[SPIE2013 8704-8] High-performance and Long-range Cooled IR Technologies...

High Performance and Long-Range Cooled IR technologies in France

Yann Reibel, Thibault Augey, Sebastien Verdet, Patrick Maillart, Laurent Rubaldo, David Billon-Lanfrey (a)

(a) SOFRADIR, 43-47 rue Camille Pelletan 92290 Chatenay-Malabry, France [email protected]

Laurent Mollard, Franois Marion, Nicolas Baier, Grard Destefanis (b)

(b) CEA Leti-MINATEC, 17 rue des Martyrs - 38054 Grenoble Cedex 9- France

ABSTRACT

Cooled IR technologies that offer high performances are at the top of DEFIRs priority list. We have been pursuing further infrared developments on future MWIR detectors, such as the VGA format HOT detector that operates at 150K and the 10m pitch IR detector which gives us a leading position in innovation In the same time Scorpio LW expands Sofradir's line of small pixel pitch TV format IR detectors from the mid-wavelength to the long-wavelength, broadening the performance attributes of its long wave IR product line. Finally, our dual band MW-LW QWIP detectors (25m, 384288 pixels) benefit to tactical platforms giving an all-weather performance and increasing flexibility in the presence of battlefield obscurants. These detectors are designed for long-range surveillance equipment, commander or gunner sights, ground-to-ground missile launchers and other applications that require higher resolution and sensitivity to improve reconnaissance and target identification. This paper discusses the system level performance in each detector type. Keywords: HgCdTe, Infrared detectors, SWAP, HOT, small pixel pitch, LWIR, BiQwip, long-range

1 INTRODUCTION

The miniaturization becomes more and more important for the compact or portable systems in order to make the equipment of the soldier lighter, playing mainly on the weight of the batteries. To answer to this demand, DEFIR Laboratory (joined laboratory between Sofradir and CEA-Leti) has put efforts within the framework of the DEFIR joined laboratory, to achieve the challenge of high operating temperature: Technological improvements on standard n on p process (in production) have led to a substantial increase

in operating temperature with strong reduction of defects exhibiting 1/f noise. Progresses are based on the use of very high quality materials made at SOFRADIR (CZT, Epilayers) and on a precise optimization of all step of PV process.

Development of p-on-n Mercury Cadmium Telluride (MCT) technology has been carried out since 2006 at CEA/LETI in order to reduce the dark current.

On the other hand, embedded systems on vehicle or airplane have not the same needs. They first target high performances and new functionalities for better ID performance like large format, lower pixel pitch, high sensibility or dual bands.

This paper gives the status of the development of MCT infrared detectors at Sofradir and CEA-Leti including: the 10m pixel pitch technology, the p-on-n technology for middle wavelength HOT and long wavelength detectors, the dual-color technology.

Invited Paper

Infrared Technology and Applications XXXIX, edited by Bjrn F. Andresen, Gabor F. Fulop, Charles M. Hanson, Paul R. Norton, Proc. of SPIE Vol. 8704, 87040B 2013 SPIE

CCC code: 0277-786X/13/$18 doi: 10.1117/12.2015601

Proc. of SPIE Vol. 8704 87040B-1

Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/13/2013 Terms of Use: http://spiedl.org/terms

SCORPIO LW640x512

MWLW

2000

10 -12 pm

2008 2012 2014 2018 2020

EPSILON SCORPIO JUPITER384x288 640x512 1280x1024

2 LOWER PITCH, HIGHER RESOLUTION

At SOFRADIR we are pursuing further infrared developments on future MWIR detectors, such as the 10m pitch IR detector giving us a leading position in innovation. In this chapter, we investigate the benefit of the small pixel pitch for longer range identification or higher compactness. In that perspective, the developers of such systems should answer to the following contradictions: Could the resolution improvement be counterbalanced by diffraction limitation? Could the image quality be degraded by reduced photon collection at pixel level? Could small pixel pitch induce readout circuit complexity requiring advanced silicon CMOS foundry? Could the power consumption be significantly affected by the format and the pitch?

Mid-TV format (320x256) detectors with 30m pitch have been manufactured at mass production level since the end of the nineties. In the meantime, detectors in larger format and smaller pixel pitch have been developed for longer range identification. Today, 15m pixel pitch is a standard for the middle wave (MW) and (LW) detectors. One can find within the Sofradir catalog a complete range of detectors with pixel pitch of 15m: Epsilon (384 x 288), Scorpio (640 x 512) and Jupiter (1280 x 1014). See Figure 1.

Figure 1: Pixel pitch reduction at SOFRADIR

In recent years, DEFIR laboratory has worked at developing improved MCT process and new hybridization process to demonstrate 10m pitch capability. When going to smaller pixel pitch, the photon flux is reduced dramatically: it seems at first that the NETD and the radiometric performance would be degraded significantly at the system level. However, the gain in resolution turns out to have major advantages for applications related to long range observation and requiring more compactness.

2.1 Lower pitch: technological breakthrough

The reduction to 10m needs some technological breakthrough at level of the pixel: first the implanted diode needs to be well mastered to avoid cross-talk, second the hybridization process shall be capable to maintain a good yield of connection and a good reliability, and third the current injection in the readout circuit shall be mastered. Indeed, with low optical aperture, the current coming from the diode is so low that injection problem may occur.

The first demonstration of a 10m pixel pitch MW technology was performed by SOFRADIR at BALTIMORE SPIE 2012.



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urre

nce

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Figure 2: NETD for 10m pitch Figure 3: Demonstration 320256 10m pixel pitch MWIR image

The small pixel pitch size usually increases the complexity and limits the performances of the readout circuit. The main architectures used for coupling with infrared photodiodes are Direct Injection (DI), Capacitive TransImpedance Amplifier (CTIA), or Source Follower per Detector (SFD). Direct Injection has many advantages as the absence of power dissipation inside the pixel, and its relatively small required room around the integration and readout capacitances. This allows huge arrays with small pixel pitches. However, its main drawback is that this kind of architecture is not adapted to low input current, as the input MOS transconductance decreases proportionally to the photodiode current, reducing thus the injection efficiency: this is a real problem in the case of pixel pitch reduction inducing lower photodiode current. CTIA coupling is thus preferably used when lowering the input current. But if this solution is well adapted to low input currents, it requires more room in the pixel than Direct Injection, and adds power consumption inside the pixel. The first issue (room in the pixel) may be partially compensated by using lower technological node for the readout circuit manufacturing. The second issue (power consumption in the pixel) is a a real problem for large arrays, especially as the trend of infrared products is to increase the number of pixels while lowering the pitch.. In the design of the infrared (IR) focal-plane-array (FPA), high resolution has become a common requirement in many applications. This leads to larger array sizes and / or smaller pixels: the 10m pitch offers to get an IR chip size equal to the well-established 640x512 15m MW with higher resolution (1024x768) in the same dewar solution. However, the storable charge shall be sufficiently large to preserve high SNR and to take full advantages of pixel pitch reduction,. This makes advanced Silicon Technology mandatory. Table 1 compares the characteristics of 1024x768-10m FPAs with DI and CTIA architectures and designed with a 0.13m technological node: the DI solution shows decisive advantages as 4 times more electrons can be handled and its power consumption is 3 times lower than what is achieved with CTIA.

Table 1 Comparison DI /10m with CTIA / 10m

DI / 10m CTIA / 10m DI / 15m

Storable charge 4,5 Me- 1 Me- 5 Me-

Dimension 1024 x 768 1024 x 768 640x512

Consumption 60mW 180mK 40mW

NETD 18mK @ 50% WF 36mK @ 50% WF 18mK @ 50% WF



BACK

GRO

UND

TEM

PERA

TURE

m * N b E E

For cold background temperature and high F-number, the incident flux with low pixel pitch is significantly reduced and the systems become photons starved. Under these conditions one of the problems of using injection-transistor-based readout circuits is that their performance degrades severely in applications with low backgrounds. The transconductance of the injection transistor decreases in proportion with the background photocurrent, causing a degradation of injection efficiency, and making the injection transistor noise substantially larger.

In that regard, e-APD MCT detector offers a significant competitive edge over other infrared technologies and opens new perspective for low power, large format and much smaller pitch. This technology amplifies the integrated photo-electrons with no noise excess (see Figure 5), so that the signal to noise ratio (SNR) is no longer degraded. Thanks to excess noise factor close to unit, NETD in MCT APDs is constant with gain and the SNR is not degraded. The pink area in Figure 4 illustrates the operating domain (background temperature and F#number) benefiting from APD amplification, that would otherwise suffers DI efficiency degradation.

Figure 4: Improved performance with e-APD

Figure 5: MCT e-APD amplification with no noise excess

DI and CTIA solution introduce limitations when going further on reducing the pitch, and increasing the number of pixels. In this case, the SFD coupling could be a cost effective solution. This kind of architecture requires less room than other type of coupling for a given technological node, and does not request power dissipation in the pixel. Its major drawbacks is first that it requires applying a high bias on the photodiodes to achieve a large voltage excursion at the readout circuit output with a good signal to noise ratio, and second that the linearity is lower than with the previous coupling architectures. Table 2 indicates the type of input stages (SFD, DI or CTIA) reachable considering the technology node.

NETD vs APD Gain & Ti

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25APD GAIN

NET

D (A

.U)

NETD Tint=25s

NETD Tint=50s

NETD Tint=100s

Limitation (degraded DI efficiency, larger noise)

Improved performance with MCT e-APD



Table 2 Input stages as a function of the technology node

Pitch ROIC Foundry Technology0,5m 0,35m 0,25m 0,18m

FOV=3IFOV=82prad

/Reduced FPA size,improved compactness

185 mm,

F#4

640 x512,15p m

Increased FPA resolution,Improved ID range

640x512,10pm

123mm,

F#2,6

,.

I'1 FOV=3

IFOV=82prad185mm,

F#4

-\FOV=3IFOV=55prad

'J Q024x768,10pm _./33% GAIN IN FOCAL LENGTH! 33% GAIN in IFOV !

0

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16

0 1 2 3 4 5 6 7

F-Number (N)

Pixe

l pitc

h

15 m pitch

10 m pitch

space for imporvement

MWIR cut-off5m

Figure 6: rule for adequate sampling (5m cut-off MWIR system)

Figure 7: gain in compactness or IFOV

In Figure 8, the identification ranges at 99% probability as a function of F# optics are compared for two systems in 640x512, 15m and 1024x728, 10m, and for a standard target (a NATO panel of size 2.3 m X 2.3 m with temperature differences relative to their surroundings of 2C). It is apparent that 10m pixel pitch significantly improves the performance with respect to 15m pixel pitch when considering an F-number lower than 4 in cold and standard climates.

With small pixel pitch, the photon flux is reduced and the integration time is increased. As a consequence the long range devices involving very low IFOV are often strongly limited by the motion blur, consequence of holder movement during the integration time. Table 4 shows the significant impact on range caused by motion blur, considering a white Gaussian noise distribution of the holder movement with a standard deviation of 133.3rad for 10ms integration time.

Table 4 Range computation

F#4, 15m Still ranges (km) Ranges with movement (km) Range decrease

Detection (1pl) 13.09 6.25 -52%

Recognition (3pl) 5.33 2.24 -58%

Identification (6pl) 2.76 1.15 -58%



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IN IN

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STANDARD CLIMATE

COLD CLIMATE

Figure 8: Identification range: 15m vs 10m pixel pitch

The most efficient way to reduce that effect is to reduce integration time. In fact, if a white Gaussian distribution is considered, reducing integration time by a factor of 4 will decrease the standard deviation of movement by a factor of 4 (i.e 2). Unfortunately, in many cases that integration time decrease is not really an option because of the strong impact it has on well fill level and SNR. Indeed, as soon as the well fill is below 40% (which may be the case on a 288K scene) division of the integration time leads to a well fill level below 10%, often synonymous of SNR degradation and non-linearity in the response. Once again, e-APD MCT turns out to have major advantages for small pixel pitch solution: the input flux is amplified with no noise excess; therefore it happens to be possible to decrease the integration time without any impact on well fill level and to keep the electronic noise floor away from the signal level. Figure 8 shows an image acquired with 80s integration time and an APD gain of 30 what is equivalent to 2400s (=30x80s) integration time. The remaining trade off to deal with is the system compromise between MTF improvement and signal to noise ratio reduction due to the reduction of integration time. The range improvements at an APD gain of 4 (integration time reduced accordingly to keep constant well fill) gives the following results:

Table 5 Range improvement with APD

System with movement (km)

10ms integration time

System with movement (km)

2.5ms integration time (APD gain=4)

Range improvement with Ti=2.5ms +APD gain=4

Detection (1pl) 6.25 8.88 42% Recognition (3pl) 2.24 3.42 53% Identification (6pl) 1.15 1.75 52%

Figure 9: 384x288, 15m On-board systems may suffer from dispendious optical-stabilized solution to reduce motion blur in presence of harsh environment. In these cases, the use of APD MCT is a cost-effective solution that provides maximum flexibility to meet changing mission requirements.

3.4 4m

+30% F#2

+15% F#2



3 HIGH OPERATING TEMPERATURE

Over the last years, SOFRADIR has improved its HgCdTe technology, with effect on dark current reduction, which opens the way for High Operating Temperature (HOT) systems that can get rid of the 80K temperature constraint, and therefore releases the Stirling cooler engine power consumption.

Technological improvements on standard n on p process (in production) have led to a substantial increase in operating temperature (> 100K). Progresses are based on the use of the very high quality materials made at SOFRADIR (CZT, Epilayers) and on a precise optimization of all critical step of PV process.

In parallel, p-on-n arsenic-ion implanted technology has been developed and improved within the framework of DEFIR joint laboratory, a collaborative effort aimed at bringing together the expertise of SOFRADIR and CEA/LETI [2].

The advantages of FPAs operating at higher temperature are first and foremost the power reduction. This is highly desirable in all IR Systems using Stirling coolers. The goals are to reduce system size, increase autonomy, reduce system cost and improve the reliability. One of the key drivers for power consumption of cooled systems is the operating temperature of the focal plane array (FPA). In that perspective, the developers of SWAP systems should answer to the following contradictions:

Smaller size and smaller weight leads to higher compactness of the portable systems, Smaller power increases the autonomy of the batteries for the portable system, Finally, what is the better trade-off for a cost-effective solution?

3.1 P-on-N MCT for Mid Wave arrays

The major limitation for standard n/p technology towards higher operating temperature is a reduced electron lifetime by Hg vacancies. This implies a higher Dark current and limits the increase of operational temperature. Our first-class P/N MCT technology has become a key enabler for the development of SWaP concept for infrared systems: Dark current, following the well known Rule 7 [3], is reduced by more than a decade (equivalent to a gain of 30K in operating temperature) with respect to standard n-on-p photodiodes. The gain becomes even larger with cut-off wavelength moved from 5m to the lower edge of the CO2 absorption notch at 4.2m. This is easily achieved with MCT, having a perfect lattice matching with CdZnTe.

At a fixed FPA temperature, Figure 10 shows a Dark current reduction of almost two decades for P-on-N technology with respect to standard n/p technology, and almost as much between blue band ([3.4 4.2m]) and broadband ([3.7-4.8m]) solutions.

1,00E-14

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1,00E+00

1,0E-3 1,2E-3 1,4E-3 1,6E-3 1,8E-3 2,0E-3

1 / c x TFPA

Dar

k cu

rren

t

N-on-P technology

P-on-N technology(rule 07)

BB P-on-N

Blue P-on-N

(1) New Technology

BB N-on-P

(2) Cut-offshortened

Figure 10: P-on-N Dark Current

3.4-4.2m

3.7-4.8m



mfr---6000 K

500 K

10"

300 K

800 K

/ 500 K1

Wavelength [pm]

According to Plancks law, the red-to-blue ratio of a blackbodys photon emission depends on its temperature While the red-to-blue ratio of objects in the room temperature range is of the order of about 3, hotter objects like, e.g., the sun at 6000 K lead to values clearly smaller than 1 (Figure 11). Thus, the impact of sun light reflexion affecting the blue part of the MWIR is much higher, making it sensitive to solar glint. Figure 12 illustrates the differences we can expect between reflective blue band and emissive red band.

Figure 11: Photon emittence Figure 12: images with blue and red bands

To illustrate the reflective behavior of blue band sensor Figure 13 presents spectral thermal flux as well as spectral reflected solar flux through atmosphere for a 0.7 emissive grey body in sunny conditions. So, it appears that reflected flux is dominant in the blue band whereas emitted flux is dominant in the red band.

Table 6 presents the proportion of solar flux with 0.3 albedo in bright sunny day irradiation condition (100 000 lux) with respect to the thermal flux with 0.9 emissivity in two spectral windows (3.4-4.2m and 3.7-4.8m). The lowest emitting scene is a cold (-30C) background with 0.9 emissivity in dark night irradiation condition (almost 0 lux). The highest emitting scenes are hot grey bodies (70C) with 0.9 emissivity in bright sunny day irradiation condition (100 000 lux). The global scene dynamic between the highest and the lowest emitting background is twice larger in 3.4 4.2m spectral window ([3,4-4,2] : 40dB, [3,7, 4,8] : 34dB). [3,7 4,8m] spectral band shows less sensitivity to solar flux than blue band (6 times lower at -20C background temperature, twice smaller at 60C).

0,0E+00

5,0E+24

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3 3,2 3,4 3,6 3,8 4 4,2 4,4 4,6 4,8 5Spectral Wavelengh (m)

Spec

tral

radi

ance

(Pho

tons

/m/

sr/s

) Thermal FluxReflected Solar Flux

Figure 13:Spectral thermal and solar reflected flux

Using advantageously the p-on-n technology, it seems at first that the system would benefit from the operation in the blue part of the MWIR spectrum leaving room for higher FPA temperature. However, the blue solution turns out to have major limitations on, at least, three aspects:

3.7 4.8m3.4 4.2m



The photons starving (4.7 times lower) in cold background environment has an effect on the performance: The resulting lower flux must be accommodated by increasing the stare time or reducing the f-number, neither of which is attractive in handheld systems.

Even under fair conditions the 3.4-4.2m suffers more image clutter caused by solar glint, Globally the solar irradiation strongly affects the perception of the scene giving a pure thermal image at

night and a more reflective image during the day. As a consequence a blue band sensor has to deal with an overall dynamic range at least two times greater

than that of a broad band and expected even much higher in real scene with specular or partially specular reflexion. This is in contradiction

Table 6 Global scene dynamic, Thermal and Solar Flux

F#5 Optics, 15m pixel pitch [3.4 4.2m] [3.7 4.8m]

BB Temperature Thermal flux with Thermal flux with

0.9 emissivity 0.9 emissivity -30C 3.4x10+6e-/s 1.6 x10+7 e-/s 4,7 times more flux 20C 4.5 x10+7 e-/s 1.6 x10+8 e-/s 70C 2.8x10+8 e-/s 8.2 x10+8 e-/s

Solar flux with 0.3 albedo (100000 lux) 6.5 x10+7 e-/s 4.6 x10+7 e-/s

Under fair conditions 20C : Sensitivity to Solar (SOLAR / Thermal) 144% 28% Global scene dynamic [70CBB+Solar/-30CBB] 40dB 34dB

Blue MCT operation may be considered to lower the power consumption (but with limited gain) or for long range airborne observation (atmospheric transmission is more stable with distance bellow 4.2m cut-off wavelength). At this stage, uncertainties on image quality and cosmetics are high with the 4.2m cut-off wavelength. In comparison the 3.7-4.8m is versatile: easier to handle, can provide superior imaging performance because it suffers less image clutter caused by solar glint (more stable, less sensitive to glint or shadows in the image). Another main advantage of the broadband solution lays in the ability to sense the missiles exhaust plume and the evolution of those features during the different phases of the missiles flight.

3.2 SWaP for Small, low Power and Cost

Most of current developments efforts in IR-module technology are concentrated on reducing the size, weight and power (SWAP), all of these being key requirements for instance for night vision goggles, miniature UAVs, Thermal Weapon Sights, or more generally all IR systems that require more (performance) for less (volume and price).

BLUE BAND [3,4 4,2] [3,7 4,8] Long distance observation + (better atmosph. transmission) -Short distance observation - + (better SNR) Range in poor conditions and high F# - (Photon starving) + SWAP - (Lower F#) + (F/5.5 possible) Glint sensitive under fair conditions - +Perception Day / Night - + (Stable) CO2 Exhaust plume + ++Power consumption ++ [3.4-4.2] P/N + [3.7-4.8] P/N



In that regards, high TFPA operating MWIR 640x512 P/N FPA in extra compact encapsulation delivers a reduction in required cooling power and offers high reliability thanks to mature cooler solution. This solution reaches SWAP-C requirements (SWAP-C stands for SWAP+Cost). Table 7 presents our SWAP-C ready products in standard and shorty cold finger configuration THALES RM1 cooler.

Table 7 SWAP-C SOFRADIR RM1 in standard and shorty cold finger configuration

SWAP-C640x512 SWAP-C SHORTY

640x512

0

0,5

1

1,5

2

2,5

3

3,5

80 100 120 140 160 180 200TFPA (K)

PREG

(Wac

)

Cooler RM1 RM1 SHORTY Cold shield F# - F/5.5 - F/5.5 Height 100mm 80mm Masse 300g 275g MTTF > 10, 000 hours > 12, 000 hours Typical FPA Temperature 150K 150K Power (Wac) @20C < 2 < 3

4 BENEFITS OF 15m LW TECHNOLOGY

4.1 SCORPIO LW P/N, 640x512, 15m

Scorpio LW, produced since 2010, was the first p on n product developed at DEFIR. It meets a mean Netd of less than 25mK altogether with an excellent operability. Using same criteria as for MW detector (+/- 30% DC, +/- 20% responsivity, +/-100% NETD), we obtained operability better than 99.2% at 110K. Another crucial performance for pixel matrix is the residual fixed pattern noise (RFPN) after non-uniformity correction (NUC) and bad pixel replacement (operability defects correction): RFPN noise remains lower than temporal noise in the calibration Well Fill (WF) domain at 95K [4]. The choice between MW (3-5 m) and LW (8-12 m) IR wavelengths is always a question that generates debate. However, there are some objective criteria that should help for the decision. The best wavelength band for a given application depends upon the atmospheric transmission, background flux, scene conditions and target contrast. Atmospheric conditions have a high impact on wavelength choice. Indeed, in very humid environment the atmospheric transmission is higher in the MWIR and contrast remains higher for greater ranges than LWIR (see Figure 1). However cold and dry environments have higher transmission in the LW allowing better identification ranges. As a consequence atmospheric transmission strongly depends on country or region, climate, season. So choice between MW and LW can depend on final operation field.

65% reduction



MW transmission

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LW transmission

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Tropical

Figure 14: Atmospheric transmission

Due to fundamental physical reason, LW spectral window minimizes the effects of battlefield obscurants and artefacts. Thats why target acquisition systems for ground applications were historically LW to better view through smokes, dust and fog. On the battlefield, hot objects such as explosions, burning tanks, sun reflexions cause detector saturation and blooming. LW is more adapted in such conditions because it has a good hardiness against blooming. MW is far more sensitive to blooming leading to partial loss of picture when hot objects are observed in the scene. The figure compares the identification ranges at 99% probability as a function of F# number for two systems in 640x512, 15m and 320x256, 30m for a standard target (a NATO panel of size 2.3 m X 2.3 m with temperature differences relative to their surroundings of 2C). It is apparent that 15m significantly improved the performance with respect to 30m pixel pitch when considering an F-number lower than 4 in cold and standard climates.

0%

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40%

50%

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70%

80%

0 1 2 3 4 5 6 7F-Number

DetectionRecognitionIdentification

Figure 15: Range increase through f-number

4.2 Dual bands

Dual bands detectors combine the benefit from both MW and LW bands.

Military interest in DB (Dual-Band) infrared imaging systems has taken up technology development over the past 15 years. The ability to image in more than one waveband using the same detector is therefore highly advantageous over a standard single colour device. It affords the user the capability of either switching between

+50% F#2



," 4jr4. IR 5.5pm 640x512 SP 2Qrm IR 9.5pmi. f

wy .. -y ..

IR 4.2pm 640x512 SP 24m IR 5.3,.1m

61 I.IR 3.1p rn 256x256 NPN 211m IR 5.1p

\+. / Ir

IR 640x512SP2 m IR 9. m

.

IR 5 p m 256x256 SP 311.1m IR 10p rn

1.00

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- MWIR batchiMWIR batch2

- LWIR batchiLWIR batch2

3.0 4.0 5.0 6.0 7.0

Lambda (pm)8.0 9.0 10.0

wavebands, when different circumstances require, or using a combination of the wavebands to enhance target detection and identification ranges in a greater number of atmospheric or battlefield conditions.

Present developments at DEFIR are in line with future market needs: very large format and advanced solution for enhanced sensitivity are the target. We are heading to megapixel with pixel pitch smaller than 20m, thus increasing resolution.

Figure 16: In parallel, Sofradir develops and produces Quantum Well Infrared Photodetectors (sinle band and dual-band MW-LW QWIP) as a complementary offer with MCT, to provide large LW staring arrays [5].

Figure 17: QWIP Dual band / MW/LW image



5 CONCLUSION

Infrared detectors that offers ease of use, image quality, low power consumption and high performances are at the top of DEFIRs, priority list. Research and Development at DEFIR do show constant improvements regarding detector performances and compactness by reducing the pixel pitch, Increasing the operating temperature, Optimizing the encapsulation. In parallel, MCT APD remarkably contributes to SWAP concept with amplification for much smaller pixel pitch array and reduction for motion blur (holder movement) with decreased integration time. SOFRADIR offers HOT MW detectors that consume less than 2 W, 15m LW detectors with increased range performance and 10m pitch large detector for higher compactness and improved indentification. On the other hand, Sofradir continues to substantially support research in order to bring customers new technologies (such as avalanche photodiodes or dual bands, that meet the requirements for cutting-edge performances).

6 ACKNOWLEDGEMENTS

The authors would like first to thank all the SOFRADIR and CEA-LETI(LIR) teams part of DEFIR, dedicated to quality work and to challenging wins. The authors thank the French MoD support of CEA-LETI(LIR) and SOFRADIR technology including the third

7 REFERENCES

[1] Driggers, R., Infrared Detector Size How Low Should You Go?, Opt. Eng. 51(6), 063202 (2012) [2] Manissadjian, A. Improved IR detectors to swap heavy systems for SWaP, Proc. SPIE, 8353, 98(2012) [3] Tennent, W.E., Rule 07'' Revisited: Still a Good Heuristic Predictor of p/ n HgCdTe Photodiode

Performance, Journal of Electronic Materials, Volume 39, Issue 7, pp.1030-1035 (2010) [4] REIBEL, Y., High-performance MCT and QWIP IR detectors at Sofradir, Proc. SPIE, 8541, 85410A

(2012) [5] REIBEL, Y., Small Pixel Pitch solutions for Active and Passive Imaging, Proc. SPIE, 8353, 78 (2012) [6] DESTEFANIS, G., "Recent Progress in MCT detectors in France," Proc. SPIE, 8704, 79 (2013)



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