光开关玻璃的飞秒光学开关特性

通过在碲玻璃中添加重金属离子,尝试制作了具有较大的非线性折射率、时间响应快、吸收小的光开关玻璃。采用超快飞秒光克尔门技术对光开关玻璃的光克尔信号进行测试,测试结果显示,光开关玻璃的光克尔信号对称性好,信号半高宽度达到~225 fs,三阶非线性极化率达到~0.810-20 m2/V2,透过率达到70%~80%;研制的光开关玻璃为皮秒和飞秒光开光材料的选取提供了依据。     

Optical Kerr shutter performance of a solution of organic nonlinearoptical material

An optical Kerr shutter with much higher efficiency than the conventional CS₂ liquid is demonstrated, utilizing a solution of π-conjugated monomer material. Third-order nonlinear optical susceptibility χ⁽³⁾ of the solution is evaluated by the efficiency of the Kerr shutter operation. The χ⁽³⁾ value of the solution depends on the molecular density, the molecular orientation behavior, and the dielectric constant of the solvent. To utilize these effects most efficiently, 4'-dimethylamino-N-methyl-4-stilbazolium methylsulfate is dissolved in formamide to the saturation concentration. This results in χ⁽³⁾ =3.0×10^-12 esu and a Kerr shutter transmission of four times that of CS₂     

超短光脉冲的超高速照象

我们提出并研制成了一种旋光色散共线光克尔快门,利用这种新型快门和迭层玻璃堆分束取样技术已成功地将以光速飞行的超短绿光脉冲做了照相记录。     

10 Gbit/s all-optical regenerator

A 10 Gbit/s optical data stream has been regenerated all-optically by clock recovery and remodulation. The regenerator consists of a fibre ring laser, modelocked by the incoming data stream, and a Kerr shutter acting as an all-optical AND gate to recode the ring laser pulses with the incoming data. Error ratio measurements for an all-optical regenerator are presented for the first time and the future potential of all-optical regeneration is discussed     

Third order autocorrelation study of amplified subpicosecond laser pulses

We have used the well-known optical Kerr effect shutter method to determine the temporal width and shape of subpicosecond pulses issued from a passively mode-locked CW dye laser, feeding a three stage amplifier. This technique corresponds to a third order correlation measurement and thus yields information on the pulse profile and especially about a possible asymmetry. The accuracy of results greatly benefits from the large dynamic range that reaches 10³.     

Ultrafast all-optical switching using highly nonlinear chalcogenideglass fiber

Ultrafast all-optical switching with a switching power of 14 W was demonstrated in a Kerr shutter configuration using a single-mode As₂S₃-based glass fiber only 48 cm long. The nonlinear refractive index of the fiber was evaluated from the switching characteristics to be n₂=4.2×10^-14 (cm²/W), which is higher by two orders of magnitude than silica glass fiber     

Polarization Dependence of Femtosecond Optical Kerr Signals in Bismuth Glasses

Using the optical Kerr shutter (OKS) technique with an 800-nm femtosecond laser, we demonstrated that the response time of the glass was less than 85 fs. The nonlinear refractive-index of Bi₂O₃-B₂O₃-SiO₂ (BI) oxide glass was estimated to be about 2.93times10^{- 15}cm²/W. By measuring the dependence of the OKS signals on the pump power and on the polarization angle between pump and probe beams, we found that the OKS signals arose mainly from the photoinduced birefringence effect, and the polarization dependence of the signals was dependent on the intensity ratio of the pump beam to the probe beam.     

光克尔快门中强绿光的自开门现象

本文报导了在光克尔快门中强绿光自开门现象,初步分析了自感应退偏振的成因。     

Applications of highly nonlinear chalcogenide glass fibers inultrafast all-optical switches

Applications of chalcogenide glass fibers in ultrafast all-optical switches have been investigated. Ultrafast all-optical switching has been accomplished in an optical Kerr shutter configuration using As₂S₃-based glass fiber. The nonlinear refractive index of the As₂S₃-based glass is estimated to be n₂=4.0×10^-14 (cm²/W ), which is higher by two orders of magnitude than that of silica glass fiber. Nonlinear absorption due to two-photon absorption has been revealed to be negligible, and up to a 2π-phase shift has been obtained. Switching speed and switching power were investigated experimentally and through calculations. A switching time of 12 ps and a switching power of 5 W can be achieved using a 10-ps gate pulse and only a 1-m chalcogenide glass fiber. However, signal transformation due to cross-phase modulation and group velocity dispersion is not negligible for shorter gate pulses. Lower switching power is possible by reducing the transmission loss and the core area and by optimizing the driving conditions     

Integrated electronic shutter for back-illuminated charge-coupleddevices

A novel electronic shutter has been integrated into the structure of a back-illuminated frame-transfer charge-coupled device (CCD) to permit short optical exposure times and to reduce the smear that occurs during the transfer of an image from the CCD detection area. The shutter consists of an n⁺ shutter drain placed in the vertical channel stop regions and stepped p-type buried layers formed by a high-energy implantation (1.0-1.5 MeV) located between the CCD n-type buried channel the and p substrate. These structures create electric fields that direct the photoelectrons to either the CCD detection region or the n⁺ shutter drain. The ratio of photons detected with the shutter open to photons detected with the shutter closed has been measured to be greater than 75000 for wavelengths below 540 nm. The corresponding shutter rise and fall times are less than 55 ns     

High-Resolution Optical Sampling of 640-Gb/s Data Using Four-Wave Mixing in Dispersion-Engineered Highly Nonlinear As$_2$S $_3$ Planar Waveguides

We present the first demonstration of an optical sampling system, using the optical Kerr effect in a chip-scale device, enabling combined capability for femtosecond resolution and broadband signal wavelength tunability. A temporal resolution ${ ≪ }500$ fs is achieved using four-wave mixing in a 7-cm-short chalcogenide planar waveguide. The use of a short length, dispersion-shifted waveguide with ultrahigh nonlinearity ($10^4;{rm W}^{-1}{cdot}{rm{km}}^{-1}$) enables high-resolution optical sampling without the detrimental effect of chromatic dispersion on the temporal distortion of the signal and sampling pulses, as well as their phase mismatch. Using the device, we successfully monitor a 640-Gb/s optical time-division multiplexing (OTDM) datastream, showcasing its potential for integrated chip-based monitoring of signals at bitrates approaching and beyond Tb/s. We discuss fundamental limitations and potential improvements.      

Measurement of quadratic electro-optic effect in polydiacetylene optical waveguide

Planar optical waveguides of the soluble polydiacetylene 9-SMBU were formed by dip-coating on silicon substrates. The quadratic electro-optic (Kerr) response was measured by guided wave polarisation interferometry. The effective electro-optic coefficient was found to be 3.7*10/sup -20/ m/sup 2/V/sup -2/ at a wavelength of 1.3 mu m.<>     

A novel optical accelerometer

A novel accelerometer based on a PIN photo-detector and a micro-machined cantilever-beam-supported optical shutter with seismic mass has been designed, fabricated, and tested. Anisotropic wet etching of 〈110〉 orientation silicon in KOH is used to fabricate an optical shutter consisting of evenly spaced vertically etched slots. The shutter, which also constitutes the seismic mass of the accelerometer, is suspended by two cantilever beams. The special structure of the device and the high aspect ratio of the cantilever beams (7.5) permit freedom of the movement for the proof mass (the shutter) on the ±X axis only. The actual size of the device is 3×4 mm and its amplified output varies linearly from -3.6 V to +3.6 V for accelerations from -84 g to +84 g. The measured resonant frequency of the device is 3.2 KHz. A dual diode structure is chosen for the photo-detector to compensate for temperature drift and the amplified output voltage changes by less than 40 mV for a temperature variation from 25°C to 50°C     

Ultrafast all-optical switching utilizing the optical Kerr effectin polarization-maintaining single-mode fibers

An ultrafast all-optical switching scheme utilizing the optical Kerr effect in two birefringent fibers concatenated with each fast axis crossed is proposed. Stable optical Kerr modulation and all-optical demultiplexing of an ultrashort (30 p.s.) optical pulse train at 1.97 GHz from a gain-switched distributed-feedback laser diode (DFB LD) have been sufficiently demonstrated using CW mode-locking Nd:YAG laser pulses as a pump. Switching speed and required pump powers are studied in terms of fiber bandwidth due to fiber birefringence, and combined effects of chromatic and polarization dispersions on Kerr modulation profiles. By utilizing the optical Kerr modulation properties in the presence of dispersions, the nondiagonal yx component of the nonlinear refractive index is also determined to be 0.34 relative to the diagonal component xx. The intrinsic stability and ultimate switching capabilities are discussed     

光纤共振喇曼光谱法探测水中超痕量生物分子

水中微量生物分子的探测、识别和控制研究是很重要的课题。采用光纤内共振喇曼光谱法,可以提高喇曼光谱的强度109倍。把少量β胡萝卜素溶于吡啶与水的混合液体,充入空心光纤中构成液芯光纤,用514.5nm,30mW激光激发,获得了浓度为10-7mol/L～10-9mol/L的β胡萝卜素喇曼光谱。该技术为研究水中微量生物分子提供了一种新的实验方法。     

Ultrahigh-speed photography of picosecond light pulses

A new technique for the display of picosecond light pulses is presented. Ultrashort (6 ps) green light pulses passing through a light-scattering medium are photographed from the side by a camera positioned behind a shutter of 10-ps framing time. The shutter is an ultrafast Kerr cell driven by infrared pulses 8 ps in duration. Color photographs show a bright spot on a dark background, revealing the unambiguous presence of well-isolated picosecond light pulses. The shape of the spot is the result of a convolution involving the three-dimensional shape of the green pulse and the time transmission function of the shutter, this function being dictated by the shape of the infrared pulse. The experiment indicates that a new technique for visualizing light pulses consists in simply observing their flight through a scattering medium from behind an ultrafast shutter having a framing time equal to the time resolution desired. The new technique has many advantages over the two-photon fluorescence display technique, such as higher sensitivity, wider spectral range, and easier interpretation. The ultrafast camera also can be used for the photographic measurement of ultrashort relaxation times in dielectrics and in fluorescent dyes.     

AlN微环谐振腔倍频程孤子光频梳（特邀）

基于光学微谐振腔的自参考耗散克尔孤子(Dissipative Kerr Solitons, DKSs)有广泛的应用，如频率合成器、相干通信、天文光谱仪校准、精密测量、光学时钟、双梳光谱学等。倍频程DKS已在氮化硅和铌酸锂微谐振腔中实现，笔者提出了一种在氮化铝(AlN)微环谐振腔中通过单一泵浦直接产生倍频程DKS的简单方案。通过将两个谐振频率相近的模式TE₀₀ 和TE₁₀分别作为泵浦谐振和辅助谐振模式，红失谐侧的辅助模式TE₁₀可以有效地平衡孤子形成过程中的热拖曳效应。慢速扫描泵浦光波长可获得稳定的倍频程展宽的孤子梳，带宽为1100~2300 nm，孤子存在范围最大为10.4 GHz(83 pm)。这是首次在AlN平台上获得倍频程展宽的克尔光孤子。该方案在单一泵浦源下就可以获得稳定的倍频程光孤子以及宽的孤子访问窗口，不同于其他方案需要额外引入复杂的控制手段和设备。     

Growth of metanitroaniline film crystal with controlled orientation for optical waveguide second-harmonic generation

The use of organic molecular crystals with large second-order nonlinear optical susceptibilities for implementing compact waveguide second-harmonic generation devices is addressed. The growth of metanitroaniline film crystal in a planar capillary with a channel/taper structure for single seed formation by zone melting recrystallization using a ridge heater is presented. Single-crystal film (5*15 mm/sup 2/, approximately 2- mu m thickness) was obtained with reproducible crystallographic orientation control. Cerenkov-radiation-type waveguide second-harmonic generation is demonstrated.<>     

谐振式空心光子带隙光纤陀螺中的光克尔效应

谐振式光纤陀螺(PROG)采用空心光子带隙(HCPBG)光纤后,光克尔效应引入的系统漂移将会与普通单模光纤(SMF)谐振式陀螺系统中的有所不同。为了研究谐振式空心光子带隙光纤陀螺中光克尔效应的变化情况,采用光场叠加的方法,从理论上分析谐振式空心光子带隙光纤陀螺中的光克尔效应,同时针对光克尔效应引入的系统漂移进行了数值仿真,并且与普通单模光纤谐振腔陀螺中的光克尔效应进行对比。理论计算表明,采用空心光子带隙光纤的谐振式光纤陀螺比采用普通单模光纤谐振式陀螺的光克尔效应有明显的降低,在光源线宽不变时,不同光纤环长度对应的光克尔效应引起的旋转角速度漂移前者比后者降低了1~2个数量级。     

CMOS image sensor with NMOS-only global shutter and enhanced responsivity

Most CMOS image sensors today use the rolling shutter approach to control the integration time. This pixel architecture is advantageous where minimal pixel size is required to increase resolution or reduce over all chip size. For imaging of a fast moving object or when used with pulsed illumination, the rolling shutter approach is not suitable since it leads to severe distortion. Therefore, these applications require image sensors with a global shutter pixel architecture, which incorporates a sample-and-hold element in each pixel. Due to the optical exposure of the in-pixel storage element, shutter leakage is critical. First approaches which use separate wells in the pixel to isolate the storage node from the photodiode showed good shutter efficiency, but are bulky and led to large pixels with poor fill factor and bad responsivity. This paper presents an NMOS-only pixel with a global shutter and subthreshold operation of the NMOS sample-and-hold transistor to increase optical responsivity by a factor of five to 9 /spl upsi/V/photon, including fill factor.