LE-1800 Pr:YLF Laser PL-4000

A. LE-1800 Pr:YLF Laser PL4000

Pr:YLF Emission Spectrum. Laser lines at 523, 607 and 638 nm

A Pr:YLF laser (a praseodymium-doped yttrium-lithium fluoride solid-state laser) is particularly well suited for the direct generation of laser light in the visible spectral range (red, orange, green) as well as for UV applications. The Pr:YLF laser is likely the only solid-state laser that directly emits visible light. It is therefore ideally suited for practical training in the fields of laser technology and photonics. Laser safety plays a major role in training and often discourages some instructors from using lasers for teaching purposes. For this reason, we have developed a Pr:YLF laser that meets the requirements of a Class 1 laser while still enabling investigations, measurements, and observations typically associated with a Class 4 laser.
Through the use of protective barriers combined with microprocessor-controlled safety features, laser light is prevented from being accessed or escaping the system under any circumstances. Various sensors, including a standard white screen, a photodiode, or a CCD camera (CC) fitted with slots for multiple filters (FB), can be connected to the system for specific measurement applications. Within each module, there is an EEPROM that stores identity information. Modules are linked through three contact pins into one of the three slots (PL). All three slots are constantly checked to identify which module is present in each slot. Using this data, the microprocessor activates or deactivates the diode laser’s power supply. Should a module be removed while the laser is running, the processor quickly shuts off the laser diode within milliseconds.
The light of the laser diode (LD) is collimated and passes a focusing lens (FL) into the Pr:YLF 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 desired laser wavelength of 523, 607 oder 638 nm. The mirror M2 has a radius of curvature of 50 mm and has a transmission of 1% for the range of 500 - 700 nm 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 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 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 laser starts lasing.