In vivo Fourier-domain full-field OCT of the human retina with 1.5 million A-lines/s

In vivo full-field (FF) optical coherence tomography (OCT) images of human retina are presented by using a rapidly tunable laser source in combination with an ultra-high-speed camera. Fourier-domain FF-OCT provided a way to increase the speed of retinal imaging by parallel acquisition of A-scans. Reduced contrast caused by cross talk was observed only below the retinal pigment epithelium. With a 100Hz sweep rate, FF-OCT was fast enough to acquire OCT images with acceptable motion artifacts. FF-OCT allows ultrafast retinal imaging, boosting image speed by a lack of moving parts and a considerably higher irradiation power.     

Applying LED in full-field optical coherence tomography for gastrointestinal endoscopy

Optical coherence tomography (OCT) has become an important medical imaging technology due to its non-invasiveness and high resolution. Full-field optical coherence tomography (FF-OCT) is a scanning scheme especially suitable for en face imaging as it employs a CMOS/CCD device for parallel pixels processing. FF-OCT can also be applied to high-speed endoscopic imaging. Applying cylindrical scanning and a right-angle prism, we successfully obtained a 360° tomography of the inner wall of an intestinal cavity through an FF-OCT system with an LED source. The 10-μm scale resolution enables the early detection of gastrointestinal lesions, which can increase detection rates for esophageal, stomach, or vaginal cancer. All devices used in this system can be integrated by MOEMS technology to contribute to the studies of gastrointestinal medicine and advanced endoscopy technology.     

Tomographic imaging of a suspending single live cell using optical tweezer-combined full-field optical coherence tomography

We propose a label-free depth-resolved tomographic scheme for imaging a single live cell in fluid. This approach utilizes a modified time-domain full-field optical coherence tomography (FF-OCT) system combined with an optical tweezer technique. The optical trap for holding a moving specimen is made by tightly focusing a 1064 nm Q-switching pulsed laser beam with a 1.0 NA microscope objective in the sample arm of the FF-OCT part. By cosharing the probe for both systems, the optical actions of trapping and cellular resolution tomographic imaging could be achieved simultaneously. Feasibility of the combined system is demonstrated by imaging micron-sized polystyrene beads and a living suspension cell in medium.     

Ultrahigh-resolution full-field optical coherence tomography using spatial coherence gating and quasi-monochromatic illumination

We developed an ultrahigh-resolution full-field optical coherence tomography (FF-OCT) microscope that is based on the spatial, rather than the temporal, coherence gating. The microscope is capable of observing three-dimensional microbiological structures as small as 0.4 μm × 0.4 μm × 1.0 μm (xyz) using quasi-monochromatic light and a liquid crystal retarder. Unlike traditional FF-OCT systems, this microscope can be operated in high resolution for any preferable wavelength with minimized defocusing and dispersion effects. High-resolution images of an onion cell are presented.     

超高速摄影中蜂窝结构转镜的设计与力学分析

 提出了蜂窝结构的三面体转镜,对这种新型转镜做了结构设计,并利用3维有限元计算技术,分析了蜂窝结构的三面体铝合金转镜的力学性能。结果表明：对镜面尺寸17.325 mm、轴向长度32.5 mm的三面体铝合金转镜,在5×10 ⁴ r/min转速下,镜面最大变形量为0.547 μm,约为原结构铝合金转镜镜面的16%,与相同结构尺寸的铍转镜镜面变形量处于相同量级;内部最大应力小于原结构铝合金转镜。     

Smart microscope: an adaptive optics learning system for aberration correction in multiphoton confocal microscopy

Off-axis aberrations in a beam-scanning multiphoton confocal microscope are corrected with a deformable mirror. The optimal mirror shape for each pixel is determined by a genetic learning algorithm, in which the second-harmonic or two-photon fluorescence signal from a reference sample is maximized. The speed of the convergence is improved by use of a Zernike polynomial basis for the deformable mirror shape. This adaptive optical correction scheme is implemented in an all-reflective system by use of extremely short (10-fs) optical pulses, and it is shown that the scanning area of an f:1 off-axis parabola can be increased by nine times with this technique.     

主动抛光盘磨制非球面的工艺与面形检测

主动抛光盘技术特别适用于磨制焦比大的深度非球面,能够根据需要对抛光盘面实时地主动变形成偏轴非球面来磨制非球面镜面。它具有较高的磨削速率和较大范围内的自然平滑(无切带)。用计算机控制磨制,可以像加工球面一样来加工一个深度的非球面。介绍了用国内首次研制成功的主动抛光盘对加工直径910mm、焦比F/2的抛物面镜的工艺方法的初步探讨,并给出了抛物面镜的检验方案和检测结果。     

Trapping and cooling a mirror to its quantum mechanical ground state

We propose a technique aimed at cooling a harmonically oscillating mirror to its quantum mechanical ground state starting from room temperature. Our method, which involves the two-sided irradiation of the vibrating mirror inside an optical cavity, combines several advantages over the two-mirror arrangements being used currently. For comparable parameters the three-mirror configuration provides a stiffer trap for the oscillating mirror. Furthermore, it prevents bistability from limiting the use of higher laser powers for mirror trapping, and also partially does so for mirror cooling. Lastly, it improves the isolation of the mirror from classical noise so that the quantum mechanical dynamics of the mirror become easier to observe. These improvements are expected to bring the task of achieving and detecting ground state occupation for the mirror closer to completion.     

The use of circular optical grating for measuring angular rotation of mirrors

This paper explores the feasible use of circular optical grating for measuring the rotation of mirrors that are commonly found in micro-systems. Both theoretical and experimental results show that distortion of the circular grating that is projected onto the mirror surface is a simple function of the angular rotation of the mirror. The circular grating may readily be generated using a standard Michelson interferometer or an LCD projector. Through manipulating the distance between the interferometer and the mirror surface, the diameter of the optical grating may be varied. Furthermore, the additional use of a converging lens enables a significant reduction in the size of the grating: with simple laboratory facility, small circular grating of about 400 μm is achieved for use on micro-systems. With the use of more sophisticated optical elements, the angular rotation of even smaller micro-mirrors may be measured.     

A steerable laser radar system for atmospheric studies

A steerable laser radar suitable for a wide range of atmospheric studies is described. The system incorporates a flashlamp-pumped dye laser and a receiving telescope with a 0.3 m mirror. The steering capability is provided by the use of a 0.61 m by 0.46 m plane mirror for both transmission and reception. Manual and automatic control of the mirror drive is provided, with its angular position being recorded. Digital counting is used in the recording electronics. The performance of the system in measurements over a large range of heights in the atmosphere is illustrated.     

Hybrid output mirror for optically pumped far infrared lasers

A hybrid metallic mesh multilayer dielectric coating mirror has been developed for use as an output mirror for optically pumped far infrared lasers. The metallic mesh provides a high reflectance in the far infrared while the multilayer dielectric coating is chosen to provide a maximum reflectivity at the pump wavelength (10 μm). This hybrid mirror has increased the output power of a CH₃F waveguide laser at 496 μm by a factor of 350 over that obtained with a hole coupling mirror. In addition, this mirror results in a far infrared output beam which has a minimum angular divergence limited only by the particular oscillating transverse waveguide mode (the EH₁₁ mode for this experiment).     

超高速摄影中三面体转镜力学特性的计算机仿真

基于弹性力学空间问题的基本理论与有限元计算技术，建立了转镜力学分析的数值方法，并与四面体钢转镜的计算结果做了对比，表明它能够较为精确地模拟出转镜的强度及其任意点处的位移.利用该方法，计算了目前常用的三面体金属铍转镜和铝合金转镜的稳态强度，得出了转镜镜面变形量及内部应力分布的定量数值.结果表明,金属铍转镜在强度和镜面变形两方面均优于铝合金转镜.     

Ultralong 250 km remote sensor system based on a fiber loop mirror interrogated by an optical time-domain reflectometer

A 253?km ultralong remote displacement sensor system based on a fiber loop mirror interrogated by a commercial optical time-domain reflectometer is proposed and experimentally demonstrated. The use of a fiber loop mirror increases the signal-to-noise ratio, allowing the system to interrogate sensors placed 253?km away from the monitoring system without using any optical amplification. The displacement sensor was based on a long period grating spliced inside of the loop mirror, which modifies the mirror reflectivity accordingly to the applied displacement.     

Diamagnetic levitation of a milligram-scale silica using permanent magnets for the use in a macroscopic quantum measurement

Verification of macroscopic quantum mechanics requires that the position measurement accuracy of mirrors of various mass scales reach the Standard Quantum Limit (SQL) derived from Heisenberg's uncertainty principle. At mg-scale, thermal noise of the suspension wire of the mirror is an issue to reach the SQL. We propose to use a magnetic levitation system consisting of permanent magnets and yokes, noting the fact that a silica mirror is diamagnetic, and have succeeded in the experimental verification to levitate a 0.1-1 mg silica mass. This is the first demonstration of the levitation system with this mass scale and this magnetic susceptibility scale using permanent magnets as far as we know. We also estimated major noise sources for a 0.1 mg silica mirror and found the noise level to be lower than the SQL at 400 Hz-18 kHz. In conclusion, the levitation system of a mg-scale mirror for the use in a macroscopic quantum measurement was realized.     

舞台屏幕激光图案构成浅析

本文从转镜的光迹出发,建立起一个简单的数学模型。由微机模拟的图象与实际观察到的转镜激光图象基本相符。文中也探讨了转镜的主要参数与图象的关系,为转镜系统的设计和使用提供依据。     

快速倾斜镜的建模与模型参考自适应控制技术研究

通过实验建模方法建立快速倾斜镜四阶模型,采用routh降阶方法将快速倾斜镜四阶模型降为二阶模型,数学仿真验证了简化模型较好的反映了原系统主要性能。提出的建模方法对快速倾斜镜的准确建模是简便、有效的,为现代控制理论的研究提供了数学基础。在建立二阶模型的基础上,设计了基于李亚普诺夫稳定理论的模型参考自适应控制器,并进行了全系统的计算机仿真。仿真结果表明,针对快速倾斜提出的基于李亚普诺夫稳定理论的模型参考自适应控制器能够减小系统稳态误差、提高系统响应速度。研究结果为倾斜镜的快速控制提供了一种新的思路。     

一种软启停正负双直流电源的设计

变形镜驱动器正负电源加电或者断电不同步,导致其在加电瞬间或者断电瞬间,输出端会输出一个-38.0V和86.0V的冲击电压,这个冲击电压使得变形镜在未开始工作时就产生了较为严重的面形畸变,为此研制了基于微处理器的软启停直流电源,它输出两路按一定时序变化的输出电压作为后续两个继电器的控制端,再通过这两个继电器分别控制变形镜驱动器正、负电源的导断,从而使得变形镜驱动器的正负电源同时加载或者卸载。在硬件平台了进行了实验验证,结果表明,使用软启停直流电源后,变形镜驱动器加电瞬间或断电瞬间,其产生的脉冲电压的峰-峰不超过0.45V,远远小于未使用软启停直流电源前的冲击电压,满足了系统的设计要求。     

High-order harmonic generation by nonlinear reflection of an intense high-contrast laser pulse on a plasma

We demonstrate the use of a plasma mirror to obtain 60-fs 10-TW laser pulses with a temporal contrast of 10(8) on a nanosecond time scale and 10(6) on a picosecond time scale, and we use these high-contrast pulses to generate high harmonics by nonlinear reflection on a plasma with a steep electronic density gradient. Well-collimated harmonics up to 20th order are observed for a laser intensity of approximately equal to 3 x 10(17) W/cm2, whereas no harmonics are obtained without the plasma mirror.     

1064nm角立方反射镜的偏振特性分析

利用TFCalc3.5薄膜设计软件设计出了对1064nm和500nm附近双波长高反射的理想膜系,并用琼斯算法对由1064nm高反射镜组成的角立方反射镜(外反射)的偏振特性进行了详细的分析与计算,得到了各种情况下角立方反射镜的本征值和本征向量,并分析得出了1064nm高反射镜的位相延迟δ=180°时,任意偏振状态的光经角立方反射镜后偏振状态保持不变。     

Unstable resonator and output-coupling design study for diffraction radiation generator near-mm sources

Configurations of unstable resonators that could be used for diffraction radiation generators (DRG's) are presented. The output coupling of a negative branch unstable resonator exhibits an extreme sensitivity to mirror radius and appears to be unsuited to DRG use. The positive branch resonator does not exhibit this sensitivity to mirror radius, and the mirror radii that are needed to give output couplings of a few percent appear practical.Work conducted at the Harry Diamond Laboratories.