Gallium Nitride Superluminescent Light Emitting Diodes for Optical Coherence Tomography Applications

Abstract

Abstract-Optical coherence tomography (OCT) exploits the coherent properties of light to permit noninvasive and in situ imaging of biological tissues. By expanding the range of OCT light sources from the traditional telecoms wavelengths to include ∼400 nm gallium nitride (GaN) based superluminescent light emitting diodes (SLEDs) subcellular axial and lateral resolution could be achieved, provided enhanced bandwidth is also achieved. Due to the focus on high-power applications for GaN SLEDs, there has been limited work on increasing the source bandwidth. In this paper, we demonstrate for the first time a ∼400 nm GaN SLED with >10 nm bandwidth employed within an OCT system, where an axial resolution of ∼7 µm is achieved. Bespoke GaN SLEDs suggest that <4 µm axial resolution imaging is imminent for short wavelength devices.Index Terms-Axial resolution, broad bandwidth, gallium nitride superluminescent light emitting diodes, optical coherence tomography.

A tutorial on laser-based lighting and visible light communications: device and technology [Invited]

“…In this section, we discuss the critical advances in light emitters for enabling high data rate VLC systems as illustrated in Fig. 4 [11,12,15,[42][43][44][45][46][47][48][49][50][51].…”

“…4. Recent advances in group-III-nitride-based laser diodes and SLD for enabling high data rate VLC systems [11,12,15,[42][43][44][45][46][47][48][49][50][51] on c-plane oriented substrates, in which the polar plane suffers from strong polarization fields and reduced internal quantum efficiency [52]. Since 2007, there has been growing research interest in developing various types of InGaN LDs on non-c-plane GaN substrates.…”

“…In recent years, nitride-based SLDs have also received significant attention owing to their optical characteristics, i.e., broadband spectrum similar to that of LEDs and high spatial coherence similar to that of LDs. Owing to its unique advantages, SLD is typically used as the source of broadband light in short-wavelength optical coherence tomography and fiber optic gyroscope systems [49]. Other examples of newly emerging applications of SLD that received increasing attention include droop-free SSL [47,97] and VLC [46].…”

“…Following these demonstrations, many studies on device optimization and system-level demonstrations have also been published. For instance, the design of waveguide structure [101,102], SLD on semipolar/non-polar substrates [47], SLD in solid-state lighting [97], optical coherence tomography [49,103], and optical communications [46] were demonstrated. Here, we summarize and discuss the key developments in SLD in both device-and system-level improvement, in particular, the practicality and feasibility in VLC.…”

Demonstration of a low-complexity memory-polynomial-aided neural network equalizer for CAP visible-light communication with superluminescent diode

“…InGaN-based laser diodes (LDs) and light-emitting diodes (LEDs), including micro-LEDs, have been used in the vast majority of the high-speed VLC systems up to date, achieving multi-Gbit/s (multi-Giga-bit-per-second) data rates [10][11][12][13][14] . The third type of device known as the superluminescent diode (SLD) combines the advantageous characteristics of both LDs and the LEDs [15][16][17][18][19] : Low etendue, high optical power density, low temporal coherence, wide frequency bandwidth, and droop-free emission, which makes the SLD attractive for VLC and other applications [20][21][22] . The SLD has been utilized as a VLC transmitter by using non-return-to-zero on-off keying (NRZ-OOK) 23,24 , which is, however, limited by the binary modulation capacity.…”