• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Effect of thickness variations of lithium niobate on insulator waveguide on the frequency spectrum of spontaneous parametric down-conversion*

    2021-11-23 07:25:18GuangTaiXue薛廣太XiaoHuiTian田曉慧ChiZhang張弛ZhendaXie謝臻達(dá)PingXu徐平YanXiaoGong龔彥曉andShiNingZhu祝世寧
    Chinese Physics B 2021年11期
    關(guān)鍵詞:徐平張弛

    Guang-Tai Xue(薛廣太) Xiao-Hui Tian(田曉慧) Chi Zhang(張弛) Zhenda Xie(謝臻達(dá))Ping Xu(徐平) Yan-Xiao Gong(龔彥曉) and Shi-Ning Zhu(祝世寧)

    1National Laboratory of Solid State Microstructures,School of Physics,School of Electronic Science and Engineering,

    College of Engineering and Applied Sciences,and Collaborative Innovation Center of Advanced Microstructures,Nanjing University,Nanjing 210093,China

    2Institute for Quantum Information and State Key Laboratory of High Performance Computing,College of Computing,National University of Defense Technology,Changsha 410073,China

    Keywords: lithium niobate on insulator,spontaneous parametric down-conversion,waveguide thickness variation,frequency spectrum

    1. Introduction

    Thin-film lithium niobate on insulator (LNOI)[1,2]is thought to be a revolutionary platform for integrated photonics,[3,4]since it allows strong optical confinement and a high integration density on lithium niobate (LN), a material possessing superior optical performance,[5]such as low optical transmission losses, large electro-optical and second-order nonlinear coefficients. In recent years, LNOIbased integrated photonic devices have achieved remarkable breakthroughs, such as low-loss waveguides,[6-9]highquality-factor microring resonators,[7,10]high-speed electrooptic modulators,[11,12]and broadband optical frequency comb generation.[13,14]

    Quasi-phase-matching (QPM)[15]spontaneous parametric down-conversion (SPDC) in periodically-poled crystals or waveguides,[16,17]typically periodically-poled LN(PPLN),[18-22]is widely used in the generation of entangled photon pairs, for the merits of high efficiency and frequency tunability. Benefiting from the strong optical confinement, ultrahigh-efficiency SPDC processes in periodically-poled LNOI(PPLNOI)waveguides were demonstrated recently.[23-25]In particular, a PPLNOI waveguide source with a brightness two orders of magnitude higher than that in the traditional PPLN waveguide was achieved in our lab,[25]as the cross-sectional area of the LNOI waveguide was~2 orders of magnitude smaller than that of the traditional LN waveguide. However, in practical experiment the nonlinear optical performance may be affected by imperfections in fabrication of the waveguide.[26-28]With stronger light confinement, such effect in LNOI-based devices could become greater. Recently, Tianet al.[26]revealed that the spectrum profile and efficiency can be greatly affected by the LNOI waveguide cross-section dimension variations, especially the thickness variations. Hence, with regard to developing photonic quantum technologies in the LNOI platform,it is of practical importance to study the effect of LNOI waveguide fabrication imperfections on SPDC.

    In this paper,we make a study on the effect of thickness variations of the LNOI waveguide on the frequency spectrum of SPDC. Our simulation results show that the central peak of SPDC frequency spectrum can be greatly affected by the waveguide thickness variations. Our study can not only give a benchmark to the LNOI waveguide fabrication, but also provide a way for the manipulation of photon frequency state.

    2. Basic principles and methods

    We consider a PPLNOI waveguide with the schematic structure shown in Fig.1(a).The LNOI wafer consists of three layers from up to bottom. The topX-cut LN film with a thickness ofH=600 nm is etched to a depth ofh=350 nm with a bottom ridge width ofw=1400 nm and a sidewall angle ofθ=60°. The middle is a 2-μm-thick silicon dioxide bonding layer and the bottom is a 0.5-mm-thick LN or silicon(Si)substrate. The length of the waveguide isLand the whole waveguide is poled with a period ofΛ. Here we consider a type-0 QPM SPDC process converting the pump photons at 780 nm to frequency-degenerate photon pairs at 1560 nm. With the COMSOL software we simulate the field distributions of TE00mode at 780 nm and 1560 nm,as shown in Figs.1(b)and 1(c),respectively. We can see that the waveguide is designed to be single mode for the SPDC photons. Note that although here we considere theX-cut LN film, our method is also applied to theZ-cut LN film. The difference is that the extraordinary light modes required in type-0 SPDC correspond to the TE and TM modes forX-cut andZ-cut LN films,respectively.

    Fig. 1. (a) Schematic of PPLNOI waveguide structure and phase matching condition. Field distribution of the TE00 mode at the wavelength of 780 nm(b)and 1560 nm(c).

    Considering the pump coupling to be optimized to excite the fundamental mode in the waveguide, and using a continues-wave(cw)laser light with a single frequencyωpas the pump,we can write the two-photon term of SPDC as[28-30]

    wherezis the propagation direction,and ?kis the phase mismatch expressed as

    withkp,ks,andkirepresenting the wave vectors of the pump,signal,and idler fields,respectively. The reciprocal wave vectorG=2π/Λresults from periodic poling and here the period is designed to make the perfect QPM condition of ?k=0 be satisfied at the central frequencies, namely, in the case ofν=0. Note that here a normalization factor of 1/Lis introduced for normalization by the amplitude when ?k=0,and in our simulation the length is fixed toL=6 mm. For the case of single-frequency pump, the joint spectral intensity can be obtained by tracing the frequency of either photon,given by

    and the joint spectral intensity is then given by

    According to Maxwell’s equations,the field nature of a waveguide is determined by its boundary conditions relating to the waveguide dimensions, such as thickness and width. For the strong-confined waveguide, a slight variation in dimension could have a great effect on the optical properties, like the refractive index, inducing the change of the phase-matching function. Here we focus on the effect of the thickness variation, denoted by ?H(z), which would be a function ofzfor an inhomogeneous variation. As a result,phase mismatch ?kbecomes

    We simulate the values ofδkfor signal/idler wavelength ranging from 1200 nm to 1700 nm when ?H=±20 nm,with the result shown in Fig.2.We can see thatδkcan be considered to be independent of the wavelength. When the thickness change range is small,we can considerδkto be a linear function of the thickness increment ?H,namely,δk=a0?H,[32]and we can estimatea0=?1.64×1012m?2from the simulation result.Therefore,Eq.(9)is rewritten as

    Fig. 2. Change of phase mismatch δk against wavelength under different thickness,with the thickness variation ?H deviated from the designed thickness of 600 nm shown in the box.

    3. Results

    With numerical simulations via the COMSOL software,we can get the effective refractive index for different wavelengths,and then according to Eqs.(10)and(4),we can calculate the joint spectral amplitude function and the joint spectral intensity under any form of thickness variations,respectively.

    We first simulate the joint spectral intensity in the case of the ideal designed structure when ?H(z) = 0, namely,H=600 nm, which is given by Eq. (7). The simulation result is plotted in Fig.3,which shows a sinc-square-type curve and the full width at half maximum(FWHM)can be estimated to be 159 nm.

    Then we consider the linear deviation case, i.e., ?His a linear function ofz,expressed as

    whereκandσare two parameters determining the range of?H. Then the joint spectral intensity can be calculated as

    In Fig. 4, we show the simulation results of joint spectral intensities for ?H=±0.4 nm,±0.8 nm,±1.2 nm,and±1.6 nm.

    Fig.3. Joint spectral intensity of the SPDC in the designed structure.

    Fig.4. Joint spectral intensity of the SPDC in the PPLNOI waveguides under different homogenous thickness variations ?H, with the corresponding values of ?H shown on the top right corner.

    Forκ ?=0,this model corresponds to a linear variation of thickness ranging fromσ ?κtoσ+κwhenzchanges from 0 toL. In Fig.5,we present some typical simulated results of the joint spectral intensities for several values ofκandσ.

    By comparing the simulation results shown in Figs. 4 and 5 with the ideal joint spectral intensity plotted in Fig. 3,we can see that the thickness variation in several nanometers may have a distinct effect on the joint spectral intensity,such as narrowing or broadening the main peak, shifting the main peak and splitting to multi-peaks. The original peak lies at 1560 nm,namely,the designed wavelength satisfying the perfect QPM condition of ?k=0. The multi-peaks mean that,due to the thickness variations, some non-degenerate phasematching amplitudes become bigger and may surpass the degenerate term. In particular, two prominent nondegenerate peaks occur in Figs.4(d),4(f),4(h),and 5(k).In addition,from Fig.5(g)-5(i), we can find that when ?H=0 lies atz=L/2 the joint spectral intensity is not affected much by the thickness deviation, and the main peak is still at 1560 nm with a much broader bandwidth. For instance,as shown in Fig.5(i),the bandwidth can be estimated to be 293 nm,which is nearly twice the value of the original bandwidth.

    Fig.5. Joint spectral intensity of the SPDC in the PPLNOI waveguides under the linear thickness variation ?H along the waveguide, with the value ranges when z changes from 0 to L shown on the top right corner.

    In fact, the surface of LNOI has certain irregular undulations, namely, roughness, and the root mean square (RMS)of the roughness is usually less than 1 nm.[2,8]In the entire wafer range,LNOI also has random fluctuations on thickness.For example,the commercial LNOI film from NANOLN Inc.has a thickness variation around 35 nm in a large range on a whole wafer.[33]To analyze the fluctuation noise on thickness,we introduce a noise parameterτ(z)and rewrite Eq.(11)as

    The 1/fnoise is another type of noise spectrum regarding to long-range fluctuations, which is characterized by spatial correlations.[27]We model the 1/fnoise following the method in Ref.[27],and simulate the resulted joint spectral intensity.We find that the 1/fnoise can bring a distinct effect to the joint spectral intensity. We present several typical results in Fig.6,including the effects of narrowing, broadening, and splitting the central peak.

    The above analysis is based on the numerical simulations of ?k. To further explain the effect in physical mechanism,we expand the signal and idler wave vectors around the central frequencies up to the second order in the detuningν, respectively,

    whereu0andg0are the group velocity and group velocity dispersion (GVD) of light at the central frequencyωs0=ωi0=ωp/2,expressed as

    Then the phase mismatch given by Eq.(3)can be written as

    In this context,with a thickness increment ?H(z),Eq.(8)becomes

    With numerical simulation, we can obtain the GVD value asg0=?80×10?30s2/mm. Note that if substituting the value into Eq. (7), we would get a slightly broader bandwidth than 159 nm shown in Fig.3, as this value only considers the dispersion up to the second order. However,such approximation is adequate to explain the effect on the spectrum.

    Fig. 6. Joint spectral intensity of the SPDC in the PPLNOI waveguides under thickness variations of 1/f noise model. The ranges of 1/f noise fluctuations shown in(a),(c),(e),and(g)are±0.8 nm,0.2±1 nm,±2.5 nm,and 0 to ?1.4 nm,respectively.

    4. Conclusion

    We presented a detailed study on the effect of waveguide thickness variations on the frequency spectrum of photon pairs generated from SPDC in the PPLNOI waveguide. We first gave a general analysis on the effect and then numerically simulated the effect of several thickness variation models,including homogenous error, linear variation, white noise, and 1/fnoise. We found that, due to the strong optical confinement in the LNOI waveguide, variations in several nanometers can have distinct effects on the joint spectral intensity. The central peak of the joint spectral intensity curve in the designed ideal case may be narrowed,broadened,and split to multi-peaks or two prominent peaks. We also found that the effects of positive and negative variations could be canceled, resulting in a variation-robust feature and a much broad bandwidth. Our study may be beneficial for the design of integrated photon sources in the LNOI platform and promote the development of LNOI-based photonic integrated technologies. Our analysis could provide a method for manipulating SPDC frequency states as well.

    猜你喜歡
    徐平張弛
    Effect of laser focus in two-color synthesized waveform on generation of soft x-ray high harmonics
    On-surface synthesis of one-dimensional carbyne-like nanostructures with sp-carbon
    Heralded path-entangled NOON states generation from a reconfigurable photonic chip
    Improving the spectral purity of single photons by a single-interferometer-coupled microring
    Bandwidth-tunable silicon nitride microring resonators
    A 90?mixed-mode twisted nematic liquid-crystal-on-silicon with an insulating protrusion structure?
    Characterize and optimize the four-wave mixing in dual-interferometer coupled silicon microrings?
    屹立
    悅行(2019年7期)2019-09-10 07:22:44
    “種”珍珠真神奇
    徐平 肩負(fù)重任的北上
    黑丝袜美女国产一区| 午夜激情av网站| 国产精品久久久久久精品电影 | 国产99久久九九免费精品| 久久久精品欧美日韩精品| 免费无遮挡裸体视频| 中出人妻视频一区二区| 国产欧美日韩精品亚洲av| 成人精品一区二区免费| 亚洲一码二码三码区别大吗| 夜夜看夜夜爽夜夜摸| 国产熟女午夜一区二区三区| 宅男免费午夜| 国产伦在线观看视频一区| 嫁个100分男人电影在线观看| 国内少妇人妻偷人精品xxx网站 | 亚洲国产看品久久| 悠悠久久av| 一级毛片女人18水好多| 搡老妇女老女人老熟妇| 村上凉子中文字幕在线| 啦啦啦观看免费观看视频高清| АⅤ资源中文在线天堂| 一进一出抽搐动态| 国产精品亚洲美女久久久| 久久天堂一区二区三区四区| 亚洲一卡2卡3卡4卡5卡精品中文| 亚洲一区二区三区不卡视频| 18禁黄网站禁片免费观看直播| 国产成人精品久久二区二区91| 亚洲第一电影网av| 国产99白浆流出| 久久亚洲真实| av电影中文网址| 亚洲狠狠婷婷综合久久图片| 亚洲三区欧美一区| www.精华液| 欧美成人一区二区免费高清观看 | 欧美日韩一级在线毛片| 88av欧美| 亚洲专区国产一区二区| 欧美成人免费av一区二区三区| 日韩视频一区二区在线观看| 午夜福利18| 搡老熟女国产l中国老女人| 香蕉国产在线看| 香蕉av资源在线| 国产黄片美女视频| 久久午夜综合久久蜜桃| 一个人观看的视频www高清免费观看 | 久久久精品欧美日韩精品| 色在线成人网| 色老头精品视频在线观看| 亚洲欧美激情综合另类| 亚洲熟妇熟女久久| 午夜免费成人在线视频| 久久精品亚洲精品国产色婷小说| 午夜精品久久久久久毛片777| 久久精品aⅴ一区二区三区四区| 欧美激情久久久久久爽电影| 亚洲精品国产一区二区精华液| 亚洲国产欧美一区二区综合| 亚洲国产毛片av蜜桃av| 人人妻人人看人人澡| 日韩有码中文字幕| 亚洲黑人精品在线| 国产av一区二区精品久久| 国产欧美日韩一区二区三| 国产精品自产拍在线观看55亚洲| 黄色女人牲交| 国产不卡一卡二| 波多野结衣av一区二区av| 国产野战对白在线观看| 亚洲精品在线观看二区| 男人舔奶头视频| 久久久久亚洲av毛片大全| 午夜免费成人在线视频| 午夜免费成人在线视频| 国内揄拍国产精品人妻在线 | 精品免费久久久久久久清纯| 亚洲中文av在线| 欧美激情极品国产一区二区三区| 国内揄拍国产精品人妻在线 | 在线观看66精品国产| 国产黄片美女视频| 国产一级毛片七仙女欲春2 | 制服丝袜大香蕉在线| 欧美成人性av电影在线观看| 俄罗斯特黄特色一大片| 日韩欧美免费精品| 精品国产美女av久久久久小说| 国产不卡一卡二| 婷婷六月久久综合丁香| 亚洲成人免费电影在线观看| 不卡av一区二区三区| 成人欧美大片| 丰满人妻熟妇乱又伦精品不卡| 国产日本99.免费观看| 99热这里只有精品一区 | 亚洲天堂国产精品一区在线| 亚洲avbb在线观看| 国产片内射在线| 欧美最黄视频在线播放免费| 国产成人av激情在线播放| 高潮久久久久久久久久久不卡| 看免费av毛片| 女人爽到高潮嗷嗷叫在线视频| 亚洲一区二区三区不卡视频| 免费观看精品视频网站| 久久热在线av| 午夜免费鲁丝| 99精品在免费线老司机午夜| 日本三级黄在线观看| 精品久久久久久成人av| 国产成人啪精品午夜网站| 欧美国产日韩亚洲一区| 精品久久蜜臀av无| 国产单亲对白刺激| 熟女少妇亚洲综合色aaa.| 熟女少妇亚洲综合色aaa.| 黄色丝袜av网址大全| 首页视频小说图片口味搜索| 色精品久久人妻99蜜桃| а√天堂www在线а√下载| 性色av乱码一区二区三区2| 亚洲五月天丁香| 高清毛片免费观看视频网站| 午夜福利在线观看吧| 国产成人精品久久二区二区91| 性色av乱码一区二区三区2| 国产亚洲精品久久久久5区| 香蕉丝袜av| 日韩高清综合在线| 男人操女人黄网站| 亚洲成av人片免费观看| 欧美成人一区二区免费高清观看 | 亚洲欧洲精品一区二区精品久久久| www.精华液| 午夜成年电影在线免费观看| 日韩欧美在线二视频| 欧美国产日韩亚洲一区| 国产aⅴ精品一区二区三区波| 国产高清videossex| 日本一本二区三区精品| 一级毛片精品| 亚洲国产欧美网| 欧美性长视频在线观看| 亚洲人成网站在线播放欧美日韩| 精品国产乱子伦一区二区三区| 中文字幕精品亚洲无线码一区 | 禁无遮挡网站| 黑丝袜美女国产一区| av有码第一页| 巨乳人妻的诱惑在线观看| 国产视频一区二区在线看| 亚洲国产日韩欧美精品在线观看 | 久久久久九九精品影院| 日本黄色视频三级网站网址| 欧美乱码精品一区二区三区| 欧美成人免费av一区二区三区| 精品欧美国产一区二区三| 一边摸一边抽搐一进一小说| 亚洲精品粉嫩美女一区| 美女免费视频网站| 国产野战对白在线观看| 精品不卡国产一区二区三区| 亚洲中文日韩欧美视频| 91老司机精品| 色综合欧美亚洲国产小说| 91国产中文字幕| 久久久久久久精品吃奶| 久久久精品欧美日韩精品| 色综合亚洲欧美另类图片| 女人高潮潮喷娇喘18禁视频| 91字幕亚洲| 亚洲专区国产一区二区| 女人爽到高潮嗷嗷叫在线视频| 中文字幕高清在线视频| 成熟少妇高潮喷水视频| 一级毛片精品| 在线观看www视频免费| 日韩欧美一区视频在线观看| 国产黄色小视频在线观看| 最近在线观看免费完整版| 亚洲色图 男人天堂 中文字幕| 中文字幕另类日韩欧美亚洲嫩草| 99久久无色码亚洲精品果冻| 欧美成人免费av一区二区三区| 精品国产乱子伦一区二区三区| 两性午夜刺激爽爽歪歪视频在线观看 | 嫁个100分男人电影在线观看| 制服丝袜大香蕉在线| 男女床上黄色一级片免费看| 欧美av亚洲av综合av国产av| 国产三级在线视频| 99久久久亚洲精品蜜臀av| 亚洲色图av天堂| 岛国在线观看网站| 三级毛片av免费| 最近最新免费中文字幕在线| 香蕉丝袜av| 97碰自拍视频| 一级毛片高清免费大全| 夜夜躁狠狠躁天天躁| 色综合欧美亚洲国产小说| 人人妻人人澡人人看| 老司机午夜十八禁免费视频| 久久久久国内视频| 性色av乱码一区二区三区2| 日本免费a在线| 久久久久久国产a免费观看| www.999成人在线观看| 国产精品二区激情视频| 久久狼人影院| 精品久久久久久,| 日韩成人在线观看一区二区三区| 丝袜在线中文字幕| ponron亚洲| 亚洲人成网站在线播放欧美日韩| 欧美性长视频在线观看| 一级黄色大片毛片| 国产熟女xx| 午夜日韩欧美国产| 美国免费a级毛片| 国产精品电影一区二区三区| 日韩大尺度精品在线看网址| 天堂影院成人在线观看| 美女扒开内裤让男人捅视频| 亚洲欧洲精品一区二区精品久久久| 少妇的丰满在线观看| 99久久精品国产亚洲精品| 十分钟在线观看高清视频www| 亚洲一卡2卡3卡4卡5卡精品中文| 亚洲五月婷婷丁香| 两性夫妻黄色片| 一个人观看的视频www高清免费观看 | 亚洲中文字幕一区二区三区有码在线看 | 欧美三级亚洲精品| 精品人妻1区二区| 国产精品精品国产色婷婷| 在线观看日韩欧美| 97超级碰碰碰精品色视频在线观看| 国内精品久久久久精免费| 777久久人妻少妇嫩草av网站| 大型黄色视频在线免费观看| 久久精品国产清高在天天线| 亚洲九九香蕉| 999久久久国产精品视频| 午夜福利一区二区在线看| 国产一区二区激情短视频| 琪琪午夜伦伦电影理论片6080| 免费看十八禁软件| 精品久久久久久成人av| 色老头精品视频在线观看| 欧美av亚洲av综合av国产av| 午夜福利免费观看在线| www.www免费av| 色综合欧美亚洲国产小说| 九色国产91popny在线| 日本熟妇午夜| 欧美亚洲日本最大视频资源| 国产不卡一卡二| 亚洲中文av在线| 亚洲av第一区精品v没综合| 禁无遮挡网站| 亚洲第一电影网av| 91九色精品人成在线观看| 欧美日韩黄片免| 久久狼人影院| 国产伦人伦偷精品视频| 禁无遮挡网站| 欧洲精品卡2卡3卡4卡5卡区| netflix在线观看网站| 自线自在国产av| 国产精品,欧美在线| 啪啪无遮挡十八禁网站| 十分钟在线观看高清视频www| 丁香六月欧美| 男人舔女人的私密视频| 国产欧美日韩一区二区三| 国语自产精品视频在线第100页| 悠悠久久av| 国产av一区在线观看免费| 亚洲精品av麻豆狂野| 法律面前人人平等表现在哪些方面| 久久青草综合色| 亚洲一区中文字幕在线| 老熟妇仑乱视频hdxx| 国产精品香港三级国产av潘金莲| 国产午夜精品久久久久久| 美女高潮到喷水免费观看| 亚洲精品美女久久av网站| 亚洲av美国av| 成人亚洲精品一区在线观看| 99在线视频只有这里精品首页| 国产精品 欧美亚洲| 韩国av一区二区三区四区| 一区二区三区激情视频| 国产蜜桃级精品一区二区三区| 视频在线观看一区二区三区| 十分钟在线观看高清视频www| 中文字幕高清在线视频| 欧美一区二区精品小视频在线| 欧美黄色片欧美黄色片| 69av精品久久久久久| 非洲黑人性xxxx精品又粗又长| 一级毛片女人18水好多| 一进一出抽搐gif免费好疼| 99热只有精品国产| 亚洲国产精品成人综合色| 老司机福利观看| 又黄又粗又硬又大视频| 日韩欧美国产一区二区入口| 国产精品自产拍在线观看55亚洲| 热99re8久久精品国产| 男女那种视频在线观看| 免费无遮挡裸体视频| 亚洲精品一区av在线观看| 亚洲av日韩精品久久久久久密| 久久久国产成人免费| 黄片播放在线免费| 成人特级黄色片久久久久久久| 欧美黑人精品巨大| 久久中文字幕一级| 夜夜夜夜夜久久久久| 在线观看舔阴道视频| 日本五十路高清| 听说在线观看完整版免费高清| 99久久国产精品久久久| 成人精品一区二区免费| 丝袜在线中文字幕| 国产精品一区二区三区四区久久 | 久久久久久大精品| 国产熟女午夜一区二区三区| 啦啦啦韩国在线观看视频| 中文字幕高清在线视频| 神马国产精品三级电影在线观看 | 精品国产一区二区三区四区第35| 国产私拍福利视频在线观看| 中国美女看黄片| 人人妻人人澡人人看| 好看av亚洲va欧美ⅴa在| 精品福利观看| 啦啦啦免费观看视频1| 欧美黑人欧美精品刺激| 午夜福利在线观看吧| 国产麻豆成人av免费视频| 午夜免费鲁丝| 日韩国内少妇激情av| 国产精品久久久久久亚洲av鲁大| 国产高清激情床上av| 精品免费久久久久久久清纯| 国产色视频综合| 九色国产91popny在线| 久久久久免费精品人妻一区二区 | 2021天堂中文幕一二区在线观 | 桃色一区二区三区在线观看| 丁香六月欧美| 精品福利观看| 亚洲第一av免费看| 亚洲精品美女久久av网站| 757午夜福利合集在线观看| 亚洲一区二区三区色噜噜| 国产成人系列免费观看| 亚洲av电影在线进入| 最近最新免费中文字幕在线| 法律面前人人平等表现在哪些方面| 啦啦啦观看免费观看视频高清| 熟女电影av网| 日本五十路高清| 欧美性猛交╳xxx乱大交人| 大香蕉久久成人网| 欧美大码av| 超碰成人久久| 在线视频色国产色| 亚洲久久久国产精品| 制服诱惑二区| 精品久久久久久成人av| 色老头精品视频在线观看| 日韩免费av在线播放| 国产精品自产拍在线观看55亚洲| 日韩大码丰满熟妇| 日韩欧美国产在线观看| 亚洲自偷自拍图片 自拍| 97人妻精品一区二区三区麻豆 | 国产色视频综合| 国产亚洲欧美精品永久| 免费在线观看视频国产中文字幕亚洲| 日韩欧美 国产精品| 欧美激情极品国产一区二区三区| 黄色片一级片一级黄色片| 亚洲av五月六月丁香网| 日韩欧美一区视频在线观看| 操出白浆在线播放| 亚洲精品国产一区二区精华液| 久久久国产成人免费| netflix在线观看网站| 亚洲人成伊人成综合网2020| 亚洲在线自拍视频| 超碰成人久久| 久久人人精品亚洲av| 国产黄a三级三级三级人| 午夜福利视频1000在线观看| 亚洲男人的天堂狠狠| 美国免费a级毛片| 国内少妇人妻偷人精品xxx网站 | 久久久久国内视频| 亚洲第一欧美日韩一区二区三区| 亚洲一区中文字幕在线| 免费看a级黄色片| 天天添夜夜摸| 午夜精品在线福利| 男女那种视频在线观看| 又紧又爽又黄一区二区| 国产在线观看jvid| 免费看美女性在线毛片视频| 午夜老司机福利片| 色播在线永久视频| 身体一侧抽搐| 久久中文字幕人妻熟女| 国产国语露脸激情在线看| 欧美绝顶高潮抽搐喷水| 国产精品久久久久久亚洲av鲁大| 久久久水蜜桃国产精品网| 好男人在线观看高清免费视频 | 国产精品久久久人人做人人爽| 亚洲欧美一区二区三区黑人| 亚洲人成网站高清观看| 欧美成人午夜精品| 免费电影在线观看免费观看| 在线观看午夜福利视频| 国产久久久一区二区三区| 又紧又爽又黄一区二区| 国产高清激情床上av| 欧美成狂野欧美在线观看| 国产aⅴ精品一区二区三区波| 18禁观看日本| 亚洲精品一区av在线观看| 黄片小视频在线播放| 热99re8久久精品国产| www日本在线高清视频| 国产一卡二卡三卡精品| 精品一区二区三区四区五区乱码| 超碰成人久久| 岛国视频午夜一区免费看| 欧美黄色淫秽网站| 一级a爱视频在线免费观看| av有码第一页| √禁漫天堂资源中文www| 麻豆久久精品国产亚洲av| 成人午夜高清在线视频 | avwww免费| 麻豆国产av国片精品| 手机成人av网站| 90打野战视频偷拍视频| 特大巨黑吊av在线直播 | 久久九九热精品免费| 一本综合久久免费| 亚洲精品美女久久久久99蜜臀| 国产激情久久老熟女| 精品国产超薄肉色丝袜足j| 亚洲黑人精品在线| 久久久久久久久中文| 深夜精品福利| 亚洲男人的天堂狠狠| 国产成人系列免费观看| 国产国语露脸激情在线看| 在线观看www视频免费| 久久中文看片网| 国产精品美女特级片免费视频播放器 | 国产伦在线观看视频一区| 丰满的人妻完整版| 国产麻豆成人av免费视频| 美女国产高潮福利片在线看| 亚洲精品色激情综合| 国内精品久久久久久久电影| 亚洲av五月六月丁香网| 亚洲精品色激情综合| 久久久久久亚洲精品国产蜜桃av| 国产激情欧美一区二区| 国产亚洲精品第一综合不卡| 黄色片一级片一级黄色片| 亚洲精品一卡2卡三卡4卡5卡| 女性生殖器流出的白浆| 国内久久婷婷六月综合欲色啪| 自线自在国产av| 给我免费播放毛片高清在线观看| 久久久久国产精品人妻aⅴ院| 长腿黑丝高跟| 午夜成年电影在线免费观看| 天天躁夜夜躁狠狠躁躁| 在线观看午夜福利视频| 精品卡一卡二卡四卡免费| 宅男免费午夜| 欧美一级毛片孕妇| 免费看a级黄色片| 久9热在线精品视频| 变态另类成人亚洲欧美熟女| 老汉色av国产亚洲站长工具| 成年女人毛片免费观看观看9| 欧美一区二区精品小视频在线| 男女视频在线观看网站免费 | 99久久综合精品五月天人人| 久久香蕉精品热| 午夜亚洲福利在线播放| 国产激情偷乱视频一区二区| 中文字幕人妻丝袜一区二区| 最近最新中文字幕大全电影3 | 国产野战对白在线观看| 男人的好看免费观看在线视频 | 欧美久久黑人一区二区| 午夜福利18| 好男人在线观看高清免费视频 | 搡老妇女老女人老熟妇| 日韩欧美国产在线观看| 中文字幕人成人乱码亚洲影| av片东京热男人的天堂| 身体一侧抽搐| 久久久久国内视频| 亚洲国产精品合色在线| 亚洲人成77777在线视频| 国产在线精品亚洲第一网站| 欧美黑人精品巨大| 性欧美人与动物交配| 天天躁夜夜躁狠狠躁躁| 一区二区三区精品91| 又黄又爽又免费观看的视频| 国内毛片毛片毛片毛片毛片| 麻豆一二三区av精品| 国产欧美日韩精品亚洲av| 精品第一国产精品| 亚洲国产看品久久| 国产区一区二久久| 身体一侧抽搐| 一边摸一边抽搐一进一小说| 欧美精品啪啪一区二区三区| or卡值多少钱| 黄色a级毛片大全视频| 亚洲成人精品中文字幕电影| 日韩av在线大香蕉| 黄片播放在线免费| 一区二区三区高清视频在线| av在线天堂中文字幕| 日韩欧美在线二视频| 动漫黄色视频在线观看| 久久久久久大精品| 成人三级做爰电影| 一级黄色大片毛片| 日韩三级视频一区二区三区| 两人在一起打扑克的视频| 激情在线观看视频在线高清| 精品国产美女av久久久久小说| 好男人在线观看高清免费视频 | 午夜视频精品福利| 黄频高清免费视频| 午夜久久久久精精品| ponron亚洲| 18禁美女被吸乳视频| 91大片在线观看| 亚洲av成人不卡在线观看播放网| 成人免费观看视频高清| 国产激情欧美一区二区| 免费观看精品视频网站| 国产又色又爽无遮挡免费看| 黄色视频,在线免费观看| 日本撒尿小便嘘嘘汇集6| 亚洲精品在线美女| 狠狠狠狠99中文字幕| 久久国产亚洲av麻豆专区| 男女做爰动态图高潮gif福利片| 国产成人一区二区三区免费视频网站| 午夜福利高清视频| 一边摸一边抽搐一进一小说| 日韩国内少妇激情av| 91av网站免费观看| 一区二区三区国产精品乱码| 在线免费观看的www视频| √禁漫天堂资源中文www| 女人高潮潮喷娇喘18禁视频| 后天国语完整版免费观看| 一区二区三区激情视频| xxxwww97欧美| 91大片在线观看| 国内揄拍国产精品人妻在线 | 国产区一区二久久| 好男人电影高清在线观看| 禁无遮挡网站| 一级a爱视频在线免费观看| 两个人视频免费观看高清| 日本在线视频免费播放| 美女免费视频网站| av片东京热男人的天堂| 国产爱豆传媒在线观看 | 最新在线观看一区二区三区| 天天躁夜夜躁狠狠躁躁| 精品欧美国产一区二区三| 国产视频一区二区在线看| 国产精品 国内视频| 少妇熟女aⅴ在线视频| 叶爱在线成人免费视频播放| 色播在线永久视频| 久久久久久国产a免费观看| 精品国产乱子伦一区二区三区| 亚洲第一青青草原| 正在播放国产对白刺激| 国产高清激情床上av| 色av中文字幕| 巨乳人妻的诱惑在线观看| 十分钟在线观看高清视频www| 国产精品影院久久| 久99久视频精品免费| 999精品在线视频| 亚洲一卡2卡3卡4卡5卡精品中文| 日本黄色视频三级网站网址| 这个男人来自地球电影免费观看|