1. Near Infrared Tunable Filter System for ATST Big Bear Solar Observatory & Solar Research Center, NJIT Aug. 25, 2003

2. NIR Tunable Filter System CCD1 CCD2 PrefilterLyot-filter FP Polarization Analyzer

3. Design Requirements Spectral coverage: 1.0~1.7  m Resolving power: 150,000 FOV: 1~3 arcmin Bandpass: ~ 0.1Å Spatial resolution: ~ 0.1 arcsec Multi-operation: narrow, medium, and broad Filter aperture: Lyot filter~36mm, FP~150mm Tunable range 1.0~1.7  m High optical quality High throughput: ~40% for polarized light Stray light: ~ 10 -3 Stability: ~ 0.05Å/hour

4. Operation Mode I - Narrow passband Configuration: Interference Filters + Lyot Filter + NIR FP Passband FWHM: 0.1Å FOV: ~ 1 arcmin Observation Mode: Imaging Spectrograph / Spectropolarimetry Interested Lines: FeI 11607.6, 11783.3, 11882.8, 11884.1, 12879.8, 15207.5, 15219.6, 15245.0, FeI 15648.5, 15652.9, 1566.0, 15723.6 H 12818, Cont 16300 HeI 10830.34, 10830.25, 10829.08 CI 10683.1, 10685.4, 10691.2, 10729.5 MgII: 10952, 10914, FeXIII 10747, 10798 CN at J-band, OH at H-band: OH 15422.4, 15419.6, 15409.3, 15407.4 Peak Transmission: ~40% for polarized light

5. Configuration: Interference Filters + Lyot Filter Passband FWHM: 2~3Å FOV: ~ 1-3 arcmin Observation Mode: Filtergram Interesting Spectral Lines: FeI 15648.5, 15652.4 HeI 10830.34, 10830.25, 10829.08 Continuum 1.63  m H (P  ) 12818 CN at J-band, OH at H-band Peak Transmission: ~ 40% for polarized light Operation Mode II - Medium passband

6. Operation Mode III - Broad passband Configuration: Interference Filters Passband FWHM: 20~50Å FOV: ~ 1-3 arcmin Observation Mode: Active Region Evolution and Morphology Analysis Peak Transmission: >80%

7. Instrument I — NIR Lyot Filter Tunable ability: 1.0~1.7  m Clear Aperture: ~ 36 mm Bandpass FWHM: 2.5 ~ 3.0 Å Peak Transmission: ~ 40% for polarized light Internal Structure: 3-module or 4-module Temperature Controller: 45 ± 0.05°C Achromatic Components: waveplates, polarizers Wavelength Tuning Methods: I. Calcite + 1/4 waveplate + Rotating 1/2 waveplate II. Calcite + LC variable retarder

8. Sketch of the NIR Tunable Birefringent Filter P: Polarizer. C: Calcite. ½: Half waveplate. ¼: Quarter waveplate. d 1 is the thickness of the thickest calcite,  i is the rotated angle of the rotating half waveplates,  is the birefrinegent index of calcite, is wavelength. C C ½ ½ ½ C C ½ P ½ ¼ P C ½ C ¼ P C ½ C ¼ P ½ ¼ P 

9. Research on the FOV of Birefringent Filter W avelength (  m) Module IModule IIModule IIIModule IV 0.05Å shifting 0.1Å shifting 0.05Å shifting 0.1Å shifting 0.05Å shifting 0.1Å shifting 0.05Å shifting 0.1Å shifting 1.042 1  011  27 2  03 2  54 4  06 1.097 1  001  26 2  02 2  52 4  04 1.159 1  011  26 2  02 2  53 4  05 1.220 1  011  26 2  02 2  53 4  04 1.273 1  001  25 2  00 2  52 4  03 1.307 1  001  25 2  01 2  51 4  00 1.497 1  001  25 2  01 2  51 4  01 1.541 1  001  25 2  01 2  51 4  01 1.609 1  001  25 2  01 2  51 4  01 1.682 1  001  25 2  01 2  51 4  01 The FOV allowed for 0.05Å and 0.1Å Shifting of Passband Compared to the FWHM (  2.4 Å) of each module of IR Lyot Filter, these shifting are negligible.

10. Instrument II — NIR Fabry-Perot Tuning Range: 1.0~1.7  m Clear Aperture: ~ 150 mm Bandpass FWHM: ~ 0.1 Å @ 15648 Å Peak Transmission: > 90% Effective Finesse: ~ 60 FOV: ~ 1 arcmin for spectropolarimeter

11. Instrument III — CCD Cameras NIR camera(CCD2) Candidate: HgCdTe & InGaAs Format: 1024  1024 A/D: 14 bit or 16 bit Readout: 4 quadrant output Fill factor: 100% FOV: 60  diffraction limit 0.1  @1.56  m sampling 0.058  QE: > 60% LN2 Cooling Visible camera(CCD1) for image alignment Si CCD Format: 2048  2048 A/D: 14 bit or 16 bit Readout: frame transfer Fill factor: 100% FOV: 60  diffraction limit 0.03  @5000Å sampling 0.029  QE: >1%

12. Progress Design of achromatic waveplates from 1.0 to 1.7  m An example of 3-component achromatic half-waveplate design in NIR Achromatic Range: 1.0 to 1.7  m

13. Progress Compared to single Waveplate, the new design is practically “achromatic”. The threshold of retardation variance is set to be 1% of the final retardation. This is basically the limit of machinery sensitivity. Retardation Variance 15648Å 10830Å Single Waveplate

14. Progress Measurement of birefringent index of calcite from 1.0 to 1.7  m Comparison of the values of birefringent index  in the literature with the measured values. Diamond: values in the literature, triangle: measured values.

15. Progress 3-module design of Lyot filter to increase transmission 3-module detailed Lyot filter transmission at FeI 1.5648  m Sidelobe contamination for 3-module is ~0.54%, compared with 0.40% for 4-module; transmission increase by21% from 37% to 45% for polarized light

16. External Requirement Room temperature control. Pressure and vibration monitoring and controlling. Frequency stabilized infrared laser source. Polarization modulator system handshake. Telescope control system handshake. CCD cameras capture system control. AO system on-off control. ………..

17. On Going…... Simulation of match between Lyot filter and Fabry-Perot Experiment of liquid crystal variable retarder Design of near infrared polarization analyzer Calculation of ghost image of near infrared filter system Consideration of dual near infrared Fabry-Perot system Study of stability and repeatability of NIR Fabry-Perot Optical design for NIR tunable filter system Optimization of NIR tunable filter system

18. Thank You !