面向谐振式微光学陀螺应用的球形谐振腔DQ乘积优化

基于谐振式光学陀螺高灵敏度、低成本与微型化的发展需求, 为了实现高灵敏度的谐振式微光机电陀螺, 提出了以集成光学微谐振腔领域里高Q值、大直径谐振腔的制作为目标, 应用方向为谐振式光学陀螺的球形光学微谐振腔核心敏感单元. 在实验中以氢火焰作为热源采用熔融法制备球形光学微谐振腔. 通过调节氢气的流量控制氢火焰热源面积, 制备了不同直径(300-2200 μm)的球形谐振腔, 分析了球形谐振腔Q 值、DQ乘积、陀螺灵敏度与谐振腔直径D的对应关系及其原因, 获得了最优参数的面向谐振式光学陀螺的球形谐振腔敏感单元. D=1260 μm时, 球腔品质因数 Q=7.18×10⁷, 得到的最优陀螺灵敏度约为10°/h, 满足商业级应用的需求, 为芯片级、高精度、低成本的新型谐振式光学微腔陀螺的研究奠定了实验基础.     

Observation of microsphere movement driven by optical pulse

A laser beam was coupled into a tapered optical fiber tip with a diameter of about 2.6 μm, and a 46 μm diameter microsphere was propelled by the outgoing optical pulse. With the change of pulse energy from 1.35 to 7.22 μJ, the calculated average velocity of the driven microsphere varied from 0.38 to 10.68 cm/s. The scanning electron microscope images of the fiber tip show that there is no thermal damage during the experiment.     

Q-factor of spherical optical silicon dioxide nanoresonators

The Q-factor of the bound optical modes of silicon dioxide spheres with a radius smaller than one micron has been studied in the visible spectrum, showing that local photonic states with a nonzero orbital momentum yield a thin structure in glow spectra, whose maxima positions depend on the diameters of SiO₂ nanospheres. A theoretical model to calculate the Q-factor of nanoresonators depending on the wavelengths of bound modes and the radius value of spheres has been proposed. It has been shown that the quality of an optical resonator increases as its diameter grows. The Q-factor values have been calculated for the visible light of the order of 10 for spheres smaller than 1 μm in diameter and 10⁶ for spheres of more than 7 μm in diameter. A dependence of bound modes’ radiation propagation outside of the sphere on their wavelengths and orbital momenta has been detected.     

Accurate measurements for cyanic laser wavelengths using resonator interferometry

Accurate measurements are described for resonant wavelengths at 311 μm and 337 μm in the HCN laser using resonator interferometry. Analysis of the theoretical and experimental conditions for laser resonator interferometry indicates that the resonant wavelengths correspond to the medium in which the scanning mirror is displaced.     

Optical properties of large germanium monocrystals

Optical characteristics of germanium monocrystals with a diameter of 150 and 200 mm grown by the Czochralski and directional crystallization methods were studied. We measured spectral transmittance of the monocrystals in the wavelength range of 2.3–25.0 μm, directional transmission and light scattering in the 2.4–3.0 μm range, and noninhomogeneity of the refractive index of monocrystals by the interference technique at 3.39 μm. The measurements were performed on antimony-doped germanium monocrystals with a diameter of 200 mm and thickness of 15 mm (grown by the directional crystallization method) and 18 mm thick (grown by the Czochralski method). Measurements were also performed on a germanium monocrystal with a diameter of 150 mm and thickness of 15 mm grown by the Czochralski method without adding a ligand. The measurement results revealed different optical quality of monocrystals, expressed in the nature and amount of refractive index inhomogeneity, which imposes restrictions on the use of blanks.     

Evaluation of single virus detection through optical biosensor based on microsphere resonator

Shift of resonance frequency in microsphere optical resonator due to attachment of a desirable particle is obtained. Our 3-D finite element numerical method (FEM) simulations’ results show the path of light through microsphere and its variation due to attachment of particle. It is apparent that after attachment of particle to microsphere's surface, light is inclined to pass through the particle. Subsequently, the path of light becomes longer than previous. Because of this phenomenon, the resonance wavelength shifts to longer wavelengths. It is shown that microsphere optical resonator is a prominent biosensor for single virus detection since we applied characteristics of virus for particle in our simulations. Response of this biosensor depends on the characteristics of particle like its radius as we show in this article. Transmission spectrum of fiber which reveals a selected resonance frequency, have been studied in the frequency range of 106.3 to 107 THz under three different sizes of particles. The results show that the amount of frequency shift rises by enhancement of particle's size.     

一种输出三波长超短光脉冲的激光源

利用对撞脉冲锁模非稳腔Ｎｄ：ＹＡＧ激光器，采用ＫＴＰ非线性晶体作腔外倍频，结合受激拉曼散射技术，在一台锁模激光器同时得到１．０６μｍ，０．５３μｍ，０．６３μｍ超短光脉冲的输出。     

Integrated Nd-doped borosilicate glass microsphere laser

A neodymium-doped BK7 glass microsphere laser integrated with a planar ion-exchanged waveguide pumped at 0.8 μm has been demonstrated. The pump radiation was launched by evanescent coupling from the waveguide, and the signal radiation was coupled out through the same waveguide, offering the potential for robustly assembled fully integrated active optical circuits. The dependence of the lasing spectra on pump power and wavelength were studied in detail to clarify the whispering-gallery-mode behavior at the pump and lasing wavelengths.     

Tm~(3+)掺杂Ge-Ga-S玻璃微球-石英光纤锥耦合系统的荧光回廊模特性

以熔融淬冷法自制了Tm~(3+)掺杂Ge-Ga-S硫系玻璃,并以此为基质材料,用漂浮粉料熔融法制备了直径分布为50—200μm的高品质因数(Q10~4)的有源硫系玻璃微球谐振腔.在显微镜下优选出一颗表面质量好、球形度较高、直径为72.84μm的微球,与氢氧焰扫描拉锥法制备的一根腰锥直径为1.93μm的石英光纤锥进行近场耦合.根据基质材料的吸收光谱特性,选用808 nm的半导体激光器作为抽运源.实验测得光纤锥倏逝波场激发出了掺Tm~(3+)硫系玻璃微球在1460 nm附近的荧光回廊模式,其典型共振峰间隔为4.39 nm.实验测得的荧光回廊模式与米氏散射理论计算结果符合度较高(最大误差仅为0.047%),验证了本文提出的掺Tm~(3+)硫系微球制备及耦合工艺的可行性.     

Non-collinear phase matched 4-wave mixing of CO2 and NH3 laser radiation in germanium

4-wave mixing has been demonstrated in room temperature germanium using a TEA CO₂ laser (9.3 μm) and an optically pumped NH₃ laser (12.8 μm) as radiation sources. Non-collinear phase matched emission near 7 μm has been observed with a mixing efficiency close to the calculated value. The extension of this mixing process to generate wavelengths in the important region near 16 μm is discussed.     

The Optical Properties of Polydisperse Glass Microsphere Ensembles in the Infrared Spectral Region

Semitransparent composites with glass microspheres are promising modern materials. In particular, they contribute to the increase of the efficiency of heat-insulating coatings. An experimental study of the transmission and scattering of infrared radiation (at wavelengths from 2 to 25 μm) by a sodium borosilicate glass microsphere powder is presented. The spectra, angular-scattering patterns, and the degree of polarization of scattered radiation were studied.     

Single-input spherical microbubble resonator

A single-input whispering gallery optical microbubble resonator is presented. Spherical microbubbles with diameters less than 100 μm, micrometer-sized wall thicknesses, and a single opening or input were fabricated by heating the tapered tip of a pressurized glass capillary using a CO(2) laser. Optical whispering gallery modes with Q factors of ～10(5) were obtained. The bubbles were filled with water and mode shifts of ～20 GHz were observed. Fano-type resonances were detected when the coupling optical fiber diameter was less than 1 μm, causing the microresonator to switch from being a band-stop filter to a bandpass filter. Larger bubbles with submicrometer wall thickness were also fabricated.     

Compact passively q-switched Nd:YAG laser for 2D micromachining

We present a compact passively q-switched diode end pumped Nd:YAG laser at 1064 nm for 2D micromachining. It consists of a 5.5 cm long plano-concave end pumped resonator carrying a Cr:YAG passive q-switch inside the cavity. With an optical conversion efficiency of 46 and 33% the laser emits 1.4 W in CW and 986 mW in q-switched mode at a current of 2.5 A. After using a 2 mm circular aperture the output is seen in TEM₀₀ mode with a single pulse energy of 5 mJ. The laser produced circular holes of diameter 75 μm in 25 μm thick Tantalum foils. Actual results of 1D and 2D machining are shown along with the diffraction patters of the samples.     

双芯复合格点光子晶体光纤的负色散特性

介绍了一种双芯复合格点负色散光子晶体光纤,其包层是由连续电介质纯硅背景上挖出的两种大小不同的空气孔构成,芯区是由掺锗的高折射率的材料构成。为了实现负色散,还移去了包层中的一圈空气孔。采用频域有限差分法对其负色散特性进行分析表明,通过调整空气孔间距和两种空气孔的尺寸,可以得到不同程度的宽带负色散。当内芯半径取0.95μm,孔间距取2.15μm,大空气孔直径取1.9μm,小空气孔直径取1.1μm时,可在1.55μm处实现宽带负色散,其半峰全宽超过了200 nm。这种光纤的包层中空气孔呈六边形分布,空气孔的尺寸均大于1μm,降低了制作的难度。这种光纤可以用于波分复用光纤通信系统中的宽带色散补偿。     

Ge/Si photodiodes and phototransistors with embedded arrays of germanium quantum dots for fiber-optic communication lines

Photodetectors based on Ge/Si multilayer heterostructures with germanium quantum dots are fabricated for use in fiber-optic communication lines operating in the wavelength range 1.30–1.55 μm. These photodetectors can be embedded in an array of photonic circuit elements on a single silicon chip. The sheet density of germanium quantum dots falls in the range from 0.3 × 10¹² to 1.0 × 10¹² cm^?2, and their lateral size is approximately equal to 10 nm. The heterostructures are grown by molecular-beam epitaxy. For a reverse bias of 1 V, the dark current density reaches 2 × 10^?5 A/cm². This value is the lowest in the data on dark current densities available in the literature for Ge/Si photodetectors at room temperature. The quantum efficiency of photodiodes and phototransistors subjected to illumination from the side of the plane of the p-n junctions is found to be 3% at a wavelength of 1.3 μm. It is demonstrated that the maximum quantum efficiency is achieved for edge-illuminated waveguide structures and can be as high as 21 and 16% at wavelengths of 1.3 and 1.5 μm, respectively.     

Self-Modulation of Scattering Intensity from a Silica Sphere Coated with a Sol-Gel Film Doped with J-Aggregates

A micrometer-sized nonlinear optical resonator constituted of a silica microsphere coated with J-aggregates has been fabricated by the sol-gel process. We determined the scattering light spectrum and discuss the application of the observed effect for the realization of an optical switching element. Optical evaluation of the sphere has been performed in the attenuated-total-reflection (ATR) configuration. We excited a whispering gallery mode and measured the nonlinear ATR signal dependence on excitation intensity. The experimental result agrees very well with the simulation results obtained using the Mie theory and the finite-difference time-domain method taking into account optical Kerr nonlinearity. The permittivity of the film of J-aggregates was measured by ATR method at several wavelengths and the value at the desired wavelength was determined by extrapolation using the Lorentz function.     

Supercontinuum generation at 1.55μm using highly nonlinear photonic crystal fiber for telecommunication and medical applications

In this paper, we present a theoretical calculation of a highly nonlinear germanium (Ge) doped photonic crystal fiber with all-normal group velocity dispersion to design a supercontinuum (SC) light source at 1.55 μm. By doping 3% higher refractive index Ge inside the host silica, the nonlinear coefficient is increased to a value as large as 60.5 W^?1 km^?1 at 1.55 μm. A 10 dB bandwidth of a 120 nm SC spectrum for a 2.5 ps input optical pulse and a 10 dB bandwidth of a 190 nm SC spectrum for a 1.0 ps input optical pulse have been found using the same fiber length of 200m and input optical power of 18 W. The coherent lengths of the generated SC light sources are found to be 8.8 μm for a 2.5 ps input optical pulse and 5.6 μm for a 1.0 ps input optical pulse. Therefore, the highest longitudinal resolution at 1.55 μm is found to be about 4.0 μm for biological tissues.     

Thulium channel waveguide laser in a monoclinic double tungstate with 70% slope efficiency

Laser experiments were performed on buried, ridge-type channel waveguides in an 8 at.?% thulium-doped, yttrium-gadolinium-lutetium codoped monoclinic double tungstate. A maximum slope efficiency of 70% and output powers up to 300 mW about 2.0 μm were obtained in a mirrorless laser resonator, by pumping with a Ti:sapphire laser near 800 nm. To the best of our knowledge, this result represents the most efficient 2 μm channel waveguide laser to date. Lasing is obtained at various wavelengths between 1810 nm and 2037 nm.     

硅薄膜的短波红外光学特性和1.30μm带通滤光片

在短波红外区域(1～3μm),硅薄膜材料因其具有折射率高、透明性好、膜层应力易匹配等诸多优点而得到广泛应用。基于改进后的Sellmeier模型拟合出了制备的硅薄膜的短波红外光学特性,以此为基础,选用硅和二氧化硅两种材料,设计并制备出中心波长在1.30μm,相对带宽2.46%的带通滤光片。利用了硅薄膜在波长小于1.0μm波段的吸收特性较好地扩展了带外截止范围。测量结果表明,具有2个谐振腔的带通滤光片峰值透射率达到85.8%,半功率带宽控制在约32nm,带外截止范围覆盖了波长小于1.75μm的光谱区域。     

掺铒磷酸盐玻璃微球吸收光谱上的形貌共振

利用高温熔融冷却法制备了直径为82．4μm的掺铒磷酸盐玻璃微球，并利用熔融拉丝法制备了锥腰直径为2．3μm的熔锥光纤与其进行耦合，发现了掺铒玻璃微球吸收光谱中出现的等间距分布的滤波谱线。利用光学微球腔理论讨论了玻璃微球吸收光谱中的形貌共振现象，计算出该耦合系统的品质因数为1．31×10^4。利用Mie散射理论计算了谱线的吸收峰位置和峰间间距，计算结果与实验结果相符合。最后比较了两种峰间间距算法的优劣。