Previous: Safety
Next: Experiment 1: Reflection, refraction, and optical power

Equipment

Opto-mechanical equipment

The opto-mechanical equipment in the laboratory provide a system for holding, positioning, aligning, rotating, and translating optical components. The figure shows a typical arrangement of opto-mechanical components aimed at positioning an optic on the optical bench. Please note that the opto-mechanical equipment in the laboratory have dimensions and standards that are mostly in English units; i.e. they are not metric.

$\begin{figure} \centerline {\epsfxsize = 3.7in \epsfbox{bench.eps}}\end{figure}$

Screws and wrenches

There are two boxes with a variety of screws. Two different thread sizes exist for the screws: 1/4-20 (large diameter) and 8-32 (small diameter). (Some optical mounts have 6-32 size set screws as well.) Cap screws have a head and a hex socket. Set screws do not have heads. Allen wrenches and ball drivers are used with the hex sockets.

Wrench set

A wrench set with different size Allen wrenches are provided. Always be careful to use the correct size wrench. Otherwise, the tip of the wrench may be damaged. Do not over-tighten any screws. A controlled amount of torque is usually enough to secure a screw.

Optical bench

The optical bench provides a platform for positioning the optical components used in the experiments. The bench has threaded holes in a rectangular array with 1 inch (2.54 mm) spacing. The threads are for 1/4-20 screws.

Bases

Bases are either screwed directly to the optical bench, or secured with a clamp. Short bases are available in situations where space is limited.

$\begin{figure} \centerline {\epsfxsize = 2.0in \epsfbox{base.eps}}\end{figure}$

Post holders

Post holders are screwed to the bases. They can hold a 1/2 inch thick post at an adjustable height. The thumb screws on the post holders are used to secure the post at the desired height. Do not over tighten the thumb screw. Post holders can also be screwed onto the rotation platform and the translation stage. Six post holders are available at two different heights.

Posts

Posts are steel rods with threaded holes on either side. One side has 1/4-20 threads, and the other side has 8-32 threads. These threads are used to connect the post to an optic holder or mount with a set screw. After this, the post goes into the post holder. There are 12 posts of various sizes available for each group.

Fixed height mounts

There are four fixed-height bases for 3 inch and one for 2 inch beam heights. Adjustable mirror mounts are connected to these fixed height bases as shown in the figure with long 8-32 screws from the bottom.

$\begin{figure} \centerline {\epsfxsize = 2.65in \epsfbox{fixed.eps}}\end{figure}$

Optic mounts

There are a variety of mounts for holding different optical components:

Adjustable mirror mount (4): These mounts are for holding 1 inch optics. The pitch and yaw angles can be adjusted using the knobs at the back. The optic is secured in its position with a nylon tipped set screw.
Small adjustable mirror mount (2): These mounts are for holding 1 inch optics. The optic is placed in a metal holder which is then secured to the mount with a set screw. In the experiments these mounts are used to hold the mirrors that steer the laser beam.
Plate holder (1): This is used to hold thick optical components. Be careful not to tighten the retaining screw too much, as this may damage the optical component.
Slide holder (2): These are used to hold optical components that are mounted in slide frames. Be careful while inserting the slides into the holder.
Fixed optic mount (3): These mounts hold 1 inch optics with little mechanical obstruction, but have no adjustments.
Threaded optic holder (4): These are used to hold optical components that are mounted in cylindrical threaded housings, such as the lenses in the lens set.

Clamps

Clamps are used to secure the bases on to the optical bench. Using clamps allows more freedom in the positioning of bases. Clamps are used as shown in the figure.

$\begin{figure} \centerline {\epsfxsize = 2.0in \epsfbox{clamp.eps}}\end{figure}$

Translation stage

The XZ translation stage provides accurate linear motion in two dimensions. The micrometers on the translation stage provide distance readings in 10 $\mu$ m increments. The total range of the micrometers is 25 mm.

Rotation stages

Two rotation stages provide calibrated angular motion around an axis that is parallel to the beam. One of the stages is dedicated to the 42 mm diameter polarizers.

Rotation base

The rotation base provides calibrated angular motion around an axis that is perpendicular to the beam.

Angle measurement rotation base

The angle measurement rotation base provides both calibrated angular motion and a mechanism for measuring the angle of a reflected beam. This base is used with magnetic component holders.

Iris

A variable iris serves as a variable diameter circular aperture. Irises are also useful as alignment tools and to block unwanted stray reflections. Be careful not to force the iris at the smaller end of its diameter range.

Right angle post clamp

The right angle post clamp can be used to connect two posts at right angles.

Ruler

A steel ruler with both mm and inch units can be used for measuring distances up to 15 cm.

Optical components and instruments

Helium-Neon laser

The Helium-Neon laser produces an intense beam of light. Observe the safety precautions outlined on page

at all times to avoid injury.

The Helium-Neon laser operates at a wavelength of 632.8 nm. Its output power is nominally 0.8 mW. The beam has a Gaussian (TEM $_{00}$ ) transverse profile and is linearly polarized. The He-Ne laser has a power supply with an on/off switch and indicator light on.

The laser takes some time to warm up after first being turned on. (Approximately 15 minutes.) The output power level may fluctuate during this time. At the beginning of the experiment, make sure that the laser is properly mounted before turning it on. Leave the laser on throughout the experiment. Use an opaque object to block the beam when not in use.

Mirrors

Four dielectric mirrors and two aluminum mirrors with flat surfaces are provided. The dielectric mirrors are broadband visible mirrors designed to be used at 0-45 $^\circ$ incidence angle. An additional aluminum mirror mounted on a magnetic mount is also provided.

Lens set

A set of lenses that are mounted in cylindrical threaded housings is provided. There are fourteen positive and two negative lenses in the set.

Polarizers

Two polarizing filters are provided. These have rotating threaded housings that fit one of the rotation stages.

Waveplates

The half-wave and quarter-wave waveplates (retarders) operate at 633 nm.

Beamsplitter

A 50% dielectric beamsplitter operating at visible wavelengths is provided. The beamsplitter is designed to work at 45 $^\circ$ incidence angle.

Compensator plate

A blank glass plate that has the same dimensions as the beamsplitter provides a method to compensate for the thickness of the beamsplitter in an interferometer.

Monochromatic lamp

A green monochromatic light source is provided.

Incandescent light source

The incandescent light source is a regular light bulb. The bulb filament temperature is 2700 K. The spectrum of the emitted light is that of a blackbody radiator at this temperature. The light source has an on/off switch on the back panel. There is a knob on the top to align the bulb filament.

Optical power meter

The power meter is used to measure the light power. It consists of a silicon photodiode, an amplifier with different scales, and a readout from a volt meter. A He-Ne filter can be used to block the room lights when measuring laser light. Be sure to turn off both the volt meter and the detector when you are done using the power meter.

Diffuser

The diffuser provides a means of obtaining diffuse light. It can be used both with the laser and the incandescent light source.

Crossed arrow target

The crossed arrow target has perpendicular arrows of different widths with a circle concentric on the crossing points of the arrows. The larger arrow contains a 15 mm scale.

Slits

A number of slits with varying slit number, width, and spacing are provided. It may be necessary to use a mask on the opposite side of the component carrier to insure that light is incident on only one pattern at a time.

Apertures and diffraction patterns

Two circular apertures with different diameters and two special diffraction patterns are provided. It may be necessary to use a mask on the opposite side of the component carrier to insure that light is incident on only one pattern at a time.

Opaque points and Fresnel zone plates

Circular opaque points and two Fresnel zone plates are provided. The two zone plates are complementary; the opaque zone of one is the transparent zone of the other. It may be necessary to use a mask on the opposite side of the component carrier to insure that light is incident on only one pattern at a time.

Orhan Aytür