By introducing multi-leaf sectorial holes into an oxidation confined 850 nm vertical cavity surface emitting laser(VCSEL),the far-field divergence angle is reduced.The finite-difference time-domain method is used to s...By introducing multi-leaf sectorial holes into an oxidation confined 850 nm vertical cavity surface emitting laser(VCSEL),the far-field divergence angle is reduced.The finite-difference time-domain method is used to simulate the far-field pattern of the multi-leaf holey VCSEL with different etching depths and different shapes of the oxide aperture in diameter R.Based on the simulation result,we design and fabricate a multi−leaf holey VCSEL and its divergence angle is only 6°.The experimental results agree well with the theoretical predication.展开更多
The performance of the oxide-confined surface-relief(SR)structure vertical-cavity surface-emitting laser(VCSEL)is simulated and analyzed by using the three-dimensional finite-difference time-domain(FDTD)method.The imp...The performance of the oxide-confined surface-relief(SR)structure vertical-cavity surface-emitting laser(VCSEL)is simulated and analyzed by using the three-dimensional finite-difference time-domain(FDTD)method.The impacts of the device structure parameters on the far-field characteristics are researched.A single-fundamental-mode SR VCSEL with an oxide-aperture of 15μm is designed and produced.The single-mode power of the VCSEL is 5 mW,the threshold current is 2.5 mA,far-field divergent angles range from 7.8°to 10.8°and the side-mode suppression ratio is over 30 dB.The optical and electrical properties of the device are in agreement with the results of FDTD simulation,which shows that the SR technology can effectively suppress the higher-order-mode lasing,and make the SR VCSEL work in a single mode under a larger oxide aperture.展开更多
An ultrabroad and sharp transition bandpass flexible terahertz(THz)filter is designed using a multiple-layered metamaterial.This bandpass filter has excellent filtering capability,with a 3 dB bandwidth of about 0.47 T...An ultrabroad and sharp transition bandpass flexible terahertz(THz)filter is designed using a multiple-layered metamaterial.This bandpass filter has excellent filtering capability,with a 3 dB bandwidth of about 0.47 THz and sharp band-edge transitions of 80 dB/THz and 96 dB/THz,respectively,and it can be realized by a coupling individual resonance mode.We find that the geometry parameters have an influence on the transmission profile,which are capable of giving us meaningful guidance in design of high profile bandpass THz filters.The numerical results show that the multiple-layered flexible metamaterial provides an effective way to achieve ultrabroad THz devices.展开更多
We report a widely tunable,narrow linewidth,pulsed Ti:sapphire laser pumped by an all-solid-state Q-switched intra-cavity frequency-doubled Nd:YAG laser.By using four dense flint glass prisms as intra-cavity dispersiv...We report a widely tunable,narrow linewidth,pulsed Ti:sapphire laser pumped by an all-solid-state Q-switched intra-cavity frequency-doubled Nd:YAG laser.By using four dense flint glass prisms as intra-cavity dispersive elements,the output wavelength can be continuously tuned over 675–970 nm and the spectral linewidth is shortened to 0.5 nm.The maximum output power of 6.65 W at 780 nm is obtained under 23.4 W pump power with repetition rate of 5.5 kHz;corresponding to an conversion efficiency of 28.4%.Due to the gain-switching characteristics of the Ti:sapphire laser,the output pulse duration is as short as 17.6 ns.展开更多
A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers(VCSELs)is presented.The VCSEL is composed by two wafers:one micro-electromechanical-system membrane wafer with f...A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers(VCSELs)is presented.The VCSEL is composed by two wafers:one micro-electromechanical-system membrane wafer with four arms to adjust the cavity length through electrostatic actuation and a"half-VCSEL"wafer consisting of a fixed bottom mirror and an amplifying active region.The measurement results of the electricity pumped tunable VCSEL with more than 9mW output power at room temperature over the tuning range prove the feasibility of the proposition.展开更多
Broadband terahertz（THz） atmospheric transmission characteristics from 0 to 8 THz are theoretically simulated based on a standard Van Vleck–Weisskopf line shape, considering 1696 water absorption lines and 298 oxyg...Broadband terahertz（THz） atmospheric transmission characteristics from 0 to 8 THz are theoretically simulated based on a standard Van Vleck–Weisskopf line shape, considering 1696 water absorption lines and 298 oxygen absorption lines.The influences of humidity, temperature, and pressure on the THz atmospheric absorption are analyzed and experimentally verified with a Fourier transform infrared spectrometer（FTIR） system, showing good consistency. The investigation and evaluation on high-frequency atmospheric windows are good supplements to existing data in the low-frequency range and lay the foundation for aircraft-based high-altitude applications of THz communication and radar.展开更多
An asymmetric quantum well (AQW) is designed to emit a terahertz (THz) wave by using difference frequency generation (DFG) with the structure of GaAs/Al_(0.2)Ga_(0.8)As/Al_(0.5) Ga_(0.5)As under a doubly resonant cond...An asymmetric quantum well (AQW) is designed to emit a terahertz (THz) wave by using difference frequency generation (DFG) with the structure of GaAs/Al_(0.2)Ga_(0.8)As/Al_(0.5) Ga_(0.5)As under a doubly resonant condition.It is found that the second-order nonlinear susceptibility χ^((2)) varies with the two pump wavelengths,and it can reach the peak value of 1.61 μm/V when the wavelengths are given as λ_(p1) =9.756 μm and λ_(p2) =10.96 μm,respectively.The numerical results show that the refractive index of one pump wave in the AQW is concerned with not only its own wavelength but also the other wavelength.Phase-matching inside the AQW can be obtained through the tuning of the two pump wavelengths.展开更多
基金by the National High Technology Research and Development Program of China under Grant No 2008AA03Z402the National Natural Science Foundation of China under Grant No 61076044the Natural Science Foundation of Beijing under Grant Nos 4092007,4102003 and 4112006.
文摘By introducing multi-leaf sectorial holes into an oxidation confined 850 nm vertical cavity surface emitting laser(VCSEL),the far-field divergence angle is reduced.The finite-difference time-domain method is used to simulate the far-field pattern of the multi-leaf holey VCSEL with different etching depths and different shapes of the oxide aperture in diameter R.Based on the simulation result,we design and fabricate a multi−leaf holey VCSEL and its divergence angle is only 6°.The experimental results agree well with the theoretical predication.
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2008AA03Z402the National Natural Science Foundation of China under Grant No 61076044the Natural Science Foundation of Beijing under Grant Nos 4092007,4102003 and 4112006.
文摘The performance of the oxide-confined surface-relief(SR)structure vertical-cavity surface-emitting laser(VCSEL)is simulated and analyzed by using the three-dimensional finite-difference time-domain(FDTD)method.The impacts of the device structure parameters on the far-field characteristics are researched.A single-fundamental-mode SR VCSEL with an oxide-aperture of 15μm is designed and produced.The single-mode power of the VCSEL is 5 mW,the threshold current is 2.5 mA,far-field divergent angles range from 7.8°to 10.8°and the side-mode suppression ratio is over 30 dB.The optical and electrical properties of the device are in agreement with the results of FDTD simulation,which shows that the SR technology can effectively suppress the higher-order-mode lasing,and make the SR VCSEL work in a single mode under a larger oxide aperture.
基金Supported by the National Basic Research Program of China under Grant No 2007CB310403the High Education Science Technology Project of Shandong Province(No J11LG74)the Science and Technology Project of Zaozhuang(No 201127).
文摘An ultrabroad and sharp transition bandpass flexible terahertz(THz)filter is designed using a multiple-layered metamaterial.This bandpass filter has excellent filtering capability,with a 3 dB bandwidth of about 0.47 THz and sharp band-edge transitions of 80 dB/THz and 96 dB/THz,respectively,and it can be realized by a coupling individual resonance mode.We find that the geometry parameters have an influence on the transmission profile,which are capable of giving us meaningful guidance in design of high profile bandpass THz filters.The numerical results show that the multiple-layered flexible metamaterial provides an effective way to achieve ultrabroad THz devices.
基金by the National Natural Science Foundation of China under Grant Nos 60978021 and 10804055the National Basic Research Program of China under Grant No 2007CB310403the Program for New Century Excellent Talents in University(NCET).
文摘We report a widely tunable,narrow linewidth,pulsed Ti:sapphire laser pumped by an all-solid-state Q-switched intra-cavity frequency-doubled Nd:YAG laser.By using four dense flint glass prisms as intra-cavity dispersive elements,the output wavelength can be continuously tuned over 675–970 nm and the spectral linewidth is shortened to 0.5 nm.The maximum output power of 6.65 W at 780 nm is obtained under 23.4 W pump power with repetition rate of 5.5 kHz;corresponding to an conversion efficiency of 28.4%.Due to the gain-switching characteristics of the Ti:sapphire laser,the output pulse duration is as short as 17.6 ns.
基金Supported by the National Basic Research Program of China under Grant No 2006CB604902the National Natural Science Foundation of China under Grant No 60908012+2 种基金the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No 39002013200801the National Natural Science Foundation of China under Grant No 61076048the Board of Education Research Project under Grant No KM2010005030.
文摘A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers(VCSELs)is presented.The VCSEL is composed by two wafers:one micro-electromechanical-system membrane wafer with four arms to adjust the cavity length through electrostatic actuation and a"half-VCSEL"wafer consisting of a fixed bottom mirror and an amplifying active region.The measurement results of the electricity pumped tunable VCSEL with more than 9mW output power at room temperature over the tuning range prove the feasibility of the proposition.
基金supported by the National Basic Research Program of China(Grant Nos.2014CB339802 and 2015CB755403)the National Natural Science Foundation of China(Grant Nos.61675146,61275102,and 61271066)the Science and Technology Support Program of Tianjin,China(Grant No.14ZCZDGX00030)
文摘Broadband terahertz（THz） atmospheric transmission characteristics from 0 to 8 THz are theoretically simulated based on a standard Van Vleck–Weisskopf line shape, considering 1696 water absorption lines and 298 oxygen absorption lines.The influences of humidity, temperature, and pressure on the THz atmospheric absorption are analyzed and experimentally verified with a Fourier transform infrared spectrometer（FTIR） system, showing good consistency. The investigation and evaluation on high-frequency atmospheric windows are good supplements to existing data in the low-frequency range and lay the foundation for aircraft-based high-altitude applications of THz communication and radar.
基金Supported by National Natural Science Foundation of China under Grant Nos 60801017,61172010,61101058,and 61107086the Science and Technology Committee of Tianjin under Grant No 11JCYBJC01100.
文摘An asymmetric quantum well (AQW) is designed to emit a terahertz (THz) wave by using difference frequency generation (DFG) with the structure of GaAs/Al_(0.2)Ga_(0.8)As/Al_(0.5) Ga_(0.5)As under a doubly resonant condition.It is found that the second-order nonlinear susceptibility χ^((2)) varies with the two pump wavelengths,and it can reach the peak value of 1.61 μm/V when the wavelengths are given as λ_(p1) =9.756 μm and λ_(p2) =10.96 μm,respectively.The numerical results show that the refractive index of one pump wave in the AQW is concerned with not only its own wavelength but also the other wavelength.Phase-matching inside the AQW can be obtained through the tuning of the two pump wavelengths.
