nm, which was obtained by changing PPLN poling
period from 27.8 to 31.6 μm at a certain temperature of 46°C, while the continuous tuning range was measured from 1475 to
1592 nm with the PPLN poling period of 30 μm by varying the temperature of nonlinear crystal PPLN from 50 to 120°C. The maximum
output power of 0.92 W at 1534 nm with the minimum pulse width of 5.17 ns was generated under the incident pump power of 9.6
W at 808 nm. The corresponding peak power and single pulse energy were calculated to be 5.94 kW and 30.7 μJ, respectively.
The M
2-factor was measured to be 2.01 at the signal power of 0.4 W. 相似文献
12.
In this paper, a broadband reflector exhibiting a flattened bandstop spectral response is proposed by using a multilayered
grating structure possessing multi-subpart profile. It is shown that with the properly configured profile and a strongly modulated
grating layer, in transverse electric (TE) polarized wave the presented reflector experimentally demonstrated a 240 nm-wide
reflection spectrum from 1.56 to 1.8 μm, very high reflectivity (>97%), and a low sensitivity to incident angle at the range
of −13.8°<θ<+14°. Effects of deviation from the design parameters on the performance of the reflector are also illustrated, and a reasonably
good tolerance of fabrication error is exhibited in the proposed device. 相似文献
13.
A plasmonic multilayer structure (PMS) is proposed for photovoltaic cells with an ultrathin active layer that is 30 nm amorphous
Si (α-Si). The optical properties of the PMS are analyzed by rigorous coupled-wave analysis (RCWA) and finite-difference time-domain
(FDTD) method. Using the PMS, the incident light can be trapped into localized surface plasmon (LSP) and then the localized
surface plasmon induces the surface plasmon (SP) that propagates transversely within the α-Si layer. Compared with the indium tin oxide (ITO)/α-Si/Ag structure, the photon number absorbed by PMS increase 28.7% while a normal incident transverse magnetic (TM) polarization
wave is applied. 相似文献
14.
Yoshio Kobayashi Hidekazu Kakinuma Daisuke Nagao Yasuo Ando Terunobu Miyazaki Mikio Konno 《Journal of nanoparticle research》2009,11(7):1787-1794
This article describes a method for silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone)
(PVP) as a stabilizer. The Co–Pt nanoparticles were prepared in an aqueous solution at 25–80 °C from CoCl2 (3.0 × 10−4 M), H2PtCl6 (3.0 × 10−4 M), PVP (0–10 g/L), and NaBH4 (4.8 × 10−3–2.4 × 10−2 M). The silica coating was performed for the Co–Pt nanoparticle colloid containing the PVP ([Co] = [Pt] = 3.0 × 10−5 M) at 25 °C in (1/4) (v/v) water/ethanol solution with tetraethoxyorthosilicate (TEOS) (7.2 × 10−5–7.2 × 10−3 M) and ammonia (0.1–1.0 M). Silica particles, which had an average size of 43 nm and contained multiple cores of Co–Pt nanoparticles
with a size of ca. 8 nm, were produced at 1.4 × 10−3 M TEOS and 0.5 M ammonia after the preparation of Co–Pt nanoparticles at 80 °C, 5 g/L PVP, and 2.4 × 10−2 M NaBH4. Their core particles were fcc Co–Pt alloy crystallites. Their saturation magnetization was 2.0-emu/g sample, and their coercive
field was 12 Oe. 相似文献
15.
We present a nondestructive technique to predict the refractive index profiles of isotropic planar waveguides, on which a thin gold film is deposited to as the cladding. The negative dielectric constant of the metal results in significant differences of effective indices between TE and TM modes. The two polarized modes and a surface plasmon resonance (SPR) with abundant information of the surface index can be used to construct the refractive index profiles of single-mode and two-mode waveguides at a fixed wavelength. 相似文献
16.
17.
N.E. Stankova I.G. Dimitrov T.R. Stoyanchov P.A. Atanasov 《Applied Surface Science》2007,254(4):1268-1272
In this work the optical and the gas sensing properties of thick TiO2 waveguide films, produced by pulsed laser deposition, were investigated by m-line spectroscopy. The films were deposited on (0 0 1) SiO2 substrates at temperature of 100 °C. The thickness of the films was measured to be in the range from 650 to 1900 nm and the roughness increases from 5 to 14.6 nm. High quality mode spectra, consisted of thin and bright TE and TM modes, were observed in the films with thickness up to 1200 nm. All the films revealed anisotropic optical properties. Gas sensitivity of the films to CO2 was examined at room temperature on the basis of the variations of the refractive index. CO2 concentration of 3 × 104 ppm was detected, which corresponds to a refractive index variation of about 1 × 10−4. The crystal structure and the optical transmittance of the films were also presented and discussed. 相似文献
18.
We fabricated and measured the far-field optical properties of a sub-wavelength Si3N4 (silicon nitride) two dimensional grating. Frequency-dependent transmission measurements from a white-light source revealed
that both transverse magnetic (TM) and transverse electric (TE) modes were excited on the grating. We determined the dispersion
relations of the modes by tilting the sample with respect to the incoming light beam and measuring the frequency shift of
the absorption features. By comparing to a simple model, we determined the effective refractive index for the TM and TE modes
and the geometrical constants for the grating. This information enables gratings with desired optical properties to be designed
and fabricated. The application of the sub-wavelength grating for surface-enhanced Raman scattering (SERS) is demonstrated. 相似文献
19.
Zhu Jian Deng Xing-chun Li Jian-jun Zhao Jun-wu 《Journal of nanoparticle research》2011,13(3):953-958
Because of the geometric features of both rod and shell, dielectric-silver core–shell ellipsoidal nanostructure with 12–40 nm
semi-major axis may bring forth four surface plasmon resonance (SPR) absorption peaks at most. Theoretical calculations based
on quasi-static approximation show that there is surrounding refractive index-dependent plasmon blending and splitting in
the absorption spectra, which makes the number of plasmon band of the silver ellipsoidal nanoshell is tunable. The sensitivity
of the plasmon blending and splitting to the surrounding refractive index may be improved by increasing the shell thickness,
aspect ratio or core refractive index. This local refractive index dependent-plasmon blending and splitting presents a new
sensing picture based on tuning the number of SPR absorption peaks. 相似文献
20.
X. Zhu S. Lu H.L.W. Chan C.L. Choy K.H. Wong 《Applied Physics A: Materials Science & Processing》2003,76(2):225-229
Compositionally graded (Ba1-xSrx)TiO3 (BST) (x:0.0∼0.25) thin films were grown on Pt (111)/TiO2/SiO2/Si (100) substrates using layer-by-layer pulsed laser deposition in the temperature range 550–650 °C. Both downgraded (Ba/Sr
ratio varying from 100/0 at the bottom surface to 75/25 at the top surface) and upgraded (Ba/Sr ratio varying from 75/25 at
the bottom surface to 100/0 at the top surface) BST films were prepared. Their microstructures were systematically studied
by X-ray diffractometry and scanning electron microscopy. A grain morphology transition from large ‘rosettes’ (>0.30 μm) to
small compact grains (70–110 nm) was observed in the downgraded BST films as the deposition temperature was increased from
550 to 650 °C. No such grain morphology transition was detected in the upgraded BST films. Dielectric measurements with metal
electrodes revealed an enhanced dielectric behavior in the downgraded films. This enhancement is mainly attributed to the
large compressive stress field built up near the interface between the downgraded film and substrate. Furthermore, the BaTiO3 layer in the downgraded BST films not only serves as a bottom layer but also as an excellent seeding layer for enhancing
the crystallization of the subsequent film layers in the downgraded films.
Received: 10 December 2001 / Accepted: 12 March 2002 / Published online: 19 July 2002
RID="*"
ID="*"Corresponding author. Fax: 86-25/359-5535, E-mail: xhzhu@public1.ptt.js.cn 相似文献