# Presentation: 174585

## Optical Vortex Coronagraph- Higher Order Concerns -

- Grover Swartzlander
*College of Optical Sciences*
*University of Arizona*
*Tucson, Arizona*
- Funding: U. S. Army Research Office, JSOP, and the State of Arizona

- Prepared for JPL Coronagraph Review, 29Sept06

**Notes:**
Title page

## Current Research Group

-   Joshua    Erin      Jennifer   Rukiah          Raul
-   Kim         Ford     Harwell   Abdul-Malik  Hernandez

**Current Research Group**

-   Missing:  Carmen Paleta-Toxqui
- 	     Radek Celechovsky
- 	     Mary Anne Peters

## Non-Achromatic Vortex Lens

- Glass Vortex Lenses of different pitch multiplicity
- Screw Pitch (d)  m waves of phase retardation

- d

**Pitch Multiplicity: ********=1 ****	****	****	****	********= 2**

- d

**Notes:**
Depiction of vortex lenses showing a single pitched and a multiple pitched spiral surface.  The pitch, or maximum step height, 
corresponds to a phase delay of m waves. The pitch multiplicity, , corresponds to the number of pitch edges.

## Circulating Momentum

- Helical Wavefront              Transverse k-Vectors

**Circulating Momentum**

**Notes:**
A plane wave is converted to a helical wavefront upon propagation through a vortex lens.
The transverse wave vectors circulate about the vortex axis.

## Vortex Intensity Profile

**Vortex Intensity Profile**

- Vortex Core: black at a SINGLE POINT owing to total destructive interference

**Notes:**
Total destructive interference occurs along the vortex axis.

## Optical Vortex Coronagraph

**Optical Vortex Coronagraph**

**Optical Vortex Coronagraph**,
- (Ret.) Lt. Col. G. Foo. D. Palacios, G. Swartzlander, Opt. Lett (2005)

**Notes:**
In the lab we null an on-axis (green) laser while leaving intact light from an adjacent source (red).
Lens L1 collimates the beams, effectively making the sources appear at infinity (like stars).
Lenses L1 and L2 comprise a telescope having a vortex mask in the afocal plane.
An aperture (“Lyot stop”) and imaging lens (L4) are placed behind the telescope.

## Optical Vortex CoronagraphExit Pupil

**Optical Vortex Coronagraph****Exit Pupil**

**Notes:**
In the plane of the Lyot stop the beam is diffracted into a large black hole.
The Lyot stop prevents light from the on-axis source from reaching the detector. 

## Optical Vortex Coronagraph- Experimental -

**Optical Vortex Coronagraph****- Experimental -**

**Notes:**
Experimental verification of the black hole.

## Optical Vortex CoronagraphStar (green) -- Planet (red)

**Optical Vortex Coronagraph****Star (green)**** -- ****Planet (red)**

**Notes:**
The off axis beam fills the Lyot stop and will therefore be imaged on the detector.

## Images

**Images**

**Notes:**
Comparisons of imaged light sources with and without the vortex lens in place.

## Fabrication

**- Finite Steps -**

**Notes:**
Higher Order Concerns

## Discrete Vortex Lens

- d

**Notes:**
Surface profile of a vortex lens made by Eric Johnson, CREOL.
The surface has discrete steps, rather than a continuous surface.
The etch depth error is roughly 5% and the pitch is designed for a specific wavelength.

## Achromatized Vortex Lens

**Notes:**
Higher Order Concerns

## Achromatic Vortex Lens

**Achromatic Vortex Lens**

- G. Swartzlander, Opt. Lett. 2006

**Notes:**
Invention of an achromatic vortex lens comprised of two transparent materials having
different refractive indexes and dispersions.  Examples are shown for lenses having
a pitch multiplicity of one and two.

## Achromatic Vortex Lens

**Achromatic Vortex Lens**

**Notes:**
Invention of an achromatic vortex lens comprised of two transparent materials having
different refractive indexes and dispersions.  Examples are shown for lenses having
a pitch multiplicity of one and two.

## Achromatic Condition

**Achromatic Condition**

**Notes:**
Calculated fidelity curves for a vortex lens achromatized in the neighborhood of a single wavelength.
The desired topological charge in this example, m=2, is achieved over a range exceeding 0.1 micrometers.
Materials from the Schott glass catalog were matched to minimize the error parameter, epsilon.

## Achromatic Condition

**Notes:**
Calculated fidelity curves for a vortex lens achromatized in the neighborhood of two wavelengths.
The desired topological charge in this example, m=2, is achieved over a range exceeding 0.15 micrometers.
Materials from the Schott glass catalog were matched to minimize the error parameter, epsilon.

## Other Approaches 

**to Achromatization**

- • Large values of m
- • Achromatize only C0 mode
- • Air-Gap Achromats
- • Subwavelength Gratings
- •  Blazed Superwavelength Grating

**Notes:**
Higher Order Concerns

## Next Experiment

- 8” f/8.8
- Telescope
- with
- ~ 5 cm
- Stop
- (> f/36)

- 10 cm Achromatic
- Doublet with
-  2mm Stop

- Piezo 1kHz Tip/Tilt Mirror

- Fast
- Camera

- Beam
- Splitter

- Imaging
- Lens

- Long
- Exposure
- Camera

- Mirror

- Lens

- Lens

- Imaging
- Lens

- Lyot
- Stop

- Specs:
- =850 nm
-   Strehl: 0.95
-   Target: Sirius B
-   Exposure: 2 min

- Vortex
- Lens

- (in collaboration with
- Laird Close and
- Mary Anne Peters)

**Notes:**
Design scheme for our next experiment that will be tested in the field.
This is a collaboration with Laird Close from Steward Observatory, Univ. Arizona.
His team is constructing a fast adaptive optics systems comprised of a fast
camera and a fast tip-tilt mirror.  The entire system is being designed to achieve 
a contrast of 1 part in 10,000. 

## What needs to be done

**What needs to be done**

- •  Fabricate high resolution masks
- •  Identify materials/configurations for achromats
- •  Experiments with high precision optics
- •  Combine with adaptive optics systems
- •  Optimization numerical studies
- •  Numerical testbed for non-ideal conditions

**Notes:**
Summary

## Slide 21

**Notes:**
Summary of optical vortex coronagraph.
Schematic shows two light sources being collimated by a lens, transmitted through an afocal telescope, and imaged.
With the vortex lens in place the on-axis and off-axis sources are separated in the plane of the Lyot stop, and 
(b) the imaged sources shows an attenuated green beam.
(c) Without the vortex lens in place both beams fill the Lyot stop, and 
(d) the green beam saturates the camera.