Diffused Lithium Niobate Research Articles

An Integrated Photonic Electric-Field Sensor Utilizing a 1 × 2 YBB Mach-Zehnder Interferometric Modulator with a Titanium-Diffused Lithium Niobate Waveguide and a Dipole Patch Antenna

We studied photonic electric-field sensors using a 1 × 2 YBB-MZI modulator composed of two complementary outputs and a 3 dB directional coupler based on the electro-optic effect and titanium diffused lithium–niobate optical waveguides. The measured DC switching voltage and extinction ratio at the wavelength 1.3 μm were ~16.6 V and ~14.7 dB, respectively. The minimum detectable fields were ~1.12 V/m and ~3.3 V/m, corresponding to the ~22 dB and ~18 dB dynamic ranges of ~10 MHz and 50 MHz, respectively, for an rf power of 20 dBm. The sensor shows an almost linear response to the applied electric-field strength within the range of 0.29 V/m to 29.8 V/m.

Performance Evaluation and Enhancement of 2×2 Ti: LiNbO3 Mach Zehnder Interferometer Switch at 1.3 μm and 1.55 μm

In this paper, the electro-optic 2×2 switching devices using titanium (Ti) diffused lithium niobate (Ti:LiNbO 3 ) as a waveguide medium in the optical switch is designed based on integrated Mach-Zehnder interferometer (MZI) at 1.3 µm and 1.55 µm. Two major design parameters; insertion loss and extinction ratio are evaluated and tested in details. The novelty of this paper is obtaining the optimum, Ti, strip thickness on MZI switch that results in improving switching per- formance at 1.3 µm and 1.55 µm. We have optimized the switch design parameters in order to reduce the overall switch losses (≤ 0.0138 dB) and to achieve the best possible extinction ratio (= 30 dB). The designed switch has a very high switching capability and a high degree of reliability.

THE GENERATION OF POLARIZATION-ENTANGLED PHOTON PAIRS USING GRATING STRUCTURES OF Ti-DIFFUSED LITHIUM NIOBATE WAVEGUIDES IN INTEGRATED OPTICS

Entangled photon source is an essential tool for quantum information experiments, such as tests of Bell inequalities, quantum teleportation, and entanglement swapping. We report the generation of polarization-entangled photon pairs using grating structures of nonlinear materials such as Ti -diffused Lithium Niobate. This approach is useful for quantum integrated optics because the size of this element is less than 325 micron. Polarization-entangled photon pairs are created using the nonlinear optical process of type-II spontaneous parametric down-conversion. The pump laser at 800 nm was doubled to a wavelength of 400 nm, which was used to produce SPDC in the grating structure of Lithium Niobate. The entangled photon pairs were generated at wavelengths 692 nm and 950 nm. The used grating structure consists of two sections. Grating period and length of the first section are 162 nm and 129.6 micron, respectively. Grating period of the second section is 193 nm and its length is equal to 193 micron.

Zn-diffused LiNbO3 waveguides fabricated by DC magnetron sputtering

One of the most popular techniques to fabricate low-loss optical waveguides is the use of zinc (Zn) ions by thermally diffusing them into lithium niobate (LN) crystal. Along this line the fabrication procedure involving lower temperatures and shorter times of diffusion would be more desirable. To this end we report a new procedure using advantages based on the DC-Magnetron sputtering technique through a 3-step waveguide fabrication process in X-cut LN; the first step was sputtering 150 nm thick Zn layer on 400 K hot LN substrate; after this, an immediate oxidation of deposited Zn layer has been done just for 10 min. in 450°C. The final step was thermal diffusion of Zn into LN in a variety of times (1–3 h) and temperatures (600–800°C). All probable changes have been characterized by XRD, RBS and double beam Spectrophotometer. Using the advantages of DC-Magnetron sputtering and simultaneous increase of substrate temperature, combined with an immediate oxidation step before final annealing; the encouraging results of RBS analysis revealed that the whole amount of Zn has diffused with a good gradient after annealing just for 3 h at 750°C; and also the comparative analysis of as-received and diffused LN demonstrated good stability in its optical and structural properties.

Programmable Coupler Ladder Based on Lithium Niobate Y-Junction Reflector

This paper presents a proposal for a novel integrated tunable coupler device called programmable coupler ladder, based on Titanium diffused lithium niobate waveguide and Y-junction reflector. Unlike the traditional serial to parallel converter, the coupler ladder sorts the output bits in the time axis using a built-in delay waveguide. With a proper control signal it can perform signal processing at the bit level. It also can generate coherent multi-channel outputs with theoretically arbitrary amplitude and phase from continuous input light source. Its application in optical microwave beam forming is briefly described. The key component, built-in delay line based on Y-junction reflector, has been experimentally verified via a loop resonator structure. I dB loss is found for each Y-junction reflector, which enables a practical coupler ladder. The loop itself is also an important device for optical signal processing.

Voltage Tunable Optical Communication Filter Design using Directional Coupler for Integrated Optics Applications

Voltage tunable optical filter using directional coupler of Titanium in diffused lithium niobate (Ti:LiNbO3) waveguides with various fabrication parameters has been designed with a centre wavelength of 1.55μm. The central wavelength varies over a wide range of wavelength with respect to the voltage across electrodes. The filter operates over a reasonably high bandwidth.

Precipitation of HNbO 3 at the Ti:LiNbO 3 surface

The conditions of HNbO 3 precipitation on the lithium niobate single-crystal and titanium diffused lithium niobate, LiNbO 3 (LN) were studied. It has been shown, that the maximum of HNbO 3 precipitation corresponds to the highest humidity of atmosphere at the annealing temperatures of 800–850 °C for 5–10 h. Moreover, the application of humid atmosphere during the annealing of LN at 600–850 °C does not ensure in full measure the lack of LiNb 3O 8 precipitation.

Extended baseline architecture for nonblocking photonic switching

A new switch architecture called extended baseline networks (EBN) is proposed for nonblocking photonic switching. This switch is a space-division multistage network using 2/spl times/2 optical switch elements which may be directional couplers fabricated on titanium diffused lithium niobate (Ti:LiNbO/sub 3/) substrates. A recursive definition for the proposed architecture is presented. Some properties including the number of switch elements required, blocking characteristics, number of crossovers, system attenuation, and signal-to-noise ratio (SNR) are derived and analyzed. Most of the characteristics are shown to be better than those of other well-known networks fabricated on single Ti:LiNbO/sub 3/ substrates.

Characterization of the magnesium diffused lithium mobate surface layer by gixrd

Characteristics of MgO-rich layer in the magnesium diffused lithium niobate single crystal surface layer are investigated with the conventional X-ray diffraction and glancing-incidence X-ray diffraction. It is found that the MgO-rich layer is composed of an unknown compound and MgNb2O6. The MgNb2O6 is in the surface layer of MgO-rich layer, the unknown compound is in the subsurface layer beneath the MgNb2O6. The compounds have apparent preferred orientation

Comparison Between the Performance of Ti:LiNbO3 and H:LiNbO3 Rotated Optical Axis Waveguides - Summary

Guided and leaky mode propagation in three-layered and five-layered c-rotated anisotropic waveguides is examined. The considered dielectric tensor configurations are the polar, longitudinal and equatorial ones. The modal characteristics of titanium diffused lithium niobate (Ti:LiNbO3 ) and proton exchanged lithium niobate (H:LiNbO3 ) waveguides are compared. The experimental results for a three layered Y-cut Ti:LiNbO3 waveguide agree very well with the calculated ones.

INFLUENCE OF LITHIUM ION OUTDIFFUSION ON THE CRYSTALLINITY OF MAGNESIUM DIFFUSED LITHIUM NIOBATE SURFACE LAYER

With the conventional X-ray diffraction and grazing-incidence X-ray diffraction. We have investigated the MgO-rich layer characteristics in the magnesium diffused lithium niobate single crystal, when the magnesium-ion indiffusion process in the layer is carried out in atmosphere. It is found that the MgO-rich layer exhibits the crystal structure of Li3Mg2NbO6 and Mg4Nb2O9, when indiffusion time for magnesium-ion is short. these aspects indicate that Li3Mg2NbO6 is in the subsurface layer of MgO-rich layer and Mg4Nb2O9 forms an uniform layer in the MgO-rich layer.When further increasing diffusion time the lithium-ion outdiffusion from the bulk of lithium niobate become prominent and Li3Mg2NbO6 and Mg4Nb2O9 compounds disappear in succession, and LiNb3O8 compound structure appears consequentially. It is observed by scanning electron microscopy that the surface of magnesium diffused lithium niobate indicates a multicrystal structure, the decomposing and disappearing processes of these surface layer compounds are also revealed

Chromium diffusion in lithium niobate for active optical waveguides

A method to fabricate chromium-doped lithium niobate substrates in which the active ions are introduced by thermal diffusion from a film is reported. Chromium concentration depth profiles have been obtained by secondary-ion-mass spectrometry and the relevant diffusion parameters have been derived. Fluorescence spectrum and upper laser level lifetime of chromium diffused proton-exchanged and chromium/titanium-diffused lithium niobate waveguides have been measured. A simple model has been used to estimate the performance of such structures as waveguide optical amplifiers and lasers.

Lithium niobate waveguides and their susceptibility to optical damage

Abstract The laser power-handling characteristics of diffused lithium niobate waveguides are reviewed in terms of laser-power-coupled, transmission length, crystal orientation, and method of preparation. Laser-induced optical damage is recorded for the first time in the new proton-exchanged lithium niobate waveguides. Optical damage is not observed, however, for propagation along the z-axis of titanium-in-diffused waveguides.

Optical Damage Resistance Of Lithium Niobate Waveguides

The optical damage resistance of diffused lithium niobate wave-guides is discussed. Long-term laser power handling performance is assessed by recording the spatial intensity changes occurring as a function of time in a waveguide's far field. Out-diffused waveguides are found to offer significantly greater long-term resistance to optical power losses caused by optical damage than do waveguides formed by either ion exchange or titanium in-diffusion. Any waveguide's resistance to optical damage is lowered by inadvertent exposure to chemical reducing conditions that can prevail during device fabrication processes. Waveguides exposed to the severe chemical reducing conditions are found to exhibit dramatically nonlinear behavior when exposed to high laser powers and short laser wavelengths.

Efficient single-mode fiber to titanium diffused lithium niobate waveguide coupling for λ = 1.32 µm

We report detailed results on the achievement of very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers. By determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss, we have achieved total measured fiber-waveguide-fiber insertion loss as low as 1 dB for a 1 cm long waveguide at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\lambda = 1.32 \mu</tex> m. The relative contributions of coupling and propagation loss are determined. Very good correlation is found between the coupling loss and the match between the fiber and waveguide mode dimensions. Design data for diffusion parameters to obtain good mode match for arbitrary fiber dimension are presented.

Efficient Single-Mode Fiber to Titanium Diffused Lithium Niobate Waveguide Coupling for Lambda = l.32 µm

We report detailed results on the achievement of very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers. By determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss, we have achieved total measured fiber-waveguide-fiber insertion loss as low as 1 dB for a 1 cm long waveguide at Lambda = 1.32 µm. The relative contributions of coupling and propagation loss are determined. Very good correlation is found between the coupling loss and the match between the fiber and waveguide mode dimensions. Design data for diffusion parameters to obtain good mode match for arbitrary fiber dimension are presented.

Stoichiometry-Control and the Performance of Electrooptic Waveguides for Integrated Optics

The laser power-handling performance of diffused lithium niobate planar waveguides, as limited by their development of laser-induced optical damage, is characterized in terms of the pertinent chemical process variables involved in their production. Lithium niobate waveguides are formed by the out-diffusion of lithium oxide under oxidizing conditions, by the in-diffusion of titanium, and by out-diffusion under nonoxidizing conditions. These three waveguide types, however, exhibit radically different laser power-handling capabilities. Out-diffused waveguides prepared under oxidizing conditions, as compared with equivalently prepared titanium in-diffused guides, are able to handle more than twenty times the laser power, at the same level of performance. An out-diffused waveguide propagates 1-5 mW at 632.8 nm with less than 2-6 percent steady-state output power loss. Out-diffused waveguides prepared under nonoxidizing conditions exhibit rapid power loss followed by equally rapid and full steady-state recovery. Waveguide chemistry, on the other hand, does not alter the manner in which the laser power is dispersed in the plane of the waveguide. Laser power is always scattered within the waveguide plane, to the negative c-axis side of the centrally propagating laser beam.

Electrically active optical bifurcation: BOA

We report the realization of an electro-optical switch based on the interference between modes in a two-mode waveguide (equivalent to a directional coupler with no gap between the guides). Switching is achieved by uniformly changing the refractive index of the guide. This permits attaining the two switching states even in the presence of fabrication errors, with a very simple electrode configuration. Crosstalks of −16 and −18 dB for command voltages of 8 and −18 V have been obtained for such a structure realized in Ti : diffused lithium niobate.

Mach-Zehnder Interferometer

Beam propagation method (BPM) was used to study 2x2 Mach-Zehnder interferometer switch with electro-optical effects in titanium diffused lithium niobate based directional coupler was used to develop the design. This design is capable of de-multiplexing the wavelength1300nm. This project intends to design high performance NxN electro-optic switch. This optical device is widely used in optical network, especially in the optical link of fiber-to-the-home (FTTH). The design is carried out using BPM_CAD, which is a very powerful and user-friendly optics waveguides modeling method as it core element. Research on optical waveguide switching using directional coupler (DC) and Mach-Zehnder interferometer (MZI) has been going on and already created great interest among the researchers. There are different types of material being used in much different way apart from the most common electro-optic materials such as lithium niobate. Recently, the study was also confined to the use of silica on silicon technology considering that the cost of the technology. Other non-linear-optic materials such as polymers have been embedded into part of the silica waveguide.