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Optical divces|8 Article(s)
Efficiency of terahertz detection in electro-optic polymer sensors with interdigitated coplanar electrodes
Qiang Jiang, Xuan Wang, Yue Wang, and Zhiyuan Li
We discuss the efficiency of an electro-optic (EO) polymer sensor with interdigitated coplanar electrodes. The developed EO sensor is used to detect terahertz radiation via EO sampling. Results show that the sensor improves more significantly detection sensitivity than does a sensor with sandwich configurations. We discuss the efficiency of an electro-optic (EO) polymer sensor with interdigitated coplanar electrodes. The developed EO sensor is used to detect terahertz radiation via EO sampling. Results show that the sensor improves more significantly detection sensitivity than does a sensor with sandwich configurations.
Chinese Optics Letters
- Publication Date: Aug. 30, 2013
- Vol. 11, Issue 9, 092301 (2013)
Terahertz Brewster polarizing beam splitter on a polymer substrate
Mengen Zhang, Xiangjun Li, Shixiong Liang, Pingan Liu, Jianjun Liu, and Zhi Hong
The performance of a terahertz (THz) Brewster polarizing beam splitter on polymer substrate is studied theoretically and experimentally. Simulations by using finite-element method demonstrate that both transmittance/reflectance and their extinction ratios are better than its 45 counterpart in a broad frequency range. Especially, the reflection extinction ratio improves significantly. The results are also verified experimentally with THz time domain spectroscopy (TDS) and backward wave oscillator (BWO) measurement system. The performance of a terahertz (THz) Brewster polarizing beam splitter on polymer substrate is studied theoretically and experimentally. Simulations by using finite-element method demonstrate that both transmittance/reflectance and their extinction ratios are better than its 45 counterpart in a broad frequency range. Especially, the reflection extinction ratio improves significantly. The results are also verified experimentally with THz time domain spectroscopy (TDS) and backward wave oscillator (BWO) measurement system.
Chinese Optics Letters
- Publication Date: Dec. 09, 2013
- Vol. 11, Issue 12, 122301 (2013)
A two-dimensional high-frequency electrostatic microscanner
Yaobo Liu, Weizheng Yuan, Dayong Qiao, Meng Wu, Xuan Yang, and Bin Lian
The design of a two-dimensional high-frequency electrostatic microscanner is presented, and an improved method for routing isolation trenches is investigated to increase the reliability and mechanical stability of the resulting device. A sample device is fabricated and tested using an optimized micromachining process. Measurement results indicate that the sample device oscillates at inherent frequencies of 11586 and 2047 Hz around the two rotational axes, thereby generating maximum twisting angles of +(-)7.28o and +(-)5.63o, respectively, under two square waves of 40 V. These characteristics confirm the validity of our design and satisfy the requirements of a laser projector with VGA standards. The design of a two-dimensional high-frequency electrostatic microscanner is presented, and an improved method for routing isolation trenches is investigated to increase the reliability and mechanical stability of the resulting device. A sample device is fabricated and tested using an optimized micromachining process. Measurement results indicate that the sample device oscillates at inherent frequencies of 11586 and 2047 Hz around the two rotational axes, thereby generating maximum twisting angles of +(-)7.28o and +(-)5.63o, respectively, under two square waves of 40 V. These characteristics confirm the validity of our design and satisfy the requirements of a laser projector with VGA standards.
Chinese Optics Letters
- Publication Date: Nov. 08, 2013
- Vol. 11, Issue 11, 112302 (2013)
Femtosecond laser-inscribed waveguides in Nd3+:Y3+:SrF2 crystals
Shengzhi Sun, Liangbi Su, Yufeng Yuan, and Zhenrong Sun
Optical waveguides are fabricated in Nd3+:Y3+:SrF2 crystals by a 1-kHz femtosecond laser using the double-line approach. Waveguides with different separations (10, 15, and 20 \mm m) between two consecutive optical breakdown tracks are produced, and their optical performances are explored by end-fire coupling to 780-and 532-nm lasers. Propagation loss of the waveguide with 20-\mm m separation is estimated. The microphotoluminescence and micro-Raman spectra indicate that the original fluorescence and lattice structure of the Nd3+:Y3+:SrF2 crystals are well preserved in the waveguide. Therefore, the obtained waveguide structures are promising candidate for application in integrated waveguide lasers. Optical waveguides are fabricated in Nd3+:Y3+:SrF2 crystals by a 1-kHz femtosecond laser using the double-line approach. Waveguides with different separations (10, 15, and 20 \mm m) between two consecutive optical breakdown tracks are produced, and their optical performances are explored by end-fire coupling to 780-and 532-nm lasers. Propagation loss of the waveguide with 20-\mm m separation is estimated. The microphotoluminescence and micro-Raman spectra indicate that the original fluorescence and lattice structure of the Nd3+:Y3+:SrF2 crystals are well preserved in the waveguide. Therefore, the obtained waveguide structures are promising candidate for application in integrated waveguide lasers.
Chinese Optics Letters
- Publication Date: Nov. 04, 2013
- Vol. 11, Issue 11, 112301 (2013)
AlGaN metal-semiconductor-metal ultraviolet photodetectors on sapphire substrate with a low-temperature AlN buffer layer
Junqin Zhang, Yintang Yang, and Hujun Jia
Unintentionally doped AlGaN thin films are grown on c-plane (0001) sapphire substrate by metal-organic chemical vapor deposition, and low-temperature AlN is deposited onto sapphire substrate used as a buffer layer. AlGaN metal-semiconductor-metal ultraviolet photodetectors with Ni/Au interdigitated contact electrodes are then fabricated by lift-off technology. The dark current of the AlGaN photodetectors is 5.61 \times 10-9 A at 2-V applied bias and the peak response occurrs at 294 nm. Unintentionally doped AlGaN thin films are grown on c-plane (0001) sapphire substrate by metal-organic chemical vapor deposition, and low-temperature AlN is deposited onto sapphire substrate used as a buffer layer. AlGaN metal-semiconductor-metal ultraviolet photodetectors with Ni/Au interdigitated contact electrodes are then fabricated by lift-off technology. The dark current of the AlGaN photodetectors is 5.61 \times 10-9 A at 2-V applied bias and the peak response occurrs at 294 nm.
Chinese Optics Letters
- Publication Date: Sep. 29, 2013
- Vol. 11, Issue 10, 102304 (2013)
Design and analysis of superlens based on complex two-dimensional square lattice photonic crystal
Somayeh Raf, Majid Ghanaatshoar, and Toshiaki Hattori
We theoretically demonstrate the imaging properties of a complex two-dimensional (2D) face-centered square lattice photonic crystal (PC) made from germanium cylinders in air background. The finite-difference time-domain (FDTD) method is employed to calculate the band structure and simulate image construction. The band diagram of the complex structure is significantly compressed. Negative refraction occurs in the second energy band with negative phase velocity at a frequency of 0.228 (2\pi c/a), which is lower than results from previous studies. Lower negative refraction frequency leads to higher image resolution. Numerical results show that the spatial resolution of the system reaches 0.7296 \lambda, which is lower than the incident wavelength. We theoretically demonstrate the imaging properties of a complex two-dimensional (2D) face-centered square lattice photonic crystal (PC) made from germanium cylinders in air background. The finite-difference time-domain (FDTD) method is employed to calculate the band structure and simulate image construction. The band diagram of the complex structure is significantly compressed. Negative refraction occurs in the second energy band with negative phase velocity at a frequency of 0.228 (2\pi c/a), which is lower than results from previous studies. Lower negative refraction frequency leads to higher image resolution. Numerical results show that the spatial resolution of the system reaches 0.7296 \lambda, which is lower than the incident wavelength.
Chinese Optics Letters
- Publication Date: Sep. 30, 2013
- Vol. 11, Issue 10, 102303 (2013)
Femtosecond laser damage of broadband pulse compression gratings
Fanyu Kong, Yunxia Jin, Shijie Liu, Shunli Chen, Heyuan Guan, Kai He, Ying Du, and Hongbo He
The fabricated gratings used for an 800-nm compressed laser pulse have more than 90% diffraction efficiency in the –1st order for TE polarization within 760–860 nm, and the maximum value is 94.3%. The laserinduced damage threshold (LIDT) of the gratings increases from 0.53 to 0.75 J/cm2 in the normal beam in a pulse width \tau of 40–100 fs. The LIDT of the gratings is observed a \tau^{0.25} scaling in the pulse width region. The damage morphologies of the gratings indicate that the initial damage of the gratings locates at the grating lines, a position that coincides with that of the electric field maximum. The fabricated gratings used for an 800-nm compressed laser pulse have more than 90% diffraction efficiency in the –1st order for TE polarization within 760–860 nm, and the maximum value is 94.3%. The laserinduced damage threshold (LIDT) of the gratings increases from 0.53 to 0.75 J/cm2 in the normal beam in a pulse width \tau of 40–100 fs. The LIDT of the gratings is observed a \tau^{0.25} scaling in the pulse width region. The damage morphologies of the gratings indicate that the initial damage of the gratings locates at the grating lines, a position that coincides with that of the electric field maximum.
Chinese Optics Letters
- Publication Date: Sep. 29, 2013
- Vol. 11, Issue 10, 102302 (2013)
Buried waveguide in neodymium-doped phosphate glass obtained by femtosecond laser writing using a double line approach
Xuewen Long, Jing Bai, Xin Liu, Wei Zhao, and Guanghua Cheng
We fabricate a buried channel waveguide in neodymium-doped phosphate glass using a double line approach by femtosecond laser writing. Raman spectra reveal an expansion of the glass network in the laser irradiated region. Given the stress-induced positive refractive index change, waveguiding between two separated tracks is demonstrated. The refractive index difference profile of the waveguide is reconstructed from the measured near-field mode. Propagation loss is measured by scattering technique. Microluminescence spectra reveal that the Nd3+ fluorescence property is not significantly affected by waveguide formation process, which indicates that the inscribed waveguide is a good candidate for active device. We fabricate a buried channel waveguide in neodymium-doped phosphate glass using a double line approach by femtosecond laser writing. Raman spectra reveal an expansion of the glass network in the laser irradiated region. Given the stress-induced positive refractive index change, waveguiding between two separated tracks is demonstrated. The refractive index difference profile of the waveguide is reconstructed from the measured near-field mode. Propagation loss is measured by scattering technique. Microluminescence spectra reveal that the Nd3+ fluorescence property is not significantly affected by waveguide formation process, which indicates that the inscribed waveguide is a good candidate for active device.
Chinese Optics Letters
- Publication Date: Sep. 29, 2013
- Vol. 11, Issue 10, 102301 (2013)
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