Optical Crosstalk and Ancillary Measurements of Free Space Coupled, InGaAs Quad Photoreceivers Exposed to Protons and Alpha Particles (2023)

Shubhashish Datta^*1, Abhay M. Joshi¹, Jeff Mertz¹, Nilesh Soni¹, Michael Sivertz², and Trevor Olsen ²
¹ Discovery Semiconductors Inc., Ewing, NJ, USA
² NASA Space Radiation Laboratory, Brookhaven National Laboratory, Upton, NY, USA.

ABSTRACT

Free space coupled, InGaAs PIN + TIA Quad Photoreceivers enable multiple space applications that require differential wavefront sensing, such as gravitational wave detectors, and position sensing and tracking, for example inter-satellite optical communication links. Optical crosstalk between the individual quadrants of the 2 × 2 photoreceiver array is a key parameter that limits the position and / or direction sensing error of the system. Therefore, it is imperative to ensure low crosstalk in the quad photoreceivers throughout the mission life. We present 1 mm, 1.5 mm, and 2 mm diameter low noise Quad Photoreceivers that demonstrate crosstalk < -30 dB up to 20 MHz frequency. These devices were subjected to 100 MeV Protons and 100 MeV/n Helium Ions up to a fluence of 1 × 10¹⁰ cm^-2. These tests not only validate the devices for Geostationary Orbit missions, but also for deep space missions outside of Earth’s protective magnetosphere where Galactic Cosmic Rays are a significant component of the radiation environment. All devices were found to be fully functional after radiation, and their crosstalk was essentially unchanged in all cases.

Pre- and Post- radiation results were also measured for Dark Current vs. Reverse Bias Voltage for the Quad Photodiodes, DC Responsivity of the Quad Photodiodes, Conversion Gain and Bandwidth of the PIN + TIA Quad Photoreceiver, TIA Drive Current, and Input Equivalent Noise Density of PIN + TIA. Although we observed an increase in dark current due to radiation induced displacement damage in the Quad Photodiode, we did not observe any change in any other parameter for Quad Photoreceivers.

INTRODUCTION

Quad Photoreceivers, namely a 2 x 2 array of p-i-n photodiodes followed by a transimpedance amplifier (TIA) per diode, are needed for multiple position and direction sensing space applications, including inter-satellite optical communication links and gravitational wave detectors. Diversity of radiation environment for various space missions, from LEO satellites to deep space missions outside Earth’s protective magnetosphere, requires testing these devices with a wider range of particles. Our prior work on space qualification of Ultra-Low Noise InGaAs Quad Photoreceivers involved testing devices of three different active area diameters with high energy Protons, Alpha Particles (Helium Ions), and Iron Ions [1]. The fluence levels and Linear Energy Transfer of these radiation tests, simulated exposure to Solar Protons and Galactic Cosmic Rays (GCR) for multi-year interplanetary or deep space missions. Additionally, the Quad Photoreceivers also passed 662 keV Gamma irradiation up to a Total Ionizing Dose (TID) of 30 krad (water) [1].

Our prior work focused on the noise performance of Quad Photoreceivers and demonstrated that 0.5 mm and 1 mm diameter devices passed all the radiation tests. The largest 2 mm diameter Quad Photoreceiver was found to be susceptible to 1 GeV/n He Ions, but passed all other tests. In this work, the InGaAs Quad Photoreceivers having 1 mm, 1.5 mm, and 2 mm diameters were further optimized, and subjected to the radiation tests summarized in the Abstract above. We were especially interested in ascertaining the resilience of the 2 mm diameter device when subjected to a harsher dose of Helium Ions. Based on prior data for heavy ion energy and linear energy transfer spectra using PSYCHIC model, the fluence levels used in this work corresponds to 10+ year mission outside the Earth’s protective magnetosphere [2].

In this work, we not only characterized the noise performance of the Quad Photoreceivers, but also analyzed the potential impact of radiation on their optoelectronic transfer function, including DC responsivity, conversion gain, and frequency response of the individual quadrants, as well as crosstalk between them.

REFERENCES

[1] A. Joshi, S. Datta, N. Soni, M. D’Angiolillo, J. Mertz, M. Sivertz, A. Rusek, J. Jardine, and J. Livas, “Comprehensive Radiation Testing of Uncooled, Free Space Coupled, InGaAs Quad Photoreceivers,” Proc. SPIE, vol. 11272, paper 112720G, 2020.

[2] M. Xapsos, C. Stauffer, J. Barth, and R. Mewaldt, “Model for Cumulative Solar Heavy Ion Energy and Linear Energy Transfer Spectra,” IEEE Trans. Nuclear Science, vol. 54, pp. 1985 – 1989, 2007.

Event: SPIE Defense + Commercial Sensing, 2023, Orlando, Florida, Proc. of SPIE Vol. 12514, Paper 1251406, 2023