An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle...

20
An Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St. Cloud State University) Edwin Mierkiewicz (University of Wisconsin) Ronald J. Reynolds (University of Wisconsin) Kurt Jaehnig (University of Wisconsin)

Transcript of An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle...

Page 1: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

An Overview ofSpatial Heterodyne Spectroscopy

Principle OII SHS participants:

Fred Roesler (University of Wisconsin)John Harlander (St. Cloud State University)Edwin Mierkiewicz (University of Wisconsin)Ronald J. Reynolds (University of Wisconsin)Kurt Jaehnig (University of Wisconsin)

Page 2: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

θ

θ

G

G

B.S.

A

incident wavefront

12 exiting wavefronts

Imaging Detector

input

B.S. θG

P1

P2

Input

Output

a) b)

θ

G

The Spatial Heterodyne SpectrometerTransmitting SHS Properties

SHS is basically a Michelsoninterferometer with the return mirrorsreplaced by fixed diffraction gratings G.

For each wavenumber in the wavefrontentering the interferometer, twowavefronts exit the system with awavenumber-dependent crossing anglebetween them.

This produces a superposition of Fizeaufringes with wavenumber-dependentspatial frequencies localized near thegratings.

A position sensitive detector records theFizeau fringe pattern produced by theinterferometer.

x

x

Page 3: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

The Spatial Heterodyne Spectrometer

The heterodyne concept is evoked by the factthat the dispersive elements may be tuned toplace zero spatial frequency at a selectedwavenumber σo, where σo is the Littrowwavenumber of the diffraction gratings(2σosinθ=m/d)

For a system tuned to σo, adjacent spectralelements σo+δσ, σo+2δσ,..σo+nδσ produce1,2,…n-cycle spatial frequencies across thedetector.

As each spectral element produces a uniquespatial frequency, the Fourier transform of therecorded spatial frequencies provides thespectrum within a limited spectral range(determined by the detector sampling) aboutthe heterodyne wavelength.

x

Zero spatial frequency at the Littrow wavenumber σo

Page 4: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

θ

θ

G

G

B.S.

A

incident wavefront

12 exiting wavefronts

Imaging Detector

input

B.S. θG

P1

P2

Input

Output

a) b)

θ

G

The Spatial Heterodyne SpectrometerTransmitting SHS Additional SHS Properties

No mechanical part is moved in thisprocess.

The resolving power is the diffraction-limited resolving power of the gratingcombination.

The throughput is that characteristic ofinterference spectrometers at the achievedresolving power.

SHS can be field-widened with fixedprisms in each arm, giving SHS anenormous throughput gain overconventional systems of similar size andresolving power.

x

x

Page 5: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

θ

θ

G

G

B.S.

A

incident wavefront

12 exiting wavefronts

Imaging Detector

input

B.S. θG

P1

P2

Input

Output

a) b)

θ

G

The Spatial Heterodyne SpectrometerTransmitting SHS

x

x

Page 6: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

The instrument described thus farproduces identical output for inputwavenumbers σo+δσ and σo-δσ. Thisambiguity can be avoided by adding aslight y-tilt to one of the gratings.

Wavenumbers σ > σo are rotatedclockwise, while σ < σo are rotatedcounter clockwise.

3726.062 A3728.81 A

Page 7: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

Diffuse [OII] 372.7nm from the Warm Ionized Medium

Science Motivation:• The warm ionized medium was surveyed with WHAM at 656.3nm• Strong evidence for previously unrecognized energy sources has

emerged• [OII] 372.7nm emission is expected to verify their existence

Why SHS?:• WHAM does not work at 372.7nm• Fabry-Perot efficiencies are low and tolerances high below 400nm• The field-widened SHS is highly efficient in the NUV• SHS is more tolerant of defects by >15 compared to a FP

Status:• Observations are underway with the OII system at PBO

Page 8: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

Pine Bluff, WI (89o 40’ W, 43o 04’ N)

Page 9: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.
Page 10: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.
Page 11: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

Ne 3727.105 APix 733

Ne 3719.8 APix 441

Ne 3713.08 APix 160

R~20,000

Page 12: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.
Page 13: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.
Page 14: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.
Page 15: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

OII SHS on

OII SHS off

Page 16: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

Slanger, Keck order 96 (high res)

OII SHS on

Page 17: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

• Diffuse [OII] 372.7nm Emission from the Warm ISM

• SHIMMERSpatial Heterodyne Imager for Mesospheric RadicalsMeasuring mesospheric OH at 308.0nmSTS 112 and STPSat-1

• Diffuse CIV 155.0mn Emission from the Hot ISM

• Interplanetary Hydrogen 121.6nm

• Comet C/Neat (2001 Q4) OH and OI

• Daysky OI, R ~300,000

Page 18: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

the end

Page 19: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.
Page 20: An Overview of Spatial Heterodyne Spectroscopy Overview of Spatial Heterodyne Spectroscopy Principle OII SHS participants: Fred Roesler (University of Wisconsin) John Harlander (St.

Monoch

rom

atic

Sourc

e (Z

n)

Em

issi

on L

ine

Sourc

e (M

nN

e)Bro

ad B

and

Sourc

e (D

2)

(Harlander et al., 2004)

Single well isolated lineat 307.59 nm; fivefringe tilt perpendicularto the dispersion plane

Several emission featuresin the bandpass; provideswavelength calibrationand spectral resolution(~0.12 A)

Continuum source,spectral shape dominatedby the prefilter; allspectral informationlocalized near zero path