基于空芯光纤(HCF)的气体激光器是实现中红外激光输出的一种有效手段,一般情况下,跃迁选择定则决定一条泵浦吸收谱线对应两条激射跃迁谱线。通过气压控制的方法实现了单一谱线的4.3 μm单程结构HCF HBr激光器。以自研的1958 nm连续波高功率窄线宽掺铥光纤放大器为泵浦源,泵浦一段5 m长、充低压HBr气体的反共振HCF,通过气压控制分别实现了同位素H ⁷⁹Br和H ⁸¹Br单一谱线4.3 μm的激光输出,最大激光功率为350 mW,总的光光转换效率约为8%。利用自行搭建的光纤扫描装置测量了输出激光光斑,结果表明其是一种基模。

粒子数反转和受激拉曼散射是实现光纤气体激光器输出的最常见的两种基本原理。与光纤气体拉曼激光光源不同,基于粒子数反转原理的光纤气体激光器是通过气体分子振转能级的本征吸收跃迁实现激光输出。由于绝大多数气体分子的振转能级对应的激射跃迁谱线都在中红外波段,这种激光器的输出波长基本都在中红外波段。简要分析了基于粒子数反转原理的光纤气体激光器在产生中红外波段激光方面的优势,重点回顾了其发展历史与研究现状,并对下一步的发展趋势进行了展望。

报道了一种基于空芯光纤的光泵浦中红外HBr气体激光器。用一台可调谐的窄线宽2 μm连续波掺铥光纤放大器泵浦一段充低压HBr气体的4.4 m反共振空芯光纤,通过将种子激光的波长精确调谐到HBr(同位素H ⁷⁹Br)气体R(2)吸收线1971.7 nm附近,使得处于振动基态 v0的H ⁷⁹Br分子跃迁至振动激发态v₂,并在振动态v₂与v₁之间形成粒子数反转,通过跃迁选择定律同时激射出两条谱线R(2)和P(4),波长分别为3977.2 nm和4165.3 nm。当HBr气压为6.2 mbar时,4 μm激光最大输出功率为125 mW,相对于耦合进空芯光纤的泵浦光功率转换效率约为10%。通过进一步改善空芯光纤的传输损耗谱,提高泵浦光耦合效率,可大幅提升激光效率和输出功率,并且利用HBr分子的能级特性,将来有望实现大范围调谐的中红外激光输出。

报道了半导体抽运的单程中红外光纤气体激光器。用一个被调制放大的可调谐1.5 μm半导体激光器抽运一段长为2.3 m、充低压乙炔气体的低损耗负曲率空心光子晶体光纤(HC-PCF)，实现了单程有效的中红外（3.1~3.2 μm）激光输出，气压为200 Pa时光光转换效率大于14.5%，100 Pa时激光阈值小于100 nJ。为实现高效紧凑的大功率中红外光纤激光器提供了一条可能的技术途径。

报道了基于空心光子晶体光纤中氢气分子振动受激拉曼散射(SRS)的单程高增益1.9 μm光纤气体激光器。用一个线偏振1064 nm 亚纳秒脉冲微芯激光器抽运一段长6.5 m、充高压氢气的低损耗负曲率空心光纤，实现了到氢气分子一级振动斯托克斯波1907 nm的有效转换。气压为2.3 MPa时最大能量转换效率大于27%，相应的量子转换效率大于48%，激光平均功率约为10 mW，峰值功率大于2000 W。为实现高功率、窄线宽、大范围调谐的紧凑型中红外光纤激光器提供了一条潜在的有效途径。

A high energy pulsed terahertz (THz) laser is studied experimentally. The laser cavity simply consists of a quartz glass waveguide, a coated GaAs input window, and a crystal quartz output window. NH₃ is filled in the cavity as gain medium, and pumped by an 8-J line-tunable transversely excited atmospheric (TEA) CO₂ laser. When 9R(16) transition acts as the pump line, 55.6-mJ THz radiation (90 \mu m) is obtained at 730-Pa NH₃ pressure. The corresponding conversion efficiency is 13.54%. Energy and optimal pressure of amplified spontaneous emission and laser oscillation are compared.

Optically pumped terahertz (THz) lasers with high pulse repetition frequency are designed. Such a laser includes two parts: the optically pumping laser and the THz laser. The structures of the laser are described and analyzed. The rate equations for the pulsed THz laser are given. The kinetic process and laser pulse waveform for this kind of laser are numerically calculated based on the theory of rate equations. The theoretical results give a helpful guide to the research of such lasers.

The design and performance of radio frequency (RF) excited partial Z-fold waveguide CO2 laser with two channels are exposed. The length of the partial Z-fold channel is 3*460 mm and that of the single channel is 460 mm. The electrodes for the two channels are common and excited by a same RF source. According to our analysis, this kind of structure can greatly improve the laser offset frequency stability. In the experiments, we studied the variation of laser output power with gas pressure for two different channels. The maximum laser output power is about 23 W for the partial Z-fold channel and about 6 W for the single channel.