Results 1 - 10 of 2278
Results 1 - 10 of 2278. Search took: 0.027 seconds
|Sort by: date | relevance|
[en] We propose an experimental method for measuring the period difference in a grating pair. The method uses the relationship between the period difference and the phase difference of diffraction beams of the grating pair when gratings are translated along the grating-vector direction. The effect of the roll angular deviation of gratings can be eliminated by phase compensation with +1st- and -1st-order diffraction beams. Far-field intensity patterns of diffraction beams are monitored to adjust the relative attitude of gratings. For a pair of gratings with periods of ∼0.674 μm, the period difference was measured to be 0.4434 nm with an expanded uncertainty (k=2) of 0.0113 nm
ConclusionA technique for replicating diffraction grating on to compliant and porous materials has been developed. The grating can be applied quickly to the specimen. It is also highly compliant and localized on the specimen surface. Three applications described illustrate replication method provides high quality fringe patterns.
[en] DFB lasers were fabricated for the first time with gratings dry etched into InP substrate by reactive ion beam etching (RIBE). Deformation-free overgrowth of these 0.2 μm deep corrugations was performed by liquid phase epitaxy (LPE). Threshold currents (cw, 25 deg C) as low as 23 mA demonstrate that no severe degradations occur in these devices due to surface damage caused by the dry etching. Single mode operation with a sidemode suppression > 35 dB is obtained due to strong couplying of the grating. HF-measurements reveal a 3 dB modulation bandwidt of 9 GHz for the DFB-DC-DCPBH structure. (author). 5 refs.; 4 figs
[en] We present a simple diffraction experiment with m-bonacci gratings as a new interesting generalization of the Fibonacci ones. Diffraction by these non-conventional structures is proposed as a motivational strategy to introduce students to basic research activities. The Fraunhofer diffraction patterns are obtained with the standard equipment present in most undergraduate physics labs and are compared with those obtained with regular periodic gratings. We show that m-bonacci gratings produce discrete Fraunhofer patterns characterized by a set of diffraction peaks which positions are related to the concept of a generalized golden mean. A very good agreement is obtained between experimental and numerical results and the students’ feedback is discussed. (paper)