Align the Laser

The OMV system allows the user to visually locate the cantilever and move the laser into position:

1.  Locate and focus on the cantilever.
   1. Ensure that the camera is in place over the microscope.
   2. In the NanoScope software, click the Setup button to access the Video panel (the video panel is also visible in the Scan view; right click and Undock to enlarge).
   3. Use the optical stage adjustment knobs to move the cantilever into view in the video panel.
   4. Focus on the cantilever.
   5. Click the mouse in the video panel on the approximate tip location on the cantilever. This will move the crosshairs to that location and enable you to know where the tip is regardless of whether the cantilever is in focus.
2. Adjust to focus on the sample surface below the cantilever.
3. Bring the head/tip down using and the stepper motor and, if applicable, the front manual screws, until the cantilever is almost in focus.

4. While maintaining focus on the sample surface, use the optical stage adjustment knobs to locate the red laser reflection spot.
5. Use the laser adjustment knobs on top of the head to move the laser onto the end of the cantilever.

Figure 1: Laser Alignment with Piece of Paper

6. Reposition the laser with the screws on top of the optical head, if necessary.

In the projection method, you will remove the MultiMode 8 head and project the laser beam onto a surface (white paper or other suitable surface) to show a silhouette of the cantilever in order to align the laser. If the laser is not on the cantilever substrate, the laser appears as a bright red spot on the surface below. When the laser is aligned on the cantilever, a shadow appears on the surface below.

In the vision system display, the X direction is right-to-left across the screen, and the Y direction is top-to-bottom.

• The right-front laser control knob, atop the optical head, controls the laser beam movement along the X direction.
• The back-left laser knob, atop the optical head moves the beam along the Y direction perpendicular to the cantilever and substrate's major axis.

The procedure for aligning the laser is slightly different depending on the Probe Tip Geometry. The sections below detail the procedures for aligning the laser on the cantilever for two common probe types.

In this procedure, shining the laser beam on a piece of white paper serves as a guide to aligning the laser beam with the end of the cantilever.

1. Verify the laser beam is visible on the surface below. If it is not, turn the front-right laser control knob counter-clockwise until the laser spot appears on the surface below.
2. Turn the front-right laser control knob clockwise to move the laser in the positive X direction (right) until the laser spot disappears from the surface below. Turn the front-right laser control knob counter-clockwise until the laser spot just reappears. The laser is now positioned at the edge of the substrate (see point 1 in Figure 2).

Figure 2: Etched Silicon Tip Laser Alignment

3. Turn the back-left laser control knob clockwise or counter-clockwise to move the laser in the Y direction (parallel to the substrate edge and perpendicular to the cantilever) until the beam crosses the cantilever and a shadow appears over the laser spot on the surface below. Turning the back-left laser control know clockwise moves the laser beam back from the front of the MultiMode 8 head. The laser is now positioned over the cantilever (see point 2 in Figure 2).
4. Verify that the laser is deflecting off the cantilever by moving the laser on, over, and off the cantilever by turning the back-left laser control knob less than 1/8 of a turn.
5. Turn the front-right laser control knob counter-clockwise to move the laser in the negative X direction on the cantilever until the laser crosses the tip-end of the cantilever and falls on the surface below.
6. Move the laser onto the tip-end of the cantilever by reversing the direction of the front-right laser control knob clockwise until the spot disappears from the surface below (see point 3 in Figure 2).

Verify the laser spot by placing a piece of paper in front of the photodetector (see Figure 1, above). If necessary, reposition the laser with the front-rear and back-left knobs.

In this procedure, the laser is aligned by shining the laser beam on a piece of paper (or other projection surface) to show a silhouette of the cantilever.

1. If the laser beam is not visible on the projection surface, turn the front-right laser control knob counter-clockwise until the laser spot appears.
2. Turn the front-right laser control knob clockwise to move the laser in the positive X direction until the laser spot is blocked by the probe substrate and the projected beam disappears. Turn the right-rear laser control knob counter-clockwise until the laser spot just reappears. The laser is now positioned at the edge of the substrate (see point 1 in Figure 3).

Figure 3: Silicon Nitride Laser Alignment

3. With the laser positioned at the edge of the substrate, use the back-left laser control knob to move in the Y direction (parallel to the edge of the substrate) until the laser is positioned at the base of a desired cantilever. Ensure that the cantilever selected is appropriate for the analysis which is to be performed. In this example, we will assume that the cantilever at point 2 is the desired one (see point 2 in Figure 3).

4. Adjust the back left and front right controls to move the laser beam position to the end of the cantilever (see point 3 in Figure 3) as seen in the projected silhouette.
5. When the beam is positioned at the point of the “V” of the cantilever, remount the head onto the scanner.
6. Verify laser alignment by placing a piece of paper into the head (see Figure 1, above).

Previous Steps:

1. Select Experiment
2. Prepare and Load the Sample
3. Prepare and Load the Probe Holder

Next Steps:

5. Maximize the SUM Signal

When working in TappingMode, the next step at this point is to tune the cantilever. See Manual Cantilever Tuning for more information.

6. Check Initial Scan Parameters
7. Engage, Scan, & Withdraw