Tunable lasers, with the ability to continuously vary their emission wavelengths, have found widespread applications across various fields such as biomedical imaging, coherent ranging, optical communications, and spectroscopy. In these applications, a wide chirp range is advantageous for large spectral coverage and high frequency resolution. Besides, the frequency accuracy and precision also depend critically on the chirp linearity of the laser. While extensive efforts have been made on the development of many kinds of frequency-agile, widely tunable, narrow-linewidth lasers, wideband yet precise methods to characterize and linearize laser chirp dynamics are also demanded. Here we present an approach to characterize laser chirp dynamics using an optical frequency comb. The instantaneous laser frequency is tracked over terahertz bandwidth at 1 MHz intervals. Using this approach we calibrate the chirp performance of 12 tunable lasers from Toptica, Santec, New Focus, EXFO, and NKT that are commonly used in fiber optics and integrated photonics. In addition, with acquired knowledge of laser chirp dynamics, we demonstrate a simple frequency-linearization scheme that enables coherent ranging without any optical or electronic linearization unit. Our approach not only presents novel wideband, high-resolution laser spectroscopy, but is also critical for sensing applications with ever-increasing requirements on performance.

中文翻译：

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用于相干测距的频率梳线性化、宽范围可调谐激光器

可调谐激光器能够连续改变其发射波长，已在生物医学成像、相干测距、光通信和光谱学等各个领域得到广泛应用。在这些应用中，宽的线性调频范围有利于大的频谱覆盖范围和高的频率分辨率。此外，频率精度和精确度还很大程度上取决于激光器的啁啾线性度。虽然人们在开发多种频率捷变、宽可调、窄线宽激光器方面做出了广泛的努力，但还需要宽带而精确的方法来表征和线性化激光啁啾动态。在这里，我们提出了一种使用光学频率梳来表征激光啁啾动态的方法。在太赫兹带宽上以 1 MHz 间隔跟踪瞬时激光频率。使用这种方法，我们校准了来自 Toptica、Santec、New Focus、EXFO 和 NKT 的 12 个可调谐激光器的线性调频性能，这些激光器常用于光纤和集成光子学。此外，凭借对激光啁啾动力学的了解，我们演示了一种简单的频率线性化方案，无需任何光学或电子线性化单元即可实现相干测距。我们的方法不仅提供了新颖的宽带、高分辨率激光光谱，而且对于性能要求不断提高的传感应用也至关重要。