Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Device Engineering

Abstract

ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract-We present a 18 mW fiber-coupled single-mode superluminescent diode with 85 nm bandwidth for application in optical coherence tomography (OCT). First, we describe the effect of quantum dot (QD) growth temperature on optical spectrum and gain, highlighting the need for the optimization of epitaxy for broadband applications. Then, by incorporating this improved material into a multicontact device, we show how bandwidth and power can be controlled. We then go on to show how the spectral shape influences the autocorrelation function, which exhibits a coherence length of <11 µm, and relative noise is found to be 10 dB lower than that of a thermal source. Finally, we apply the optimum device to OCT of in vivo skin and show the improvement that can be made with higher power, wider bandwidth, and lower noise, respectively.Index Terms-Optical coherence tomography (OCT), quantum dot (QD), skin imaging, superluminescent diodes (SLEDs).

QD Ultrafast and Continuous Wavelength Laser Diodes for Applications in Biology and Medicine

“…It does show that QDs are suitable for OCT imaging of skin and are in fact comparable to commercial QW devices [105]. It seems that this field of OCT will benefit greatly when the great bandwidths possible from QDs are realized and enable cellular resolution.…”

“…This material was then fabricated into a multisection contact, single-pass device with a curved output [104]. The multisection contacts allow the emission spectrum to be tuned, obtaining simultaneously broad spectral width and high powers coupled into a single-mode fiber (85 nm, 18 mW exfiber) [105]. At low frequencies (<100 kHz), the relative intensity noise (RIN) for the QD SLD was found to be 8-15 dB Hz −1 lower than that of a QW SLD, and this was attributed to the QDs being operated in gain saturation.…”

“…Miniature MEMS systems also have the benefit of reducing cavity length and system footprint [122] relative to the fiber-based systems. Finally, filters without moving parts, such as the tunable distributed Bragg reflector (DBR) offer the highest possible speeds since they only depend on the electric field [108] or carrier density [105] inside a semiconductor.…”

Gain spectrum measurement using the segmented contact method with an integrated optical amplifier

“…Full details of the epitaxial process and the device fabrication details are given elsewhere. 13,21 Devices were selected based upon the front four sections having identical I-V characteristics, with the assumption that this would result in identical spectral L-I characteristics.…”

“…However, Xin et al commented on the possible use of the mode-filter as an amplifier. 10 GaAs based quantum dot (QD) devices are of interest due to their low cost, temperature insensitive threshold current density 11,12 and their current applications in biomedical imaging, 13 mode-locking applications, 14 and optical communications. 15 However, the gain spectrum in QD materials is complicated by inhomogeneous and homogeneous broadening, 16 strong state-filling effects, 17 and by free carrier effects.…”