McFerran J J
School of Physics, Mailstop M013, The University of Western Australia, Nedlands, 6009, WA, Australia.
Appl Opt. 2009 May 10;48(14):2752-9. doi: 10.1364/ao.48.002752.
Details for constructing an astronomical frequency comb suitable as a wavelength reference for échelle spectrographs associated with optical telescopes are outlined. The source laser for the frequency comb is a harmonically mode-locked fiber laser with a central wavelength of 1.56 microm. The means of producing a repetition rate greater than 7 GHz and a peak optical power of approximately 8 kW are discussed. Conversion of the oscillator light into the visible can occur through a two-step process of (i) nonlinear conversion in periodically poled lithium niobate and (ii) spectral broadening in photonic crystal fiber. While not necessarily octave spanning in spectral range to permit the use of an f -to- 2f interferometer for offset frequency control, the frequency comb can be granted accuracy by linking the mode spacing and a comb tooth to separate frequency references. The design avoids the use of a Fabry-Perot cavity to increase the mode spacing of the frequency comb; however, the level of supermode suppression and sideband asymmetry in the fiber oscillator and in the subsequent frequency conversion stages are aspects that need to be experimentally tested.
概述了构建一种适用于与光学望远镜相关的阶梯光栅光谱仪的波长参考的天文频率梳的详细信息。频率梳的源激光是中心波长为1.56微米的谐波锁模光纤激光器。讨论了产生大于7 GHz的重复率和大约8 kW的峰值光功率的方法。振荡器光转换为可见光可通过两步过程实现：（i）在周期性极化铌酸锂中的非线性转换和（ii）在光子晶体光纤中的光谱展宽。虽然频率梳在光谱范围内不一定是倍频程跨度以允许使用f - 2f干涉仪进行偏移频率控制，但通过将模式间距和梳齿链接到单独的频率参考，可以提高频率梳的精度。该设计避免使用法布里 - 珀罗腔来增加频率梳的模式间距；然而，光纤振荡器以及随后的频率转换阶段中的超模抑制水平和边带不对称性是需要通过实验测试的方面。
