Megahertz FDML Laser with up to 143nm Sweep Range for Ultrahigh Resolution OCT at 1050nm

TL;DR

This paper introduces a novel FDML laser with a record 143nm sweep range at 1050nm, enabling ultrahigh resolution OCT imaging with detailed vascular visualization and an axial resolution of 6.0um.

Contribution

A new FDML laser design achieving the widest sweep range at 1um wavelength, significantly enhancing OCT resolution and imaging capabilities.

Findings

Achieved 143nm sweep range at 1um wavelength.

Demonstrated in vivo retinal imaging with 6.0um axial resolution.

Analyzed challenges like water absorption at high bandwidth.

Abstract

We present a new design of a Fourier Domain Mode Locked laser (FDML laser), which provides a new record in sweep range at ~1um center wavelength: At the fundamental sweep rate of 2x417 kHz we reach 143nm bandwidth and 120nm with 4x buffering at 1.67MHz sweep rate. The latter configuration of our system is characterized: The FWHM of the point spread function (PSF) of a mirror is 5.6um (in tissue). Human in vivo retinal imaging is performed with the MHz laser showing more details in vascular structures. Here we could measure an axial resolution of 6.0um by determining the FWHM of specular reflex in the image. Additionally, challenges related to such a high sweep bandwidth such as water absorption are investigated.