Cascaded crystalline Raman lasers for extended wavelength coverage: continuous-wave, third-Stokes operation
Cascaded crystalline Raman lasers for extended wavelength coverage: continuous-wave, third-Stokes operation
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DOI：
10.1364/optica.5.001406
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发表时间：
2018-11
期刊：
影响因子：
10.4
通讯作者：
Riccardo Casula;J. Penttinen;M. Guina;A. Kemp;J. Hastie
中科院分区：
文献类型：
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作者：
Riccardo Casula;J. Penttinen;M. Guina;A. Kemp;J. Hastie
具有窄发射的高功率激光源的发展，在1.7 μm左右的水传输窗口内可调谐，对于医学成像和大气传感等各种应用都很感兴趣。在没有合适的激光增益介质的情况下，通常通过非线性频率转换来实现该光谱区域中的操作，并且光学参量振荡器（OPO）是常见的解决方案。为了避免双折射或准相位匹配要求，OPO的实际替代方案是在合适的材料内使用受激拉曼散射，以经由一个或多个斯托克斯位移将泵浦源转换为更长的波长;然而，由于这是χ（3）非线性过程，因此这种频率转换通常是高能脉冲激光器的保留。另一方面，半导体盘形激光器（SDLs）具有非常高精细度的外部谐振器，即使在连续波（CW）操作中也适用于高效的腔内非线性转换。本文报道了第一台连续三阶斯托克斯晶体拉曼激光器和SDL泵浦的最长发射波长的拉曼激光器，实现了高功率、连续输出和1.73 μm左右的宽波长调谐。采用1.18 μ mInGaAs基SDL腔内泵浦KGd（WO 4）2（KGW）拉曼激光器，实现了1.32 μm，1.50 μm和1.73 μm波长的连续斯托克斯振荡，并在每个波长获得了瓦级输出。1.73 μm斯托克斯辐射是衍射极限（M2<1.01）和窄线宽（<46 pm FWHM;测量极限）。通过旋转放置在基本谐振腔中的双折射滤波器，我们获得了三个可调谐的发射波长带，一个中心在每个斯托克斯分量，并实现了高达65 nm的调谐的第三斯托克斯拉曼激光从1696 nm到1761 nm。因此，我们展示了一种平台激光器技术，该技术采用成熟的基于InGaAs的SDLs，并使用市售组件在近红外水传输窗口中提供光谱覆盖和高性能。
The development of high-power laser sources with narrow emission, tunable within the water transmission window around 1.7 μm, is of interest for applications as diverse as medical imaging and atmospheric sensing. Where suitable laser gain media are not available, operation in this spectral region is often achieved via nonlinear frequency conversion, and optical parametric oscillators (OPOs) are a common solution. A practical alternative to OPOs, to avoid birefringent- or quasi-phase-matching requirements, is the use of stimulated Raman scattering within a suitable material to convert a pump source to longer wavelengths via one or more Stokes shifts; however, as this is a χ(3) nonlinear process, such frequency conversion is usually the preserve of high-energy pulsed lasers. Semiconductor disk lasers (SDLs), on the other hand, have very high-finesse external resonators, suitable for efficient intracavity nonlinear conversion even in continuous-wave (CW) operation. Here we report, to the best of our knowledge, the first continuous-wave third-Stokes crystalline Raman laser and the longest emission wavelength from an SDL-pumped Raman laser, achieving high power, CW output, and broad wavelength tuning around 1.73 μm. The KGd(WO4)2 (KGW) Raman laser, which was intracavity-pumped by a 1.18 μm InGaAs-based SDL, demonstrated cascaded CW Stokes oscillation at 1.32 μm, 1.50 μm, and 1.73 μm with watt-level output achievable at each wavelength. The 1.73 μm Stokes emission was diffraction limited (M2<1.01) and narrow linewidth (<46 pm FWHM; measurement limited). By rotation of a birefringent filter placed within the fundamental resonator, we attained three tunable emission wavelength bands, one centred at each Stokes component, and achieved up to 65 nm tuning for the third-Stokes Raman laser from 1696 nm to 1761 nm. We have thus demonstrated a platform laser technology that takes well-developed InGaAs-based SDLs and provides spectral coverage and high performance in the near-infrared water transmission windows using commercially available components.