A. LE-1600 Ruby Laser RL4000

The LE-1600 blue diode pumped Ruby laser is designed as a class 1 laser, albeit a class 4 diode laser (LD) is used generating class 3 laser radiation. By using protective shields and a micro processor controlled safety functions, under no circumstances laser light is accessible or leaves the system. For the different measurement tasks different sensors like an ordinary white screen, a photodiode or a CCD camera (CC) with slots for different filters (FB) can be attached to the system. Each module is equipped with an EEPROM carrying the information about what it is. The modules are plugged via three contact pins into one of the three slots (PL). All three slots are permanently scanned, providing the information what is plugged to which slot. Bases on this information the micro processor allows or prevents powering up the diode laser.
If a module is removed while the laser is powered up, the processor shuts the laser diode down within milliseconds.
The light of the laser diode (LD) is collimated and passes a focusing lens (FL) into the Ruby crystal (RC). Both lenses are integral part of the laser diode. The optical cavity is formed by the flat laser mirror M1 and the curved mirror M2. Both mirrors are mounted into adjustment holder allowing the adjustment of the cavity by the students.
The mirror M1 is a flat mirror with a high transmission for the pump light (405 nm) and a high reflectivity for the ruby laser wavelength of 694 nm. The mirror M2 has a radius of curvature of 50 mm and has a transmission of 1% for the ruby laser wavelength and a high reflectivity for the pump radiation. The adjustment holder for the mirror M2 can be translated by turning the knob CL by 5 mm. The translation range corresponds to a cavity length from 47 mm to 52 mm.
The Figure A. shows the setup with the CCD camera module CC using a 12 MP chip as it is used in the Raspberry cameras. It is connected with a flat ribbon cable to the Raspberry PI attached to the standard 7 inch Monitor (MO). In front of the camera a filter box is plugged in where neutral density filters can be inserted to reduce the intensity of the Ruby laser light down to low levels suitable for the CCD chip. With this simple and economic beam profiler the different transversal modes can be displayed and documented. The camera is also a useful device for the initial alignment of the Ruby Laser. The fluorescence spots originating from the mirrors M1 and M2 are observed by the camera and displayed on the monitor (MO). By aligning the mirrors such that both spots are centered to each other, the Ruby laser starts lasing.

B. Basic version of the Ruby Laser RL4000 with white screen (SC)
But also without the camera module, the initial alignment can be done when using the white screen (SC). In a moderate darkened room the fluorescence spot can be seen on the screen. Aligning bot spots concentrically to each other starts the laser as well. Furthermore the laser modes can be visualized on the screen and pictures taken with mobile cameras.

C. Ruby Laser RL4000 with attached photodetectors P1 and P2
The photodetector P1 is used to detect the fluorescence light of the Ruby crystal. Instead of the photodetector also a fiber adapter can be placed to take the florescence spectrum with a fiber coupled spectrometer. The photodetector P2 is used to analyze the Ruby laser radiation. The timely varying as well as steady signals can be observed. Both detectors can be connected via the BNC (FB) inputs of the integrated controller (DP). Via the software menus and the control knob (SK) of the control panel the sensitivity as well as the gain can be selected. The output of the (FB) can either be connected to an oscilloscope or to a digital voltmeter.