1. David T. D. Childs

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    1. Mentioned In 22 Articles

    2. 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 ...
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    3. 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 ...
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    4. 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 ...
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    5. Simulation of broad spectral bandwidth emitters at 1060 nm for retinal optical coherence tomography

      Simulation of broad spectral bandwidth emitters at 1060 nm for retinal optical coherence tomography
      The simulation of broad spectral bandwidth light sources (semiconductor optical amplifiers (SOA) and superluminescent diodes (SLD)) for application in ophthalmic optical coherence tomography is reported. The device requirements and origin of key device parameters are outlined, and a range of single and double InGaAs/GaAs quantum well (QW) active elements are simulated with a view to application in different OCT embodiments. We confirm that utilising higher order optical transitions is ...
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    6. 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 ...
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    7. 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 ...
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    8. GaAs-Based Superluminescent Light-Emitting Diodes with 290-nm Emission Bandwidth by Using Hybrid Quantum Well/Quantum Dot Structures

      GaAs-Based Superluminescent Light-Emitting Diodes with 290-nm Emission Bandwidth by Using Hybrid Quantum Well/Quantum Dot Structures
      A high-performance superluminescent light-emitting diode (SLD) based upon a hybrid quantum well (QW)/quantum dot (QD) active element is reported and is assessed with regard to the resolution obtainable in an optical coherence tomography system. We report on the appearance of strong emission from higher order optical transition from the QW in a hybrid QW/QD structure. This additional emission broadening method contributes significantly to obtaining a 3-dB linewidth of ...
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    9. Lasers and SLEDs for optical coherence tomography

      Lasers and SLEDs for optical coherence tomography
      Optical coherence tomography (OCT) allows for the generation of 3D tomographic images of sub-surface structures in-vivo. This non-destructive, non-ionising process has found application in biological science and clinical diagnosis. Specifically, two versions of the OCT technique have proved optimal for different applications. For retinal imaging through a long length of water, near infrared wavelength super-luminescent diodes (SLEDs) with silicon array detector spectrometer systems have dominated. For imaging turbid media such ...
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    10. Feature Of The Week 7/3/11: Swept-Source Laser Based on a Quantum Dot Semiconductor Optical Amplifier

      Feature Of The Week 7/3/11: Swept-Source Laser Based on a Quantum Dot Semiconductor Optical Amplifier
      Researchers at the University of Sheffield have been very active in publishing novel results on high performance semiconductors for Optical Coherence Tomography. Recently in collaboration with Innolume they published on a swept-source laser based on a quantum-dot semiconductor optical amplifier. Below is a summary of that work.Swept source lasers (SSL) are a crucial component in Fourier domain optical coherence tomography (OCT) systems. Most SSLs use semiconductor optical amplifiers (SOA ...
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    11. Evaluation of a swept-laser optical coherence tomography light source based on a novel quantum-dot based semiconductor optical amplifier

      Evaluation of a swept-laser optical coherence tomography light source based on a novel quantum-dot based semiconductor optical amplifier
      ...ast, with the stratum corneum, epidermis, rete ridges and epidermal-dermal junction visualized. Nik Krstajic, David Childs, Negin Peyvast, Deepa Kasaragod, Stephen J. Matcher, Igor Krestnikov and Richard Hogg, "Evaluatio...
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    12. 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 ...
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    13. Common path Michelson interferometer based on multiple reflections within the sample arm: sensor applications and imaging artefacts

      Common path Michelson interferometer based on multiple reflections within the sample arm: sensor applications and imaging artefacts
      We present a simple common path dual beam interferometric sensor platform using a low-coherence source. In our implementation we exploit (in a controlled manner) the multiple reflections within the sample arm to provide the reference arm. This simple setup removes the need for a separate reference arm and allows an alternative architecture for using low-coherence sources in interferometric sensors. We demonstrate the sensor characteristics by using it as a vibrometer ...
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    14. 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 ...
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  2. About David T. D. Childs

    David T. D. Childs

    David Childs received the B.Sc. degree in physics, the. M.Sc. degree in semiconductor science and technology, and the Ph.D. degree from Imperial College, London. He then spent five years with the R&D Department of Marconi Optical Components and Bookham Technology at the Caswell Semiconductor Research and Fabrication Facility, where he was involved in development of a range of telecoms lasers. He is currently with the Department of Electronic and Electrical Engineering, the University of Sheffield.  He is engaged in developing optoelectronic devices for to applications such as multi-photon imaging, optical communications and optical coherence tomography.