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1.
Demonstrates a narrowband (≈1 nm) LiNbO3 acoustically tunable optical filter with a tuning range adequate to span the 1.3-1.55 μm wavelength range, exploiting the considerable advantages of an unconventional x -cut design 相似文献
2.
A TE-TM mode converter, useful at either 0.632 or 0.840 μm, has been fabricated on y -cut LiNbO3 by Ti indiffusion with the channel waveguide placed parallel to the z -axis. For TE polarized input, the maximum TM modulation depth is 97 percent at 0.632 μm with a 5-V (pp) drive and 99 percent at 0.840 μm with a 12-V (pp) drive. A similar device operating at 1.3 μm displays 98-percent TE-TM switching at 68 V. Operation involves only coplanar electrodes placed alongside the channel acting on the r 61 electrooptic coefficient. A separately deposited buffer layer is unnecessary. Testing indicates a substantially greater tolerance to electrode misalignment than afforded by similar structures formed in x -cut substrates. Data illustrating immunity to photorefractive drift in the presence of a DC bias voltage is presented for 0.840-μm wavelength operation 相似文献
3.
Proton-exchanged Z -cut LiNbO3 planar waveguides formed using phosphoric acid were characterized optically. The refractive index profile and the diffusion parameters were studied systematically. These waveguides have propagation losses of less than 1 dB/cm and exhibit properties that are different from those obtained using benzoic acid. The index profile is not a simple step function and can be modeled accurately by a polynomial expression. A maximum surface index increase of 0.145 was measured at a 0.633-μm wavelength. The diffusion constant D 0 and the activation energy Q for the proton-exchange process using this acid were found to be 6.43×108 μm2/h and 82.91 kJ/mol, respectively. The annealing properties of these waveguides were also established, and the effects of annealing on surface index change and waveguide depth increase were found to follow a power-law relationship 相似文献
4.
A single-stage low-sidelobe weighted-coupled integrated acoustooptic tunable filter (IAOTF) operating at the optical wavelength of 1.31 μm has been realized on a Y -cut X -propagating LiNbO3 substrate for the first time. The weighted-coupling, which enabled the achievement of low-sidelobe levels, was facilitated by focused surface acoustic waves generated by a curved interdigital transducer. First sidelobe levels as low as -17.6 dB have been obtained. Optical bandwidth of 4 nm and tuning range of 170 nm for an interaction length of 6 mm were also accomplished 相似文献
5.
The first demonstration of Bragg reflector grating filters in Ti:LiNbO3 single-mode channel guides is reported. Filter bandwidths as narrow as 0.14 nm centred at 1.476 μm have been achieved for TE polarisation in Y -cut (X -propagating) material 相似文献
6.
Jiang P. Zhou F. Laybourn P.J.R. De La Rue R.M. 《Photonics Technology Letters, IEEE》1992,4(8):881-883
Buried optical waveguide polarizers on LiNbO3 have been realized by titanium indiffusion, followed by proton-exchange and annealing. The proton-exchange process decreases the ordinary refractive index and so modifies the index profile of the titanium indiffused waveguide. The measured intensity profile is in good agreement with calculation. An aluminum film absorbs the surface TM mode on z -cut LiNbO3, leaving a buried nearly symmetric TE mode with lower optical loss than surface-guided TE modes. The extinction ratio obtained is estimated to be greater than 50 dB/cm at 0.633 μm 相似文献
7.
A wavelength-tunable, single-frequency GaInAsP-InP laser diode using an intracavity electrooptic LiNbO3 crystal as the wavelength selective component is discussed. Wavelength tuning is achieved by applying a driving voltage on the crystal electrodes. First results indicate a tuning rate of 1 GHz/V over a tuning range of about 4 nm. This performance was obtained using a nonoptimized X -cut, Z -propagating LiNbO3 crystal. A potential tuning rate of 6.5 GHz/V is possible with reasonable improvements 相似文献
8.
An LiNbO3 optical integrated circuit pigtailed with two single-mode fibres, which allows time-division two-dimensional velocity measurement, is discussed. To detect time-division multiplexed beat signals corresponding to velocity components v X and v γ of a moving object, a waveguide switch is integrated on a Z -propagating LiNbO3 substrate of 28×7 mm2 in addition to a waveguide interferometer with a frequency shifter. In the optical IC, either v X or v γ could be measured selectively with signal-to-noise ratio of 20 dB by driving an electronic gate placed after a photodiode in synchronization with the waveguide switch 相似文献
9.
Optimal pump wavelength in the4I 15/2-4I 13/2 absorption band for efficient Er3+-doped fiberamplifiers
Zyskind J.L. Giles C.R. Desurvire E. Simpson J.R. 《Photonics Technology Letters, IEEE》1989,1(12):428-430
The authors report the measured gain of a highly efficient erbium-doped fiber amplifier pumped at wavelengths between 1.46 and 1.51 μm. The optimal pump wavelength, λopt, was determined to be 1.475 μm. At this wavelength, the maximum gain coefficients for signals at 1.531 and 1.544 μm were 2.3 and 2.6 dB/mW, respectively. At λopt, high gains ranging from 32 dB at pump power P p=20 mW up to 40 dB at P p=80 mW were obtained. These modest pump powers are within the capabilities of currently available 1.48-μm diode lasers. The width about λopt for 3-dB gain variation exceeded 27 nm for P p=10 mW and 40 nm for P p >20 mW. With this weak dependence on pump wavelength, single-longitudinal-mode lasers do not have a significant advantage over practical Fabry-Perot multimode pump lasers 相似文献
10.
The magnitudes of linear electrooptic coefficients r 13 and r 33 in Zn:LiTaO3 repoled channel waveguides are reported. The measurements were made at 0.633-μm wavelength using a Fabry-Perot interferometer. The waveguides were produced by diffusion from the vapor phase at a temperature above the Curie temperature. For full recovery of the Pockels effect, an electric field of 200 V/cm is needed during repoling. The measured values of r 13 and r 33 at 32-MHz modulation frequency are 7.2 and 30.3 pm/V, respectively. The difference between unclamped and clamped coefficients is comparable to that from bulk crystals. Measurements were also made on Ti:LiNbO3 waveguides that did not require repoling, and good agreement with bulk crystal values was obtained 相似文献
11.
An electrooptic switch that is insensitive to parameter tolerances is proposed for use in crossbar switching arrays. It makes use of intrinsically mismatched and tapered directional couplers and allows the realization of switching arrays with the same switching voltage for each element. Computations are carried out to verify a realization with Ti:LiNbO3 waveguides and to compare the latter with conventional directional couplers. Switching elements on Z -cut LiNbO3 with a crosstalk of -27 dB for zero voltage and a switching voltage of 27.5 V have been realized for use at 1.3 μm 相似文献
12.
Kawano K. Kitoh T. Jumonji H. Nozawa T. Yanagibashi M. Suzuki T. 《Microwave Theory and Techniques》1991,39(9):1595-1601
Hybrid-mode and quasi-TEM analyses are carried out for coplanar waveguide traveling-wave electrodes applicable to z -cut Ti:LiNbO3 optical modulators. The analyses are based on the spectral-domain approach. The microwave effective index and the characteristic impedance are clarified, together with the microwave conductor loss. These are incorporated to accurately predict the modulator characteristics. It is shown that these characteristics can be greatly improved by employing a thicker buffer layer. High-speed and low-driving-power Ti:LiNbO3 optical modulators are realized at 1.52 μm wavelength. Agreement between the calculated and measured results is good 相似文献
13.
Ashley P.R. Chang W.S.C. Buchal C.J. Thomas D.K. 《Lightwave Technology, Journal of》1989,7(5):855-862
Electrooptic modulators in Ti-ion-implanted LiNbO3 waveguides are discussed. Low loss (<1-dB/cm) planar and channel waveguides were fabricated and compared to indiffused waveguides. Higher Δn values are obtained, allowing smaller waveguide geometries and tighter mode confinement. Wavelengths of 0.85 and 1.3 μm are used. The small mode profiles resulting from the Ti doses up to 4×1017 Ti/cm2 resulted in V -L products of 8.8 V-mm at 0.85 μm and 20 V-mm at 1.3 μm. These values are lower than any previously reported for a Mach-Zehnder modulator using a buffer layer. Comparison of diffused and implanted waveguide modulators indicated that modular efficiency can be optimized by electrode gap spacing and enhanced with smaller mode profiles achievable in implanted guides 相似文献
14.
The principle of the wavelength-dependent two-mode interference (TMI) in guided wave devices is utilized to build up integrated-optic dual-channel wavelength-division multi-/demultiplexers (WDM) for single-mode systems. The device characteristics are analyzed by analytical and numerical methods where special emphasis is given to the wavelength dependence of the channel spacing. These devices are fabricated by titanium indiffusion into X -cut and Y - and Z -propagating LiNbO3, where the Z -propagating configuration is preferred for polarization independent operation. In the wavelength range between 1.3 and 1.6 μm, insertion losses (fiber-waveguide-fiber) below 3 dB, channel spacings of 30-40 nm, and far-end crosstalk values of 26-40 dB are achieved. The measured low temperature sensitivity of the wavelength shift of 5.6×10-2 nm/°C and the possibility of electrooptic tuning at a rate of 2.5 nm/V allow the realization of high performance devices at reduced fabrication tolerances 相似文献
15.
Minority-carrier electron lifetime, mobility and diffusion length in heavily doped p-type Si were measured at 296 and 77 K. It was found that a 296 K μn (pSi)≈μn (nSi) for N AA≲5×1018 cm-3, while μn (pSi)/μn (nSi)≈1 to 2.7 for higher dopings. The results also show that for N AA≲3×1019 cm-3, D (pSi) at 77 K is smaller than that at 296 K, while for higher dopings D n (pSi) is larger at 77 K than at 296 K. μn (pSi) at 77 K increases with the increasing doping above N AA>3×1018 cm-3, in contrast to the opposite dependence for μn (nSi) in n+ Si 相似文献
16.
An integrated optical frequency shifter that utilizes guided-wave acoustooptic Bragg diffractions in cascade from two tilted- and counterpropagating-surface acoustic waves is reported. The doubly and frequency-shifted diffracted light propagates in a fixed direction, but spatially resolved from the incident light, irrespective of the magnitude of frequency tuning. A device fabricated in a Y -cut LiNbO3 planar waveguide has demonstrated desirable characteristics, including single-sideband suppressed-carrier properties, a frequency shift centered at 1 GHz, a tunable bandwidth of 165 MHz, a linear dynamic range greater than 41 dB, and high efficiency at the optical wavelength of 0.63 μm. These preliminary results suggest that a compact integrated acoustooptic frequency shifter module capable of multigigahertz center frequency and gigahertz bandwidth can be realized in a common LiNBO3 substrate 0.2 cm×1.0 cm×1.5 cm in size 相似文献
17.
Measurements were made of the temperature dependence (between 23 and 65°C) of the phase-matching angle &thetas;pm for type I frequency doubling of 1064-nm laser light in lithium iodate (LiIO3). The measured value of d &thetas;pm/dT is -14.7±1 μrad/°C, which corresponds to a thermal sensitivity βT =0.24±0.02 cm-1/°C for this process. Also calculated is a value of d &thetas;pm/dT using experimentally determined thermooptic data available in the literature. The calculated value of d &thetas;pm/dT is -31±18 μrad/°C using literature values of n and dn /dT for LiIO3. The extreme sensitivity of the calculated value of d &thetas;pm/dT to small errors in the thermooptic coefficients may be the reason for this discrepancy 相似文献
18.
Canarelli P. Benko Z. Hielscher A.K. Curl R.F. Tittel F.K. 《Quantum Electronics, IEEE Journal of》1992,28(1):52-55
The nonlinear optical characteristics of AgGaS2 were investigated by measuring visible parametric fluorescence with a pump wavelength of 600 nm. A value of d 36 [AgGaS2 ]=31±5×10-12 m/V for the nonlinear coefficient was determined. The temperature dependence of phase matching up to 100°C was studied. A significant temperature effect, although much smaller than for LiNbO3, was found and results in a change in the infrared difference frequency generated of ~0.6 cm-1 -°C-1 相似文献
19.
A simple relationship between the inductance matrix and the auxiliary capacitance matrix is given. For a multiconductor transmission line consisting of N c conducting cylinders in inhomogeneous media consisting of N d homogeneous regions with permeabilities μi and permittivities ϵ i, the inductance matrix [L ] for the line is obtained by solving the magnetostatic problem of N c conductors in N d regions with permeabilities μ i. The capacitance matrix [C ] for the line is obtained by solving the electrostatic problem of N c conductors in N d regions with permittivities ϵ i. It is shown that [L ]=μ0ϵ0[C '] -1, where [C '] is the capacitance matrix of an auxiliary electrostatic problem of N c conductors in N d regions with relative permittivities set equal to the reciprocals of the relative permeabilities of the magnetostatic problem, i.e. ϵ' i/ϵ0=μ0/μi 相似文献
20.
Lee W.-S. Enoki T. Yamahata S. Matsuoka Y. Ishibashi T. 《Electron Devices, IEEE Transactions on》1992,39(12):2694-2700
A self-aligned process is developed to obtain submicrometer high-performance AlGaAs/GaAs heterojunction bipolar transistors (HBTs) which can maintain a high current gain for emitter sizes on the order of 1 μm2. The major features of the process are incorporation of an AlGaAs surface passivation structure around the entire emitter-base junction periphery to reduce surface recombination and reliable removal of base metal (Ti/W) deposits from the sidewall by electron cyclotron resonance (ECR) plasma deposition of oxide and ECR plasma etching by NF3. A DC current gain of more than 30 can be obtained for HBTs with an emitter-base junction area of 0.5×2 μm2 at submilliampere collector currents. The maximum f T and f max obtained from a 0.5×2 μm2 emitter HBT are 46 and 42 GHz, respectively at I C=1.5 and more than 20 GHz even at I C=0.1 mA 相似文献