Swept Light Source Research Articles

High-Speed Two-Dimensional Spectral-Scanning Coherent LiDAR System Based on Tunable VCSEL

Non-mechanical LiDAR systems have attracted extensive research interests due to their advantages of robustness and high beam-steering speed. Recently, spectral scanning has emerged as a promising solid-state beam-steering method, which combines dispersive elements with frequency-swept laser sources to perform ultrafast beam-steering. However, swept light sources used in LiDAR systems, such as semiconductor lasers and supercontinuum sources, are usually suffering from low sweep rate, bulky and high-cost that severely hinder the development of spectral-scanning LiDAR. Here, we propose a non-mechanical spectral-scanning frequency-modulated continuous-wave (FMCW) LiDAR system based on a simple compact tunable vertical-cavity surface-emitting laser (VCSEL). The fast-swept VCSEL together with wavelength division multiplexing (WDM) technology is employed for high-speed beam-steering. Millimeter-level ranging accuracy and a lateral resolution of 0.286° with an overall depth voxel acquisition rate of 128 kHz are achieved experimentally.

Simultaneously imaging and quantifying in vivo mechanical properties of crystalline lens and cornea using optical coherence elastography with acoustic radiation force excitation.

The crystalline lens and cornea comprise the eye’s optical system for focusing light in human vision. The changes in biomechanical properties of the lens and cornea are closely associated with common diseases, including presbyopia and cataract. Currently, most in vivo elasticity studies of the anterior eye focus on the measurement of the cornea, while lens measurement remains challenging. To better understand the anterior segment of the eye, we developed an optical coherence elastography system utilizing acoustic radiation force excitation to simultaneously assess the elasticities of the crystalline lens and the cornea in vivo. A swept light source was integrated into the system to provide an enhanced imaging range that covers both the lens and the cornea. Additionally, the oblique imaging approach combined with orthogonal excitation also improved the image quality. The system was tested through first ex vivo and then in vivo experiments using a rabbit model. The elasticities of corneal and lens tissue in an excised normal whole-globe and a cold cataract model were measured to reveal that cataractous lenses have a higher Young’s modulus. Simultaneous in vivo elasticity measurements of the lens and cornea were performed in a rabbit model to demonstrate the correlations between elasticity and intraocular pressure and between elasticity and age. To the best of our knowledge, we demonstrated the first in vivo elasticity of imaging of both the lens and cornea using acoustic radiation force-optical coherence elastography, thereby providing a potential powerful clinical tool to advance ophthalmic research in disorders affecting the lens and the cornea.

Electro-Optic Deflector Based on KTN Crystal for Phase-Stable Swept Light Source for OCT

Electro-Optic Deflector Based on KTN Crystal for Phase-Stable Swept Light Source for OCT

電気光学結晶KTa<sub>1-x</sub>Nb<sub>x</sub>O<sub>3</sub>を用いた高速光偏向器による波長掃引光源に関する研究と光コヒーレンストモグラフィーへの応用

電気光学結晶KTa<sub>1-x</sub>Nb<sub>x</sub>O<sub>3</sub>を用いた高速光偏向器による波長掃引光源に関する研究と光コヒーレンストモグラフィーへの応用

Detailed Visualization of the Anterior Segment Using Fourier-Domain Optical Coherence Tomography

To study details of the anterior chamber drainage angle using Fourier-domain optical coherence tomography in healthy subjects and patients with angle abnormalities. A high-speed anterior segment optical coherence tomography prototype was developed using a 1310-nm-wavelength swept light source. Six healthy subjects and 6 patients with glaucoma were imaged in an observational cross-sectional study. Schlemm's canal and the trabecular meshwork were visualized in all of the patients. Fifteen-millimeter scans enabled entire anterior segment visualization providing configuration details of the iris with respect to the angle. Four-millimeter scans permitted detailed views of the angle configuration and its structures. Volumetric imaging was possible and Schlemm's canal was visualized along part of its circumference. Anterior segment Fourier-domain optical coherence tomography permits detailed noncontact imaging of the angle and its structures, providing a tool to improve our understanding of the pathogenesis of narrow-angle glaucoma.

140-nm Quasi-Continuous Fast Sweep Using SSG-DBR Lasers

We demonstrate a single-mode and fast wavelength swept light source by employing superstructure-grating distributed Bragg reflector (SSG-DBR) lasers for use in optical frequency-domain reflectometry optical coherence tomography. A noteworthy feature is that our laser employs a thermal drift compensator (TDC). By utilizing the TDC, we achieved a fast wavelength sweep without any unexpected mode hopping. We newly designed and fabricated SSG-DBR lasers covering the following four wavelength bands: 1496-1529, 1529-1564, 1564-1601, and 1601-1639 nm. We achieved a stable operation for the whole wavelength range. A wide wavelength tuning of 143 nm was achieved within 1.4 ms. A single-mode, wide, and fast wavelength sweep was demonstrated.