Non-Linear Optical Phenomena in Detecting Materials as a Possibility for Fast Timing in Detectors of Ionizing Radiation
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-10-13 |
| Journal | IEEE Transactions on Nuclear Science |
| Authors | M. Korjik, E. Auffray, Đ. Đ. ĐŃганОв, A. Fedorov, I. Emelianchik |
| Institutions | TU Wien, European Organization for Nuclear Research |
| Citations | 5 |
| Analysis | Full AI Review Included |
6CCVD Technical Analysis & Documentation
Section titled â6CCVD Technical Analysis & DocumentationâExecutive Summary
Section titled âExecutive SummaryâThis study investigates Non-Linear Optical (NLO) phenomena, specifically Two-Photon Absorption (TPA), in wide bandgap materials, including synthetic diamond, as a method for achieving ultra-fast (10-20 ps) timing in ionizing radiation detectors.
- Ultra-Fast Timing Potential: Current detector time resolution (50-70 ps) is limited by slow carrier relaxation. TPA, probed by femtosecond (fs) laser pulses, provides an optical time mark in the sub-picosecond domain, suitable for defining the exact moment of ionization interaction.
- Diamond Performance: Synthetic diamond (both HPHT and CVD) showed significant TPA effects. The kinetics of differential absorption in HPHT diamond demonstrated a critical fast decay component (less than 1 ps), confirming its suitability for high-speed timing applications.
- Mechanism Explored: The NLO mark relies on elastic polarization caused by local lattice distortions following the initial displacement of electrons and holes generated by ionizing radiation.
- Material Dependence: TPA spectra in diamond were found to be heavily influenced by intrinsic defects (Nitrogen, Nickel), demonstrating the need for precise material engineering for optimal response.
- 6CCVD Relevance: The requirements for high-purity, defect-controlled Single Crystal Diamond (SCD) and custom polycrystalline diamond (PCD) dimensions, along with specialized metalization, align directly with 6CCVDâs core capabilities in MPCVD growth.
- Proposed Technique: The research validates a novel detection technique exploiting simultaneous TPA (timing) and scintillation (energy absorption) signals from the same crystalline medium.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research paper detailing the experimental parameters and material characteristics relevant to fast timing detector development.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Detector Time Resolution | 10-20 | ps | Required for next-generation high-energy physics experiments |
| Conventional Detector Time Limit | 50-70 | ps | Defined by carrier relaxation and recombination time |
| Femtosecond Pump Pulse Duration | 140 / 200 | fs | Used in Al${2}$O${3}$:Ti$^{3+}$ and Yb:KGW laser systems, respectively |
| Pump Laser Repetition Rate (Setup 2) | 30 | kHz | Yb:KGW laser system parameter |
| HPHT Diamond Transmission Cutoff | Near 420 | nm | Due to presence of nitrogen (N) defects |
| TPA Fast Decay Component (HPHT Diamond) | < 1 | ps | Response time suggesting suitability for fast timing mark |
| Diamond Indirect Transition TPA Energy | 5.5 | eV | Lowest TPA band (Total energy of two photons) |
| Diamond Direct Transition TPA Energy | 6.5 | eV | Observed transition energy |
| HPHT Diamond Scintillation Output (vs. CWD) | 3x | Higher | Scintillation light output compared to CVD diamond |
| Bandgap Energy (Gd${3}$(Ga${0.5}$-Al${0.5}$)${5}$O$_{12}$) | 6.4 | eV | Sub-band formed by Gd$^{3+}$ ions below conduction band |
Key Methodologies
Section titled âKey MethodologiesâThe two-photon absorption effects were studied using a high-precision, femtosecond pump-and-probe optical absorption technique across various scintillation crystals.
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Pump-Probe Setup 1 (High Power, Broadband Probe):
- Pump Source: 140 fs pulses, second harmonic of an Al${2}$O${3}$:Ti$^{3+}$ laser.
- Pump Wavelength: Fixed at 395 nm.
- Probe Source: White continuum generated in water, covering 400 nm to 1100 nm.
- Purpose: Used to study kinetics across a broad spectrum of probe energies.
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Pump-Probe Setup 2 (Tunable Pump):
- Pump Source: 200 fs pulses from a femtosecond Yb:KGW laser (1030 nm fundamental, 30 kHz repetition rate).
- Pump Wavelength: Tunable range from 346 nm to 650 nm.
- Purpose: Used to measure TPA responses at specific spectral overlaps and high pump pulse energies.
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Material Preparation & Testing:
- Diamond Samples: Both High Pressure High Temperature (HPHT, nitrogen-doped) and Chemical Vapor Deposition (CVD, low defect) synthetic diamond crystals were tested.
- Dimensions: HPHT samples were 4x4x0.3 mm; CVD samples were 4x2x0.15 mm.
- Characterization: Samples were fitted with electrodes and tested for response to $\text{}^{238}$Pu alpha-particles via charge collection readout and scintillation light output at room temperature.
- Measurement Target: Differential absorption (mOD) was tracked as a function of the delay (in picoseconds) between the pump and probe pulses.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe findings confirm that diamond remains a leading candidate for ultra-fast detector applications, provided the material propertiesâpurity, doping, and surface qualityâare rigorously controlled. 6CCVD is uniquely positioned to supply the requisite advanced MPCVD diamond materials for replicating and advancing this time-resolved spectroscopy research.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the studyâs findings and explore optimized TPA responses, 6CCVD recommends materials tailored to specific defect and purity requirements:
| Research Requirement | 6CCVD Material Recommendation | Material Context & Optimization |
|---|---|---|
| HPHT Replication (Nitrogen/Defects): Study showed fast decay linked to defects in HPHT (yellow coloration). | Nitrogen-Doped Single Crystal Diamond (SCD) | Provides controllable concentration of defects necessary to investigate TPA bands (~465 nm, 550 nm, 700 nm) related to nitrogen/nickel centers, which dictate the timing mark. |
| CVD Replication (High Purity): Study explored low-defect, high-purity diamond for intrinsic TPA effects. | Optical Grade Single Crystal Diamond (SCD) | High-purity material with Ra < 1 nm finish is essential for minimizing scattering of the high-intensity femtosecond pump and probe beams. Ideal for studying intrinsic band-to-band TPA effects (6.5 eV direct transition). |
| Scintillation/Charge Integration: Need for robust plates for detector prototypes. | Polycrystalline Diamond (PCD) Wafers | Available in large area formats (up to 125 mm) with custom thickness (up to 500 Âľm), suitable for scaling up validated fast-timing prototype designs. |
Customization Potential
Section titled âCustomization PotentialâThe utilization of pump-probe spectroscopy and the goal of integrating optical timing with electrical readout necessitates precise material preparation that 6CCVD provides in-house.
- Custom Dimensions: The paper used specific 4x4x0.3 mm and 4x2x0.15 mm samples. 6CCVD offers custom laser cutting and wafer dicing services to provide SCD and PCD substrates in any specified dimension required for advanced optical setups or monolithic detector integration.
- Integrated Metalization: The researchers utilized evaporated electrodes for charge collection testing. 6CCVD offers internal capability for custom metalization, including deposition of Ti/Pt/Au, W, or Cu contact layers, essential for integrating electrical readout alongside optical probing.
- Surface Preparation: Achieving high-efficiency coupling of femtosecond laser pulses requires exceptional surface quality. We guarantee SCD polishing to Ra < 1 nm and large-area PCD polishing to Ra < 5 nm, ensuring minimal beam distortion and scattering loss.
Engineering Support
Section titled âEngineering SupportâThe observed effectsâTPA mechanisms, elastic polarization timing, and defect correlationâare complex challenges requiring expert material science input.
- 6CCVDâs in-house PhD team can assist with material selection, doping regime determination, and crystal orientation for similar ultra-fast radiation detection and particle physics projects. We ensure that the chosen diamond substrate optimizes the fast decay component (< 1 ps) crucial for high-resolution timing marks.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The time resolution of the detectors currently in use is limited by 50-70 ps due to the spontaneous processes involved in the development of the response signal, which forms after the relaxation of carriers generated during the interaction. In this study, we investigate the feasibility of exploiting sub-picosecond phenomena occurring after the interaction of scintillator material with ionizing radiation by probing the material with ultra-short laser pulses. One of the phenomena is the elastic polarization due to the local lattice distortion caused by the displacement of electrons and holes generated by ionization. The key feature of the elastic polarization is its short response time, which makes it prospective for using as an optically detectable time mark. The nonlinear optical absorption of femtosecond light pulses of appropriate wavelength is demonstrated to be a prospective tool to form the mark. This study was aimed at searching for inorganic crystalline media combining scintillation properties and non-linear absorption of ultra-short laser pulses. The nonlinear pump-and-probe optical absorption technique with 200 fs laser pulses was used to study the effects in lead tungstate, garnet-type, and diamond scintillator crystals