Phase matching using an isotropic nonlinear optical material

Abstract

Nature © Macmillan Publishers Ltd 19988 radius apertures following the standard prescription 28 . Additional corrections were made as follows: (1) +0.05 mag to correct for the so-called 'long exposure' effect 29 ; (2) −0.04 mag, which is the appropriate colour term to convert to standard Cousin's I magnitudes for red stars with V Ϫ I Ϸ 1:5 (ref. 28); and (3) −0.04 mag to allow for the expected foreground extinction 30 . We estimate that the combined uncertainty from the zero-point calibration and the various correction terms amounts to 0.06 mag. Clearly extended sources were removed from the catalogue by restricting our analysis to sources with a DAOPHOTsharpness parameter Ϫ 0:6 Ͻ s Ͻ 0:4. A similar procedure was also followed for the HDF control field. Finally, we created 12 test data sets in which 265 simulated stars were added to the real data frames. The input magnitudes of the simulated stars covered the range from 23.5 to nearly 30. We then processed these frames in the same way as the original data, and produced a matrix relating the recovered magnitudes and detection efficiency to the input magnitudes of the simulated stars. From these simulations we estimate that the catalogue is ϳ80% complete at I ¼ 27:9, and use this as the limiting magnitude in our analysis.

Birefringence evaluation of multimode multilayer AlGaAs/AlAs waveguides

“…4͑c͒, where two features are noticeable: on the one hand the MB between TE 00 and TM 00 is greatly enhanced by oxidation, from 0.0138 to 0.08. 3 On the other hand, while N(TE 10 )ӶN(TM 00 ) in the as-grown samples, oxidation lowers N(TM 00 ) far more than N(TE 10 ), thus reducing the corresponding MB from 0.125 to 0.11. Line pairs associated with larger ⌬N's fell outside the CCD field of view.…”

“…9 In general, due to form birefringence, the field in low-index layers is higher for TM than for TE polarization. 3,6,10 It is therefore expected that by selectively lowering the refractive indices of thin AlAs layers, the effective indices of TM modes decrease more than TE. This is experimentally verified and visible in Fig.…”

“…1 Concerning waveguide design, significant efforts have been recently undertaken to tailor modal birefringence ͑MB͒ with two main goals: ͑i͒ MB minimization for fibercompatible, polarization-degenerate devices through geometrical compensation of material anisotropy; 2 ͑ii͒ controlled MB through form birefringence, for phase matching in parametric wavelength generators. 3 In this letter we describe a one-shot technique which allows the simultaneous measurement of the TE/TM birefringence of all the eigenmodes supported by a multimode optical waveguide in a quadratically nonlinear composite semiconductor. Our approach exploits surface emitting second harmonic generation ͑SESHG͒, first demonstrated in 1981 using Ti:LiNbO 3 waveguides.…”

Noncollinear type-II second-harmonic generation in a Al(0.3)Ga(0.7)As/Al2O3 one-dimensional photonic crystal

“…In particular, during the last decade finite one-dimensional ͑1D͒, periodic or quasiperiodic multilayer stacks, the simplest types of PBG structures, have been widely investigated theoretically and experimentally. [6][7][8][9][10][11][12] The main advantage that these artificial structures offer is the ability to enhance the nonlinear response normally associated with bulk (2) materials thanks to the localization of light at frequencies tuned at the photonic band edge, and the simultaneous availability of effective phase matching ͑PM͒ conditions. [6][7][8][9] In fact, the natural dispersion of ordinary materials can be compensated by introducing geometrical dispersion, which is brought about and controlled by properly juxtaposing a high and a low index material.…”

Bloch theory of entangled photon generation in nonlinear photonic crystals

“…One-dimensional photonic crystals had been considered before for classical frequency conversion in the limit that the optical wavelength is much larger than the periodicity [7,8,9]. Two-dimensional non-linear photonic crystals have also been considered for classical frequency * corresponding author: william@physics.ucsb.edu † Present address: Huygens Laboratory, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands conversion [10].…”