共查询到20条相似文献,搜索用时 31 毫秒
1.
Korkishko Y.N. Fedorov V.A. Laurell F. 《IEEE journal of selected topics in quantum electronics》2000,6(1):132-142
Reflection second-harmonic generation from the polished waveguide end face is used to investigate the second-order nonlinear optical properties of as-exchanged and annealed proton-exchanged (PE) waveguides in different HxLi1-xNbO3 phases. A detailed correlation is done between the nonlinear properties, the processing conditions, the refractive index changes, and the optical losses of the waveguides. It is found that for the direct PE samples, where the β4, β3, and β1 phases are generated at the surface, the nonlinearity in the guide is strongly reduced by more than 85% of its bulk value, while for waveguides prepared in the β2 phase, the nonlinear coefficient is about 55% of the bulk one. A consequence is that the step-like βi-phase PE LiNbO3 waveguides with large refractive index increase are advantageous for efficient SHG in Cherenkov configuration. The nonlinearity, strongly reduced after the initial proton exchange, is found to be restored and even increased after annealing. However, this apparent increase of the nonlinearity is accompanied by a strong degradation of the quality of the second-harmonic generation reflected beam in the region of initial waveguides due to beam scattering. The graded proton exchange technique and dilute melt proton exchange have been shown to produce high-quality waveguides with essentially undergraded nonlinear optical properties. It has been also shown that the nonlinear properties of annealed proton exchanged LiNbO3 waveguides can be effectively recovered by the reverse proton exchange technique. The results obtained are important for the design, fabrication, and optimizing of guided-wave nonlinear optical devices in LiNbO3 相似文献
2.
A theory of dispersion in single-mode symmetric waveguides is presented for phase-matching second harmonic generation (SHG) of the fundamental modes, based on the approximate analytical waveguide theory of Botez. The theory is used to derive new equations for the maximum phase-matching distance allowed when there are random fluctuations in waveguide thicknesses, under critical and noncritical phase-matching conditions. The theory is also used to calculate the overlap integral as a function of the waveguide parameters Vω and V2ω. A new expression is derived for the efficiency of SHG in waveguides in terms of waveguide parameters that can be used to optimize SHG. Theoretical results are presented for typical LiNbO3 and polymer waveguides. Quasi-phase-matched (QPM) waveguides are fabricated from nonlinear optical (NLO) polymers using the techniques of periodic poling and bleaching, and channel waveguides are printed by the bleaching of the NLO polymers. The NLO polymers are characterized for their refractive indexes, optical loss, NLO coefficients, and bleaching characteristics. Phase-matched SHG results are presented for the different fabrication methods over a distance of 0.5 cm, and an assessment is given of the relative strengths and weaknesses of the different fabrication approaches 相似文献
3.
Pelusi M.D. Ta'eed V.G. Libin Fu Magi E. Lamont M.R.E. Madden S. Duk-Yong Choi Bulla D.A.P. Luther-Davies B. Eggleton B.J. 《IEEE journal of selected topics in quantum electronics》2008,14(3):529-539
Ultrahigh nonlinear tapered fiber and planar rib Chalcogenide waveguides have been developed to enable highspeed all-optical signal processing in compact, low-loss optical devices through the use of four-wave mixing (FWM) and cross-phase modulation (XPM) via the ultra fast Kerr effect. Tapering a commercial As2Se3 fiber is shown to reduce its effective core area and enhance the Kerr nonlinearity thereby enabling XPM wavelength conversion of a 40 Gb/s signal in a shorter 16-cm length device that allows a broader wavelength tuning range due to its smaller net chromatic dispersion. Progress toward photonic chip-scale devices is shown by fabricating As2S3 planar rib waveguides exhibiting nonlinearity up to 2080 W-1ldr km-1 and losses as low as 0.05 dB/cm. The material's high refractive index, ensuring more robust confinement of the optical mode, permits a more compact serpentine-shaped rib waveguide of 22.5 cm length on a 7-cm- size chip, which is successfully applied to broadband wavelength conversion of 40-80 Gb/s signals by XPM. A shorter 5-cm length planar waveguide proves most effective for all-optical time-division demultiplexing of a 160 Gb/s signal by FWM and analysis shows its length is near optimum for maximizing FWM in consideration of its dispersion and loss. 相似文献
4.
Chryssou C.E. Di Pasquale F. Pitt C.W. 《IEEE journal of selected topics in quantum electronics》2000,6(1):114-121
Er3+-doped tellurite and Er3+-doped alumina optical waveguide amplifiers are analyzed both as single amplifiers and as elements of 16-channel wavelength-division multiplexing (WDM) systems; their performances are compared with that from Er3+-doped Al/P silica waveguide amplifiers. The amplifier model is based on propagation and population-rate equations and includes both uniform and pair-induced up-conversion mechanisms. It is solved numerically by combining finite elements and the Runge-Kutta algorithm. The analysis predicts that Er3+-doped tellurite waveguides exhibit improved gain characteristics compared with alumina and Al/P silica waveguides. Using Er3+-doped tellurite waveguide amplifiers, it is suggested that 16 WDM channels may be transmitted to a maximum distance of 4250 km. By using in-line notch gain equalizing filters, the maximum transmission distance can be increased to 5250 km 相似文献
5.
This paper reports the progress in the patterning of nonlinear optical crystal lines on a glass surface by laser irradiation techniques. Two techniques for the patterning of crystal lines have been developed, i.e., rare-earth atom heat processing and transition metal atom heat processing, in which continuous-wave lasers such as Nd:YAG laser (wavelength: lambda = 1064 nm) are irradiated onto the glasses containing rare-earth ions such as Sm3+ and Dy3+ or transition metal ions such as Ni2+ and Cu2+. The patterning of lines consisting of nonlinear optical crystals such as beta-BaB2O4, SmxBi1- xBO3, (Sr,Ba)Nb2O6, and LiNbO3 has been achieved. It is clarified from the azimuthal dependence of second harmonic intensities and polarized micro-Raman scattering spectra that nonlinear optical crystals in the lines are highly oriented along the laser scanning direction, i.e., the patterning of single-like crystal lines. It is also possible to pattern two-dimensional crystal bending or curved lines by just changing the laser scanning direction, and such bending crystal lines have a potential for optical waveguides. 相似文献
6.
McDougall S.D. Kowalski O.P. Hamilton C.J. Camacho F. Bocang Qiu Maolong Ke De La Rue R.M. Bryce A.C. Marsh J.H. 《IEEE journal of selected topics in quantum electronics》1998,4(4):636-646
A novel technique for quantum-well intermixing is demonstrated, which has proven a reliable means for obtaining postgrowth shifts in the band edge of a wide range of III-V material systems. The technique relies upon the generation of point defects via plasma induced damage during the deposition of sputtered SiO2, and provides a simple and reliable process for the fabrication of both wavelength tuned lasers and monolithically integrated devices. Wavelength tuned broad area oxide stripe lasers are demonstrated in InGaAs-InAlGaAs, InGaAs-InGaAsP, and GaInP-AlGaInP quantum well systems, and it is shown that low absorption losses are obtained after intermixing. Oxide stripe lasers with integrated slab waveguides have also enabled the production of a narrow single lobed far field (3°) pattern in both InGaAs-InAlGaAs, and GaInP-AlGaInP devices. Extended cavity ridge waveguide lasers operating at 1.5 μm are demonstrated with low loss (α=4.1 cm-1) waveguides, and it is shown that this loss is limited only by free carrier absorption in waveguide cladding layers. In addition, the operation of intermixed multimode interference couplers is demonstrated, where four GaAs-AlGaAs laser amplifiers are monolithically integrated to produce high output powers of 180 mW in a single fundamental mode. The results illustrate that the technique can routinely be used to fabricate low-loss optical interconnects and offers a very promising route toward photonic integration 相似文献
7.
Tzyy-Jiann Wang Way-Seen Wang 《IEEE journal of selected topics in quantum electronics》2000,6(1):94-100
A novel Ni-diffused abrupt waveguide bend on LiNbO3 using proton-exchanged microprism is presented. With the phase delay caused by the microprism, the guided wavefront can be appropriately tilted such that most of the optical power can be kept within the waveguide after passing through the bend corner. The simulated normalized transmitted power of the proposed waveguide bend can be as high as 93.33% for a bend angle of 10°. The effects of microprism parameters are also discussed to facilitate the optimal design of the proposed waveguide bend. The experimental results show that the proton-exchanged microprism on LiNbO3 does significantly enhance the transmitted power 相似文献
8.
《IEEE journal of selected topics in quantum electronics》2008,14(6):1496-1501
9.
Korkishko Yu.N. Fedorov V.A. 《IEEE journal of selected topics in quantum electronics》1996,2(2):187-196
We show that proton exchanged HxLi1-xNbO3 single-crystalline solid solutions exhibit very complex structural chemistry, which is different from those known for powders. Seven crystallographic phases have been identified in HxLi1-xNbO3 layers. Correlation between the crystal structure and the ordinary and extraordinary refractive indices has been experimentally determined which allows us to explain some of the observed optical phenomena and to predict the characteristics of the great variety of proton exchanged waveguides 相似文献
10.
Min-Cheol Oh Hua Zhang Cheng Zhang Erlig H. Yian Chang Tsap B. Chang D. Szep A. Steier W.H. Fetterman H.R. Dalton L.R. 《IEEE journal of selected topics in quantum electronics》2001,7(5):826-835
Based on a nonlinear optical polymer with a highly nonlinear chromophore (CLD) dispersed in an amorphous polycarbonate (APC), we have developed electrooptic (EO) polymer modulators operating at 1550-nm wavelength with low loss and good thermal stability. By incorporating polymer insulation layer, push-pull poling was successfully performed without film damages. We also demonstrated that the propagation loss of the EO polymer waveguide could be reduced as low as 1.2 dB/cm at 1550 nm when the large core waveguide structure was incorporated. The long-term reliabilities of the EO polymer modulator made of CLD/APC polymer were investigated. When the modulator was hermetically sealed in an inert gas, the Vπ change of a Mach-Zehnder modulator was negligible over 30 d of operation with 20-mW exposure to the waveguide input. In the thermal stability measurement, 25% Vπ increase was observed from the sample heated to 60°C over 40 d, though the sample left at room temperature showed no decay of nonlinearity 相似文献
11.
Bogaerts W. Selvaraja S. K. Dumon P. Brouckaert J. De Vos K. Van Thourhout D. Baets R. 《IEEE journal of selected topics in quantum electronics》2010,16(1):33-44
12.
A simple and efficient adaptive mesh generation algorithm is proposed for the full-wave finite-element analysis of optical waveguides using edge/nodal hybrid elements. We employ a local weight defined by a difference between the fundamental and the higher order element solutions. This method can be used for both the guided-mode analysis and the beam-propagation analysis. To show the validity and usefulness of the present scheme, the guided-mode analysis of a rib waveguide and the beam-propagation analysis of a Y-branching polarization converter based on hybrid supermodes are performed 相似文献
13.
Hikita M. Tomaru S. Enbutsu K. Ooba N. Yoshida R. Usai M. Yoshida T. Imamura S. 《IEEE journal of selected topics in quantum electronics》1999,5(5):1237-1242
We describe three different applications of polymeric waveguide films as short-distance optical interconnects. We fabricated the waveguide films, which were 6.5 cm long and mounted in MT-compatible (MTC) connectors by passive alignment, for MM fiber systems with a 50-μm diameter graded index (GI) core. The average insertion loss of these devices was approximately 0.6 dB at 0.85-μm wavelength. We also fabricated waveguide films with a 350 mirror and an MTC connector for use as 90° out-of-plane optical deflectors, and they exhibited an insertion loss of 1 dB. Two silica planar waveguides for single-mode (SM) fiber systems were also connected by a polymeric waveguide film. Low insertion losses were obtained in both MM and SM films designed to be employed as bending waveguides. This reveals their good potential for use as practical short-distance optical interconnects 相似文献
14.
Petrov V. Rotermund F. Noack F. Ringling J. Kittelmann O. Komatsu R. 《IEEE journal of selected topics in quantum electronics》1999,5(6):1532-1542
We review the linear and nonlinear optical properties of crystals transparent near and below 200 nm and suitable for up conversion of femtosecond Ti:sapphire laser sources, β-BaB2O4 , the crystal with the largest birefringence of all presently available materials, is investigated experimentally as a quadrupler by mixing the fundamental and the third harmonic both using a 1-kHz repetition rate Ti:sapphire regenerative amplifier and a 82-MHz mode-locked Ti:sapphire laser. Milliwatt average powers near 200 nm are achieved in both cases. The sub-200-fs pulses at the fourth harmonic are almost bandwidth limited. Sum-frequency generation as a method for upconversion of femtosecond pulses is experimentally studied by mixing the fourth harmonic generated down to 189 nm by the regenerative amplifier with a parametrically generated femtosecond pulse in the infrared. Pulse energies at the microjoule level are produced with LiB 3O5 above 180 nm. Li2B4O7 shows superior performance in the 170-180-nm range, and the shortest wavelength achieved with KB5 O8·4H2O is 166 nm 相似文献
15.
Ostroverkhov V. Ostroverkhova O. Petschek R.G. Singer K.D. Sukhomlinova L. Twieg R.J. 《IEEE journal of selected topics in quantum electronics》2001,7(5):781-792
This paper describes the development and optimization of chiral, nonpolar media with large second-order nonlinear optical responses. We employ molecular engineering, quantum-mechanical sum-over-states theory, and measurements of molecular hyperpolarizability by means of Kleinman-disallowed hyper-Rayleigh scattering in order to understand molecular properties. Then we analyze the appropriate arrangement of the chromophores that produce an optimum axial nonlinear optical medium. Chromophores with large Kleinman disallowed traceless symmetric second-rank tensor hyperpolarizabilities β can be aligned so as to result in large susceptibilities χ(2) in structures that lack polar order. We found that Λ-shaped chromophores with C2v or similar symmetry are good candidates for these materials, as they can exhibit large second-rank components of the hyperpolarizability tensor. A wide variety of techniques can be used to fabricate bulk materials belonging to the chiral nonpolar symmetry groups D∞ and D2. The microscopic chromophore alignment schemes that optimize the nonlinear optical response in such materials are deduced from general symmetry consideration for both molecules and bulk. We also speculate on the possible application of such materials as high-bandwidth spatial light modulators 相似文献
16.
Janz S. Baribeau J.-M. Delage A. Lafontaine H. Mailhot S. Williams R.L. Xu D.-X. Bruce D.M. Jessop P.E. Robillard M. 《IEEE journal of selected topics in quantum electronics》1998,4(6):990-996
The index of refraction for pseudomorphic Si1-xGex layers grown on Si has been measured at wavelengths λ=1310 mn and λ=1550 nm. The refractive index values were obtained from waveguide mode profile measurements on a series of Si-Si1-xGe x-Si waveguides with Gex concentrations between x=0.01 and x=0.1. The index of refraction, n, is significantly larger for light polarized parallel to the growth direction than for light polarized in the plane of the epilayer. This birefringence is consistent with the anisotropic index change predicted using photoelastic theory, given the biaxial strain present in the pseudomorphic Si1-xGe x layers. At all wavelengths and polarizations, n varies linearly with the Ge concentration. The pseudomorphic Si1-xGe x waveguides layer are stable against lattice relaxation during short anneals at 950°C, but exhibit partial relaxation after annealing at 1200°C 相似文献
17.
Rukhlenko I. D. Premaratne M. Agrawal G. P. 《IEEE journal of selected topics in quantum electronics》2010,16(1):200-215
18.
Chollet F. de Labachelerie M. Fujita H. 《IEEE journal of selected topics in quantum electronics》1999,5(1):52-59
We report the design and the realization of an out-of-plane bending structure supporting a waveguide that is used as an optical attenuator and an optical switch. Both devices are based on evanescent field interaction induced by spatial confinement either between two waveguides or between one waveguide and an absorbing medium. The attenuator exhibits typical attenuation of 65 dB/cm. Even if the bad quality of the waveguide has prevented the correct operation of the switch, we show that the attenuation figure establishes the feasibility of a compact evanescent optical coupler with mechanical drive featuring a total length below 1 mm 相似文献
19.
Eggleton B.J. Ahuja A.K. Feder K.S. Headley C. Kerbage C. Mermelstein M.D. Rogers J.A. Steinvurzel P. Westbrook P.S. Windeler R.S. 《IEEE journal of selected topics in quantum electronics》2001,7(3):409-424
An emerging class of fiber waveguide structures is being used to increase the functionality of fiber gratings, enabling new devices critical to the performance of next generation light-wave communications systems. These devices rely on advances in the fabrication of optical fiber waveguides, which go beyond the conventional doped silica design and fall into two general categories: 1) local modifications to the waveguide after fabrication and 2) fibers drawn with modified claddings that include nonsilica regions throughout their length. This paper provides a comprehensive review of emerging fiber waveguide structures that enhance the functionality of optical fiber grating devices. Two examples of technologies that fall into the first category are thin metal films deposited onto the cladding surface, which can be used for thermal tuning and infusion of nonsilica materials into the air regions, which change the waveguide structure and can provide enhanced tunability. The second category is typified by air-silica microstructured optical fibers, which contain air-voids that run along the length of the fiber. These fibers have unique cladding mode properties that can be exploited in fiber grating based devices 相似文献
20.
Reid D.T. Kennedy G.T. Miller A. Sibbett W. Ebrahimzadeh M. 《IEEE journal of selected topics in quantum electronics》1998,4(2):238-248
We describe the operation and characterization of Ti:sapphire laser-pumped femtosecond and picosecond optical parametric oscillators based the new quasi-phase-matched nonlinear materials of periodically poled LiNbO3 and RbTiOAsO4 with broad tunability in the near- to mid-infrared. We discuss the merits of the two materials for use in ultrafast optical parametric oscillators (OPOs) and compare and contrast their properties to the birefringent materials. We demonstrate an extended spectral coverage from <1 μm to >5 μm, pump power thresholds as low as 45 mW, average mid-infrared output powers in excess of 100 mW, and pulse durations of 100-200 fs and 1-2 ps at ~80 MHz repetition rate. We also report the efficient operation of Ti:sapphire-pumped femtosecond OPOs in all-solid-state configurations by utilizing diode-laser-based input pump sources 相似文献