Spatial Light Modulators and Fourier Optics

In summary, the conversation discusses using a Digital Micro-mirror Device (DMM) to convert a laser from a gaussian to flat-head intensity profile and make the beam oscillate on a camera. The speaker mentions being naive to think that moving the image pattern on the SLM would cause movement in the focus plane. Another person suggests checking if the SLM is correctly placed in a conjugate plane to either the image or the FT plane. The placement is clarified and it is suggested to adjust the phase at the FT plane to translate the beam at the image plane. The use of a cylindric lens is also mentioned but with undesirable interference patterns.
  • #1
Qiao
13
0
Hi,
I'm working with a Digital Micro-mirror Device type SLM and my goal is to convert my laser from a gaussian to flat-head intensity profile. And then the tricky part is to make the beam oscillate up and down on the camera using just the SLM.

Apparently I was to naive to think that moving my image pattern on the SLM equals movement in the focus plane.

Does anyone have any suggestions or ideas I should try?
 
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  • #2
Is your SLM correctly placed in a conjugate plane to either the image or the FT plane?
 
  • #3
The SLM is placed in the front focus plane of the first lens then there is a second lens afterwards with a shorter focal distance w.r.t. the first lens. Then a camera is placed at the end such that the camera is in both the back focal planes of both lenses.
So to answer the question, it's placed conjugate to the FT plane of the first lens.
 
  • #4
Then, in order to translate the beam at the image plane, you need to adjust the phase at the FT plane. AFAIK, DMM devices only modulate the intensity, so if you instead place your device at a plane conjugate to the image, you should be able to do what you need.
 
  • #5
Thanks, I'll try that. I've also managed to get oscillation using a cylindric lens, but only in the axis where the beam is unfocused. But the intensity profile is still very ugly with higher order interference patterns.
 

1. What is a spatial light modulator (SLM)?

A spatial light modulator is a device that can manipulate the properties of light, such as its intensity, phase, and polarization, in a spatially varying manner. This allows for precise control over the propagation of light and enables various applications in optics and photonics.

2. How does an SLM work?

SLMs are typically made up of an array of pixels, each of which can be individually controlled to change the phase or intensity of the incident light. This is achieved through the use of liquid crystals, micro-electromechanical systems (MEMS), or digital micromirror devices (DMDs), which respond to an applied electric field to modulate the light passing through them.

3. What is the role of Fourier optics in SLMs?

Fourier optics is a branch of optics that deals with the spatial filtering, manipulation, and analysis of light using the principles of Fourier transforms. In SLMs, Fourier optics is used to encode information onto the incident light and then decode it at the output using Fourier transforms. This allows for complex wavefronts to be generated and manipulated with high precision.

4. What are the applications of SLMs in research and technology?

SLMs have a wide range of applications in research and technology, including holography, optical tweezers, adaptive optics, optical communications, and 3D display technology. They are also used in fields such as microscopy, astronomy, and biophotonics for their ability to control and manipulate light at the spatial level.

5. What are the advantages of using SLMs over traditional optical components?

One of the main advantages of SLMs is their versatility and programmability. Unlike traditional optical components, which are fixed and cannot be easily changed, SLMs can be reconfigured to perform different functions and can be controlled in real-time. This makes them highly adaptable for various applications and eliminates the need for multiple bulky optical elements.

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