Tang Q.,Wuhan National Laboratory for Optoelectronics
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013
The fundamental relations of the ultraviolet (UV) light transmittance of the soft polymer film filled by a large number of basic micro-pattern-structures composed of micro-squares, are acquired experimentally. The polymer films with different distribution density of basic color-micro-pattern-structure in the visible range, are also constructed easily, so as to perform single photomask photolithography for fabrication microlenses with very fine surface profile. The patterned polymer films demonstrate a modulated UV-light penetrating property. Models for describing the penetrating behaviors of UV-light over polymer films covered by a large number of basic grayscale or colorscale micro- patternstructures constructed, for instance, typical micro-square and other micro-pattern-structures shaped by partially overlapping several micro-squares, are set up. Several key factors, which influence the penetrating behavior of UV-light, and then the surface character, and also the quality of correspondent functioned micro-structures in photoresist and further substrate, such as diffractive or refractive microlens, are discussed carefully. The UV-light transmitting measurements demonstrate a desired UV-light intensity variance trend, which is basically consistent with theoretical prediction. © 2013 SPIE.
Dong H.,Institute for Infocomm Research |
Tang M.,Wuhan National Laboratory for Optoelectronics |
Tang M.,Huazhong University of Science and Technology |
Gong Y.,Institute for Infocomm Research
Optics Express | Year: 2013
Rotatable retarder fixed polarizer (RRFP) Stokes polarimeters are most commonly used to measure the state of polarization (SOP) of an electromagnetic (EM) wave. Most of commercialized RRFP Stokes polarimeters realize the SOP measurements by rotating a 90° retarder to N (N ≥ 5) uniformly spaced angles over 360° and performing a discrete Fourier transform of data. In this paper, we address the noise properties of such uniformly-rotating RRFP Stokes polarimeters employing a retarder with an arbitrary retardance. The covariance matrices on the measurement noises of four Stokes parameters are derived for Gaussian noise and Poisson noise, respectively. Based on these covariance matrices, it can be concluded that 1) the measurement noises of Stokes parameters seriously depend on the retardance of the retarder in use. 2) for Gaussian noise dominated RRFP Stokes polarimeters, the retardance 130.48° leads to the minimum overall measurement noises when the sum of the measurement noises of four Stokes parameters (viz., the trace of the covariance matrix) is used as the criterion. The retardance in the range from 126.06° to 134.72° can have a nearly-minimum measurement noise which is only 1% larger than the minimum. On the other hand, the retardance 126.87° results in the equalized noises of the last three Stokes parameters. 3) for Poisson noise dominated RRFP Stokes polarimeters, the covariance matrix is also a fuction of the SOP of the incident EM wave. Even so, the retardance in the range from 126.06° to 134.72° can also result in nearly-minimum measurement noise for Poisson noise. 4) in the case of Poisson noise, N=5,10,12 uniformly spaced angles over 360° have special covariance matrices that depend on the initial angle (the first angle in use). Finally, simulations are performed to verify these theoretical findings. © 2013 Optical Society of America.
Zheng H.,Huazhong University of Science and Technology |
Liu S.,Huazhong University of Science and Technology |
Liu S.,Wuhan National Laboratory for Optoelectronics |
Luo X.,Huazhong University of Science and Technology
Journal of Lightwave Technology | Year: 2013
High angular color uniformity (ACU) is strongly required in many illumination applications. In this study, we presented the phosphor dip-transfer coating method to realize high ACU for phosphor-converted white LEDs. The phosphor mixture was coated on top surfaces of LED chips and formed thin and convex phosphor layers by the dip-transfer coating. The optical simulations and experiments were conducted for performance verifications. Both numerical and experimental results show that the present method can obtain very high ACU. The angular correlated color temperature (CCT) deviation reaches 378 K when the average CCT of white LEDs is around 6200 K and it reduces to 63 K at the average CCT of about 4000 K. © 1983-2012 IEEE.
Kang S.,Huazhong University of Science and Technology |
Kang S.,Wuhan Polytechnic University |
Zhang X.,Huazhong University of Science and Technology |
Xie C.,Wuhan National Laboratory for Optoelectronics |
Zhang T.,Huazhong University of Science and Technology
Applied Optics | Year: 2013
A focus-swing liquid-crystal (LC) microlens with two patterned electrodes and filled in nematic liquid crystal is proposed. In order to lower the level of the applied voltage signal and effectively increase the focus-swing range, the bottom electrode is designed as a circular patterned structure. The top electrode is composed of four stripe-patterned subelectrodes, which are powered, respectively to generate expecting potential and drive the focus swing in the focal plane of the microlens. The common optical properties of the LC microlens and the swing behavior of the formed focus in the focal plane are demonstrated experimentally. © 2013 Optical Society of America.
Qian Y.,Huazhong University of Science and Technology |
Cao F.,Huazhong University of Science and Technology |
Guo W.,Wuhan National Laboratory for Optoelectronics
Tetrahedron | Year: 2013
A novel series of solution-processable 3,6-disubstituted-fluorene-carbazole based host materials 36FCzG1 and 36FCzG2 are designed and synthesized. Owing to the highly asymmetry tetrahedral configuration, these hosts exhibit high glass transition temperatures (Tg) (161 and 162 C, respectively), high triplet energy levels (2.80 and 2.80 eV, respectively), excellent film forming capabilities, and chemical miscibility. Phosphorescent organic lighting-emitting diodes (OLEDs), which base on these host materials doped with the guests of iridium(III) bis(4,6-difluorophenylpyridinato)-picolinate (FIrpic) by spin coating, possesses a low turn-on voltage of 4.0 V, a maximum efficiency of 18.5 cd/A (8.1 lm/W), and a maximum external quantum efficiency of 10.3%. These results show that the devices are among the excellent solution processable blue phosphorescent OLEDs based on dendrimers. Furthermore, a novel way is developed to construct solution processable small molecules based on 3,6-disubstituted fluorene and carbazole dendrimers combined in a highly rigid configuration. © 2013 Elsevier Ltd. All rights reserved.