Probing the Concepts of Photonic Crystals on Scintillating Materials

Kronberger, M.; Auffray, E.; Lecoq, P.

doi:10.1109/tns.2008.922827

Cited by 56 publications

(28 citation statements)

References 12 publications

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“…For crystals with high aspect ratios, as the ones used in PET scanners, up to 50% of the scintillation light will not be collected [28], even if Teflon wrapping and optical coupling are used, and a large fraction of the collected photons will be delayed by multiple bouncings in the crystal. Several years ago, we proposed to use photonic crystal slabs (PhC slabs), defined as thin dielectric layers structured with a 2D or 3D periodic pattern, to increase this efficiency [29]. A higher light output, combined with a reduction of the average path length of the photons in the crystal before their extraction, leads to a better energy and time resolution.…”

Section: Rationale For Photonic Crystalsmentioning

confidence: 99%

“…The idea of introducing photonic crystals to increase the performance of scintillating crystals used in ionizing radiation detection had been first introduced in 2008 [29]. The first goal was to overcome the problem of light extraction and light coupling inefficiencies from the crystal to the photodetector because of the high refractive index mismatch between the crystal (generally high) and the out-coupling medium (generally low).…”

Section: Perspectivesmentioning

confidence: 99%

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Enhancing Light Extraction of Inorganic Scintillators Using Photonic Crystals

et al. 2018

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Abstract:Inorganic scintillators are commonly used as sensors for ionizing radiation detectors in a variety of applications, ranging from particle and nuclear physics detectors, medical imaging, nuclear installations radiation control, homeland security, well oil logging and a number of industrial non-destructive investigations. For all these applications, the scintillation light produced by the energy deposited in the scintillator allows the determination of the position, the energy and the time of the event. However, the performance of these detectors is often limited by the amount of light collected on the photodetector. A major limitation comes from the fact that inorganic scintillators are generally characterized by a high refractive index, as a consequence of the required high density to provide the necessary stopping power for ionizing radiation. The index mismatch between the crystal and the surrounding medium (air or optical grease) strongly limits the light extraction efficiency because of total internal reflection (TIR), increasing the travel path and the absorption probability through multiple bouncings of the photons in the crystal. Photonic crystals can overcome this problem and produce a controllable index matching between the crystal and the output medium through an interface made of a thin nano-structured layer of optically-transparent high index material. This review presents a summary of the works aiming at improving the light collection efficiency of scintillators using photonic crystals since this idea was introduced 10 years ago.

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Section: Rationale For Photonic Crystalsmentioning

confidence: 99%

Section: Perspectivesmentioning

confidence: 99%

Enhancing Light Extraction of Inorganic Scintillators Using Photonic Crystals

et al. 2018

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“…This not only leads to a reduction of light collected at the photo detector, with consequences on the photo statistics described above, but also to multiple light reflections within the scintillator, which can contribute as much as 150 ps FWHM in a 2 2 20 mm LSO pixel. A possible solution to overcome the problem of total internal reflection is to improve the light extraction efficiency at the crystal/photo detector interface by means of photonic crystals (PhCs), i.e., media with a periodic modulation of the dielectric constant [12], [13]. Fig.…”

Section: Light Transportmentioning

confidence: 99%

Factors influencing time resolution of scintillators and ways to improve them

Lecoq

Auffray

Brunner

et al. 2009

2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)

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Abstract-The renewal of interest in Time of Flight PositronEmission Tomography (TOF-PET), as well as the necessity to precisely tag events in high energy physics (HEP) experiments at future colliders are pushing for an optimization of all factors affecting the time resolution of the whole acquisition chain comprising the crystal, the photo detector, and the electronics. The time resolution of a scintillator-based detection system is determined by the rate of photo electrons at the detection threshold, which depends on the time distribution of photons being converted in the photo detector. The possibility to achieve time resolution of about 100 ps Full Width at Half Maximum (FWHM) requires an optimization of the light production in the scintillator, the light transport and its transfer from the scintillator to the photo detector. In order to maximize the light yield, and in particular the density of photons in the first nanosecond, while minimizing the rise time and decay time, particular attention must be paid to the energy transfer mechanisms to the activator as well as to the energy transition type at the activator ion. Alternatively other light emission mechanisms can be considered. We show that particularly Cerenkov emission can be used for this purpose. Special emphasis was put on the light transport within the crystal and at its interface with the photo detector. Since light is produced isotropically in the scintillator the detector geometry must be optimized to decrease the optical path-length to the photo detector. Moreover light bouncing within the scintillator, affecting about 70% of the photons generated in currently used crystals, must be reduced as much as possible. We also investigate photonics crystals that are specifically designed to favor specific light propagation modes at the limit of total reflection inside and outside of the crystal and how they might increase the light transfer efficiency to the photo detector and hence improve time resolution. Examples for the production and deposition of photonics crystals as layers on Lutetium Yttrium Ortho-Silicate (LYSO) and Lutetium Yttrium Aluminum Perovskite (LuYAP) crystals are shown here, as well as first results on an improved light extraction resulting from this method.

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“…EVERAL years ago, we identified photonic crystals (PhCs) as a tool with a high potential to significantly improve the performance of scintillator-based detectors [1], [2]. We have shown that well-designed PhCs can enhance the light output of dense scintillators with a high refractive index (between 1.8 and 2.2 for the majority of scintillators) by a large factor ( 2 in air and by at least 50% in grease) [3], [4].…”

mentioning

confidence: 99%

“…As a consequence, PhCs can offer attractive perspectives in the search for higher timing resolution in scintillator-based detectors [5]. Increasing the light output and, as a consequence, the rate of photoelectrons produced in the photodetector at the early stage of the signal generation has a direct impact on the timing resolution by virtue of the improved photostatistics as illustrated by the following formula derived from Hyman theory: (1) where is the scintillator decay time, is the number of photoelectrons and is the excess noise factor of the photodetector.…”

mentioning

confidence: 99%

How photonic crystals can improve the timing resolution of scintillators

Lecoq¹,

Auffray²,

Knapitsch³

2012

2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)

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Abstract-Photonic crystals (PhCs) and quantum optics phenomena open interesting perspectives to enhance the light extraction from scintillating media with high refractive indices as demonstrated by our previous work. By doing so, they also influence the timing resolution of scintillators by improving the photostatistics. The present contribution will demonstrate that they are actually doing much more. Indeed, photonic crystals, if properly designed, allow the extraction of fast light propagation modes in the crystal with higher efficiency, therefore contributing to increasing the density of photons in the early phase of the light pulse. This is of particular interest to tag events at future high-energy physics colliders, such as CLIC, with a bunch-crossing rate of 2 GHz, as well as for a new generation of time-of-flight positron emission tomographs (TOFPET) aiming at a coincidence timing resolution of 100 ps FWHM. At this level of precision, good control of the light propagation modes is crucial if we consider that in a -mm LSO crystal, the time spread (peak to peak) of extracted photons can be as large as 400 ps considering simple light bouncing only. This paper presents a detailed analysis of the light propagation and extraction modes in a LSO crystal combining the LITRANI light ray tracing and the CAMFR PhC simulation codes. Ongoing measurement results are shown with an attempt to unfold the contribution from the improved photostatistics that result from the total enhanced light output on one side and from the improved contribution of fast propagation mode extraction on the other side. Some results are also shown on a new and more industrial process to produce PhCs by the use of nano-imprint technology.

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Probing the Concepts of Photonic Crystals on Scintillating Materials

Cited by 56 publications

References 12 publications

Enhancing Light Extraction of Inorganic Scintillators Using Photonic Crystals

Enhancing Light Extraction of Inorganic Scintillators Using Photonic Crystals

Factors influencing time resolution of scintillators and ways to improve them

How photonic crystals can improve the timing resolution of scintillators

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