UV photon-counting CCD detectors that enable the next generation of UV spectroscopy missions: AR coatings that can achieve 80-90% QE

Abstract

We describe recent progress in the development of anti-reflection coatings for use at UV wavelengths on CCDs and other Si-based detectors. We have previously demonstrated a set of coatings which are able to achieve greater than 50% QE in 4 bands from 130nm to greater than 300nm. We now present new refinements of these AR-coatings which will improve performance in a narrower bandpass by 50% over previous work. Successful test films have been made to optimize transmission at 190nm, reaching 80% potential transmission.

FIREBall-2: advancing TRL while doing proof-of-concept astrophysics on a suborbital platform

“…Despite this, they have several drawbacks: low efficiencies, especially compared to typical efficiencies of detectors at other wavelengths, count rate limits that exclude the brightest targets, and loss of gain (gain sag) over time, all of which have operational impacts. [18][19][20] The recent development 21,22 and flight testing of delta-doped silicon based CCD detectors has now opened a new opportunity in UV space astrophysics. Delta-doped CCDs in many ways are a perfect compliment to MCPs: delta-doped CCD efficiency, stability, and dynamic range are significantly better.…”

“…The reflection of Si in the UV limits the overall QE of the detectors, and so a custom 3-layer anti-reflection coating was developed to reduce reflection in the FIREBall bandpass. 22,[29][30][31][32] Measured QE is shown in Figure 4 The detector performance was verified via testing at JPL and at Caltech. JPL testing included QE verification, 33 while the Caltech test set-up measured QE at limited wavelengths using NUVU v2 and v3 CCCP controllers 34 and a custom flight printed circuit board (PCB).…”

Quantum yield estimation for an electron-multiplying charge-coupled device from photon counting test data

“…1 Large-area silicon charge-coupled device (CCD) and complementary metal-oxidesemiconductor (CMOS) detectors for near-UV and visible wavelengths are a mature technology. There are numerous optimization processes that can improve the UV detection efficiency of silicon semiconductor material, such as antireflection coatings, 6 chemisorptions treatment, 7 and delta-doping. 8 Due to these factors, much of the technology development effort to address the needs of future UV space astronomy missions is focused on silicon detector arrays.…”

High efficiency CCD detectors at UV wavelengths

“…We explore in particular the improvements in quantum efficiency beyond that in our recent work [16][17][18] in Section 2 and describe additional work for towards increasing throughput via other optical surfaces in Section 3. Finally, we discuss the theoretical overall throughput of FIREBall-2 as compared to FIREBall-1 in Section 4.…”

“…17 We reported on work with more complex coatings in 2012, 18 including initial modeling of three and five layer films. These models were optimized for use at 155 nm, 205 nm, and 255 nm as an example of the range in peak wavelengths, although in principle they can be created for nearly any wavelength above 130 nm.…”