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Sources and mechanisms of terahertz radiation|4 Article(s)
Compact and high-power broadband terahertz source based on femtosecond photonic crystal fiber amplifier
Feng Liu, Xiaokun Hu, Jiang Li, Changlei Wang, Yi Li, Yanfeng Li, Youjian Song, Bowen Liu, Minglie Hu, Lu Chai, Qirong Xing, Chingyue Wang, and Weili Zhang
We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier. The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient. Broadband THz pulses of 150 μW extending from 0.1 to 3.5 THz are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 fs and a repetition rate of 52 MHz. A strong saturation effect is observed, which is attributed to pump pulse absorption; a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1 040 nm. A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscopy. We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier. The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient. Broadband THz pulses of 150 μW extending from 0.1 to 3.5 THz are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 fs and a repetition rate of 52 MHz. A strong saturation effect is observed, which is attributed to pump pulse absorption; a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1 040 nm. A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscopy.
Chinese Optics Letters
- Publication Date: Sep. 27, 2011
- Vol. 9, Issue 11, 110005 (2011)
Recent progress on terahertz generation based on difference frequency generation: from power scaling to compact and portable sources (Invited Paper)
Yujie J., Pu Zhao, Srinivasa Ragam, Da Li, and Ioulia B.
The progress achieved on power scaling and compact and portable THz sources is reviewed. By reversely stacking the GaP plates, the photon conversion efficiency is improved from 25% to 40% which corresponds to the maximum value. When the number of the plates is increased from four to five, the output power decreases because of back conversion. The THz generation is also investigated by mixing the two frequencies generated by a single Nd:YLF solid-state laser. The average output power reaches 1 \mu W. The introduction of two Nd:YLF crystals significantly improves the output power to 4.5 μW. This configuration facilitates the generation of different output frequencies. The progress achieved on power scaling and compact and portable THz sources is reviewed. By reversely stacking the GaP plates, the photon conversion efficiency is improved from 25% to 40% which corresponds to the maximum value. When the number of the plates is increased from four to five, the output power decreases because of back conversion. The THz generation is also investigated by mixing the two frequencies generated by a single Nd:YLF solid-state laser. The average output power reaches 1 \mu W. The introduction of two Nd:YLF crystals significantly improves the output power to 4.5 μW. This configuration facilitates the generation of different output frequencies.
Chinese Optics Letters
- Publication Date: Sep. 30, 2011
- Vol. 9, Issue 11, 110004 (2011)
Quantum cascade lasers operating from 1.4 to 4 THz (Invited Paper)
Sushil Kumar
The development of teranertz (THz) quantum cascade lasers (QCLs) has progressed considerably since their advent almost a decade ago. THz QCLs operating in a frequency range from 1.4 to 4 THz with electron-phonon scattering mediated depopulation schemes are described. Several different types of GaAs/AlGaAs superlattice designs are reviewed. Some of the best temperature performances are obtained by the so-called resonant-phonon designs that are described. Operation above a temperature of 160 K has been obtained across the spectrum for THz QCLs operating at \nu >1.8 THz. The maximum operating temperature of previously reported THz QCLs has empirically been limited to a value of ~\hbar \omega/kB. A new design scheme for THz QCLs with scattering-assisted injection is shown to surpass this empirical temperature barrier, and is promising to improve the maximum operating temperatures of THz QCLs even further. The development of teranertz (THz) quantum cascade lasers (QCLs) has progressed considerably since their advent almost a decade ago. THz QCLs operating in a frequency range from 1.4 to 4 THz with electron-phonon scattering mediated depopulation schemes are described. Several different types of GaAs/AlGaAs superlattice designs are reviewed. Some of the best temperature performances are obtained by the so-called resonant-phonon designs that are described. Operation above a temperature of 160 K has been obtained across the spectrum for THz QCLs operating at \nu >1.8 THz. The maximum operating temperature of previously reported THz QCLs has empirically been limited to a value of ~\hbar \omega/kB. A new design scheme for THz QCLs with scattering-assisted injection is shown to surpass this empirical temperature barrier, and is promising to improve the maximum operating temperatures of THz QCLs even further.
Chinese Optics Letters
- Publication Date: Sep. 30, 2011
- Vol. 9, Issue 11, 110003 (2011)
Studies on the mechanisms of powerful terahertz radiations from laser plasmas (Invited Paper)
Weimin Wang, Zhengming Sheng, Yutong Li, Liming Chen, Quanli Dong, Xin Lu, Jinglong Ma, and Jie Zhang
A survey on the mechanisms of powerful terahertz (THz) radiation from laser plasmas is presented. Firstly, an analytical model is described, showing that a transverse net current formed in a plasma can be converted into THz radiations at the plasma oscillation frequency. This theory is applied to explain THz generation in a gas driven by two-color laser pulses. It is also applied to THz generation in a tenuous plasma driven by a chirped laser pulse, a few-cycle laser pulse, a DC/AC bias electric field. These are well verified by particle-in-cell simulations, demonstrating that THz radiations produced in these approaches are nearly single-cycles and linear polarized. In the chirped laser scheme and the few-cycle laser scheme, THz radiations with the peak field strength of tens of MV/cm and the peak power of gigawatt can be achieved with the incident laser intensity less than 10^{17} W/cm2. A survey on the mechanisms of powerful terahertz (THz) radiation from laser plasmas is presented. Firstly, an analytical model is described, showing that a transverse net current formed in a plasma can be converted into THz radiations at the plasma oscillation frequency. This theory is applied to explain THz generation in a gas driven by two-color laser pulses. It is also applied to THz generation in a tenuous plasma driven by a chirped laser pulse, a few-cycle laser pulse, a DC/AC bias electric field. These are well verified by particle-in-cell simulations, demonstrating that THz radiations produced in these approaches are nearly single-cycles and linear polarized. In the chirped laser scheme and the few-cycle laser scheme, THz radiations with the peak field strength of tens of MV/cm and the peak power of gigawatt can be achieved with the incident laser intensity less than 10^{17} W/cm2.
Chinese Optics Letters
- Publication Date: Oct. 25, 2011
- Vol. 9, Issue 11, 110002 (2011)
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