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

Abstract

In the last 2 years, the field of micro-electro-mechanical systems tunable vertical cavity surface-emitting lasers (MEMS-VCSELs) 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 ultra-broad 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.