Optical Subsystem

Roy Esplin

Dave McLain

Internal Optics Bench Subassembly

2

Gut Ray

Dichroic Beamsplitter(MWIR reflected, LWIR transmitted)

LWIR Lens

Cold Entrance Aperture

Fold Mirror

MWIR Lens

Fold Mirrors

Thermal Isolator Mount

LN2 Heat Exchanger

LWIR FPA

Fold Mirror(MWIR Grating Replacement)

LWIR Grating

Cold Entrance Aperture

Position of cold aperture precisely controlled by mounting cold aperture assembly on MWIR/LWIR dichroic mount

Cold aperture covers larger hole in cold shield that is less accurately positioned

Cold aperture size can be changed by replacing the aperture assembly

Making this cold aperture the aperture stop rather than the telecope exit pupil would reduce the sensitivity to temperature changes of the optics in front of COB, but it would decrease the optical throughput.

3

Cold Aperture Assembly

Cold Shield

MWIR/LWIR Dichroic Mount

Replacement P2 Splitter Mount

Optical Design Highlights

New optical prescriptions for the Port 4 (LWIR) and Port 3 (MWIR) were developed starting from the ZMAX prescriptions MASModelPort4.zmx and MASModelPort3.zmx and provided to SDL by UCSC

New optical prescriptions use the telescope ±0.065º by ±0.065º IFOV used in MASModelPort4.zmx and MASModelPort3.zmx

Telescope field stop 0.381 mm x 0.381 mm, entrance pupil diameter 150mm, afocal magnification 6X, exit pupil diameter 25 mm

Lenses optimized together with the telescope and other optics in front of COB using Code V

LWIR prescription name: EMAS_Port4_V5f_Cold.len

MWIR Single-Element prescription name: EMAS_Port4_SE_V2f_Cold.len

MWIR Path-Forward prescription name: EMAS_Port3_V3e_Cold.len

Focal length of both the LWIR and MWIR lenses combined with the telescope is 250 mm. The focal length for the lenses alone is 250/6=41.7 mm

Lens optimized with operational temperature indices of refraction

Fabrication specifications for lens radii and the length of lens spacers adjusted for CTE difference between operational and ambient temperatures

4

5 Lens elements made of Germanium and ZnSe as shown on drawing

View looking down at lens shows direction of dispersion

Rays for only bands L1 and L12 are shown

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LWIR Lens

ZnSeGeZnSeGe Ge

Location of L1 Image of Field Stop

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LWIR Grating

LWIR Fold Mirror

LWIR Filter

L1 rays(Zoom 1)

L1 Image of Field Stop

LWIR Lens Elements

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Lens Srf Mat Radius Th FtPr CA Edge ΔRadius ΔTh ΔCA ΔEdge Radius Th CA Edge(#) (#) (NA) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm)

1 38 ZnSe 43.05482 7.500 52.572 54.934 58.430 0.051 0.009 0.066 0.070 43.106 7.509 55.000 58.50039 44.94675 NA 48.556 50.939 58.430 0.054 NA 0.061 0.070 45.000 NA 51.000 58.500

2 40 Ge 50.46084 7.500 49.040 50.953 53.950 0.047 0.007 0.047 0.050 50.508 7.507 51.000 54.00041 85.35718 NA 45.640 47.955 53.950 0.079 NA 0.045 0.050 85.437 NA 48.000 54.000

3 42 Ge 139.1719 7.500 44.550 46.956 53.950 0.130 0.007 0.044 0.050 139.301 7.507 47.000 54.00043 95.21671 NA 39.800 42.960 53.950 0.089 NA 0.040 0.050 95.305 NA 43.000 54.000

4 44 ZnSe Infinity 6.000 38.824 41.950 46.445 NA 0.007 0.050 0.055 Infinity 6.007 42.000 46.50045 53.4822 NA 34.420 36.956 46.445 0.064 NA 0.044 0.055 53.546 NA 37.000 46.500

5 46 Ge 29.26814 7.500 33.050 34.468 36.966 0.027 0.007 0.032 0.034 29.295 7.507 34.500 37.00047 39.11058 NA 28.030 29.473 36.966 0.036 NA 0.027 0.034 39.147 NA 29.500 37.000

Dimensions at 80K Change going from 80K to 295K Dimensions at 295K

Lens 1 Lens 3Lens 2 Lens 4 Lens 5

• Coatings R ≤ 1.5% avg. 6.4µm-14.0µm wavelengths both ZnSe & Ge elements

• Supplier: RMI

MWIR Single-Element Lens

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Lens Srf Mat Radius Th FtPr CA Edge ΔRadius ΔTh ΔCA ΔEdge Radius Th CA Edge(#) (#) (NA) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm)

1 38 Si 38.86864 7.000 31.022 34.992 37.991 0.009 0.002 0.008 0.009 38.877912 7.002 35.000 38.00039 55.53489 NA 27.742 31.992 37.991 0.013 NA 0.008 0.009 55.548141 NA 32.000 38.000

Dimensions at 80K Change going from 80K to 295K Dimensions at 295K

• Lens Material: Silicon • First surface, S2 is an ellipse

with conic constant K= -0.112339

• Coating R ≤ 1.0% avg. 3.0 µm - 5.0 µm wavelengths

• Supplier: ISP

Worst-Case Total Wavefront Errors (Design Residual + 2σ Tolerance Contribution)

Worst-case means across IFOV

Optics with a wavefront error of 0.07 RMS waves are essentially diffraction limited

Tolerances include all optical components including nominal tolerances on telescope and other optics in front of COB

1 mrad primary tilt

1.5 mrad secondary tilt

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LWIR BandsBand Zoom Band Wavelength RMS Wavefront Error

(#) (µm) (Waves at Band Wavelength)L1 12 6.715 0.096L2 11 7.325 0.077L3 10 8.280 0.065L4 9 8.550 0.064L5 8 9.730 0.061L6 7 10.200 0.060L7 6 11.030 0.058L8 5 12.020 0.056L9 4 12.600 0.055L10 3 13.335 0.056L11 2 13.635 0.057L12 1 13.935 0.059

MWIR BandBand Band Wavelength RMS Wavefront Error

(µm) (Waves at Band Wavelength)MWIR 3.730 0.127

Lens barrel showing spring-loading of lenses

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Lens barrel with first element removed to show hard stops for radial locating

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Selection of Grating Blaze Wavelength

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6.000 7.000 8.000 9.000 10.000 11.000 12.000 13.000 14.0000.00

0.20

0.40

0.60

0.80

1.00

1.20

Theoretical Grating Efficiency

9.73 Micron Blaze Wave-length

10.2 Micron Blaze Wave-length

Wavelength (µm)

Eff

icie

nc

y

9.73 µm Blaze Selected

Blaze Wavelength (µm) 9.73 10.20Blaze Angle (Degrees) 15.27 16.40Blaze Depth (mm) 5.460E-03 5.743E-03Wavelength (µm)

6.715 0.46 0.337.325 0.67 0.558.288 0.89 0.828.550 0.93 0.879.730 1.00 0.99

10.200 0.99 1.0011.030 0.95 0.9812.020 0.87 0.9112.600 0.81 0.8613.335 0.74 0.8013.635 0.71 0.7713.935 0.68 0.74

Theoretical Effi ciency

Incidence and Diffracted Rays for 9.730 µm Wavelength

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Incident Gut Ray

Diffracted Gut Ray at 9.730 µm

Grating

Bisector of Angle Formed by Incident and Diffracted Rays is Facet Normal

LWIRFold Mirror

LWIR Lens

Plane of Grating facet and Plane Containing Incident and Diffracted Rays and Facet Normal for 9.730 µm Wavelength

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Plane of Grating Facet

Plane of Incident & Diffracted Rays and Facet Normal at 9.730 µm

Diffracted Gut Ray at 9.730 µm

Incident Gut Ray

Facet Normal

Grating Blazed for 9.730 µm Wavelength with Facets Shown Oversize (Grating Blaze Angle 15.73º)

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Yellow Line Outlines Plane of Grating Facet

Grating

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• Material: Stress-Relieved Aluminum• Type: Original Burnished Rulings• Coating: Gold • Grating spacing: 0.020 mm• Ruling Spatial Frequency: 50 lines/mm• Operational temperature: 80K

Optical Beam Footprint on Grating

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LWIR Images of Field Stop on Detector Array

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A p e r t u r e F u l l X W i d t h : 1 6 . 4 0 0 0A p e r t u r e F u l l Y H e i g h t : 0 . 5 5 8 0

Scale: 0.5800 Millimeters

6 . 7 1 5 0 7 . 3 2 5 0 8 . 2 8 0 0 8 . 5 5 0 0 9 . 7 3 0 0 1 0 . 2 0 0 0 1 1 . 0 3 0 0 1 2 . 0 2 0 0 1 2 . 6 0 0 0 1 3 . 3 3 5 0 1 3 . 6 3 5 0 1 3 . 9 3 5 0

E M A S _ P o r t 4 _ V 5 f _ C o l d . Z M XC o n f i g u r a t i o n 1 o f 1

F o o t p r i n t D i a g r a mM A S M o d e l1 1 / 1 3 / 2 0 1 0S u r f a c e 5 0 : D E T E C T O RR a y X M i n = - 8 . 3 8 1 0 R a y X M a x = 8 . 3 4 9 2R a y Y M i n = - 0 . 2 8 7 5 R a y Y M a x = 0 . 6 3 7 9M a x R a d i u s = 8 . 3 8 1 1 W a v e l e n g t h = A l l

% r a y s t h r o u g h = 6 3 . 6 5 %

Band CENTER WAVELENGTHlabel (µm)

L1 6.715L2 7.325L3 8.280L4 8.550L5 9.730L6 10.200L7 11.030L8 12.020L9 12.600

L10 13.335L11 13.635L12 13.935

LWIR Detector Active Areas & Field Stop Images

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Dimensions: millimeters (mm)Solid lines: Active AreasPhantom Lines: Field Stop Images

LWIR Channel Passbands

50% points estimated by ascertaining wavelength gut ray strikes the left and right edges of detector active area

0% points estimated by finding wavelength for with ray moves from the left edge to right edge and vice versa

The values given for Band L4 need to be moved slightly longer because the spatial gap between L3 and L4 recently had to be increased from 13µm to 19µm to accommodate the capabilities of the detector fabrication process

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Band 0% 50% 100% 50% 0% Width at 50% Width at 0%label (µm) (µm) (µm) (µm) (µm) (µm) (µm)

L1 6.459 6.589 6.715 6.842 6.972 0.253 0.513L2 7.065 7.195 7.325 7.455 7.586 0.260 0.521L3 8.017 8.147 8.280 8.411 8.541 0.264 0.524L4 8.287 8.417 8.550 8.681 8.811 0.264 0.524L5 9.468 9.599 9.730 9.861 9.992 0.262 0.524L6 9.939 10.070 10.200 10.331 10.462 0.261 0.523L7 10.769 10.900 11.030 11.16 11.291 0.260 0.522L8 11.760 11.891 12.020 12.149 12.280 0.258 0.520L9 12.342 12.473 12.600 12.728 12.859 0.255 0.517

L10 13.072 13.204 13.335 13.467 13.598 0.263 0.526L11 13.376 13.507 13.635 13.766 13.897 0.259 0.521L12 13.674 13.805 13.935 14.058 14.189 0.253 0.515

LWIR Detector Array Layout

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FPA Mother Board

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LWIR Detector Package Solid Model

Order Sorting Filter 16.565µm -10.450µm passband

Order Sorting Filter 210.780µm -14.085µm passband

L1 detectorL12 detector

LWIR Detector Package Drawing

L6 L7

Drawing dimensions are in inches

Connector mounted on circuit board

0.250 mm space between filter and detectors

LWIR Order-Sorting Filter

Two bandpass filters on a monolithic Germanium substrate

No uncoated areas except at edges

Filter 1 and Filter 2 coatings overlap in 0.240 mm wide transition region

Filter 1 Transmittance:≥ 80% average 6.565 µm - 10.450 µm

≥ 72% absolute 6.565 µm - 10.450 µm

≤ 0.1% absolute UV – 5.85 µm

≤ 0.1% absolute 11.6 µm – 18 µm

Filter 2 Transmittance:≥ 80% average 10.780 µm – 14.085 µm

≥ 72% absolute 10.780 µm – 14.085 µm

≤ 0.1% absolute UV – 9.45 µm

≤ 0.1% absolute 15.45 µm – 18 µm

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Drawing dimensions in millimeters (mm)

0.240 mm wide region where Filter 1 and Filter 2 coatings overlap

Diffraction orders greater than 1 are blocked:Wavelengths > 5.85 µm in diffraction orders > 1 are dispersed to the right of Filter 1. (2*5.85 = 11.7)

Wavelengths > 9.45 µm in diffraction orders > 1 are dispersed to the right of Filter 2. (2* 9.45 = 18.9)

Zero-Order Diffraction is Blocked by LWIR Lens

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Spacer Between the First Two Lens Elements of LWIR Lens Painted To Minimize Scattered Light From Zero-Order

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Spacer Lens 1 Lens 2

Zero-Order Rays

Mirrors

Substrates: 6061-T6 Aluminum

Machining, stress-relieving, and thermal cycling to be done by SDL

Diamond turning, post-polishing, lapping and coating to be provided by NU-TEK

Optical Surface Coating:Protected Gold

Reflectance ≥ 97.5% @3.6 µm to 14.1 µm and 22.5º AOI

Flatness ≤ λ/4 @ 633 nm

Surface Roughness ≤ 250 Angstroms

Mounting Pads Lapped or Diamond Turned

3 Identical Fold MirrorsDiameter 1.307 inches

Clear Aperture 1.246 inches

1 Grating Replacement MirrorDiameter 1.417 inches

Clear Aperture 1.279 inches

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Fold Mirrors MWIR Grating Replacement Mirror

Drawing Dimensions in inchesOPTICAL FOOTPRINT ON MIRRORSMirror Diameter

(in)LWIR Fold up 1.168MWIR Fold Side ways 1.233MWIR Fold up 1.246MWIR Grating Replacement 1.279

New Port 3 Dichroic Beamsplitter

New Port 3 Beamsplitter required for new cryogenic mounting inside COB

Operational temperature: 80K

Substrate: ZnSe

Diameter: 38.10 mm

Thickness: 6.00 mm

Clear Aperture: 34.0 mm

Surface Flatness:Before coating: λ/4 @ 633 nm

After coating: 2λ power, λ/2 irreg. @633 nm

Angle of incidence: 25º

Reflectance:≥ 93% average 3.66µm to 5.552 µm

≥ 83% minimum absolute 3.66µm to 5.552 µm

Transmittance:≥ 80% average 6.56µm to 14.09 µm

≥ 70% minimum absolute 6.56µm to 14.09 µm

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P3 Splitter @ 25 Degrees AOI

0

10

20

30

40

50

60

70

80

90

100

3 4 5 6 7 8 9 10 11 12 13 14 15

Wavelength

Refl

Trans

DSI Design

Window

Substrate: ZnSe

Diameter: 44.00 mm

Thickness: 3.00 mm

Clear Aperture: 37.0 mm

Coated Area: ≥ 41.0 mm

Surface Flatness: ≤ λ/4 @ 633 nm

Angle of incidence: 30º

BAR Coating Surface Reflectance:≤ 2% avg. 3.6 µm to 14.1 µm

≤ 4% max. 3.6 µm to 14.1 µm

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BAR Coating Reflectance Curve From ISP Optics

Optical Component Status & Drawing Numbers

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Component Drawing # Vendor Delivery CommentsLWIR FPA SDL 155-0004-A Teledyne Judson Technologies (TJT) 3/21/2011 SDL providing help on packageFilter SDL 155-0005- JDSU 1/14/2011 UCSC supplied partLWIR Grating SDL 155-0003- Bach Research Associates 1/24/2011 Early delivery expectedLWIR Lens 1 SDL 155-0007A Rocky Mountain Instrument (RMI) 1/5/2011LWIR Lens 2 SDL 155-0009A Rocky Mountain Instrument (RMI) 1/5/2011LWIR Lens 3 SDL 155-0010A Rocky Mountain Instrument (RMI) 1/5/2011LWIR Lens 4 SDL 155-0011A Rocky Mountain Instrument (RMI) 1/5/2011LWIR Lens 5 SDL 155-0012A Rocky Mountain Instrument (RMI) 1/5/2011MWIR Singlet Lens SDL 155-0013A ISP Optics UCSC supplied part (14 weeks ARO)Window SDL 155-0015- ISP Optics 1/19/2011Fold Mirror SDL 155-0017A NU-TEK Optical Corp 1/26/2011 SDL provide blanks by 12/15/2010MWIR Grat, Replace. Mir. SDL 155-0018A NU-TEK Optical Corp 1/26/2011 SDL provide blanks by 12/15/2010MWIR/LWIR Dichroic SDL 155-0016- Deposition Sciences Inc. (DSI) UCSC supplied part (6 weeks ARO)MWIR Single Det. FPA UCSC supplied part

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“Path Ahead” There is room in COB for this MWIR lens and grating in

future

Si

Ge Filter MWIR Grating

Si SiGe

Prescription: EMAS_Port3_V3e_cold.len