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2012 Advanced Materials Characterization Workshop

June 7, 2012

Jason McClure Chief Scientist

Princeton Instruments

The Schmidt-Czerny-Turner Spectrograph

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Outline

• Czerny-Turner imaging spectrograph

– Applications

– Limitations of the traditional design – image aberrations

• Schmidt-Czerny-Turner spectrograph

– Application Highlights

• Hyper-spectral imaging

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Applications involving the CT-Spectrograph

• Raman, PL, PLE

• Transmittance / Reflectance

• Spectral domain Optical Coherence Tomography (OCT)

• Fourier Domain Dispersive Spectroscopy

– There is a movement towards multimodality techniques that generate

information rich data at the micro/nano scale

• Hyperspectral micro-Raman imaging

• TERS, NSOM

• OCT/micro-Raman mapping – cancer detection

• MRI/X-ray CT/Photoluminescence – Small animal imaging

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Applications involving the CT-Spectrograph

• Where are the innovations occurring?

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Applications involving the CT-Spectrograph

• Where are the innovations occurring?

Nature Nanotechnology 4, 496 - 499 (2009) Published online: 26 July 2009

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Applications involving the CT-Spectrograph

• Where are the innovations occurring?

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Applications involving the CT-Spectrograph

• Where are the innovation occurring?

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Applications involving the CT-Spectrograph

• Where are the innovations occurring?

?

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The Czerny-Turner Spectrograph

• The CT spectrograph has not seen significant

innovation in ~30 years!

– Strong movement towards multimodality techniques which require

spatially resolved spectral data

– The CT spectrograph is the final optical element light sees before your

detector does.

• There are three primary image aberrations that can be observed in any

traditional CT type spectrograph

– Spherical

– Coma

– Astigmatism

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Image Aberrations

• Spherical aberration

– Cause: Using a spherical mirrors to focus light to form an image

– Appearance: Diffuse symmetric blur about an image

• e.g. image of a fiber through a spectrograph will have a diffuse blur

around a more intense center

– Affects on spectroscopy: Limits both spatial and spectral resolution of a

spectrograph

Example:

Symmetric blur seen

about a fiber optic image

150 um fiber core

3#

1

fWI

Wavefront Aberration

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Image Aberrations

• Coma aberration

– Cause: Using mirrors to image a source off axis

– Appearance: Comet shaped tail to focused images or spectral lines

• e.g. spectral lines are asymmetrically broadened

– Affects on spectroscopy: Limits spectral resolution of a spectrograph,

however, is completely corrected at one grating angle or wavelength.

Example:

Asymmetry in spectral

line profile

2#

1

fWII

Wavefront Aberration

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Image Aberrations

• Astigmatism aberration

– Cause: Using lenses or mirrors to image a source off axis

– Appearance: Vertical or horizontal elongation of an image

• e.g. The “Bow-Tie” effect, vertical distortion of fiber image

– Affects on spectroscopy: Limits both spectral and spatial resolution of a

spectrograph. Is completely corrected at the center of the focal plane.

Example:

Elongation of

Fiber core images

#

1

fWIII

Wavefront Aberration

Traditional CT focal plane

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Image Aberrations

• Astigmatism aberration

– Cause: Using lenses or mirrors to image a source off axis

– Appearance: Vertical or horizontal elongation of an image

• e.g. The “Bow-Tie” effect, vertical distortion of fiber image

– Affects on spectroscopy: Limits both spectral and spatial resolution of a

spectrograph. Is completely corrected at the center of the focal plane.

SPECTROSCOPY GROUP

Image Aberrations

• Astigmatism aberration

– Cause: Using lenses or mirrors to image a source off axis

– Appearance: Vertical or horizontal elongation of an image

• e.g. The “Bow-Tie” effect, vertical distortion of fiber image

– Affects on spectroscopy: Limits both spectral and spatial resolution of a

spectrograph. Is completely corrected at the center of the focal plane.

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Current state of the art Czerny-Turner spectrograph

f/4 class spectrograph Schmidt-Czerny-Turner

Row #

Wavelength

Dispersed image of a continuous source (QTH Lamp)

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Application Highlight - Hyperspectral Imaging

• 1 um monodisperse polystyrene spheres

– Self assemble into 2D hcp arrays

– Dark field illumination

– Diffraction through multilayer

Olympus IX-71

100 X Illumination

10 mm

Annular aperture

Objective

PMMA array

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Application Highlight - Hyperspectral Imaging

• 10X dark field illumination of PMMA lattice

Witness camera on IX-71 0 order image seen through SCT

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Application Highlight - Hyperspectral Imaging

Row #

Wavelength Entrance Slit

Full 2D spectral image

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Application Highlight - Hyperspectral Imaging

Spectra from two differently oriented grains Resulting Hyperspectral

image

Dark field QTH illumination, Line exposure time = 0.1 sec

Objective lens = Olympus 10X APO

Grating = 1200 g/mm blazed at 500 nm

Spectrometer slit = 20 um

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Application Highlight - Hyperspectral Imaging

Data collected using NanoPhoton Confocal Microscope

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Acknowledgements

• Katsumasa Lab – Osaka University

– Isoplane testing with NanoPhoton

confocal microscope

• Acton Engineering

– Lloyd Wentzell

– Bob Fancy

– Mike Case

– Paulo Goulart

– Bob Jarratt

• Trenton Engineering

– Bill Asher

– Harry Grannis

– Bob Bolkus

– Bill Hartman

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Questions?

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Features

Feature Specification

Aperture ratio f/4.6

Focal length 320 mm

Wavelength Scan Range 0-1400 nm

CCD resolution 0.07nm *4mm x 10 um slit at 435nm

Astigmatism 0.0 um *any wavelength

Coma 0.0 um *at 500 nm with 1200 g/mm grating

Spherical Aberration 0.0 um *any wavelength