Photonically integrated spectroscopy platform using grating-to-grating coupling (Conference Presentation)

Abstract

In the pursuit of developing a portable wavelength reference, a photonically integrated chip (PIC) was developed to perform high resolution spectroscopy in a small package. The PIC outcouples light from one grating into free space where it is reflected and directed into an adjacent grating that couples into a separate waveguide. These gratings are extreme-mode-converters which convert the confined mode with a characteristic mode size of less than a micron to a collimated 100 micron diameter beam in order to mitigate transit time broadening for high resolution spectroscopy as well as reduce the diffraction angle. A miniature atomic vapor cell is inserted in the path of the beam to complete the spectroscopic platform. Preliminary results demonstrate sub-Doppler features. Coupling into the chip is achieved using fiber arrays enabling the spectroscopic signal to be routed back through an optical fiber and monitored. A laser is then locked to these sub-Doppler features completing an integrated wavelength reference. Analysis of the atom-light interactions made available by this platform will be discussed with an emphasis on the application of such structures to portable wavelength metrology.