During the alt-azimuth telescope tracking, due to the frame structure of tracking support and relative movement of each mirror in Coude optical path, image plane is rotating. To eliminate the effects of image rotation for imaging and subsequent image processing, dove prism or K mirror are generally used. A set of K mirror system designed for 2m telescope. Affected by various errors in the alignment process, the rotating axis K, the optical axis of the K mirror, and the optical axis of the telescope’s optical system can’t be fully coincide. This causes the track optical axis drawn on the image is not a point, but a Pascal’s limacon. The impact caused by the various sources of error were analyzed in this paper and simulation results have important guiding significance for the alignment error distribution.
A novel 980nm bottom-emitting VCSELs array with high power density and good beam property of Gaussian far-field
distribution is reported. This array is composed of 5 symmetrically-arranged elements of 200&μm,150μm and
100μm-diameterμwith the center spacings of 300μm and 250μm respectively. The maximum power is 880mW at a
current of 4A, corresponding to 1KW/cm<sup>2</sup> average optical power density. The differential resistance is Ω with a
threshold of 0.56A. The novel array is compared with a 300μm-aperture-size single device and a 4*4 2-D array with
50μm element aperture size and 250μm centre spacing. The three devices have the same lasing area. The conclusion is
that the novel array is better in the property of output power, threshold current, lasing spectra, far-field distribution etc.
Whispering-Gallery-Mode (WGM) photonic crystal microcavity is a kind of photonic crystal application and can
potentially be used for miniaturized photonic devices, such as thresholdless lasers. In this paper we study the WGM of
photonic crystal microcavities focusing on the so called H2 cavities which are formed by removing seven air holes. The
WGM in these large-size cavities has some advantages compared with single defect WGM in the view of real device
applications. We further add a central air hole in the cavity region to analyze the effect on WGM in the microcavity by
finite difference time domain (FDTD) and plane wave expansion (PWE). It is found that the tolerance of WGM is large
enough for the fabrication of electrical injection structure.
Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in
ridge-waveguide QW laser fabrication. We apply this method in 980nm VCSELs fabrication to form a high-quality
native oxide current blocking layer, which simplify the device process. A significant reduction of threshold current and a
distinguished device performance are achieved. The 500μm-diameter device has a current threshold as low as 0.48W.
The maximum CW operation output power at room temperature is 1.48W. The lateral divergence angle <i>θ</i><i><sub>parallel</sub></i>and vertical divergence angle <i>θ</i><sub>perpendicular</sub> are as low as 15.3° and 13.8° without side-lobes at a current of 6A.