To meet the application need for agile precision beam steering, a novel liquid crystal prism device with a simple structure, convenient control, low cost and applicable performance is presented, and analysed theoretic...To meet the application need for agile precision beam steering, a novel liquid crystal prism device with a simple structure, convenient control, low cost and applicable performance is presented, and analysed theoretically and experimentally. The relationships between the optical path and the thickness of the liquid crystal cell under different voltages are investigated quantitatively by using a theoretical model. Analysis results show that the optical path profile of the liquid crystal prism has a quasi-linear slope and the standard deviation of the linear slope is less than 16 nm. The slope ratio can be changed by a voltage, which achieves the programmable beam steering and control. Practical liquid crystal prism devices are fabricated. Their deflection angles and wavefront profiles with different voltages are experimentally tested. The results are in good agreement with the simulated results. The results imply that the agile beam steering in a scope of 100μrad with a micro-rad resolution is substantiated in the device. The two-dimensional beam steering is also achieved by cascading two liquid crystal prism devices.展开更多
In this work, a method to reduce increase in optical density (OD) caused by multiple scanning in radiochromic film dosimetry in combination with a flatbed scanner is presented. Gafchromic EBT3 films are scanned with E...In this work, a method to reduce increase in optical density (OD) caused by multiple scanning in radiochromic film dosimetry in combination with a flatbed scanner is presented. Gafchromic EBT3 films are scanned with Epson Pro 1680 Expression scanner and time intervals of 15 minutes and 30 minutes are observed between consecutive scans to reduce the increase in temperature of the scanner. The maximum variations in OD after consecutive scans are calculated and compared to the values obtained for scans without interruption. For film irradiated to 3 Gy, a time interval of 15 minutes between two successive scans leads to a reduction of the OD increase of 56.2% compared to when films are scanned without interruption. Reductions of OD increase of 86.72% and 78.72% respectively for film irradiated to 1 Gy and 2 Gy are obtained when a time interval of 30 minutes is left between two successive scans. These results show that when time intervals are observed between consecutive scans, the increase in OD has significantly reduced. However, the method has the drawback of increasing the time needed to perform radiochromic film dosimetry.展开更多
We demonstrate the non-mechanical beam steering and amplifier operation of a vertical cavity surface emitting laser(VCSEL)integrated Bragg reflector waveguide amplifier with a cut-off wavelength detuning design,which ...We demonstrate the non-mechanical beam steering and amplifier operation of a vertical cavity surface emitting laser(VCSEL)integrated Bragg reflector waveguide amplifier with a cut-off wavelength detuning design,which enables unidirectional lateral coupling,continuous electrical beam steering,and diffraction-limited divergence angle.We present the modeling of the proposed structure for unidirectional coupling between a seed single-mode VCSEL and slow-light amplifier.We also present the detailed operating characteristics including the near-field and far-field patterns,light/current characteristics,and lasing spectrum.The experimental measurements exhibit a single-mode output of over 8 mW under CW operation,a continuous beam steering range of 16°,and beam divergence below 0.1°as an optical beam scanner.The integrated amplifier length is as small as 0.9 mm,and thus we could expect much higher powers and higher resolution points by increasing the amplifier lengths.展开更多
基金supported by the National High Technology Research and Development Program of China(Grant No.2009AA8042017)the Postdoctoral Science Foundation of University of Electronic Science and Technology of China
文摘To meet the application need for agile precision beam steering, a novel liquid crystal prism device with a simple structure, convenient control, low cost and applicable performance is presented, and analysed theoretically and experimentally. The relationships between the optical path and the thickness of the liquid crystal cell under different voltages are investigated quantitatively by using a theoretical model. Analysis results show that the optical path profile of the liquid crystal prism has a quasi-linear slope and the standard deviation of the linear slope is less than 16 nm. The slope ratio can be changed by a voltage, which achieves the programmable beam steering and control. Practical liquid crystal prism devices are fabricated. Their deflection angles and wavefront profiles with different voltages are experimentally tested. The results are in good agreement with the simulated results. The results imply that the agile beam steering in a scope of 100μrad with a micro-rad resolution is substantiated in the device. The two-dimensional beam steering is also achieved by cascading two liquid crystal prism devices.
文摘In this work, a method to reduce increase in optical density (OD) caused by multiple scanning in radiochromic film dosimetry in combination with a flatbed scanner is presented. Gafchromic EBT3 films are scanned with Epson Pro 1680 Expression scanner and time intervals of 15 minutes and 30 minutes are observed between consecutive scans to reduce the increase in temperature of the scanner. The maximum variations in OD after consecutive scans are calculated and compared to the values obtained for scans without interruption. For film irradiated to 3 Gy, a time interval of 15 minutes between two successive scans leads to a reduction of the OD increase of 56.2% compared to when films are scanned without interruption. Reductions of OD increase of 86.72% and 78.72% respectively for film irradiated to 1 Gy and 2 Gy are obtained when a time interval of 30 minutes is left between two successive scans. These results show that when time intervals are observed between consecutive scans, the increase in OD has significantly reduced. However, the method has the drawback of increasing the time needed to perform radiochromic film dosimetry.
文摘We demonstrate the non-mechanical beam steering and amplifier operation of a vertical cavity surface emitting laser(VCSEL)integrated Bragg reflector waveguide amplifier with a cut-off wavelength detuning design,which enables unidirectional lateral coupling,continuous electrical beam steering,and diffraction-limited divergence angle.We present the modeling of the proposed structure for unidirectional coupling between a seed single-mode VCSEL and slow-light amplifier.We also present the detailed operating characteristics including the near-field and far-field patterns,light/current characteristics,and lasing spectrum.The experimental measurements exhibit a single-mode output of over 8 mW under CW operation,a continuous beam steering range of 16°,and beam divergence below 0.1°as an optical beam scanner.The integrated amplifier length is as small as 0.9 mm,and thus we could expect much higher powers and higher resolution points by increasing the amplifier lengths.
