Systems and methods for particle pulse modulation

Patent metadata

Field	Value
Publication number	US-9536698-B2
Application number	US-201514832056-A
Country	US
Kind code	B2
Filing date	Aug 21, 2015
Priority date	Aug 22, 2014
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

Methods and apparatus for modulating a particle pulse include a succession of Hermite-Gaussian optical modes that effectively construct a three-dimensional optical trap in the particle pulse's rest frame. Optical incidence angles between the propagation of the particle pulse and the optical pulse are tuned for improved compression. Particles pulses that can be modulated by these methods and apparatus include charged particles and particles with non-zero polarizability in the Rayleigh regime. Exact solutions to Maxwell's equations for first-order Hermite-Gaussian beams demonstrate single-electron pulse compression factors of more than 100 in both longitudinal and transverse dimensions. The methods and apparatus are useful in ultrafast electron imaging for both single- and multi-electron pulse compression, and as a means of circumventing temporal distortions in magnetic lenses when focusing ultra-short electron pulses.

First claim

The invention claimed is:

1. A method for modulating a particle pulse, the method comprising:
A) propagating the particle pulse at a velocity ν along a first direction; and
B) propagating an electromagnetic pulse along a second direction at an oblique angle θ with respect to the first direction in a laboratory frame of reference so as to cause the electromagnetic pulse to at least partially overlap with the particle pulse, the electromagnetic pulse having an intensity profile with a minimum along at least one line passing through a center of the electromagnetic pulse,
wherein the oblique angle θ is based at least in part on the velocity ν of the particle pulse;
wherein the oblique angle θ is substantially equal to arctan(1/γβ), β=(ν/c), γ=(1−β 2 ) −1/2 , and c is a speed of light in a vacuum.

2. The method of claim 1 , wherein the particle pulse comprises at least one of a plurality of charged particles or a plurality of polarizable neutral particles.

3. The method of claim 1 , wherein the electromagnetic pulse comprises a Hermite-Gaussian mode of an order greater than zero.

4. The method of claim 1 , wherein the electromagnetic pulse comprises at least one of a Laguerre-Gaussian mode, an Ince-Gaussian mode, a Bessel-Gaussian mode, or a Hypergeometric-Gaussian mode.

5. The method of claim 1 , wherein A) comprises propagating the particle pulse in a central region including the minimum of the intensity profile so as to compress the particle pulse in the first direction.

6. The method of claim 1 , wherein A) comprises propagating the particle pulse in a sloped region of the intensity profile behind the minimum in the first direction so as to accelerate the particle pulse.

7. The method of claim 1 , wherein A) comprises propagating the particle pulse in a sloped region of the intensity profile before the minimum in the first direction so as to decelerate the particle pulse.

8. The method of claim 1 , further comprising:
propagating a second electromagnetic pulse substantially along the first direction so as to compress the particle pulse in a direction orthogonal to the first direction.

9. The method of claim 1 , further comprising:
generating the electromagnetic pulse by combining a plurality of Hermite-Gaussian modes of order greater than one.

10. The method of claim 1 , further comprising:
generating the electromagnetic pulse by propagating a first half of a fundamental Gaussian pulse through a half waveplate.

11. The method of claim 1 , further comprising:
generating the particle pulse using a radio frequency (RF) electron gun.

12. An apparatus for modulating a particle pulse propagating at a velocity ν along a first direction, the apparatus comprising:
an electromagnetic radiation source to provide an electromagnetic pulse having an intensity profile with a minimum along at least one line passing through a center of the electromagnetic pulse; and
a beam steering optic, in optical communication with the electromagnetic radiation source, to direct the electromagnetic pulse along a second direction at an oblique angle θ with respect to the first direction in a laboratory frame of reference so as to cause the electromagnetic pulse to at least partially overlap with the particle pulse in a first interaction,
wherein the oblique angle θ is based at least in part on the velocity ν of the particle pulse;
wherein the oblique angle θ is substantially equal to arctan(1/γβ), β=(ν/c), γ=(1−β 2 ) −1/2 , and c is a speed of light in a vacuum.

13. The apparatus of claim 12 , wherein the electromagnetic radiation source comprises a laser configured to provide the electromagnetic pulse comprising at least one laser pulse in a Hermite-Gaussian mode of an order greater than zero.

14. The apparatus of claim 12 , wherein the electromagnetic radiation source comprises:
a laser to provide a first laser pulse in fundamental Gaussian mode; and
a half waveplate, in optical communication with the laser, to transmit a first portion of the laser pulse so as to generate a second laser pulse in Hermite-Gaussian mode of an order greater than zero.

15. The apparatus of claim 12 , wherein the electromagnetic radiation source comprises:
at least one laser to provide a plurality of laser pulses, each laser pulse in the plurality of laser pulses configured to be in a Hermite-Gaussian mode of an order greater than one; and
at least one beam combining optic, in optical communication with the at least one laser, to generate the electromagnetic pulse based at least in part on a superposition of the plurality of laser pulses.

16. The apparatus of claim 12 , further comprising a particle source to provide the particle pulse.

17. The apparatus of claim 16 , wherein the particle source comprises at least one of a charged particle source and a polarizable neutral particle source.

18. The apparatus of claim 16 , further comprising a particle accelerator, operably coupled to the particle source, to accelerate the particle pulse to the velocity ν.

19. The apparatus of claim 12 , wherein the beam steering optic is configured to tune the oblique angle with respect to the first direction over a range of about 10° to about 80°.

20. The apparatus of claim 12 , wherein the beam steering optic is configured to overlap a central region including the minimum of the intensity well with the particle pulse so as to longitudinally compress the particle pulse.

21. The apparatus of claim 12 , wherein the beam steering optic is configured to overlap a first region of the intensity profile, behind the minimum along the first direction, with the particle pulse so as to accelerate the particle pulse.

22. The apparatus of claim 12 , wherein the beam steering optic is configured to overlap a second region of the intensity profile, before the minimum along the first direction, with the particle pulse so as to accelerate the particle pulse.

23. The apparatus of claim 12 , further comprising:
a second beam steering optic, in optical communication with the electromagnetic radiation source, to direct a second electromagnetic pulse, provided by the electromagnetic radiation source, substantially along the first direction so as to compress the particle pulse in a direction orthogonal to the first direction.

24. The apparatus of claim 12 , further comprising:
a second electromagnetic radiation source to provide a second electromagnetic pulse propagating substantially along the first direction so as to compress the particle pulse in a direction orthogonal to the first direction.

25. The apparatus of claim 12 , further comprising:
a reflector, in optical communication with the electromagnetic source and disposed at a distance D away from a propagation axis defined by the first direction, to reflect the electromagnetic pulse along a third direction toward the propagation axis, wherein the third direction is substantially at the oblique angle θ with respect to the first direction so as to allow a second interaction between the electromagnetic pulse and the particle pulse after first interaction with the particle pulse.

26. The apparatus of claim 25 , wherein the distance D is at least two times greater than τc/γ, wherein τ is a pulse duration of the electromagnetic pulse, c is a speed of light in a vacuum, and γ=(1−(ν/c) 2 ) −1/2 .

27. An apparatus for providing electron pulses, the apparatus comprising:
an electron source to provi

Assignees

• Wong Liang Jie
• Freelon Byron
• Rohwer Timm
• Gedik Nuh
• Johnson Steven Glenn
• Massachusetts Inst Technology

Inventors

• Wong Liang Jie
• Freelon Byron
• Rohwer Timm
• Gedik Nuh
• Johnson Steven Glenn

Classifications

• H01J37/06 Primary

  Electron sources; Electron guns · CPC title

• H01J2237/0475

  decelerating · CPC title

• H01J2237/047

  Changing particle velocity · CPC title

• H01J2237/063

  Electron sources · CPC title

• H01J2237/0473

  accelerating · CPC title