High Efficient, Intense and Compact Pulsed D 2 O Terahertz Laser Pumped With a TEA CO 2 Laser
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High Efficient, Intense and Compact Pulsed D2O Terahertz Laser Pumped With a TEA CO2 Laser Lijie Geng & Yanchen Qu & Weijiang Zhao & Jun Du
Received: 26 June 2013 / Accepted: 21 August 2013 / Published online: 3 September 2013 # Springer Science+Business Media New York 2013
Abstract A high efficient, intense and compact pulsed D2O terahertz laser is presented, which is pumped by a multi-transverse mode TEA CO2 laser. For D2O gas as the active medium, with the cavity length of 120 cm, pulse energy of the THz laser has been investigated as the variation of pump energy and gas pressure. When the pump energy was 1.41 J, the maximum single pulse energy of 6.2 mJ was achieved at the wavelength of 385 μm. Photon conversion efficiency as high as 36.5% was obtained when laser operated at the maximum output energy. As the pump energy was raised from 0.57 to 1.41 J, the optimum pressure was slightly changed from 400 to 700 Pa. The THz pulse consisted of a spike pulse with pulse width of 120 ns and a tail pulse with pulse width of about 170 ns. The peak power of the spike pulse is about 44.3 kW. Comparing with the occurring time and pulse width of pump pulse, 70 ns delay and 10ns broadening were observed in the THz spike pulse. Keywords High efficient . Terahertz . TEA CO2 laser . D2O gas PACS 42.55.Lt
1 Introduction Diverse applications such as THz imaging [1, 2], THz digital holography [3], THz radar [4], remote sensing of the atmosphere [5], and molecular spectroscopy [6] place strict requirements on terahertz radiation source, in particular, an efficient, intense and coherent terahertz output. A number of methods to generate terahertz radiation have been developed such as difference frequency generation (DFG), THz parametric oscillation (TPO), THz quantum cascade laser (QCL), and optically pumped THz laser. The methods of DFG and TPO can generate tuning coherent terahertz radiation from 1 THz to 3 THz. However, the energy of DFG and TPO were too low (about from pJ to nJ) to apply in many fields [7]. In recent years, QCL has been considered to be one powerful THz laser because it could obtain more than one hundred mW output in the frequency range from 3 to 4.4 THz [8]. But QCL has to operate in low temperature environment and it is hard to obtain high power below 2 THz [9]. L. Geng : Y. Qu (*) : W. Zhao : J. Du National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology, Harbin 150080, China e-mail: [email protected]
J Infrared Milli Terahz Waves (2013) 34:780–786
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Since the first report of optically pumped THz radiation was reported by Chang and Bridges [10], optically pumped THz laser is always one of the most powerful ways to generate coherent THz radiation. Especially the intense optically pumped gas THz laser has received much attention for remote THz imaging and radar system. with heavy water gas (D2O gas) as the active medium, high power optically pumped gas THz laser have been reported by Super-radiation configurations [11–13] and more complicated cavity configuratio
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