September 28, 2007LGS for SAM – PDR – Optics1 LGS for SAM Optical Alignment R.Tighe, A.Tokovinin. LGS for SAM Design Review September 2007, La Serena

September 28, 2007LGS for SAM – PDR – Optics2 Flexure measurements of SOAR IR Nasmyth Optical Nasmyth Laser Box on one of the serrurier trusses at bent-cass port #2 at 45Deg from IR Nasmyth. Note: As shown in SAM SDN; SAM-AD (SOAR flexure measurements), the flexure seems due to elevation ring sag. Mounting the laser box on the truss should decrease the effect. So the expected flexure is less than the above values. Beam Transfer Laser Launch Telescope The SOAR Maximum Flexure (Top Ring w/r to Elevation Ring): (Top Ring w/r to Optical Axis): Displacement [Y]≈ 2mm. Tilt [  x] ≈ 1 Arcmin. Tilt [  x] ≈ 20” (5” corr.ON).

September 28, 2007LGS for SAM – PDR – Optics3 The Laser-Box Alignment ~1.5m Alignment Mirrors Am1&Am2 (coating nm) Blue Laser UV Laser Co-align UV and Blue Lasers, e.g. by center and auto-collimation from a distant target (~10m) or any other method, Laboratory work. ~10m

September 28, 2007LGS for SAM – PDR – Optics4 Beam Transfer The LGS beam transfer Adjustments (Alignment done with the blue laser) LLT IR m4 m3 SOAR Elevation Ring The Laser Box Adjustments: Tilts:  x=±0.5º;  y=±0.5º. Target on m4. The m 4 Adjustments: Active Tilts:  x=±2º;  y=±2º. Target on LLT entrance. The m 3 Adjustments: Tilts:  x=±2º;  y=±2º. Auto-collimation back to Laser.

September 28, 2007LGS for SAM – PDR – Optics5 The LLT Alignment Step 1: The general procedure: Center and Auto-collimate from LLTm2. X-Y (and Z) displacement of LLTm1 until the foci of both mirrors are coincident. Tip-Tilt LLTm1 pivoting around the common focal point, until beam is centered in LLTm1. The active tip-tilt of m4 will keep the beam centered on LLTm2 (and LLTm1) and therefore IQ stays coma free up to ~1º of LLT pointing correction (need < 1’). LLTm1 LLTm2 LLTm2 Center of curvature LLTm2 focus LLTm1focus

September 28, 2007LGS for SAM – PDR – Optics6 8mm parallel beam only Center Field 485mm Step 0: The general procedure. Center and Auto-collimate from LLTm2. Re-center (or tilt) LLTm1 to make both mirrors’ foci coincident. The LLT Alignment Step 2: In the Laboratory: The auto-collimated beam (into CCD or back to Laser) is measured with a WFS.

September 28, 2007LGS for SAM – PDR – Optics7 The LLT Alignment Step 3: 1 rst Pointing Alignment. The Optical Axes of the LLT and SOAR telescope are made coincident by Tip- Tilting the LLT as a whole (daytime).

September 28, 2007LGS for SAM – PDR – Optics8 The LLT Alignment Step 4: 2 nd Pointing Alignment and m3 Adjustment. The Optical Axes of the LLT and SOAR telescope are fine tuned with a Star image and m3 is adjusted to mount LLT onto the beam transfer optics. Image the star in the predefined position on the LLT alignment & pointing CCD camera. The Pointing Tuning: The m3 final Adjustment: Two checks: 1) Laser auto- collimation (flat mirror on LLT). 2) Star image in CCD- camera at m 4 or at laser box.

September 28, 2007LGS for SAM – PDR – Optics9 The LGS beam Control UV VIS Soleil-Babinet Compensator 8x Beam Expander Beam Profiler CCD 355nm Tripled Nd:Yag Laser 355nm laser-line Dump switch-Mirror Alignment Mirrors Am1&Am2 (coating nm ) Beam Dump / Power meter Blue Alignment Laser (473nm) (or better nm?) 8mm Gaussian Beam Exit Window Intra-cavity Shutter ~1.5m Laser GB quality control: Power Check replacing beam-dump with power-meter. Also a photodiode checks the LLT outgoing beam. M² check with Beam profiler. GB centering on LLT m 2: By 4 photodiodes at the edge of LLT m 1. LGS quality control: Flux return and spot size in the LGS WFS. LLT alignment control: Donut (or defocused star) image on LLT alignment/pointing CCD camera.

September 28, 2007LGS for SAM – PDR – Optics10 Experiments and To Do List Experiments: Test the Beam-Expander. Parallel beam and waist image formation as well as chromatic focus differences. Test the S-B compensator and measure phase shifts. Test the Beam profiler and Power meter. Calibrate photodiodes. To Do: Purchase the Laser-Box and beam transfer optics. Refine the LLT Opto-mechanical design and do the optical procurement.