High-speed ultra-broad tuning MEMS-VCSELs for imaging and spectroscopy

In the last 2 years, the field of micro-electro-mechanical systems tunable vertical cavity surface-emitting lasers (MEMSVCSELs) has seen dramatic improvements in laser tuning range and tuning speed, along with expansion into unexplored wavelength bands, enabling new applications. This paper describes the design and performance of high-speed ultrabroad tuning range 1050nm and 1310nm MEMS-VCSELs for medical imaging and spectroscopy. Key results include achievement of the first MEMS-VCSELs at 1050nm and 1310nm, with 100nm tuning demonstrated at 1050nm and 150nm tuning at shown at 1310nm. The latter result represents the widest tuning range of any MEMS-VCSEL at any wavelength. Wide tuning range has been achieved in conjunction with high-speed wavelength scanning at rates beyond 1 MHz. These advances, coupled with recent demonstrations of very long MEMS-VCSEL dynamic coherence length, have enabled advancements in both swept source optical coherence tomography (SS-OCT) and gas spectroscopy. VCSEL-based SS-OCT at 1050nm has enabled human eye imaging from the anterior eye through retinal and choroid layers using a single instrument for the first time. VCSEL-based SS-OCT at 1310nm has enabled real-time 3-D SS-OCT imaging of large tissue volumes in endoscopic settings. The long coherence length of the VCSEL has also enabled, for the first time, meter-scale SS-OCT applicable to industrial metrology. With respect to gas spectroscopy, narrow dynamic line-width has allowed accurate high-speed measurement of multiple water vapor and HF absorption lines in the 1310nm wavelength range, useful in gas thermometry of dynamic combustion engines.