Abstract: Embodiments herein describe various arrangements of an optical bench used to perform spectroscopy. For example, a spectroscopy system may include a pump optical signal and a probe optical signal that are transmitted through a vapor cell on the optical bench. The optical bench can further include one or more optical components (e.g., beam splitter and a thin film polarizer) for redirecting a portion of the probe and pump optical signals to photodiodes. In one embodiment, the measurements obtained from the photodiodes can be used to perform multiple tasks. For example, the measurements can be used to adjust the power of the optical signals in the optical bench (e.g., make DC power adjustments), perform amplitude modulation correction, and lock a laser frequency to a peak of an absorption spectrum of the vapor in the vapor cell.