Nonlinear Optical Elements Research Articles

Revisiting the optical properties of Nd doped yttrium orthovanadate

Neodymium doped YVO(4) is becoming an increasingly popular material for solid state lasers. Among the advantages of vanadates over more traditional materials are that the absorption cross section at 808 nm is significantly larger, the emission cross sections are higher, leading to lower lasing thresholds, and the bandwidth for pump absorption is higher. We report new measurements of the refractive index and thermo-optic coefficient of this material that will aid in the design of laser cavities and other nonlinear optical elements.

Feedback-controlled nonresonant laser cooling

We present a new approach to nonresonant laser deceleration and cooling of atoms based on their interaction with a bistable optical cavity. The cooling mechanism presents a photonic version of Sisyphus cooling, in which the conservative motion of atoms is interrupted by sudden transitions between two stable states of the cavity mode. The mechanical energy is extracted due to the hysteretic nature of those transitions. The bistable character of the cavity may be achieved by an external feedback loop, or by means of nonlinear intracavity optical elements. In contrast to the conventional cavity cooling, in which atoms experience a viscoustype force, bistable cavity cooling imitates “dry friction” and stops atoms much faster. Based on this novel approach, we explore the prospects of using optical bistability for efficient radiation pressure cooling of micromechanical devices that are modeled as a Fabry-Perot resonator with one fixed and one oscillating mirror. In all cases, analytical results are presented, supported by realistic numerical examples.

Preparation of ferroelectric nanoparticles for their use in liquid crystalline colloids

In this paper we summarize our many years of experience in the preparation and optimization of stable colloids of ferroelectric nanoparticles dispersed in an isotropic carrier and in a liquid crystal host. The colloids are of interest for use in electro-optic devices, photorefractive hybrids and nonlinear optical elements. We also outline some of the most interesting features the nanoparticles bring to liquid crystals, along with the potential of these relatively new colloids.

Network Synthesis of Linear Dynamical Quantum Stochastic Systems

The purpose of this paper is to develop a synthesis theory for linear dynamical quantum stochastic systems that are encountered in linear quantum optics and in phenomenological models of linear quantum circuits. In particular, such a theory will enable the systematic realization of coherent/fully quantum linear stochastic controllers for quantum control, amongst other potential applications. We show how general linear dynamical quantum stochastic systems can be constructed by assembling an appropriate interconnection of one degree of freedom open quantum harmonic oscillators and, in the quantum optics setting, discuss how such a network of oscillators can be approximately synthesized or implemented in a systematic way from some linear and nonlinear quantum optical elements. An example is also provided to illustrate the theory.

Configurationally locked, phenolic polyene organic crystal 2-{3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene}malononitrile: linear and nonlinear optical properties

We show that the organic polyene crystal 2-{3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene}malononitrile (OH1) is a new material with excellent nonlinear optical and electro-optical properties. The principal refractive indices and the absorption constants have been determined over a broad wavelength range from 0.6to2.2 μm. OH1 shows a large birefringence of Δn>0.55 and a low absorption of α<1 cm−1 in a large wavelength range between 800 and 1400 nm. Furthermore, the nonlinear optical tensor elements d333=120 ± 10 pm/V, d223=13 ± 2 pm/V, and d322=8.5 ± 2 pm/V have been determined by the Maker-fringe technique at the fundamental wavelength of 1.9 μm. The electro-optic coefficients r333, r223, and r113 have been measured at the wavelengths of 633, 785, 1064, and 1319 nm, and it is shown that the dispersion can be described by a one-oscillator model. OH1 is a promising material for nonlinear optical and electro-optical applications due to the large nonlinear coefficient d333, the large electro-optic coefficient r333=109 ± 4 pm/V at 632.8 nm, the favorable crystal growth properties, as well as the orthorhombic crystal symmetry (point group mm2), which renders crystal preparation and orientation much simpler than in most organic nonlinear optical crystals.

Linear and nonlinear optical properties of the organic crystal DSTMS

We report on the linear and nonlinear optical properties of the novel organic crystal 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS). The principal refractive indices n1, n2, and n3 have been determined by a direct measurement of the group index dispersion over a broad wavelength range from 0.6 to 1.6 μm. The linear absorption coefficients for light polarized along the dielectric axes have been measured in the transparency range from 600 to 2000 nm. DSTMS crystals show a large birefringence of Δn=0.5 and low absorption α<0.7 cm−1 in the telecommunication wavelength range at 1.55 μm. Furthermore, the nonlinear optical tensor elements d111, d122, and d212 have been determined by the Maker-fringe technique at the fundamental wavelength of 1.9 μm. DSTMS crystals exhibit a very large nonlinear activity with a nonlinear optical coefficient d111=214±20 pm/V. Phase-matching curves determined from our optical data showed that parametric oscillation can be achieved in the wavelength range from 1 to 2.2 μm with effective nonlinear optical coefficients larger than 25 pm/V.

Resonant Nonlinear Optical Coefficients of Ferroelectrics

We review our work on the resonant nonlinear response of bulk ferroelectric materials in the frequency region of the optic mode, in particular our attention is focused on the derivation and calculation of the nonlinear optical (NLO) susceptibilities in this region. Properties of the nonlinear susceptibilities both in the paraelectric and ferroelectric phases are briefly described, where in general it is found that the non-vanishing nonlinear optical tensor elements of each susceptibility are governed by resonances in both input and output waves; and the resonance frequencies are temperature-dependent soft modes. The connection of NLO susceptibilities with the subject of morphotropic phase boundary which occurs in various mixed ferroelectrics crystals is also briefly discussed.

All-optical digital 3-input AND gate using sum- and difference-frequency generation in PPLN waveguide

Demonstrated is an all-optical bit-wise 3-input AND gate using a single periodically-poled-lithium-niobate (PPLN) waveguide as a nonlinear optical element. The module generates output ‘1’ bits only when all inputs are ‘1’, with negligible power penalty.

Nonlinear Diffractive Optical Elements

We propose diffractive optical elements with a spatially-varying nonlinear refractive index. Such a component acts as a diffractive optical element whose properties depend on the intensity of the incoming beam. We present a method for designing such elements, and as specific examples we study three types of nonlinear diffractive optical elements: Nonlinear Fresnel Zone Plates, Two-foci Nonlinear Fresnel Zone Plate, and Fresnel Zone Plate to Grating interpolator.

Some reasons for the formation of grain boundaries and melt inclusions in growing large BBO crystals by TSSG technique

Data reported in this work are the result of the first crystallomorphological analysis of the formation of most typical structural defects in growing large BBO crystals by the top seeded solution growth (TSSG) technique combined with pulling. These defects are grain boundaries with varying scales of disordered angle orientations and melt inclusions. It is these defects that to a great degree restrict the yield of suitable material of high-optical quality from grown BBO boules. We believe that the main reason for the formation of these defects is the incoherent joining of different sectors of independent growth, which form the crystal volume, and the specific features of crystallization at the interface of regeneration type. The results presented in this paper may be useful in improving technologies for the production of large BBO single crystals by correcting growth conditions, and optimizing the schemes of cutting them to produce high-quality nonlinear optical (NLO) elements.

Complete Deterministic Linear Optics Bell State Analysis

We show how hyperentanglement allows us to deterministically distinguish between all four polarization Bell states of two photons. In this proof-of-principle experiment, we employ the intrinsic time-energy correlation of photon pairs generated with high temporal definition in addition to the polarization entanglement obtained from parametric down-conversion. For the identification, no nonlinear optical elements or auxiliary photons are needed. The new possibilities this complete Bell measurement offers are demonstrated by realizing an optimal dense coding protocol.

Bit error rate improvement by nonlinear optical decision element

We present a novel approach to the improvement of the bit error rate (BER) in optical communications. We propose a design of advanced optical receiver enhanced by a nonlinear all-optical decision element. As a particular example, we demonstrate a substantial improvement in the BER over the conventional receiver for operation at 40 Gbits/s.

Analysis and design equations for phase matching using Bragg reflector waveguides

In this paper, we introduce and analyze a novel wave-guide design to provide phase matching for nonlinear optical processes. Phase matching is achieved by designing the structure to guide the fundamental frequency by total internal reflection and the second harmonic (SH) frequency by transverse Bragg reflection. By forcing the SH mode to operate in the middle of the Bragg stopband, we solve for the waveguide dimensions for arbitrary waveguide materials, given the material dispersion between the fundamental and SH frequencies. Using GaAs-AlGaAs as an example, we analytically investigate and quantify properties such as nonlinear coupling efficiency, bandwidth, tunability, and limitations due to dispersion. The technique shows tremendous promise when compared to alternate technologies, where it is particularly attractive as an effective means to obtain ultralow-loss nonlinear optical elements for monolithic integration with coherent light sources and other active devices.

All-optical half adder using an SOA and a PPLN waveguide for signal processing in optical networks

We demonstrate an all-optical half adder for bit-wise addition of two serial data streams that simultaneously generates Sum and Carry outputs. The module performs the required XOR and AND operations using only two nonlinear optical elements. Difference Frequency Generation in a periodically poled lithium niobate waveguide serves as the AND gate and cross-gain modulation in a semiconductor optical amplifier is employed to generate the XOR output. Error free operation for RZ data is reported.

Characteristics of all-optical ultrafast gate switches using cascade of second-harmonic generation and difference frequency mixing in quasi-phase-matched lithium niobate waveguides

In all-optical gate switches that employ the cascade of second-harmonic generation and difference frequency mixing in quasi-phase-matched (QPM) lithium niobate (LN) devices, walkoff between the fundamental and second-harmonic pulses causes crosstalk of the switch. We numerically calculate the switching performance of QPM-LN waveguide devices with consideration for the crosstalk effect, and discuss the favorable choice of the nonlinear optical tensor element for the LN crystal. In the analyses, the device length is maximized for a given bit rate under the condition that the crosstalk is maintained below a critical level that is determined by the allowable power penalty for the switched signal. It is shown that the time offset between the gate and signal pulses can compensate for the walkoff, and can significantly improve the switching efficiency. In ultrafast operation beyond 1 Tbps, the use of the nonlinear optical tensor element d/sub 31/ is found to be favorable when compared to the use of the commonly used maximum tensor element d/sub 33/.

Melt-solution BBO crystal growth under change of the heat field symmetry and its rotation

The regime of crystal growth of β -BaB 2O 4 (BBO) from melt-solution was improved through the change of the symmetry of a heat field and its rotation. Such a new approach resulted in the patterning of contact-free induced convective flows, improvement of convection and in the increase of the yield coefficient before the system was constitutionally supercooled. Thus grown BBO crystals from a crucible 80 mm in diameter can be used to produce 15×15×15 mm 3 non-linear optical elements and 6×6×22 mm 3 electro-optical elements for Pockel's cells cut along the optical axis.

Ultra-fast quantum-well saturable absorber devices and their application to all-optical regeneration of telecommunication optical signals

We review recent advances in the investigation of vertical cavity saturable absorber devices and their use for the all-optical regeneration of telecommunication signals in ultra-long-haul transmission systems. Such devices are polarization-insensitive and operate as fully passive nonlinear optical elements. Two approaches for obtaining fast recovery absorber materials are described, relying upon ion irradiation or upon iron doping. The vertical micro-cavity devices are designed so as to optimize the switching contrast and the operating power. Their functional behaviour as extinction ratio amplifiers has been characterized and their optimal operating conditions have been determined. The potential application of these devices to all-optical regeneration has been investigated through numerical simulations and fully demonstrated in several long-distance transmission loop experiments, with results obtained at 10, 20 and 40 Gbit/s, showing significant improvements in system haul or operational margins. A four-channel fibered module has also been fabricated, as a perspective towards the development of wavelength division multiplexing (WDM) saturable absorber modules.

High-fidelity teleportation of entanglements of running-wave field states

We describe a scheme for the teleportation of entanglements of zero- and one-photon running-wave field states. In addition to linear optical elements, Kerr nonlinearity is also employed so as to achieve a 100% probability of success in the ideal case. A comprehensive phenomenological treatment of errors in the domain of running-wave physics, for linear and nonlinear optical elements, is also given, making it possible to calculate the fidelity of the teleportation process. A strategy for carrying out the Bell-type measurement which is able to probe the absorption of photons in the optical elements is adopted. Such strategy, combined with usually small damping constants characterizing the optical devices, results in a high fidelity for the teleportation process. The feasibility of the proposed scheme relies on the fact that the Kerr nonlinearity it demands can be achieved through the recently reported ultraslow light propagation in cold atomic media [Phys. Rev. Lett. 84, 1419 (2000); Phys. Rev. A 65, 033833 (2002)].

Nonlinear surface magneto-optics of ferromagnetic Ni/Cu(001) from first principles

We present first-principles calculations of the nonlinear optical (NLO) response of a Ni/Cu(001) bilayer. The calculations are based on the full potential linearized augmented plane wave (FLAPW) method with the additional implementation of spin–orbit coupling (SOC). On the basis of this set of eigenstates the magneto-optical transition-matrix elements are evaluated. Using the surface-sheet model the optical reflection properties are determined for the cases of the magnetization vector perpendicular to the surface (polar magneto-optical configuration (MOC)) and for the in-plane magnetization (longitudinal MOC). The nonlinear optical susceptibility tensor elements χ(2) ijk for different magnetization directions as well as the spectral dependence of χ(2) ijk, the resulting intensities, and Kerr angles are presented for the Ni/Cu(001) bilayer. The results show that the magnetic tensor elements of the χ(2) ijk tensor are smaller than the nonmagnetic ones by only one order of magnitude, confirming the important role of magnetic properties in the NLO response.

Nonlinear frequency conversion in coupled ring cavities

The steady-state distribution of circulating power in coupled, unidirectional ring resonators containing a diode-pumped laser crystal and nonlinear optical elements is computed. The full set of transcendental nonlinear equations describing the interactions between the circulating power and the optical elements is solved by a numerical root find function of a commercial mathematics software. The method allows computation of the output of sequential nonlinear processes such as laser gain, second harmonic generation and optical parametric amplification as a function of the input diode pump power. It is also possible to optimize the nonlinear interaction by selecting the optimum interaction cross-section or crystal length. The circulating power may thereby be re-distributed to obtain the lowest possible passive loss.