Gamma radiation effects in amorphous silicon and silicon nitride photonic devices

Space-qualifying silicon photonic modulators and circuits

Reducing the form factor while retaining the radiation hardness and performance matrix is the goal of avionics. While a compromise between a transistor's size and its radiation hardness has reached consensus in microelectronics, the size-performance balance for their optical counterparts has not been quested but eventually will limit the spaceborne photonic instruments' capacity to weight ratio. Here, we performed space experiments of photonic integrated circuits (PICs), revealing the critical roles of energetic charged particles. The year-long cosmic radiation exposure does not change carrier mobility but reduces free carrier lifetime, resulting in unchanged electro-optic modulation efficiency and well-expanded optoelectronic bandwidth. The diversity and statistics of the tested PIC modulator indicate the minimal requirement of shielding for PIC transmitters with small footprint modulators and complexed routing waveguides toward lightweight space terminals for terabits communications and intersatellite ranging.

A doped-polymer based porous silicon photonic crystal sensor for the detection of gamma-ray radiation

In this research, a theoretical investigation of the one-dimensional defective photonic crystals is considered for the detection of gamma-ray radiation. Each unit cell of the considered one-dimensional photonic crystals (1D PhCs) is composed of two layers designed from porous silicon infiltrated by poly-vinyl alcohol polymer doped with crystal violet (CV) and carbol fuchsine (CF) dyes (doped-polymer) with different porosity. In addition, a single layer of doped-polymer is included in the middle of the designed 1D PhCs to stimulate the localization of a distinct resonant wavelength through the photonic band gap. In particular, the appearance of this resonant mode represents the backbone of our study towards the detection of γ-ray radiation with doses from 0 to 70 Gy. The Bruggeman's effective medium equation, the fitted experimental data to the refractive index of the doped-polymer, and the Transfers Matrix Method (TMM) serve as the mainstay of our theoretical treatment. The numerical findings provide significant contributions to some of the governing parameters such as the thicknesses of the considered materials on the performance of the presented sensor, the effect of incidence angle and the porosity of the considered materials on the resonance wavelength. In this regard, at optimum values of these parameters the sensitivity, quality factor, signal-to-noise ratio, detection limit, sensor resolution, and figure of merit that are obtained are 205.7906 nm RIU^-1, 9380.483, 49.315, 2.05 × 10^-5 RIU, 3.27 × 10^-5, and 2429.31 RIU^-1, respectively. Therefore, we believe that the suggested design could be of significant interest in many industrial, medical, and scientific applications.

Radiation-hardened silicon photonic passive devices on a 3 µm waveguide platform under gamma and proton irradiation

Silicon photonics is considered to be an ideal solution as optical interconnect in radiation environments. Our previous study has demonstrated experimentally that radiation responses of device are related to waveguide size, and devices with thick top silicon waveguide layers are expected to be less sensitive to irradiation. Here, we design radiation-resistant arrayed waveguide gratings and Mach-Zehnder interferometers based on silicon-on-insulator with 3 µm-thick silicon optical waveguide platform. The devices are exposed to ⁶⁰Co γ-ray irradiation up to 41 Mrad(Si) and 170-keV proton irradiation with total fluences from 1×10¹³ to 1×10¹⁶ p/cm² to evaluate performance after irradiation. The results show that these devices can function well and have potential application in harsh radiation environments.

High energy irradiation effects on silicon photonic passive devices

In this work, the radiation responses of silicon photonic passive devices built in silicon-on-insulator (SOI) technology are investigated through high energy neutron and ⁶⁰Co γ-ray irradiation. The wavelengths of both micro-ring resonators (MRRs) and Mach-Zehnder interferometers (MZIs) exhibit blue shifts after high-energy neutron irradiation to a fluence of 1×10¹² n/cm²; the blue shift is smaller in MZI devices than in MRRs due to different waveguide widths. Devices with SiO₂ upper cladding layer show strong tolerance to irradiation. Neutron irradiation leads to slight changes in the crystal symmetry in the Si cores of the optical devices and accelerated oxidization for devices without SiO₂ cladding. A 2-µm top cladding of SiO₂ layer significantly improves the radiation tolerance of these passive photonic devices.

Gamma radiation effects on passive silicon photonic waveguides using phase sensitive methods

Passive silicon photonic waveguides are exposed to gamma radiation to understand how the performance of silicon photonic integrated circuits is affected in harsh environments such as space or high energy physics experiments. The propagation loss and group index of the mode guided by these waveguides is characterized by implementing a phase sensitive swept-wavelength interferometric method. We find that the propagation loss associated with each waveguide geometry explored in this study slightly increases at absorbed doses of up to 100 krad (Si). The measured change in group index associated with the same waveguide geometries is negligibly changed after exposure. Additionally, we show that the post-exposure degradation of these waveguides can be improved through heat treatment.

1,2-Dihydroxyanthraquinone: Synthesis, and induced changes in the structural and optical properties of the nanostructured thin films due to γ-irradiation

1,2‑Dihydroxyanthraquinone (Alizarin-AZ) is available, low-cost organic compound. Besides, AZ has multiple applications owing to its drawing attention photoactivity. This paper is devoted to study the influence of Gamma irradiation on the morphology, optical, and dielectric properties of AZ nanostructured thin films. Nanostructure powder of Alizarin is synthesized according to chemical routes. Subsequently, thin films of AZ are fabricated via thermal evaporator. The bared thin film is irradiated at different doses of ⁶⁰Co γ-rays. Furthermore, the bared and irradiated films are characterized via X-ray diffraction (XRD), atomic force microscope (AFM) and UV-Vis-NIR spectroscopy. XRD investigations reveal that the bared film has a nanostructure and the average particle size increases gradually as the γ-irradiation dose increases. AFM images show remarkable increment in the surface roughness of the irradiated film over the bared one. In the light of structure induced changes, clear variations in the optical properties are addressed. Of these, the energy gap decreases gradually as the irradiation dose increases. The film irradiated at 45 kGy shows the highest optical conductivity. Based on our results we suggest AZ nanostructured thin films as potential candidate for optoelectronics devices.

Assessing Radiation Hardness of Silicon Photonic Sensors

In recent years, silicon photonic platforms have undergone rapid maturation enabling not only optical communication but complex scientific experiments ranging from sensors applications to fundamental physics investigations. There is considerable interest in deploying photonics-based communication and science instruments in harsh environments such as outer space, where radiation damage is a significant concern. In this study, we have examined the impact of cobalt-60 γ-ray radiation up to 1 megagray (MGy) absorbed dose on silicon photonic devices. We do not find any systematic impact of radiation on passivated devices, indicating the durability of passivated silicon devices under harsh conditions.