User:Pranav Rathi/Notebook/OT/2010/08/02/x & y Signal Drift Issue

(Difference between revisions)
 Revision as of 17:23, 2 August 2010 (view source) (→Setup & procedure)← Previous diff Revision as of 17:38, 25 August 2010 (view source)Next diff → Line 1: Line 1: ===Goal=== ===Goal=== + The goal has been achieved today. The drift problem is solved by imaging the beam waist (1.26mm; exists inside the AOM) with 1:1 telescope on the QPD. I am very positive that this works, but I am still verifying that it is not happening due to small beam waist at the QPD. I will right the full detail later ; how we achieved it. Investigate the x & Y signal drift:  What is causing it; AOM or the laser (most probable it’s the AOM), magnitude of the effect, and possible solution. Investigate the x & Y signal drift:  What is causing it; AOM or the laser (most probable it’s the AOM), magnitude of the effect, and possible solution.

Contents

Goal

The goal has been achieved today. The drift problem is solved by imaging the beam waist (1.26mm; exists inside the AOM) with 1:1 telescope on the QPD. I am very positive that this works, but I am still verifying that it is not happening due to small beam waist at the QPD. I will right the full detail later ; how we achieved it. Investigate the x & Y signal drift: What is causing it; AOM or the laser (most probable it’s the AOM), magnitude of the effect, and possible solution.

Setup & procedure

The setup is fairly simple; laser --> AOM --> two mirrors (down and upstream) --> telescope (1:1)--> QPD.

under work

Steps

1. Measure the beam waist (2 x W=1.5) at the eyepiece lens of the telescope.
2. Setup the (1:1) telescope: In this case two planoconvex lenses (f=38.1mm of both) are used.
3. Measure the beam waist again (2 x W =1.5) at QPD, to make sure that the ratio is 1:1.
4. Straighten the beam after the telescope, using two aperture techniques [[1]].
5. Setup the QPD on the xyz translation stage.