Gary D. Landry

Efficient nonlinear phase shifts due to cascaded second-order processes in a counterpropagating quasi-phase-matched configuration

A counterpropagating quasi-phase-matched configuration is examined that is capable of efficiently producing second-order cascaded nonlinear phase shifts with minimal power lost to the second harmonic. For all-optical switching in a nonlinear Mach-Zehnder interferometer, the calculated minimum input power needed for switching (i.e., to yield a +/-pi/2 phase shift) is 40 times smaller than the power needed in the standard typeI copropagating configuration. The throughput of this counterpropagating device is 96% at the optimum switching point.

Gaussian beam transmission and reflection from a general anisotropic multilayer structure.

Transmission and reflection of Gaussian beams from a general anisotropic multilayer structure are investigated. The principal axes of the layers are oriented arbitrarily with respect to each other and with respect to a fixed reference coordinate system. The Gaussian beam is assumed to have an arbitrary angle of incidence and linear polarization orientation. Two numerical examples are presented: a single slab of uniaxial calcite and a multilayer structure of biaxial 4-(N, N-dimethylamino)-3-acet amidonitrobenzene with antireflection coatings on the input and output faces. Results show the distortions of the beam caused by the anisotropy of the structure.

Switching and second harmonic generation using counterpropagating quasi-phase-matching in a mirrorless configuration

Numerical solutions to the set of coupled nonlinear wave equations for a novel mirrorless counterpropagating quasi-phase-matched (c-QPM) device are presented. Mirrorless c-QPM is investigated in stand-alone and in two interferometric configurations for all-optical switching (AOS) applications. The switching intensity is found to be very low using existing materials (e.g., 500 mW in a 1-cm-long KTP waveguide with a 10 /spl mu/m/sup 2/ effective area). Additionally, parameter sets are found that minimize pulse breakup and improve the possibility of a practical implementation. Although second harmonic generation (SHG) is also investigated in the stand-alone device, the conversion efficiency is shown to be eight times less efficient than the mirrored configuration.

More VCSELs at Finisar

In this paper we describe progress in moving VCSELs toward production-ready status in several applications, among others including substantially higher modulation speeds (14-25 Gbps, or even higher) than in current production. In addition we describe potential VCSEL failure mechanisms not previously published, as well as the limitations of some reliability testing techniques.

Second-harmonic generation and cascaded second-order processes in a counterpropagating quasi-phase-matched device

Numerical solutions to the nonlinear coupled-wave equations of a counterpropagating quasi-phase-matched device are analyzed by numerical methods for both second-harmonic generation and cascaded processes. Normalized derivations for second-harmonic generation efficiency are also presented. The nonlinear phase shifts acquired in this device by cascaded second-order processes are promising in all-optical-switching applications. Specifically, a pi/2 phase shift is shown to be achievable with 42 times less input intensity than the standard Type I configuration and 100% throughput. The effects of metallic mirrors are also presented. Careful use of the phase mismatch is shown to compensate for nonideal mirrors. Finally, conservation of power in this configuration is briefly investigated.

Zigzag analysis of interference effects in an arbitrarily oriented biaxial single layer

A wave-vector zigzag analysis is developed to investigate the complicated interference effects among the four extraordinary waves in a biaxial slab with general principal-axes orientation; the four corresponding zigzag Poynting vectors have distinct walk-off directions. Expressions for transmission and reflection coefficients, analogous to Airy’s summation for isotropic slabs, are determined for an arbitrarily oriented linearly polarized monochromatic plane wave at oblique incidence. A KTP slab is analyzed with the derived method, and the results are compared with those obtained with the 4 × 4 matrix method. Some common applications of this theory include analysis of multilayer structures and waveguides.

Ray tracing through a two ball uniaxial sapphire lens system in a single mode fiber-to-fiber coupler

A worst case ray trace analysis is presented for a two ball uniaxial lens system in a single mode fiber-to-fiber coupler. The purpose is to determine if the e-wave Poynting vector walkoff effect contributes adversely to coupling loss due to beam offset. Sapphire ball lenses with radii of 250 /spl mu/m separated by 500 /spl mu/m are used to produce numerical results at /spl lambda/=1.3 /spl mu/m. A worst case offset of 4.302 /spl mu/m is calculated at the coupler exit. In addition, aberration due to birefringent focusing is examined; uniaxial ball lenses focus the o-wave and e-wave at different points.

Pulse simulations of a mirrored counterpropagating-QPM device

A basic mirrored counterpropagating quasi-phase-matched device is studied with a pulsed input fundamental plane wave using the method of lines and the relaxation method. Several examples are given under varying spatial pulse length to device length ratios. An approximate upper bound on the device length is established from this study for practical pulsed applications; the largest usable length is approximately the same as the spatial length of the pulse.

Nonlinear Phase Shifts in a Counterpropagating Quasi-Phase-Matched Configuration

Recently, there has been a large interest in cascaded second order processes for many applications including optical transistors,1 and all optical switching.2 One important aspect of these processes is the ability to produce large nonlinear phase shifts at relatively low input intensities. This poster presents a novel quasi-phase matching scheme to obtain nonlinear phase shifts via cascaded second order processes in a counterpropagating configuration.

Ray tracing through a two ball uniaxial lens system in a single mode fiber-to-fiber coupler

Two ball lens systems are frequently used for single mode fiber-to-fiber coupling. Sapphire is often considered for this type of application due to its high index (for reduced spherical aberration) and its mechanical integrity. However, sapphire is negative uniaxial, and the effect of optical birefringence on coupling loss has not been formally studied for ball lenses. Therefore, the purpose of this study is to determine if Poynting vector walk-off of the e-wave, which leads to beam displacement, contributes adversely to coupling loss (birefringence aberration).