TM-polarized Modes Research Articles

Cutoff wavenumbers in truncated waveguides

Truncated waveguides are used in some microwave components. The cutoff wavenumbers in truncated circular waveguide and truncated square waveguide are desired but usually difficult to be computed. In this paper, they are efficiently determined using the unified method that we proposed earlier. Both TE-polarized and TM-polarized modes are studied. To demonstrate the applicability and correctness of this method, two practical examples are considered, one is a truncated circular waveguide and the other is a truncated square waveguide. Results obtained for the two cases are compared with existing data in literature and a good agreement is observed. A further extension of the work is made to compute cutoff wavenumbers of a truncated elliptical waveguide. It is found from the analysis that the cutoff wavenumbers in these irregular waveguides can be computed easily, rapidly, and accurately using the unified method.

Astigmatism of the radiation of semiconductor stripe-geometry lasers

The effect of injection current on the intensity and angular distribution of radiation in TE- and TM-polarized modes of diode lasers with a stripe geometry and double GaAs-AlGaAs-based heterostructure is investigated. The analysis of the angular distribution of radiation revealed the nonmonotonic behavior of its astigmatism with increase in the current. The coefficient of astigmatism in the mode of lasing is substantially higher for the TE-mode than for the TM-mode. An increase in radiation astigmatism is accompanied by a decrease in the differential effectiveness and polarization degree. These specific features are explained by the interaction of the defocusing action of distribution of the refractive index n(x) in the plane of the p-n-transition with a minimum under the center of the stripe contract (at x=0) with the focusing action of the gain coefficient distribution.

Nonlinear polarization switching in a semiconductor single quantum well optical amplifier

Efficient nonlinear or power-dependent polarization switching in a semiconductor quantum-well amplifier is reported. In the experiment, an amplifier with an InGaAs/GaAs single quantum well structure which lases at 974 nm is used. Efficient self-switching is observed at 940 nm with signals 3 psec wide when gain and absorption saturation occur in the TM and TE polarization modes, respectively. The switching peak intensity is estimated to be lower than 13.2 MW/cm2. A theoretical model is adopted to show the consistent trends of switching behaviors with the experimental data.

Wavelength insensitive passive polarization converter fabricated by poled polymer waveguides

A passive TE to TM polarization mode converter is fabricated by using poled polymer waveguides. The optic axis of the poling induced waveguide is slowly rotated 90° by using a slowly varying structure of poling electrodes. Thus the polarization conversion is achieved as the guided mode propagates through the waveguide. TE to TM mode conversion is observed with a polarization extinction ratio higher than 30 dB, and the excess loss is less than 1 dB. The polarization conversion is relatively insensitive to wavelength since the device contains no periodic structures. These devices are easier to fabricate than others containing periodic structures.

TM-polarized surface-plasma modes on metal-coated dielectric cylinders

TM-polarized surface plasma modes on a thin metallic cylindrical shell embedded in dielectric media are investigated. The dispersion characteristics of both bound modes and leaky waves are obtained for two sets of material parameters, the first corresponding to an optical fiber in which the metallic shell occupies a region between the core and the cladding and the second corresponding to a metal coated cylindrical rod in vacuum.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mode-selective detection of optical guided waves by integrated metal–oxide–metal structures

We show that a metal-oxide-metal (Al-AlO(x)-Al) tunnel junction fabricated directly upon a planar ion-exchange glass waveguide can be used to detect the guided radiation through evanescent coupling. Carriers photogenerated in the electrode next to the guide can be internally photoemitted over the oxide barrier to generate a photocurrent. Because of the greater metallic absorption of TM-polarized modes, the process is polarization sensitive. 32-dB TM selectivity is achieved in a simple device.

Transverse-magnetic-polarized nonlinear modes guided by a symmetric five-layer dielectric structure

TM-polarized nonlinear modes supported by a symmetric five-layer dielectric structure consisting of a nonlinear medium of thickness theta (characterized by the diagonal dielectric tensor (1l) = (22) identical with (0), (33) = (0) + alpha|E(3)|(2), where E(3) is the TE-field component) sandwiched between two linear films of thickness beta (with dielectric constant (1)), which are bounded from the free ends by the same nonlinear medium, are analyzed. Dispersion relations and the expressions for the power flow, derived for the symmetric and antisymmetric modes, show that for a sufficiently large value of beta/lambda, where lambda is the wavelength, these modes should show bistable behavior, provided that power flow is the control parameter.