So take a look at this diagram from Wikipedia illustrating a Red Laser Pointer beam being focused.Like other electromagnetic beams, lasers undergo divergence that is measured in degrees or milliradians.There are standard calculations to calculate the width of a laser beam at a given distance.If the telescope has a diameter of 1 meter and you arrange for the laser beam to be expanded.

In general, the thicker your starting powerful laser pointer beam, the more collimated it is, so if you manage to make a (visible wavelength) laser with beam starting at 1cm thickness, you'll have almost perfectly collimated laser beam.The exact calculation takes into account the Gaussian profile of the laser beam, in other words.I attended a laser-physics workshop back in 1988.

This is common e.g. in data sheets of powerful laser pointer diodes and light-emitting diodes.So you can't say that photons go in the same direction - this is just a simplified description of laser operation.The intensity of a laser beam is not uniform, rather the intensity is at a maximum.Since all laser beams diverge, the actual focus is located farther from the lens than the ideal focal length.

The CCD detector surface will be located exactly at the lens back focal length for the green laser pointer wavelength.The rest of the measurement is just like using the focal length method, but here fill in the distance from the laser to the camera instead of the focal length.When we measure beam width at f, the laser isn't yet focused, so we get a positive divergence from the equation, depending on the size of the laser.

In a semiconductor green laser pointer , the end mirrors might be planar crystal faces.Well in fact one can think of semiconductor laser's mirrors as perfectly parallel.Beam divergence measures how much the laser beam expands per meter.A laser with a beam divergence of 1.0mRad will have a beam that expands 1.0mm per meter.Optotronics handheld laser products have a divergence spec. of 1.2mrad orless.

They are designed and tested for high power Violet Laser Pointer applications at a specified wavelength.They are commonly chosen when the collimated laser beam is to be between one and five millimeters.I've already aquired my laser diode and have tested it using a my own little test rig.I just wanted to know what a typical laser pointer is capable achieves in terms of divergence.