1. Articles from David T. D. Childs

    1-8 of 8
    1. Near-infrared and mid-infrared semiconductor broadband light emitters

      Near-infrared and mid-infrared semiconductor broadband light emitters

      Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications, especially for optical coherence tomography systems. Although near-infrared broadband light emitters have found increasingly wide utilization in these imaging applications, the requirement to simultaneously achieve both a high spectral bandwidth and output power is still challenging for such devices. Owing to the relatively weak amplified spontaneous emission, as a consequence of the very short non-radiative carrier lifetime of the inter-subband transitions in quantum cascade structures, it is even more challenging to obtain desirable mid-infrared broadband light emitters. There have been ...

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    2. Gallium nitride light sources for optical coherence tomography

      Gallium nitride light sources for optical coherence tomography

      The advent of optical coherence tomography (OCT) has permitted high-resolution, non-invasive, in vivo imaging of the eye, skin and other biological tissue. The axial resolution is limited by source bandwidth and central wavelength. With the growing demand for short wavelength imaging, super-continuum sources and non-linear fibre-based light sources have been demonstrated in tissue imaging applications exploiting the near-UV and visible spectrum. Whilst the potential has been identified of using gallium nitride devices due to relative maturity of laser technology, there have been limited reports on using such low cost, robust devices in imaging systems. A GaN super-luminescent light emitting diode ...

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    3. Towards in-situ process monitoring in selective laser sintering using optical coherence tomography

      Towards in-situ process monitoring in selective laser sintering using optical coherence tomography

      Selective laser sintering (SLS) enables fast, flexible and cost-efficient production of parts directly from 3D CAD data. However, compared with more established machine tools, there is a marked lack of process monitoring and feedback control of key process variables to optimize production parameters in-situ. We apply optical coherence tomography (OCT) to evaluate components produced by SLS and suggest a route for its application in in-situ process monitoring within the SLS tool for real-time monitoring of the SLS process for assurance, or even dynamic correction of defects during the build. OCT is shown to be a viable technique for evaluation of ...

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    4. Superluminescent diode with a broadband gain based on self-assembled InAs quantum dots and segmented contacts for an optical coherence tomography light source

      Superluminescent diode with a broadband gain based on self-assembled InAs quantum dots and segmented contacts for an optical coherence tomography light source

      We report a broadband-gain superluminescent diode (SLD) based on self-assembled InAs quantum dots (QDs) for application in a high-resolution optical coherence tomography (OCT) light source. Four InAs QD layers, with sequentially shifted emission wavelengths achieved by varying the thickness of the In 0.2 Ga 0.8 As strain-reducing capping layers, were embedded in a conventional p-n heterojunction comprising GaAs and AlGaAs layers. A ridge-type waveguide with segmented contacts was formed on the grown wafer, and an as-cleaved 4-mm-long chip (QD-SLD) was prepared. The segmented contacts were effective in applying a high injection current density to the QDs and obtaining ...

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    5. Evaluation of selective laser sintering processes by optical coherence tomography

      Evaluation of selective laser sintering processes by optical coherence tomography

      Selective laser sintering (SLS) enables the fast, flexible and cost-efficient production of parts directly from 3D CAD data. Unlike more established machine tools, there is a marked lack of process monitoring and feedback control of key process variables. In-situ analysis techniques permit the emergence of repair techniques, in-process optimization of production parameters, and will also serve to save time and material. In this study, optical coherence tomography (OCT) is used for the first time to evaluate components produced by SLS. Using a Polyamide-PA2200, surface defects are analyzed and the limiting factors associated with the measurement technique are quantified. OCT is ...

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    6. Swept-Source Laser Based on Quantum-Dot Semiconductor Optical Amplifier—Applications in Optical Coherence Tomography

      Swept-Source Laser Based on Quantum-Dot Semiconductor Optical Amplifier—Applications in Optical Coherence Tomography
      We present a swept-source laser based on a quantum-dot semiconductor optical amplifier (QD SOA) (designed and manufactured by Innolume Gmbh, Germany) as the gain medium. The properties of the laser are as follows: center wavelength is 1220 nm, sweep range is 94 nm (up to 120 nm in manual mode), the peak laser power is 16 mW, and the sweep speed is 100 Hz. We apply the laser in an optical coherence tomography (OCT) configuration and present images of in vivo skin. QD SOA are well suited to OCT and we show the setup can be improved for power, sweep ...
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    7. Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Device Engineering

      Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Device Engineering

      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 $mu$m, 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.

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    8. Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Skin Imaging

      Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Skin Imaging

      We present a high-power (18 mW continuous wave exiting a single-mode fiber and 35 mW exiting the facet), broadband (85 nm full-width at half-maximum) quantum dot-based superluminescent diode, and apply it to a time-domain optical coherence tomography (OCT) setup. First, we test its performance with increasing optical feedback. Then we demonstrate its imaging properties on tissue-engineered (TE) skin and in vivo skin. OCT allows the tracking of epidermal development in TE skin, while the higher power source allows better sensitivity and depth penetration for imaging of in vivo skin layers.

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    1-8 of 8
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  2. Topics in the News

    1. (8 articles) University of Sheffield
    2. (8 articles) David T. D. Childs
    3. (6 articles) Richard A. Hogg
    4. (5 articles) Steven J. Matcher
    5. (3 articles) Nikola Krstajic
    6. (2 articles) Marco Bonesi
    7. (1 articles) Medical University of Vienna
    8. (1 articles) University of St. Andrews
    9. (1 articles) Igor Krestnikov
    10. (1 articles) Innolume
    11. (1 articles) University of Illinois at Urbana-Champaign
    12. (1 articles) Duke University
    13. (1 articles) Joseph A. Izatt
    14. (1 articles) Stephen A. Boppart
    15. (1 articles) Sina Farsiu
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    Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Skin Imaging Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Device Engineering Swept-Source Laser Based on Quantum-Dot Semiconductor Optical Amplifier—Applications in Optical Coherence Tomography Evaluation of selective laser sintering processes by optical coherence tomography Superluminescent diode with a broadband gain based on self-assembled InAs quantum dots and segmented contacts for an optical coherence tomography light source Towards in-situ process monitoring in selective laser sintering using optical coherence tomography Gallium nitride light sources for optical coherence tomography Near-infrared and mid-infrared semiconductor broadband light emitters IMAGING TECHNIQUE FROM BECKMAN LAB NAMED TOP 10 MICROSCOPY INNOVATION Optical coherence refraction tomography University of Southern California Receives NIH Grant for Imaging Cerebral and Retinal Microvasculature in Cerebral Small Vessel Disease Columbia University Receives NIH Grant  for Measures of Human Receptor and post Receptor Activity