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15 Sep 2005

Volume 98, Issue 6, Articles (06xxxx)

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By-emitter degradation analysis of high-power laser bars

S. Bull, J. W. Tomm, M. Oudart, J. Nagle, C. Scholz, K. Boucke, I. Harrison, and E. C. Larkins

J. Appl. Phys. 98, 063101 (2005); http://dx.doi.org/10.1063/1.2058182 (4 pages) | Cited 6 times

Online Publication Date: 23 September 2005

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The study of degradation process in high-power laser diodes, in particular, high-power laser bars, has become increasingly important as the output power of these devices continues to rise. We present a “by-emitter” degradation analysis technique, which examines degradation processes at both the bar and emitter levels. This technique focuses on understanding the dynamic mechanisms by which packaging-induced strain and operating conditions lead to the formation of defects and subsequent emitter and bar degradations. In the example presented, we examine a highly compressively strained bar, where thermally induced current runaway is found to be an important factor in the bar degradation and eventual device failure.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Focusing properties of a rectangular-rod photonic-crystal slab

Shuai Feng, Zhi-Yuan Li, Zhi-Fang Feng, Kun Ren, Bing-Ying Cheng, and Dao-Zhong Zhang

J. Appl. Phys. 98, 063102 (2005); http://dx.doi.org/10.1063/1.2058190 (6 pages) | Cited 9 times

Online Publication Date: 23 September 2005

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The focusing properties of a photonic-crystal (PC) slab consisting of a square lattice of rectangular dielectric rods in the air background are studied theoretically. We employ the finite-difference time-domain method to investigate the field patterns of a point source placed in the vicinity of the PC slab and find that an image can form in the opposite side of the slab in a frequency window located slightly below the fundamental band gap. We change the orientation of the rectangular rods and find that when the rods are arranged asymmetrically with respect to the surface normal of the slab, the image spot can show a vertical shift relative to the point source. The influence of the PC slab thickness on the quality of the image is also analyzed. From these simulation results and the equifrequency-surface contour analysis, we find that the dominant physical mechanism that shapes the focusing behavior of these rectangular-rod PC slabs in the ground photonic band is the self-collimation effect instead of the negative refraction effect.
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42.70.Qs Photonic bandgap materials
02.70.Bf Finite-difference methods

Nonlinear AlGaAs waveguide for the generation of counterpropagating twin photons in the telecom range

M. Ravaro, Y. Seurin, S. Ducci, G. Leo, V. Berger, A. De Rossi, and G. Assanto

J. Appl. Phys. 98, 063103 (2005); http://dx.doi.org/10.1063/1.2058197 (9 pages) | Cited 21 times

Online Publication Date: 27 September 2005

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We have designed and fabricated a set of AlGaAs multilayer waveguides, which can serve as a source of entangled photons at 1.55 μm through parametric fluorescence. In our scheme two counterpropagating, orthogonally polarized signal/idler modes are nonlinearly generated by a pump wave impinging on the upper surface of the waveguide. To check the compliance with design specifications on phase-matching wavelength and parametric gain, we have systematically measured effective indices and surface-emitting second-harmonic generation, respectively. This characterization allowed us to single out a nominal sample with optimum performances, which we numerically modeled for counterpropagating parametric fluorescence. We predict a pair generation efficiency ηPF = 4×10−13 (signal photons per pump photon). For a 1 W (peak), 100 ns pump pulse at normal incidence, this corresponds to about 14 photons per dark count with state-of-the-art avalanche photodiodes.
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42.79.Gn Optical waveguides and couplers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
03.67.Hk Quantum communication
42.15.Eq Optical system design
42.50.Dv Quantum state engineering and measurements
03.67.Mn Entanglement measures, witnesses, and other characterizations
42.86.+b Optical workshop techniques

Effect of structural variation on the photonic band gap in woodpile photonic crystal with body-centered-cubic symmetry

Yuankun Lin and P. R. Herman

J. Appl. Phys. 98, 063104 (2005); http://dx.doi.org/10.1063/1.2058171 (4 pages) | Cited 3 times

Online Publication Date: 27 September 2005

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A woodpile photonic crystal template with body-centered-cubic symmetry can be fabricated by exposing the photoresist to a four-beam interference pattern or a pattern generated through a diffractive optical element. We present detailed photonic band-gap calculations for photonic structures obtained under various possible fabrication conditions. The woodpile photonic crystal has a full photonic band gap up to 19% of the gap center frequency when the photoresist template is converted into silicon. The tolerance of the band gap to deviations of the structural parameters from their optimum values indicates great flexibility of the holographic fabrication process.
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42.70.Qs Photonic bandgap materials
42.86.+b Optical workshop techniques
42.40.My Applications

Near-field focusing by a photonic crystal concave mirror

Y. Saado, M. Golosovsky, D. Davidov, and A. Frenkel

J. Appl. Phys. 98, 063105 (2005); http://dx.doi.org/10.1063/1.2058179 (7 pages) | Cited 2 times

Online Publication Date: 29 September 2005

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We have studied the electric-field distribution in the photonic crystal (PC) concave mirror. This was done numerically and was verified in experiment. The field mapping in our experiments was performed using the Slater’s perturbation technique which was modified for nonresonant structures. The PC consists of a planar array of dielectric rods with a trapezoidal depression that forms the concave mirror. At the midgap frequency of the first stopband of the underlying photonic crystal, the mirror allows focusing to a subwavelength spot size of 0.2λ×0.2λ. The intensity is enhanced by 16 times at the focal point, as compared with the incident wave.
Show PACS
42.70.Qs Photonic bandgap materials
42.79.Bh Lenses, prisms and mirrors
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