Holography Process using Lloyd Mirror Setup for Diffraction Gratings

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1. Process

   1. Slide Prep
      1. Scrub Glass Slide with Acetone, rinse with Isopropanol, then dry with nitrogen gun.
      2. Apply Surpass 4000 to one side of slide, letting it "soak" for 1 minute (you will need to re-spread the surpass often, as it has a tendency to flow to the middle of the slide.
      3. Rinse slide with distilled water.
      4. Dry slide with nitrogen gun.
      5. Bake the slide at 90 C for 1 min to ensure that the slide it dry.
   2. Alternative Slide Prep
      1. Scrub Glass Slide with Acetone, rinse with Isopropanol, then dry with nitrogen gun.
      2. Deposit 200nm+ Low Pressure Oxide in the PECVD.
         1. Perform Dehydration Bake for 30min+ in the Dehydration Oven if slides are left unprocessed for longer than a day.
   3. Spin
      1. Spin thinned resist for 1 minute at 6000 RPM on Solitech Spinner.
         1. The thinned resist is a Mixture of 2 parts Shipley 1.2L resist with 1 part Shipley 1.2L Resist Thinner
         2. Resist should spin to a thickness of ~380nm
      2. Soft bake the resist coated slide at 90 C for 1 minute.
   4. Expose
      1. Using the Argon Laser and Lloyd's Mirror setup (outputting 130-140 µW/cm3), expose slide for 250-260 sec.
      2. To aid in AFM measurement of the gratings, use a mask with intermittent lines to expose down to the glass using the MA 150 Aligner.
      3. Post Expose bake the slide at 115 C for 1 minute.
   5. Develop
      1. Develop slide for 7-10 seconds in non-diluted Shipley 26A developer.
      2. Rinse with distilled water.
      3. Dry with nitrogen gun.
      4. Hard Bake slide at 115 C for 5 minutes.

2. Using the laser at BYU

   1. General Information
      1. Located in 495 CB
      2. Looks like this:

         

   2. Startup
      1. 
      2. 4 Steps
         1. Turn Water Supply valve counter clockwise to open
            1. This image shows the open Water supply valve
               1. 
         2. Lift the breaker switch to the up position
            1. This image shows the breaker switch in the up position
               1. 
            2. The Switch labeled with B is the Warning light switch, to be used during exposures
               1. 
         3. Turn Key on Power Supply Clockwise to the Standby Position
            1. This image shows the Power Supply in the Standby position.
               1. 
         4. Press the "on" Button on the Laser Controller
            1. There will be a delay while the laser prepares to turn on.
            2. This image shows the readout for the laser after its initial delay.
               1. 
      3. After performing the 4 steps to turn on the Laser, Wait 15-30 minutes for the laser to stabilize before using it to expose
   3. Operation
      1. Before exposure, using a power meter, verify that the power density maximum just in front of the Lloyd Mirror setup is ~130 µm
      2. Turn on the Laser Warning Light by flipping the switch up.
      3. Set the Timer(1) for the number of seconds of your exposure
         1. 
      4. Verify that the delay switch(2) is off
      5. Verify that the Time/Man switch(3) is up
      6. Put on 364nm sensitive Safety Goggles.
      7. Push the Reset/Start(4) switch down or depress the red button on the "Clicker Switch"(5)
   4. Shutdown
      1. Turn off laser on the Laser Controller
      2. Turn Key on power supply counter-clockwise to off position
      3. Flip Breaker Switch down
      4. Turn water supply valve off
      5. Turn off Warning Light switch

3. Lloyd's Mirror setup

   1. General Information
      1. The Lloyd's Mirror Setup is mounted on a rotational stage that can be rotated using labview to adjust the period of the interference.
      2. 
   2. Basic Theory
      1. The Lloyd Mirror setup uses constructive and deconstructive interference to cause a sinusoidal intensity profile of exposure on the sample. This works due to the fact that half of the beam reflects off the mirror and on to the sample. That reflection changes the phase of the beam slightly. As a result, when the reflected and incident beams meet on the face of the sample the constructive and deconstructive interference create a sinusoidal intensity pattern to expose valleys into the resist. (see picture below)
      2. 
      3. Lloyd mirror configuration angle calculation.