Detector Characterization of a Near-Infrared Discrete Avalanche Photodiode 5x5 Array for Astrophysical Observations

TL;DR

This paper characterizes a near-infrared avalanche photodiode array for astrophysical transient detection, detailing its performance metrics and suitability for a wide-field, fast-time response search for extraterrestrial technosignatures.

Contribution

It provides the first detailed characterization of a 5x5 NIR avalanche photodiode array for astrophysical applications, including dark count rate, PDE, and non-linearity.

Findings

Dark count rate of 3.3x10^6 cps

Photon detection efficiency of 14.8% at 1050 nm

Saturation at 1.2x10^8 photons/sec

Abstract

We present detector characterization of a state-of-the-art near-infrared (950nm - 1650 nm) Discrete Avalanche Photodiode detector (NIRDAPD) 5x5 array. We designed an experimental setup to characterize the NIRDAPD dark count rate, photon detection efficiency (PDE), and non-linearity. The NIRDAPD array was illuminated using a 1050 nm light-emitting diode (LED) as well as 980 nm, 1310 nm, and 1550 nm laser diodes. We find a dark count rate of 3.3x10$^6$ cps, saturation at 1.2x10$^8$ photons per second, a photon detection efficiency of 14.8% at 1050 nm, and pulse detection at 1 GHz. We characterized this NIRDAPD array for a future astrophysical program that will search for technosignatures and other fast (>1 Ghz) astrophysical transients as part of the Pulsed All-sky Near-infrared Optical Search for Extraterrestrial Intelligence (PANOSETI) project. The PANOSETI program will consist of an all-sky optical (350 - 800 nm) observatory capable of observing the entire northern hemisphere instantaneously and a wide-field NIR (950 - 1650 nm) component capable of drift scanning the entire sky in 230 clear nights. PANOSETI aims to be the first wide-field fast-time response near-infrared transient search.

Tables

Table 1. Table 1: Operating parameters and characteristics of the NIRDAPD 5x5 array.

o 0.8 — X[c] — X[c] — Parameter	Value
Operating Bias	-61.1V
Amplifier Bias	+12V
Operating Temperature	250 K
Total Detector Area	500 x 500 microns
Pixel Dimension	100 x 100 microns
Pixel Pitch	81 $\%$

Equations

$$PDE(\%)=\frac{N_{detector}}{N_{incident}}=\frac{N_{counts}-N_{dark}}{P_{incident}}\frac{A_{powermeter}}{A_{NIRDAPD}}\frac{hc}{\lambda }$$

Full text

1 INTRODUCTION

One of the most effective means of interstellar communication is the laser[1], which with today’s technology can produce pulses up to petawatts in power and picoseconds in duration [2]. If used for interstellar communication on Earth, these lasers would outshine our own sun by at least 4 orders of magnitude and be bright enough to be easily distinguished from natural astrophysical sources by civilizations with high resolution meter class telescopes from thousands of light years away. [3]

Most Searches for Extraterrestrial Intelligence (SETI) have focused on the radio and visible spectra [4, 5, 6, 7, 8]. However, the transmission of near-infrared signals over large distances in the Galactic plane can be advantageous over the transmission of both radio and optical signals due to lower extinction factors through ionized interstellar medium [9] and negligible pulse width distortion from scattering [3], suggesting that near-infrared lasers could also be used by intelligent extraterrestrial civilizations for interstellar communication. Previous near-infrared astrophysical surveys and SETI programs on Earth have been limited by the timing resolutions of modern photodetectors. The introduction of the InGaAs/InP Single Photon Avalanche Detector (SPAD) has opened up the possibility of probing the near-infrared Universe in the nanosecond regime to search for and characterize fast ($>$1 GHz) transient events. These novel detectors operate between 950 nm and 1650 nm and are p-n junction reverse-biased semiconductor detectors that utilize avalanche multiplication [10]. The Near-Infrared Discrete Avalanche Photodetector (NIRDAPD) from Amplification Technologies is a SPAD that uses Internal Discrete Amplification (IDA) technology and surpasses previous InGaAs/InP SPADs with reported faster responses ($>$ 1 GHz), higher gains (1x105), higher photon detection efficiencies (15$\%$ at 1550 nm) and lower noise ($\sim$ 106 counts per second) [10].

The Pulsed All-sky Near-infrared Optical Search for Extraterrestrial Intelligence (PANOSETI) project aims to probe the largely unexplored near-infrared nanosecond regime using state-of-the-art NIRDAPD technology by searching for technosignatures and other astrophysical transients. The PANOSETI program will consist of an all-sky optical (350 - 800 nm) observatory capable of instantaneously observing the entire northern hemisphere and a wide-field near-infrared (950 - 1650 nm) component capable of drift scanning the entire sky in 230 clear nights. PANOSETI aims to be the first wide-field fast-time response near-infrared technosignature search.

Two single pixel NIRDAPDs from Amplification Technologies were commissioned on the 1 meter Nickel telescope at Lick Observatory for the Near Infrared and Optical Search for Extraterrestrial (NIROSETI) project, the predecessor to PANOSETI, in March 2015. [9]. NIROSETI has the sensitivity to detect laser emissions from up to 50 parsecs away and has since observed 2,000 celestial objects[11].

We characterized the dark count rate, linearity, saturation, photon detection efficiency, and pulse detection of a 5x5 NIRDAPD array (1550 series) from Amplification Technologies to explore the feasibility of replacing the current single pixel NIRDAPD detectors at Lick Observatory with NIRDAPD arrays to increase our search area and sensitivity. We also evaluate the feasibility of using NIRDAPD arrays for other observational programs searching for fast near-infrared signals of astrophysical origin.

2 Experimental Setup

The experimental setup can be seen in Figure 1. The NIRDAPD array was housed inside a light tight dark box containing a 25.4 mm diameter sealed cable feed-through. Darkness at 950 nm and 1050 nm was verified throughout the box using a power meter (ThorLabs PM100D) with a sensitivity of 0.1 nW and an accuracy of $\pm$0.5$\%$. The NIRDAPD array was hermetically sealed inside a TO-8 can, mounted on a breakout board supplied by Amplification Technologies, and cooled using a thermoelectric cooler (ThorLabs TTC001) and thermistor. Detector parameters can be seen in Table 2. The pixel layout and orientation can be seen in Figure 2 and will be used to reference the location of pixels throughout this paper.

A single count was defined as a pulse with an amplitude greater than half the amplitude produced by a single photoelectron (threshold = 0.5 mV). Counts per second were obtained using a 4 channel 2.5 GHz oscilloscope (Agilent MSO9254A) with MATLAB installed. A two layered system consisting of ten four-way BNC switch boxes was constructed to change pixels while minimizing disturbances to the NIRDAPD array between measurements. Measurements were taken three pixels at a time, leaving the fourth oscilloscope channel connected directly to an arbitrary pixel (Pixel 13) to monitor for any changes in counts per second over time. A cooling system consisting of fans and radiators was constructed to remove excess heat inside the dark box produced by the breakout board. The NIRDAPD array and amplifier were allowed to settle for at least 30 minutes before taking dark count measurements and 90 minutes before taking measurements with a light source.